text stringlengths 454 608k | url stringlengths 17 896 | dump stringclasses 91
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value | word_count int64 101 114k | flesch_reading_ease float64 50 104 |
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C++ Count Number of Digits in a given Number
Hello Everyone!
In this tutorial, we will learn how to determine the number of digits in a given number, using C++.
Code:
#include <iostream> using namespace std; int main() { cout << "\n\nWelcome to Studytonight :-)\n\n\n"; cout << " ===== Program to count the number of digits in a given number ===== \n\n"; //variable declaration int n, n1, num = 0; //taking input from the command line (user) cout << " Enter a positive integer : "; cin >> n; n1 = n; //storing the original number //Logic to count the number of digits in a given number while (n != 0) { n /= 10; //to get the number except the last digit. num++; //when divided by 10, updated the count of the digits } cout << "\n\nThe number of digits in the entered number: " << n1 << " is " << num; cout << "\n\n\n"; return 0; }
Output:
We hope that this post helped you develop a better understanding of the logic to compute the number of digits in an entered number, in C++. For any query, feel free to reach out to us via the comments section down below.
Keep Learning : ) | https://studytonight.com/cpp-programs/cpp-count-number-of-digits-in-a-given-number | CC-MAIN-2021-04 | refinedweb | 186 | 58.15 |
September 23, 2021 Single Round Match 813 Editorials
LightbulbRow
We can proceed as follows:
- Count the currently lit bulbs. Determine whether we need more or less (or whether we are good).
- Move from the starting location all the way to the leftmost bulb.
- For each bulb: If we need more lit bulbs and it’s off, turn it on. If we need fewer lit bulbs and it is on, turn it off. Then, if this is not the last bulb, take a step right.
The first phase requires no actions at all. The second phase requires at most N-1 steps. The third phase requires at most N lightbulb toggles and N-1 steps. Together, we need at most 3N-2 actions.
public String solve(String bulbStates, int startIndex, int goalCount) { int N = bulbStates.length(); boolean[] bulbs = new boolean[N]; for (int n=0; n<N; ++n) bulbs[n] = (bulbStates.charAt(n) == 'O'); int currentlyLit = 0; for (boolean bulb : bulbs) if (bulb) ++currentlyLit; String answer = ""; int where = startIndex; while (where > 0) { answer += '<'; --where; } for (int n=0; n<N; ++n) { if (currentlyLit < goalCount && !bulbs[n]) { answer += 'S'; ++currentlyLit; } if (currentlyLit > goalCount && bulbs[n]) { answer += 'S'; --currentlyLit; } if (currentlyLit == goalCount) return answer; answer += '>'; } return answer; }
Challenge: Can you solve the same problem if we decrease the limit from 3*N to at most 2.5*N actions?
LooRollPyramid
For an obvious reason, our pyramid sizes are called triangular numbers in math. The size of a pyramid with bottom length n is triangle(n) = 1+2+…+n = n(n+1)/2. Thus, if we know the bottom length of our pyramid, we can calculate its full size, and from that we can determine the number of rolls we are missing.
Our partial pyramid surely consists of two parts:
- At the bottom, zero or more rows with some rolls.
- At the top, zero or more completely empty rolls.
Thus, the rolls we are missing from a complete pyramid are the C rolls that finish the current potentially-incomplete row, plus the rolls used to fill the remaining completely empty rows. All we need to determine C is to determine the number of empty rows.
The number of empty rows is the largest r such that triangle(r) is at most equal to the total number of rolls we are missing from a complete pyramid. And once we make this observation, we can find this r efficiently: We can either derive a formula for r, or we can find it in O(log A) time using binary search.
(It was also possible to find the number of non-empty rows this way: here, we are looking for the smallest n such that A + (A-1) + … + (A+n-1) is greater than or equal to B. The approach is essentially the same as above, only the math is a tiny bit more complicated.)
Once we find r, the answer we need is C = triangle(A) – B – triangle(r), and we are done.
long triangle(long side) { long x = side, y = side+1; if (x % 2 == 0) x /= 2; else y /= 2; return x*y; } public int[] countMissing(int Q, int[] A, long[] B) { int[] C = new int[Q]; for (int q=0; q<Q; ++q) { long full = triangle( A[q] ); int lo = 0, hi = A[q]+1; while (hi - lo > 1) { int med = (lo + hi) / 2; if (B[q] + triangle(med) <= full) lo = med; else hi = med; } C[q] = (int)(full - B[q] - triangle(lo)); } return C; }
PartialRaceResults
The key to solving this task is realizing that each information of the form “X:YZ” can be represented as two separate pieces of information: Y must finish before X, and X must finish before Z. These pieces of information can be stored as directed edges of a graph. Once we do this, all that remains is finding any one finishing order that matches all the information we have – i.e., a topological order in the digraph we just constructed.
Given how small the graph is (at most 62 vertices), we can use essentially any polynomial-time algorithm. The simplest implementation is probably obtained by implementing Warshall’s transitive closure algorithm (which is a simpler but almost identical version of the Floyd-Warshall all-pairs shortest paths algorithm). If there are any cycles in the graph – i.e., if any vertex is reachable from itself – there is no topological order. Otherwise, we can construct one valid order by sorting all vertices according to the number of incoming edges they have in the transitive closure. (Of course, a standard DFS-based implementation of the topological order algorithm can be used instead of the algorithm we just described. This approach solves the problem in linear time.)
int toID(char c) { if (c >= 'a' && c <= 'z') return c - 'a'; if (c >= 'A' && c <= 'Z') return 26 + c - 'A'; if (c >= '0' && c <= '9') return 52 + c - '0'; return -47; } char toChar(int id) { if (id < 26) return (char)(id + 'a'); if (id < 52) return (char)(id - 26 + 'A'); return (char)(id - 52 + '0'); } public String reconstruct(String[] memories) { boolean[] present = new boolean[62]; boolean[][] G = new boolean[62][62]; for (String memory : memories) { int x = toID(memory.charAt(0)); int y = toID(memory.charAt(2)); int z = toID(memory.charAt(3)); present[x] = present[y] = present[z] = true; G[y][x] = true; G[x][z] = true; } for (int k=0; k<62; ++k) for (int i=0; i<62; ++i) for (int j=0; j<62; ++j) G[i][j] = (G[i][j] || (G[i][k] && G[k][j])); for (int k=0; k<62; ++k) if (G[k][k]) return ""; int[] dependencies = new int[62]; for (int i=0; i<62; ++i) for (int j=0; j<62; ++j) if (G[i][j]) ++dependencies[j]; int P = 0; for (boolean p : present) if (p) ++P; int[] order = new int[P]; for (int i=0; i<62; ++i) if (present[i]) order[--P] = i; P = order.length; for (int i=0; i<P; ++i) for (int j=i+1; j<P; ++j) if (dependencies[order[j]] < dependencies[order[i]]) { int t=order[i]; order[i]=order[j]; order[j]=t; } String answer = ""; for (int x : order) answer += toChar(x); return answer; }
RaftingOnDunajec
There are multiple ways of counting these combinatorial objects. We will show one of them.
If there was no restriction that each sight must be covered by some company, we could easily count all ways in which C companies can offer their services: each company has (S+1 choose 2) options which service to offer, their choices are independent, so there are arbitrary(S,C) = (S+1 choose 2)^C total schedules.
In order to count the good schedules, we will now count the bad schedules and subtract those from the total. Let good(S,C) and bad(S,C) denote the number of good and bad schedules with S sights and C companies, respectively.
In each bad schedule there are some sights that are never covered. We can divide all bad schedules into disjoint groups based on which is the first (smallest-numbered) sight that is not covered by any company.
Suppose we are in group f – i.e., sight f (using 0-based numbering) is the first uncovered sight. This means that each company operates either completely before f, or completely after. We can further divide the schedules in this group into buckets based on the number x of companies that are operating upstream of sight number f.
As all the buckets are disjoint, we can compute bad(S,C) simply by summing the sizes of all the buckets.
Now, consider any bucket (f,x). How many different schedules does it contain? We have:
- (C choose x) ways to choose which companies operate before the first bad sight f.
- good(f,x) ways to choose the offers for those companies so that they completely cover the sights before sight f
- arbitrary(S-f-1,C-x) ways to choose the offers for the remaining companies anywhere on the sights after sight f
And as all three choices we can make are mutually independent, the size of the bucket (f,x) is the product of the three values described above.
This recurrence gives us an O(S^2 C^2) algorithm to compute good(S,C) using dynamic programming.
public int count(int S, int C) { long MOD = 1_000_000_007; long[][] comb = new long[1001][]; for (int n=0; n<=1000; ++n) { comb[n] = new long[n+1]; for (int k=0; k<=n; ++k) { if (k == 0 || k == n) { comb[n][k] = 1; } else { comb[n][k] = (comb[n-1][k-1] + comb[n-1][k]) % MOD; } } } long[][] good = new long[S+1][C+1]; long[][] arbitrary = new long[S+1][C+1]; good[0][0] = 1; for (int s=0; s<=S; ++s) arbitrary[s][0] = 1; for (int s=1; s<=S; ++s) for (int c=1; c<=C; ++c) { arbitrary[s][c] = comb[s+1][2]; if (c > 1) { arbitrary[s][c] *= arbitrary[s][c-1]; arbitrary[s][c] %= MOD; } } for (int s=1; s<=S; ++s) for (int c=1; c<=C; ++c) { good[s][c] = arbitrary[s][c]; // iterate over the first bad (unvisited) sight for (int fb=0; fb<s; ++fb) { // iterate over the # of companies before sight #fb for (int left=0; left<=c; ++left) { long curr = comb[c][left]; curr *= good[fb][left]; curr %= MOD; curr *= arbitrary[s-fb-1][c-left]; curr %= MOD; good[s][c] -= curr; good[s][c] += MOD; good[s][c] %= MOD; } } } return (int)good[S][C]; }
PrettyPrimes
As above, this problem also has multiple approaches that can get you to a working solution. We’ll describe one we like because it uses some number theory insights to keep the implementation reasonably simple.
For small values of D we can easily solve the task by iterating over all D-digit numbers. This is always a good idea, as it automatically gets rid of all small special cases. Depending on the approach used for the rest of the task, cases like pattern=11 and D=2 can be nasty. (This is the only pattern of the form XX that actually has all D-1 possible occurrences. Within our constraints all bigger numbers with all digits equal are composite.)
The insight we’ll need for bigger D is that primes are quite frequent: according to the prime number theorem, around the number n there is approximately one prime in each ln(n) numbers. This means that on average one out of 28 random 12-digit numbers will be prime. If we restrict ourselves to numbers that aren’t obviously composite due to their last digit, the expectation goes down to roughly one prime per 11 attempts.
As soon as we have a number that is not just the copies of our desired pattern but also a few extra digits, the count of such numbers quickly becomes quite large – and even though these number aren’t distributed exactly the same way an uniformly random subset would be, their distribution is still arbitrary enough (in a way unrelated to primes). Thus, we should expect that for large D there will always be some almost-perfect solutions. And the number of candidates for almost-perfect solutions is so small that we can generate and check all of them. In fact, the number of possible inputs is so small that we can afford to do this for all possible inputs. In the best-case scenario, we will know that we are done with the task. (Spoiler: this is what actually happens.) In a theoretically possible worse scenario, we may identify several problematic inputs where we need to deepen our search. But if worse comes to worst, those inputs can then always be precomputed using brute force.
In the next two paragraphs we go in detail over two examples to illustrate the above intuition in detail.
For the first example let’s consider the case where pattern=47 and D=12. The only 12-digit number with six occurrences of our pattern is 474,747,474,747, and that clearly isn’t a prime – it’s a multiple of 47. (This will clearly always be the case.) The next best thing are five occurrences of the pattern. There are 2,040 such numbers, which is way more than 28. Even though these aren’t chosen exactly uniformly at random, we expect that an appropriate fraction among them should be prime. And indeed, they are. In this particular case, 169 out of those 2,040 numbers are prime, which is roughly one in 12 – about what we would expect for a collection of random numbers in which most numbers end in a 7.
For the second example consider pattern=42 and D=12. Here, most of the numbers with five occurrences of the pattern will end in 42 and therefore they will be composite. But still, among the 2,040 twelve-digit numbers with five occurrences of this pattern there are 236 that end with 1, 3, 7, or 9. (One of the extra digits is the last odd digit. We have six possible positions and usually ten possible values for the other extra digit.) Out of those 236, 21 are prime – which is again somewhere between one in 11 and one in 12. Seeing 21 primes in this example case makes it highly unlikely that for any other two-digit pattern the number of primes will drop all the way to zero.
In the sample implementation shown below we generate a set of candidates by taking the repeated pattern and inserting at most three extra digits into it in all possible ways. Note how we do it without special-casing each number of extra digits. Also note that this generates some numbers with a smaller number of pattern occurrences if we insert the new digits in dumb places, but we don’t care about those, as they will never get processed in the later steps and the total number of candidates is still small enough.
Then we group the candidates by the number of pattern occurrences they actually contain, and we then test everything in those groups for primality until we find a group that works. We can easily verify that in each case that group is still one of those for which we generated all possible members, and therefore the solutions we found are all correct.
set<long long> generate_candidates(int pattern, int D) { // generate all numbers that can be obtained from a repeated pattern // by inserting at most three extra digits set<long long> answer; vector<int> repeated = { pattern/10, pattern%10 }; if (repeated[0] == 0) repeated[0] = repeated[1]; for (int a=0; a<D+3; ++a) for (int b=a+1; b<D+3; ++b) for (int c=b+1; c<D+3; ++c) { for (int va=0; va<10; ++va) for (int vb=0; vb<10; ++vb) for (int vc=0; vc<10; ++vc) { if (a == 0 && va == 0) continue; // no leading zeros long long curr = 0; for (int i=0, p=0; i<D; ++i) { if (i == a) curr = 10*curr + va; else if (i == b) curr = 10*curr + vb; else if (i == c) curr = 10*curr + vc; else curr = 10*curr + repeated[(p++)%2]; } answer.insert(curr); } } return answer; } bool is_prime(long long N) { if (N < 2) return false; for (long long d=2; ; ++d) { if (d*d > N) return true; if (N%d == 0) return false; } } int count_occurrences(long long N, int pattern) { int answer = 0; if (pattern >= 10) { while (N >= 10) { if (N % 100 == pattern) ++answer; N /= 10; } } else { while (N > 0) { if (N % 10 == pattern) ++answer; N /= 10; } } return answer; } int solve(int pattern, int D) { map<int, vector<long long> > buckets; for (auto cand : generate_candidates(pattern, D)) buckets[ count_occurrences(cand,pattern) ].push_back(cand); for (int d=D; d>=0; --d) { vector<long long> found; for (auto cand : buckets[d]) if (is_prime(cand)) found.push_back(cand); if (!found.empty()) { long long answer = 0; for (auto cand : found) answer = (answer + cand) % 1000000007; return answer; } } return -47; }
misof | https://www.topcoder.com/blog/single-round-match-813-editorials/ | CC-MAIN-2022-40 | refinedweb | 2,694 | 64.64 |
VudalVudal
Modal window component based on Semantic UI design. (Does not require semantic ui, it is completely independent)
Install plugin
import { VudalPlugin } from 'vudal'; Vue.use(VudalPlugin);
Possible options:
- hideModalsOnDimmerClick (defaults to true) lets control whether clicking on dimmer will hide opened modals
Inside your component make preparations
import Vudal from 'vudal'; ... components: { Vudal } ...
Component usage example
<vudal name="myModal"> <div class="header"> <i class="close icon"></i> Title </div> <div class="content"> Content </div> <div class="actions"> <div class="ui cancel button">Cancel</div> <div class="ui button">Ok</div> </div> </vudal>
Params:
- name modal name
- parent parent modal name (if any)
- close-by-esc close by
ESCbutton (true by default)
- stickyHeader set sticky header block (class .header) (false by default)
- stickyActions set sticky actions block (class .actions) (false by default)
Parent-child relationship is needed when second (child) modals is opened, but you close first modal (parent), child should also be closed. Also parent modal is blurred when child is opened.
Events:
- show fired when modal is starting to show
- hide fired when modal is starting to hide
- hidden fired when modal finished hiding animation
- visible fired when modal finished show animation
Methods:
- $toggle toggle visibility
- $show self explanatory
- $hide self explanatory
- $isActive check whether modal is visible
- $remove destroy modal
Selector
'.actions .cancel' call method $hide on click.
Also global
$modals object is available to control modals.
You can access modals by name, for example
this.$modals.myModal.
Example:
this.$modals.myModal.$show() to show modal.
Use
this.$modals.hideAll() to hide all active modals.
Custom modalsCustom modals
If you need to create your own custom looking modal, you can use
modalMixin that will drive your modal.
It adds everything specified above, except
.actions selector thing.
It also adds
.vudal class to root element and
.show,
.hide and
.mobile class for visible, hidden and opened on mobile device accordingly. | https://reposhub.com/vuejs/Overlay-modal-alert-dialog-lightbox-popup/Egorvah-vudal.html | CC-MAIN-2021-21 | refinedweb | 312 | 56.05 |
53045/read-multiple-xml-files-in-spark
You can do this using globbing. See the Spark dataframeReader "load" method. Load can take a single path string, a sequence of paths, or no argument for data sources that don't have paths (i.e. not HDFS or S3 or other file systems).
val df = sqlContext.read.format("com.databricks.spark.xml")
.option("inferschema","true")
.option("rowTag", "address") //the root node of your xml to be treated as row
.load("/path/to/files/*.xml")
load can take a long string with comma separated paths
.load("/path/to/files/File1.xml, /path/to/files/File2.xml")
As parquet is a column based storage ...READ MORE
You lose the files because by default, ...READ MORE
Below is an example of reading data ...READ MORE
Hey,
You can try this:
from pyspark import SparkContext
SparkContext.stop(sc)
its late but this how you can ...READ MORE
Yes, you can go ahead and write ...READ MORE
OR | https://www.edureka.co/community/53045/read-multiple-xml-files-in-spark | CC-MAIN-2019-35 | refinedweb | 161 | 79.06 |
chown, fchown - change ownership of a file
#include <sys/types.h>
#include <unistd.h>
int chown(const char *path, uid_t owner, gid_t group);
int fchown(int fd, uid_t owner, gid_t group);
The owner of.
On success, zero is returned. On error, -1 is returned,
and errno is set appropriately. sys-
tem.
EFAULT path points outside your accessible address
space.
ENAMETOOLONG
path is too long.
ENOENT The file does not exist.
ENOMEM Insufficient kernel memory was available.
ENOTDIR A component of the path prefix is not a direc-
tory.
EACCES Search permission is denied on a component of
the path prefix.
ELOOP path contains a circular reference (i.e., via a
symbolic link)
The general errors for fchown are listed below:
EBADF The descriptor is not value.
ENOENT See above.
EPERM See above.
EROFS See above.
The prototype for fchown is only available if __USE_BSD is
defined.
chmod(2), flock(2) | http://www.linuxonlinehelp.com/man/chown.html | crawl-001 | refinedweb | 150 | 71.41 |
Introduction
We would urge you to first do this tutorial and then study the Allegro Prolog documentation if necessary. This is a basic tutorial on how to use Prolog with AllegroGraph 3.3. It should be enough to get you going but if you have any questions please write to us and we will help you. In this example we will focus mainly on how to use the following constructs:
When consulting the Reference Guide, one should understand the conventions for documenting Prolog functors. A Prolog functor clause looks like a regular Lisp function call, the symbol naming the functor being the first element of the list and the remaining elements being arguments. But arguments to a Prolog functor call can either be supplied as input to the functor, or unsupplied so that the clause might return that argument as a result by unifying some data to it, or may be a tree of nodes containing both ground data an Prolog variables. The common example is the functor
append which has three arguments and succeeds for any solution there the third argument is the same as the first two arguments appended. The remarkable thing about Prolog semantics is that append is a declarative relation that succeeds regardless which arguments are supplied as inputs and which are supplied as outputs.
<ret> indicates where the user would type a return to ask Prolog to find the next result.
> (?- (append (1 2) (3) ?z)) ?z = (1 2 3) <ret> No. > (?- (append (1 2) ?y (1 2 3))) ?y = (3) <ret> No. > (?- (append ?x ?y (1 2 3))) ?x = () ?y = (1 2 3) <ret> ?x = (1) ?y = (2 3) <ret> ?x = (1 2) ?y = (3) <ret> ?x = (1 2 3) ?y = () <ret> No. > (?- (append ? (1 ?next . ?) (1 2 1 3 4 1 5 1))) ?next = 2 <ret> ?next = 3 <ret> ?next = 5 <ret> No.
The last example successively unifies to each element in the list immediately preceded by a
1. It shows the power of unification against partially ground tree structure.
Now we return to the the notational convention: A functor argument that is an input to the functor and which must be supplied is marked in the documentaiton with a
+. A functor argument that is returned by the functor and which must not be supplied is marked with a
-. An argument that can be either is marked with ±. (Prolog documentation generally used
? for this, but in Lisp-bnased Prologs that character is used as the first character of a symbol that is a Prolog variable, overloading using it to indicate and input-output argument would be very confusing.) Within this convention append would be notated as
(append ±left ±right ±result
). But a functor like
part= which simply checks whether two parts are the same UPI and which requires two actual which requires two actual future-part or UPI arguments, would be documented
(part= +upi1 +upi2).
The rest of this tutorial will be based on a tiny genealogy database of the Kennedy family.
Please open the file
kennedy.ntriples that came with this distribution in a text editor or with TopBraidComposer and study the contents of the file. Notice that people in this file have a type, sometimes multiple children, multiple spouses, multiple professions, and go to multiple colleges or universities.
This tutorial uses Lisp as the base language but there is also a Java example with the same content.
First let us get AllegroGraph ready to use:
> (require :agraph) ;; .... output deleted. > (in-package :triple-store-user) #<The db.agraph.user package> > (enable-!-reader) #<Function read-!> t > (register-namespace "ex" "" :errorp nil) ""
Now we can create a triple-store and load it with data. The function create-triple-store creates a new triple-store and opens it. If you use the triple-store name "temp/test", then AllegroGraph will create a new directory named
temp in your current directory (use the top-level command
:pwd if you want to see what this is). It will then make another directory named
test as a sub-directory of
temp. All of this triple-store's data will be placed in this new directory
temp/test:
> (defun fill-kennedy-db () (create-triple-store "temp/test" :if-exists :supersede) (time (load-ntriples #p"sys:agraph;tutorial-files;kennedy.ntriples")) (index-all-triples)) fill-kennedy-db > (fill-kennedy-db) ;; .... output deleted.
So let us first look at
person1 in this database:
> (print-triples (get-triples-list :s !ex:person1)) <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> . <> <> <> .
Now we are ready to try the select statement in combination with the Prolog q functor. Let us try to find all the children of
person1. Just type the following in the listener. Afterward, I'll explain.
> (select (?x) (q- !ex:person1 !ex:has-child ?x)) (("") ("") ("") ("") ("") ("") ("") ("") (""))
select is a wrapper used around one or more Prolog statements. The first element after select is template for the format and variables that you want to bind and return. So in this example above we want to bind the variable
?x. The rest of the elements tell Prolog what we want to bind
?x to.
This
statement has only one clause, namely (q- !ex:person1 !ex:has-child ?x)`
If you have studied how get-triples works you probably can guess what happens here.
q- is a Prolog functor that is our link to the data in the triple-store. It calls
get-triples and unifies the
?x with the objects of all triples with subject
!ex:person1 and predicate
!ex:has-child.
So let us make it a little bit more complex. Let us find all the children of the children of person1. Here is how you do it:
> (select (?y) (q- !ex:person1 !ex:has-child ?x) (q- ?x !ex:has-child ?y)) (("") ("") ("") ("") ("") ("") ("") ("") ("") ("") ...)
Although Prolog is a declarative language, a procedural reading of this query works better for most people. So the previous query can be read as
Find all triples that start with
!ex:person1
!ex:has-child. For each match set
?xto the object of that triple; then for each triple that starts with
?x
!ex:has-childfind the
?y
The following example should now be easy to understand. Here we are trying to find all the spouses of the grand-children of
?z. Notice that we ignore the
?x and
?y in the query. The select will only return the
?z
> (select (?z) (q- !ex:person1 !ex:has-child ?x) (q- ?x !ex:has-child ?y) (q- ?y !ex:spouse ?z)) (("") ("") ("") ("") ("") ("") ("") ("") ("") ("") ...)
Now if you wanted to you could get the other variables back. Here is the same query but now you also want to see the grand-child.
> (select (?y ?z) (q- !ex:person1 !ex:has-child ?x) (q- ?x !ex:has-child ?y) (q- ?y !ex:spouse ?z)) (("" "") ("" "") ("" "") ("" "") ("" "") ("" "") ("" "") ("" "") ("" "") ("" "") ...)
So now we understand the
select and the
q statement. We are halfway there. Let us now define some Prolog functors.
The following defines a functor that says:
?x is a male if in the triple store I can find an
?x that has the
!ex:sex
!ex:male.
> (<-- (male ?x) (q- ?x !ex:sex !ex:male)) male
Let us try it out by finding all the sons of person1.
> (select (?x) (q- !ex:person1 !ex:has-child ?x) (male ?x)) ;;; Note how we use NO q here! (("") ("") ("") (""))
Now this is not too exciting, and it is equivalent to the following:
(select (?x) (q- !ex:person1 !ex:has-child ?x) (q- ?x !ex:sex !ex:male))
So let us make it more complex:
> (<-- (female ?x) (q- ?x !ex:sex !ex:female)) female > (<-- (father ?x ?y) (male ?x) (q- ?x !ex:has-child ?y)) father > (<-- (mother ?x ?y) (female ?x) (q- ?x !ex:has-child ?y)) mother
The female, father, mother relations are all simple to understand. The following adds the idea of multiple rules (or functors). Notice how we define the parent relationship with two rules, where the first rule uses <-- and the second rule uses <-. The reason is that <-- means: wipe out all the previous rules that I had about parent and start anew whereas <- means, add to the existing rules for parent.
The following should be read as:
?xis the parent of
?yif
?xis the father of
?yor
?xis the parent of
?yif
?xis the mother of
?y.
(<-- (parent ?x ?y)
(father ?x ?y)) parent
(<- (parent ?x ?y)
(mother ?x ?y)) parent
So let us try it out by finding the grand children of person1
> (select (?y) (parent !ex:person1 ?x) (parent ?x ?y)) (("") ("") ("") ("") ("") ("") ("") ("") ("") ("") ...)
We could have done the same thing by defining a grandparent functor. See the next definition.
> (<-- (grandparent ?x ?y) (parent ?x ?z) (parent ?z ?y)) grandparent > (<-- (grandchild ?x ?y) (grandparent ?y ?x)) grandchild
And here it gets really interesting because we now go for the first time to a recursive functor.
> (<-- )) (("") ("") ("") ("") ("") ("") ("") ("") ("") ("") ...)
And then here are some puzzles that you can work out for yourself.. Note the use of
not and part= in these statements. 'not' can contain any expression.
part= will compare its two arguments as UPIs; It will not unify.
> (<-- the value computed by the progn body into the Prolog clause.
There is a problem with the syntax for the Prolog cut and AllegroGraph's future-part syntax. Prolog uses the exclamation point ! to denote the cut operation. When executed, a cut clears all previous backtracking points within the current predicate. For example,
> (<-- (parent ?x) (parent ?x ?) !)
defines a predicate that tests whether the argument person a parent, but if so succeeds only once. ?) \!)
Be aware that sometimes names with syntax parent/2 will appear in Prolog documentation and in the debugger. The portion of the name is the predicate name -- also called a functor and the same as the Lisp symbol naming the predicate. The non-negative integer after the slash is the arity, which is the number of arguments to the predicate. Two predicates with the same functor but different arity are completely unrelated to one another. In the example above the predicate parent/1 has no relation to the parent/2 predicate defined earlier in this document and which it calls. | http://franz.com/agraph/support/documentation/3.3/prolog-tutorial.html | CC-MAIN-2016-18 | refinedweb | 1,672 | 66.84 |
Perform an automatic click on a webpage
- manuel2459
Hello everybody,
I am a beginner in Qt and I would like to build a program able to click automatically on some link on webpages, depending on signals with Qt.
For example, if I want to click automatically on a part of google.com, i wrote this:
@#include <QApplication>
#include <QWebView>
#include <QCursor>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QWebView *pageWeb = new QWebView;
pageWeb->load(QUrl(""));
QCursor::setPos(220,130);
void QTest::mousePress ( QWidget * widget, Qt::MouseButton button, Qt::KeyboardModifiers modifier = 0, QPoint pos = QPoint(220,30), int delay = -1 )
return app.exec();
}
@
Could you help me on this please?
Many thanks for your help!
I would say, this is more a topic for dealing with the DOM structure of a web page but not with sending signals in Qt. Also, be aware that the position you calculate heavily depends on font sizes, window sizes, etc. You might consider JavaScript for dealing with that.
Well if you require not a very high speed... you could look into "IMacros" for firefox e.g.
No programming needed, it does what you tell him to do ;)
If you want to do it more seriously, well you should look into Script languages, like Volker pointed out.
Qt and C++ are not really helping in that matter ;) | https://forum.qt.io/topic/12538/perform-an-automatic-click-on-a-webpage | CC-MAIN-2017-34 | refinedweb | 224 | 62.27 |
24695/how-to-exit-from-python-without-traceback
shutil has many methods you can use. One ...READ MORE
Perhaps you're trying to catch all exceptions ...READ MORE
Using the default CSV module
Demo:
import csv
with open(filename, "r") ...READ MORE
print(*names, sep = ', ')
This is what ...READ MORE
suppose you have a string with a ...READ MORE
You can also use the random library's ...READ MORE
Syntax :
list. count(value)
Code:
colors = ['red', 'green', ...READ MORE
can you give an example using a ...READ MORE
Assuming you don't have extraneous whitespace:
with open('file') ...READ MORE
you can check the version of python ...READ MORE
OR
Already have an account? Sign in. | https://www.edureka.co/community/24695/how-to-exit-from-python-without-traceback?show=24697 | CC-MAIN-2020-45 | refinedweb | 116 | 79.77 |
#include <oping.h> int ping_host_add (pingobj_t *obj, const char *host); int ping_host_remove (pingobj_t *obj, const char *host);
The obj argument is a pointer to an liboping object, as returned by ping_construct(3).
The host parameter is a '\0' terminated string which is interpreted as a hostname or an IP address. Depending on the address family setting, set with ping_setopt(3), the hostname is resolved to an IPv4 or IPv6 address.
The ping_host_remove method looks for host within obj and remove it if found. It will close the socket and deallocate the memory, too.
The names passed to ping_host_add and ping_host_remove must match. This name can be queried using ping_iterator_get_info(3).
ping_host_remove returns zero upon success and less than zero if it failed. Currently the only reason for failure is that the host isn't found, but this is subject to change. Use ping_get_error(3) to receive the error message.
(c) 2005-2009 by Florian octo Forster. | http://www.makelinux.net/man/3/P/ping_host_add | CC-MAIN-2014-15 | refinedweb | 156 | 66.23 |
Introduction
This tutorial is based on Building Ogre with boost 1.50 upwards and MinGW. I decided to write this after I have spent several days making Ogre compile on windows. There are some small things you can overlook, or forgot to do. On linux you basicaly run one sudo-apt-get-install command, one hg-clone, cd, mkdir build, make install -j8 and you are done. In windows this is not that simple. So here is mine command by command guide.
You almost do not have to think and you should end up with ogre ready to work. You just insert command after command in your command line.
Download them all
You need to download all this and place/install it into the right directories (boost, MinGW). In case of ogre and ogre-dependencies you can run command in whatever place you like, the path to download is present in commands itselfs.
Build Boost
set PATH=%PATH%;C:\MinGW\bin;C:\MinGW\msys\1.0\bin mkdir c:\boost\build cd c:\boost\tools\build\v2 bootstrap.bat gcc b2 install --prefix=C:\boost\build set PATH=%PATH%;C:\boost\build\bin cd c:\boost b2 --build-dir=C:\boost\build toolset=gcc --build-type=complete stage
get a cofee, lunch or go to sleep, this will take several hours
move stage\lib ./ set PATH=%PATH%;C:\boost set BOOST_ROOT=C:\boost set Boost_DIR=C:\boost setx BOOST_ROOT C:\boost setx Boost_DIR C:\boost
Build Ogre dependencies
set PATH=%PATH%;C:\MinGW\bin;C:\MinGW\msys\1.0\bin;C:\boost;C:\Program Files (x86)\CMake 2.8\bin cd c:\ogre-dep mkdir build cd build cmake -G "MSYS Makefiles" .. make install
This should take few minutes
cmake .. -DCMAKE_BUILD_TYPE=Debug make clean make install #again... max few minutes set OGRE_DEPENDENCIES_DIR=C:\ogre-dep\build\ogredeps setx OGRE_DEPENDENCIES_DIR C:\ogre-dep\build\ogredeps
Build Ogre
These three build can run in separated command lines - you can save some time by this, provided you have more cores. Building Ogre will take few hours.
#Regular set PATH=%PATH%;C:\MinGW\bin;C:\MinGW\msys\1.0\bin;C:\boost;C:\Program Files (x86)\CMake 2.8\bin cd c:\ogre hg update v1-9 mkdir build cd build cmake -G "MSYS Makefiles" .. -DOGRE_BUILD_RENDERSYSTEM_D3D11=FALSE make install
#Debug cd c:\ogre mkdir buildd cd buildd cmake .. -G "MSYS Makefiles" -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=C:/ogre/build/sdk -DOGRE_BUILD_RENDERSYSTEM_D3D11=FALSE make install
#Small size librearies cd c:\ogre mkdir buildmin cd buildmin cmake .. -G "MSYS Makefiles" -DCMAKE_BUILD_TYPE=MinSizeRel -DCMAKE_INSTALL_PREFIX=C:/ogre/build/sdk -DOGRE_BUILD_RENDERSYSTEM_D3D11=FALSE make install
And finaly
set OGRE_HOME=C:\ogre\build\sdk setx OGRE_HOME C:\ogre\build\sdk
Add things to PATH
Let us fall back to gui...
right click on "The computer"
Pick properties
Go to system variables
add this:
;C:\MinGW\bin;C:\MinGW\msys\1.0\bin;C:\boost;C:\Program Files (x86)\CMake 2.8\bin
to the end of PATH
Let us test
I have prepared small clean project which compiles fine under Linux and Windows
cd path/to/dev/directory git clone cd ogreclean
With these steps you will build and run this projects. If you have problems with off_t and off64_t, please see troubleshooting section at the end.
cd d:\some_path_to_your_project mkdir build cd build cmake .. -G "MSYS Makefiles" -DOGRE_FRAMEWORK_INCLUDES=c:/ogre/build/sdk/include -DOGRE_FRAMEWORK_PATH=c:/ogre/build/sdk make install cd dist/bin NameOfYourApp.exe #If you want to have min size libraries use this cmake instead: cmake .. -G "MSYS Makefiles" -DOGRE_FRAMEWORK_INCLUDES=c:/ogre/build/sdk/include -DOGRE_FRAMEWORK_PATH=c:/ogre/build/sdk -DCMAKE_BUILD_TYPE=MinSizeRel
Troubleshooting
Problems with off_t and off64_t
run editor on this file C:\MinGW\include\sys\types.h
You need to move change few line to look like this...
I know this is ugly, i did not have time to look for better solution, if you have one, please edit this page.
#ifndef _OFF_T_ #define _OFF_T_ typedef long _off_t; typedef _off_t off_t; #ifndef __STRICT_ANSI__ #endif /* __STRICT_ANSI__ */ #endif /* Not _OFF_T_ */ #ifndef _OFF64_T_ #define _OFF64_T_ typedef __int64 _off64_t; typedef __int64 off64_t; #ifndef __STRICT_ANSI__ #endif /* __STRICT_ANSI__ */ #endif /* ndef _OFF64_T */ | https://wiki.ogre3d.org/Building+Ogre+Dummy+Guide+MinGW | CC-MAIN-2021-49 | refinedweb | 687 | 57.57 |
.
I don't have the anger of the previous post, but...
The fact that namespaces is not baked into ExtJS (2.2.1) is a little weird. How could that possibly be?
ExtJS cannot be all things to everyone, and I understand the commitment to JSON (and open source), but maybe this is an area that could be improved.
This can't work
This approach lets you search for names with namespace prefixes, but not namespaces. Throughout a document the same namespace can be used with different prefixes. The DOM API should be level 2 and for the additional selector-based query functions it should be possible to declare the prefixes for the namespaces that will be used in the selectors. Those prefixes are not related to those in the XML document.
Werner Donné.
Bah, I'm really dissapinted. This still doesn't work with ExtJS 4.X
I must say this is shameful! | https://www.sencha.com/forum/showthread.php?19574-xml-namespaces-with-Ext.DomQuery&p=438225&viewfull=1 | CC-MAIN-2015-35 | refinedweb | 154 | 76.01 |
Why can't I stop the loop even after I put
while ("answer" != 0);
on the answer input I press 0, but the loop still continue.
Please help.
Code://User input poll of "Do you like _______ ?" //3 possible poll responds; r1, r2, r3. #include <iostream>; #include <string>; using namespace std; int main() { //question string poll; //answers string answer; string y; string n; int count1;//yes int count2;//no int count3;//no idea cout << "NOTE: There are only 3 possibles answers to this poll:\n"; cout << "1.yes.\n"; cout << "2.no. \n"; cout << "3.no idea \n"; cout << "Press the answer's number and then ENTER to add poll.\n"; cout << "Example: press 1 to answer yes.\n"; cout << "To end poll, press 0.\n"; cout << "What would you like to ask? (Type below) \n\n"; getline(cin, poll); do { cout << "Vote for yes? y/n \n"; cin >> answer; if ( answer != "y" || answer != "n") { cout << "Invalid choice.\n"; } } while ( "answer" != 0); system("pause"); return 0; } | http://cboard.cprogramming.com/cplusplus-programming/153169-help-looping-problem.html | CC-MAIN-2015-06 | refinedweb | 166 | 87.52 |
This is some very preliminary work based on some ideas Masami and I
have talked about over the past few years. Seeing his disassembler in
action made me decide to take a stab at the in kernel lines for
locations chanages.
What does this patch set do at a high level?
It should be fairly obvious if you take a look at a call to panic()
inside a kernel module without the patch and then with the patch.
Call to panic() without the patch set
-------------------------------------
Call Trace:
[] panic+0xbd/0x1c3
[] ? printk+0x68/0x6c
[] panic_write+0x25/0x30 [test_panic]
[]
Call to panic() with the patch set
----------------------------------
Call Trace:
[] panic+0xbd/0x14 panic.c:111
[] ? printk+0x68/0xd printk.c:765
[] panic_write+0x25/0x30 [test_panic] test_panic.c:189
[] proc_file_write+0x76/0x21 generic.c:226
[] ? __proc_create+0x130/0x21 generic.c:211
[] proc_reg_write+0x88/0x21 inode.c:218
[] vfs_write+0xc8/0x20 read_write.c:435
[] sys_write+0x51/0x19 read_write.c:457
[] ia32_do_call+0x13/0xc ia32entry.S:427
The key difference here is that you get the source line information in
any kind of oops/panic/backtrace, including inside kernel modules. Of
course this comes at the expense of some memory you do not get to use
because these tables have to get stored in a place that is accessible
after a crash. On a system with 4 gigs of ram however, the cost is
nearly insignificant when you have to give up a few megs for the
capability. The idea is to make it a bit easier to just jump into a
source tree without having to use any tools to decode the dump (which
I know every kernel developer out there already has anwyay :-)
Using this patch is fairly straight forward. From a developer / end
user perspective here are the steps:
* set CONFIG_KALLSYMS_LINE_LOCATIONS=y
* Build a kernel that has debug information
* Copy the unstripped kernel modules to the target system
--
So how does this work?
There are two separate pieces, one for the core kernel and one for the
kernel modules. In both cases we need debug information generated
into the elf files for the purpose of obtaining the .debug_line
section which has the tables of where all the address / source line
information lives.
For the core kernel, all the line location information is added to the
kallsyms table using a new symbol type '0xff'. These symbols will not
show up if you "cat /proc/kallsyms", such that no user space
applications break. The new line location symbols are added to the
kallsyms table using a modified version of readelf which can only read
the .debug_line section of a vmlinux file. This output is sent into
scripts/kallsyms and where it is encoded into an assembly file and
then compiled and linked into the kernel. The internal kallsyms
encoding was changed in order to have fast lookups of the symbol type
information, and then a new function call was added to provide line
location lookups inside the kernel.
For a kernel module, the kernel module loader will look for a
.debug_line section after completing the kallsyms processing. If it
finds one of these locations it will process the relocations and then
dynamically create a set of linked lists of the compilation units that
were used to create the kernel module. Each compilation unit in the
linked list 2 arrays, one for the for source locations, and another
for address offset, source line number, and source line index into the
source file array.
Finally the symbol lookup used by printk was changed to request the
lines for location data when it exists.
--
One of the interesting things you can do if you are tight on memory
but can afford kallsyms, is to only use lines for locations in a
single kernel module and even leave out lines for locations for the
kernel core.
Example backtrace using the same kernel as above
------------------------------------------------
Call Trace:
[] panic+0xbd/0x1c3
[] ? printk+0x68/0x6c
[] panic_write+0x25/0x30 [test_panic] test_panic.c:189
[]
--
More details...
The first two patches in this series really are not all that
interesting. The first simply adds in readelf.c from binutils 2.14,
the second strips it down such that it actually compiles and runs just
to emit source/line information from a vmlinux file. The remainder of
the readelf patches fix it to work properly with the objective of
pushing the information into the kallsyms table. At least this way we
have the complete history of how this was derrived.
If you are wondering why I pulled in an modified readelf? It is
because most of the pre-built versions of readelf I tried were not
working properly on 32 or 64 bit combinations of machines.
What is left to do here?
* Decide if this is worthy at all for the mainline
* Perhaps change the implementation so to use a different table
for the core kernel or also use .debug_line data
* Check the memory usage in kallsyms with and without the type array
* Provide some stats on how much memory this really uses (cost/benefit)
* Perhaps split the elf functions out of module.c into their own file
* Add in an optional kbuild option to not strip the .debug_line section
from kernel module files
* Fix the bug where the symbol offset isn't right when using lines
for locations built into the kernel
* Fix the bounds checking in the print_symbol because there is
clearly a buffer overrun if you put a _really_ long file name in.
As always comments are welcome. :-)
Cheers,
Jason.
git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb.git
lines_for_locations
--
Jason Wessel (8):
readelf: check in a direct copy of readelf.c from binutils 2.14
readelf: remove code unrelated to .debug_line section processing
readelf: emit simple to parse line .debug_line data
readelf: Fix dumping a 64 bit elf file on a 32 bit host
kallsyms: convert the kallsyms storage to store the type separately
kallsyms: Add kallsyms kallsyms_line_loc_lookup and print function
modules: decode .debug_line sections if provided by insmod
kallsyms,modules: add module_address_line_lookup() to
kallsyms_line_loc_lookup()
Makefile | 9 +-
include/linux/kallsyms.h | 12 +
include/linux/module.h | 32 ++
init/Kconfig | 11 +
kernel/kallsyms.c | 140 +++++--
kernel/module.c | 549 ++++++++++++++++++++++++++
scripts/Makefile | 2 +
scripts/kallsyms.c | 49 ++-
scripts/namespace.pl | 1 +
scripts/readelf.c | 1855
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
10 files changed, 2618 insertions(+), 42 deletions(-)
create mode 100644 scripts/readelf.c | http://article.gmane.org/gmane.linux.kernel/1285510 | CC-MAIN-2016-50 | refinedweb | 1,060 | 64.2 |
This is part of a larger project on the practical application of quantal response equilibrium and related concepts of statistical game theory.
It is inspired in part by several recent papers by Camerer, Palfrey, and coauthors, developing various generalizations of quantal response equilibrium (including heterogeneous QRE) and links between QRE and cognitive hierarchy/level-k models.
These are exciting developments (in the view of this researcher) because this appears to offer a coherent and flexible statistical framework to use as a foundation for behavioural modeling in games, and a data-driven approach to behavioural game theory.
What we will do in this talk is to use the facilities in Gambit to explore how to fit QRE to small games. We'll focus on small games so that all computations can be done live in this Jupyter notebook - making this talk equally a useful practical tutorial, and automatically documenting all the computations done in support of the development of the lines of thought herein.
Advertisement: Thanks to some friends of Gambit at Cardiff (and support from a Google Summer of Code internship), Gambit is being integrated into the SAGE package for computational mathematics in Python (). Also as part of this, it will soon be possible to interact with Gambit (alongside all of the mathetmatical tools that SAGE bundles) using notebooks like this one, on a server via your web browser.
We begin by looking at some of the examples from the original Quantal Response Equilibrium paper:
McKelvey, R. D. and Palfrey, T. R. (1995) Quantal response equilibrium for normal form games. Games and Economic Behavior 10: 6-38.
We will take the examples slightly out of order, and look first at the non-constant sum game of "asymmetric" matching pennies they consider from
Ochs, J. (1995) Games with unique mixed strategy equilibria: An experimental study. Games and Economic Behavior 10: 174-189.
import math import numpy import scipy.optimize import pandas import matplotlib.pyplot as plt %matplotlib inline import gambit
gambit.__version__
'16.0.0'
Set up the payoff matrices. McKPal95 multiply the basic payoff matrix by a factor to translate to 1982 US cents. In addition, the exchange rates for the two players were different in the original experiment, accounting for the different multiplicative factors.
m1 = numpy.array([[ 4, 0 ], [ 0, 1 ]], dtype=gambit.Decimal) * gambit.Decimal("0.2785") m2 = numpy.array([[ 0, 1 ], [ 1, 0 ]], dtype=gambit.Decimal) * gambit.Decimal("1.1141") m1, m2
(array([[Decimal('1.1140'), Decimal('0.0000')], [Decimal('0.0000'), Decimal('0.2785')]], dtype=object), array([[Decimal('0.0000'), Decimal('1.1141')], [Decimal('1.1141'), Decimal('0.0000')]], dtype=object))
Create a Gambit game object from these payoff matrices (
from_arrays is new in Gambit 15.1.0)
g = gambit.Game.from_arrays(m1, m2) g
NFG 1 R "" { "1" "2" } { { "1" "2" } { "1" "2" } } "" { { "" 1.1140, 0.0000 } { "" 0.0000, 1.1141 } { "" 0.0000, 1.1141 } { "" 0.2785, 0.0000 } } 1 2 3 4
First, we can verify there is a unique mixed strategy equilibrium. Player 1 should randomize equally between his strategies; player 2 should play his second strategy with probability 4/5. It is the "own-payoff" effect to Player 1 which made QRE of interest in this game.
gambit.nash.enummixed_solve(g)
[[[Fraction(1, 2), Fraction(1, 2)], [Fraction(1, 5), Fraction(4, 5)]]]
Now, we set out to replicate the QRE estimation using the fixed-point method from the original paper. We set up a mixed strategy profile, which we populate with frequencies of each strategy. Data are reported in blocks of 16 plays, with $n=128$ pairs of players.
data1 = g.mixed_strategy_profile() data1[g.players[0]] = [ 16*128*0.527, 16*128*(1.0-0.527) ] data1[g.players[1]] = [ 16*128*0.366, 16*128*(1.0-0.366) ] data1
With the data in hand, we ask Gambit to find the QRE which best fits the data, using maximum likelihood.
qre1 = gambit.nash.logit_estimate(data1) qre1
LogitQREMixedStrategyProfile(lam=1.845871,profile=[[0.6156446318590159, 0.38435536814098414], [0.383281508340127, 0.616718491659873]])
We successfully replicate the same value of lambda and the same fitted mixed strategy profile as reported by McKPal95. Note that the method Gambit uses to find the maximizer is quite accurate; you can trust these to about 8 decimal places.
What Gambit does is to use standard path-following methods to traverse the "principal branch" of the QRE correspondence, and look for extreme points of the log-likelihood function restricted to that branch. This is the "right way" to do it. Some people try to use fixed-point iteration or other methods at various values of lambda. These are wrong; do not listen to them!
What does not quite match up is the log-likelihood; McKPal95 claim a logL of -1747, whereas ours is much larger in magnitude. I have not been able to reconcile the difference in an obvious way; it is much too large simply to be rounding errors.
numpy.dot(list(data1), numpy.log(list(qre1)))
-2796.2259707889207
The unexplained variance in log-likelihood notwithstanding, we can move on to periods 17-32 and again replicate McKPal95's fits:
data2 = g.mixed_strategy_profile() data2[g.players[0]] = [ 16*128*0.573, 16*128*(1.0-0.573) ] data2[g.players[1]] = [ 16*128*0.393, 16*128*(1.0-0.393) ] qre2 = gambit.nash.logit_estimate(data2) qre2
LogitQREMixedStrategyProfile(lam=1.567977,profile=[[0.6100787526260509, 0.389921247373949], [0.40502047327790697, 0.5949795267220931]])
And for periods 33-48:
data3 = g.mixed_strategy_profile() data3[g.players[0]] = [ 16*128*0.610, 16*128*(1.0-0.610) ] data3[g.players[1]] = [ 16*128*0.302, 16*128*(1.0-0.302) ] qre3 = gambit.nash.logit_estimate(data3) qre3
LogitQREMixedStrategyProfile(lam=3.306454,profile=[[0.6143028691464325, 0.38569713085356744], [0.30108853856548057, 0.6989114614345194]])
And finally for periods 49-52 (the caption in the table for McKPal95 says 48-52). Our lambda of $\approx 10^7$ translates essentially to infinity, i.e., Nash equilibrium.
data4 = g.mixed_strategy_profile() data4[g.players[0]] = [ 4*128*0.455, 4*128*(1.0-0.455) ] data4[g.players[1]] = [ 4*128*0.285, 4*128*(1.0-0.285) ] qre4 = gambit.nash.logit_estimate(data4) qre4
LogitQREMixedStrategyProfile(lam=1040316.548725,profile=[[0.5000005980476384, 0.4999994019523616], [0.20000000000165133, 0.7999999999983487]])
As an estimation method, this works a treat if the game is small. However, under the hood,
logit_estimate is solving a fixed-point problem, and fixed-point problems are computationally difficult problems, meaning the running times does not scale well as you make the size of the problem (i.e., the game) larger. A practical feasible limit for estimating QRE is with games of perhaps 100 strategies in total - less if one also wants to recover estimates of e.g. risk-aversion parameters (of which more anon).
Recently, in several papers, Camerer, Palfrey, and coauthors have been using a method first proposed by Bajari and Hortacsu in 2005. The idea is that, given the actual observed data, under the assumption that the model (QRE) is correct, then one can compute a consistent estimator of the expected payoffs for each strategy from the existing data, and from there compute a consistent estimator of lambda.
This is an interesting development because it finesses the problem of having to compute fixed points, and therefore one can compute estimates of lambda (and more interestingly of other parameters) in a computationally efficient way.
To fix ideas, return to
data1. We can ask Gambit to compute the expected payoffs to players facing that empirical distribution of play:
p1 = data1.copy() p1.normalize() p1
p1.strategy_values()
[[0.40772400000000003, 0.17656900000000003], [0.5269693, 0.5871307000000001]]
The idea of Bajari-Hortacsu is to take these expected payoffs and for any given $\lambda$, say the $\lambda=1.84$ estimated above, compute the logit response probabilities, say for the first player:
resp = 1.84*numpy.array(p1.strategy_values(g.players[0])) resp = numpy.exp(resp) resp /= resp.sum() resp
array([ 0.60475682, 0.39524318])
To estimate $\lambda$, then, it is a matter of picking the $\lambda$ that maximises the likelihood of the actual choice probabilities against those computed via the logit rule. If we assume for the moment the same $\lambda$ for both players, we see this is going to be very efficient: the choice probabilities are monotonic in $\lambda$, and we have a one-dimensional optimisation problem, so it is going to be very fast to find the likelihood-maximising choice -- even if we had hundreds or thousands of strategies!
It takes just a few lines of code to set up the optimisation:
import scipy.optimize, None),)) return res.x[0]
Now, we can estimate the QRE using the same data as above, for each of the four groups of periods, and compare the resulting estimates of $\lambda$. In each pair, the first value is the $\lambda$ as estimated by the payoff method, the second as estimated by the (traditional) fixed-point path-following method.
estimate_payoff_method(data1), qre1.lam
(1.0070478027919727, 1.8458712502750365)
estimate_payoff_method(data2), qre2.lam
(1.5178672707029293, 1.567976743237242)
estimate_payoff_method(data3), qre3.lam
(3.3446122798176647, 3.30645430631916)
estimate_payoff_method(data4), qre4.lam
(0.0, 1040316.5487249079)
We get different estimates $\hat{\lambda}$ for the different methods. This is of course completely OK; they are different estimation procedures so we don't expect to get the same answer. But there are some patterns: in three of the four cases, the payoff method estimates a smaller $\hat{\lambda}$ than the fixed-point method, that is, it estimates less precise behaviour. In the last case, where the fixed-point method claims play is close to Nash, the payoff method claims it is closest to uniform randomisation.
We can pursue this idea further by some simulation exercises. Suppose we knew that players were actually playing a QRE with a given value of $\lambda$, which we set to $1.5$ for our purposes here, as being roughly in the range observed over most of the Ochs experiment. Using Gambit we can compute the corresponding mixed strategy profile.
qre = gambit.nash.logit_atlambda(g, 1.5) qre
LogitQREMixedStrategyProfile(lam=1.500000,profile=[[0.608210533987243, 0.391789466012757], [0.4105548658372969, 0.5894451341627032]])
We knock together a little function which lets us simulate two players playing the game $N$ times according to the QRE mixed strategy profile at $\lambda$, and then, for each simulated play, we use both methods to estimate $\hat\lambda$ based on the realised play. This is repeated
trials times, and then the results are summarised for us in a handy dataset (a
pandas.DataFrame).
def simulate_fits(game,) + [ gambit.nash.logit_estimate(freqs).lam, estimate_payoff_method(freqs), lam ] for freqs in samples ], columns=labels + [ 'fixedpoint', 'payoff', 'actual' ])
Let's have a look at 100 simulations of 50 plays each with $\lambda=1.5.$
simdata = simulate_fits(g, 1.5, 50) simdata
100 rows × 7 columns
In what proportion of these simulated plays does the fixed-point method estimate a higher $\hat\lambda$ than the payoff-based method? (This very compact notation that pandas allows us to use will be familiar to users of e.g. R.)
(simdata.fixedpoint>simdata.payoff).astype(int).mean()
0.85999999999999999
We can also get summary descriptions of the distributions of $\hat\lambda$ for each method individually. This confirms the payoff method does return systematically lower values of $\hat\lambda$ - and that they are lower than the true value, which we know by construction.
simdata.fixedpoint.describe()
count 100.000000 mean 1.495753 std 0.778820 min 0.000000 25% 1.052218 50% 1.459426 75% 1.881626 max 5.172218 Name: fixedpoint, dtype: float64
simdata.payoff.describe()
count 100.000000 mean 1.352604 std 0.784515 min 0.000000 25% 0.871240 50% 1.257109 75% 1.641344 max 5.441656 Name: payoff, dtype: float64
We can visualise the results by doing a scatterplot comparing the estimated $\hat\lambda$ by the two methods for each simulated play. Each point in this scatterplot corresponds to one simulated outcome.
def method_scatterplot(df, lam): plt.plot([ row['payoff']/(1.0+row['payoff']) for (index, row) in df.iterrows() ], [ row['fixedpoint']/(1.0+row['fixedpoint']) for (index, row) in df.iterrows() ], 'kp') plt.plot([ 0, 1 ], [ 0, 1 ], 'k--') plt.plot([ lam/(1.0+lam) ], [ lam/(1.0+lam) ], 'm*', ms=20) plt.xticks([ 0.0, 0.25, 0.50, 0.75, 1.00 ], [ '0.00', '0.50', '1.00', '2.00', 'Nash' ]) plt.xlabel('Estimated lambda via payoff method') plt.yticks([ 0.0, 0.25, 0.50, 0.75, 1.00 ], [ '0.00', '0.50', '1.00', '2.00', 'Nash' ]) plt.ylabel('Estimated lambda via fixed point method') plt.show()
method_scatterplot(simdata, 1.5)
In the case of a 2x2 game, we can do something else to visualise what is going on. Because the space of mixed strategy profiles is just equivalent to a square, we can project the QRE correspondence down onto a square. This next function sets that up.
def correspondence_plot(game, df=None): corresp = gambit.nash.logit_principal_branch(game) plt.plot([ x.profile[game.players[0]][0] for x in corresp ], [ x.profile[game.players[1]][0] for x in corresp ], 'k--') plt.xlabel("Pr(Player 0 strategy 0)") plt.ylabel("Pr(Player 1 strategy 0)") for lam in numpy.arange(1.0, 10.1, 1.0): qrelam = gambit.nash.logit_atlambda(game, lam).profile plt.plot([ qrelam[game.players[0]][0] ], [ qrelam[game.players[1]][0] ], 'kd') if df is None: return for (index, sample) in df.iterrows(): lam = sample['payoff']] ], 'r') lam = sample['fixedpoint']] ], 'b')
correspondence_plot(g)
Now, we can add to this correspondence plot information about our simulated data and fits. For each simulated observation, we plot the simulated strategy frequencies. We then plot from that point a red line, which links the observed frequencies to the fitted point on the QRE correspondence using the payoff method, and a blue line, which links the observed frequencies to the fitted point using the fixed-point method. It becomes clear that the fixed-point method (blue) lines generally link up to points farther along the correspondence, i.e. ones with higher $\lambda$.
correspondence_plot(g, simdata)
It is reasonable to ask whether this biased performance is due to some special characteristic of the games studied by Ochs. We can look to some other games from McKelvey-Palfrey (1995) to investigate this further.
The second case study is a constant-sum game with four strategies for each player reported in
O'Neill, B. (1987) Nonmetric test of the minimax theory of two-person zerosum games. Proceedings of the National Academy of Sciences of the USA, 84:2106-2109.
matrix = numpy.array([ [ 5, -5, -5, -5 ], [ -5, -5, 5, 5 ], [ -5, 5, -5, 5 ], [ -5, 5, 5, -5 ] ], dtype=gambit.Rational) matrix
array([[5, -5, -5, -5], [-5, -5, 5, 5], [-5, 5, -5, 5], [-5, 5, 5, -5]], dtype=object)
We again follow McKPal95 and translate these payoffs into 1982 cents for comparability.
matrix *= gambit.Rational(913, 1000) game = gambit.Game.from_arrays(matrix, -matrix)
We simulate our data around the $\hat\lambda\approx 1.3$ reported by McKPal95.
simdata = simulate_fits(g, 1.3, 50)
(simdata.fixedpoint>simdata.payoff).astype(int).mean()
0.79000000000000004
simdata.fixedpoint.describe()
count 100.000000 mean 1.330206 std 0.863340 min 0.000000 25% 0.720926 50% 1.256126 75% 1.844871 max 3.610687 Name: fixedpoint, dtype: float64
simdata.payoff.describe()
count 100.000000 mean 1.137151 std 0.768048 min 0.000000 25% 0.602237 50% 1.080477 75% 1.599950 max 3.032108 Name: payoff, dtype: float64
method_scatterplot(simdata, 1.5)
Another game considered by McKPal95 is a 5x5 constant-sum game from
Rapoport, A. and Boebel, R. (1992) Mixed strategies in strictly competitive games: A further test of the minimax hypothesis. Games and Economic Behavior 4: 261-283.
We put the estimation approaches through their paces, around the $\hat\lambda \approx 0.25$ reported by McKPal95.
matrix = numpy.array([ [ 10, -6, -6, -6, -6 ], [ -6, -6, 10, 10, 10 ], [ -6, 10, -6, -6, 10 ], [ -6, 10, -6, 10, -6 ], [ -6, 10, 10, -6, -6 ] ], dtype=gambit.Rational) matrix *= gambit.Rational(713, 1000) game = gambit.Game.from_arrays(matrix, -matrix) simdata = simulate_fits(g, 0.25, 50)
simdata.fixedpoint.describe()
count 100.000000 mean 0.467369 std 0.568382 min 0.000000 25% 0.000000 50% 0.301702 75% 0.757745 max 2.084625 Name: fixedpoint, dtype: float64
simdata.payoff.describe()
count 100.000000 mean 0.399141 std 0.493687 min 0.000000 25% 0.000000 50% 0.264003 75% 0.643454 max 1.925047 Name: payoff, dtype: float64
method_scatterplot(simdata, 0.25)
While it appears, from these (still preliminary) results, that the payoff method for estimating $\lambda$ is biased towards estimates which are more "noisy" than the true behaviour, this may not in practice be much of a concern.
In the view of this researcher, the real strength of the logit model is in using it to estimate other parameters of interest. The logit model has some attractive foundations in terms of information theory which make it ideal for this task (in addition to being computationally quite tractable).
It is precisely in these applications where the payoff-based estimation approach is most attractive. The fixed-point method becomes progressively more computationally infeasible as the game gets larger, or as the number of parameters to be considered grows. The payoff approach on the other hand scales much more attractively. What we really want to know, then, is not so much whether $\hat\lambda$ is biased, but whether estimates of other parameters of interest are systematically biased as well.
We pick this up by looking at some examples from
Goeree, Holt, and Palfrey (2002), Risk averse behavior in generalized matching pennies games.
matrix1 = numpy.array([ [ 200, 160 ], [ 370, 10 ]], dtype=gambit.Decimal) matrix2 = numpy.array([ [ 160, 10 ], [ 200, 370 ]], dtype=gambit.Decimal) game = gambit.Game.from_arrays(matrix1, matrix2)
The idea in GHP2002 is to estimate simultaneously a QRE with a common constant-relative risk aversion parameter $r$. This utility function transforms the basic payoff matrix into (scaled) utilities given CRRA paramater $r$.
def transform_matrix(m, r): r = gambit.Decimal(str(r)) return (numpy.power(m, 1-r) - numpy.power(10, 1-r)) / \ (numpy.power(370, 1-r) - numpy.power(10, 1-r))
The next few functions set up the optimisation. For the purposes of the talk, we simply look over a discrete grid of possible risk aversion parameters (to keep the running time short and reliable for a live demo!)
def estimate_risk_fixedpoint] qre = gambit.nash.logit_estimate(profile) logL = numpy.dot(numpy.array(list(freqs)), numpy.log(list(qre.profile))) return logL results = [ (x0, log_like(x0)) for x0 in numpy.linspace(0.01, 0.99, 100) ] results.sort(key=lambda r: -r[1]) return results[0][0], 10.0),)) return log_like(freqs, v, res.x[0]) def estimate_risk_payoff] logL = estimate_payoff_method(profile) return logL results = [ (x0, log_like(x0)) for x0 in numpy.linspace(0.01, 0.99, 100) ] results.sort(key=lambda r: -r[1]) return results[0][0]
This is a variation on the simulator driver, where we will focus on collecting statistics on the risk aversion parameters estimated.
def simulate_fits(game, matrix1, matrix2, r,) + [ estimate_risk_fixedpoint_method(matrix1, matrix2, freqs), estimate_risk_payoff_method(matrix1, matrix2, freqs), r ] for freqs in samples ], columns=labels + [ 'r_fixedpoint', 'r_payoff', 'actual' ])
GHP02 report a risk aversion parameter estimate of $r=0.44$ for this game, so we adopt this as the true value. Likewise, they report a logit parameter estimate of $\frac{1}{\lambda}=0.150$ which we use as the parameter for the data generating process in the simulation.
game = gambit.Game.from_arrays(transform_matrix(matrix1, gambit.Decimal("0.44")), transform_matrix(matrix2, gambit.Decimal("0.44")))
simdata = simulate_fits(game, matrix1, matrix2, 0.44, 1.0/0.150, 100, trials=30) simdata
simdata.r_fixedpoint.describe()
count 30.000000 mean 0.550485 std 0.151260 min 0.346566 25% 0.462879 50% 0.519798 75% 0.606414 max 0.910808 Name: r_fixedpoint, dtype: float64
simdata.r_payoff.describe()
count 30.000000 mean 0.554444 std 0.149471 min 0.356465 25% 0.470303 50% 0.524747 75% 0.608889 max 0.910808 Name: r_payoff, dtype: float64 | https://nbviewer.jupyter.org/url/gambit-project.org/games2016/estimate-qre.ipynb | CC-MAIN-2017-13 | refinedweb | 3,339 | 52.36 |
Unsupported provider
Created on 2009-01-03 10:51 by TFinley, last changed 2009-01-08 05:21 by rhettinger. This issue is now closed..
I.
Will spend a while mulling this over and taking it under advisement.
Initially, I am disinclined for several reasons.
1. For many use cases, r>n is an error condition that should not pass
silently.
2. While it's possible to make definitions of comb/perm that define the
r>n case as having an empty result, many definitions do not. See the
wikipedia article on permutations:
"""
In general the number of permutations is denoted by P(n, r), nPr, or
sometimes P_n^r, where:
* n is the number of elements available for selection, and
* r is the number of elements to be selected (0 ≤ r ≤ n).
For the case where r = n it has just been shown that P(n, r) = n!. The
general case is given by the formula:
P(n, r) = n! / (n-r)!.
"""
That discussion is typical and I think it important the number of items
returned matches the formula (which fails when r>n because (n-r)! would
call for a negative factorial).
Also see the wikipedia article on combinations (the "choose" function)
which also expresses a factorial formula that fails for r>n. No mention
is made for special handling for r>n.
3. For cases where you need a more inclusive definition that assigns a
zero length result to cases where r>n, the workaround is easy.
Moreover, in such cases, there is some advantage to being explicit about
those cases being handled. In the example provided by the OP, the
explicit workaround is:
all(triangle_respected(*triple) for triple in
itertools.combinations(group, 3) if len(group)>=3)
or if you factor-out the unvarying constant expression in the inner-loop:
len(group)>=3 or all(triangle_respected(*triple) for triple in
itertools.combinations(group, 3))
For other cases, it may be preferable to write your own wrapper:
def myperm(pool, r=None):
'custom version of perm returning an empty iterator when r>n'
if r is not None and r > len(pool):
return iter([])
return itertools.permutations(pool, r)
I like this because it is explicit about its intended behavior but
doesn't slow-down the common case where some work actually gets done.
4. Don't want to break any existing code that relies on the ValueError
being thrown. It's too late to change this for 2.6 and 3.0 and possibly
for 2.7 and 3.1 without having a deprecation period. While this hasn't
been out long, it will have been once 2.7 is released. Code that relies
on the ValueError may be hard to spot because it is implicitly relying
on the ValueError aborting the program for invalid input (invalid in the
sense of how the result is being used).
5. I personally find the r>n case to be weird and would have a hard time
explaining it to statistics students who are counting permutations and
relating the result back to the factorial formulas.
On the flip side, I do like Mark's thought that the r>n case being empty
doesn't muck-up the notion of combinations as returning all "r-length
subsequences of elements from the input iterable." Also, I can see a
parallel in the string processing world where substring searches using
__contains__ simply return False instead of raising an exception when
the substring is longer that the string being searched.
Those are my initial thoughts. Will ponder it a bit more this week.
Quick notes so I don't forget:
The two main pure python equivalents in the docs would need to be
updated with the new special cases (currently they raise IndexError for
r>n). The other two pure python equivalents would automatically handle
the proposed new cases.
The Mathematica definition of permutations does not discuss or allow for
the r>n case, . One of
the other tools that actually lists permutations and takes a second
argument (most do not) is in Mathematica, . It is
unclear from their docs whether the r>n case is supported as a
zero-length output or as an error condition.
Hi Raymond, thanks for your well reasoned and thorough reply. Just a
couple small thoughts... I'll borrow your numbers if you don't mind.
1. I'd ask you to discount this argument. There are many situations in
the Python library where empty results are possible return values.
There are likewise many places in mathematics where a set as defined
winds up being empty. And sure, absolutely, sometimes this empty result
will be an error condition. However, right off the top of my head, I
can't really think of any other place in the Python library where an
empty returned iterator/list is automatically assumed to necessarily be
an error.
The closest I can think of right now might be key/index errors on dicts
and sequences... but that's a user explicitly asking for exactly one
element, in which case non-existence would be bad.
In a larger sense, if a result computed by a function is sensible and
well defined in itself, it doesn't seem even possible for a function to
anticipate what answers might be considered error conditions by calling
code. Potentially any return value for any function might be an error
for some user code. So... the question then becomes, is the empty
result a sensible and well defined answer. And here we differ again I
see. :D
2. OK on perms. If you don't mind, I'm going to talk about combinations
since that was my real motivation.
Also see the wikipedia article on combinations (the
"choose" function) which also expresses a factorial
formula that fails for r>n. No mention is made for
special handling for r>n.
Hmmm. Are you looking at the definition of "choose function" under
Wikipedia?
Notice the material after the "and," after the first part of the
definition, in case you missed it in your first reading. So, this is
the def I was taught through high school and undergrad, perhaps the same
for Mark judging from his reply. You were taught it was undefined? It
does sort of complicate some other defs that rely on binomial
coefficients though, I'd think, but I guess you could make those work
with little effort. It's not as though subtly different but
incompatible definitions of basic terms are that uncommon in math...
never knew the binomial coef was in that category though. You teach
stats I take it? I suppose you'd know then... never heard of it, but
that doesn't mean much. Oh well. (You can perhaps feel my pain at
seeing the current behavior, given my understanding.)
3. For your "replacement" myperm (let's say mycomb), if you insert a
"pool=tuple(iterable)" into the beginning, you'll have my fix, statement
for statement. You advance this as desirable, while to my eye it was
nasty enough to motivate me to submit my first patch to Python. So, you
can imagine we have a slight difference of opinion. ;) Let's see if I
can't present my view effectively...
Saying the fix is more explicit suggests there's something implicit
about the concise solution. If the choose function is defined for those
values, then itertools.combinations is just unnecessarily forcing code
to treat something as a special case even when it's not. So, I'd be
careful to draw a distinction between "more verbose" and "more explicit."
4. Can't really speak to that. It's probably worth changing
documentation in any event, even if you reject the patch. The provided
equiv code and the actual behavior in this "error case" differ anyway as
you noted in your second reply. Also, this error condition isn't
evident from the documentation without reading and parsing the source code.
A third and extraneous comment, if you do wind up changing the docs
anyway, perhaps a shorter recursive solution would be easier to
understand? Maybe it's just me since I'm sort of a functional type of
guy, but I found the equivalent code a little hard to parse.
5. Yeah. Actually, I'm pretty sure that's why the choose function is
defined piecewise, since negative factorials are undefined as you say.
1. This is the most important issue. Is the r>n case typically an
error in the user's program or thought process. If so, then the utility
of a ValueError can be weighed against the utility of other cases where
you want combs/perms to automatically handle the r>n cases with an empty
output. These use cases are what I'm mulling over this week.
2. I see your wikipedia link. The one I was looking at was:
3. I wasn't clear on the issue of explictness. The potential problem
that it isn't immediately obvious to me what comb/perm does when r>n, so
if I see code that isn't explictly handling that case, I have to lookup
what comb/perm does do to make sure the code works.
In the math module, it is a virtue that math.sqrt(-1) raises a
ValueError. In the cmath module, it is a virtue that it does not. The
latter case is distinguished because the programmer has explicitly
requested a routine that can handle complex numbers -- that is a good
clue that the surrounding code was designed to handle the complex result.
4. Not too worried about this one. Essentially the thought is that code
that wasn't designed with the r>n case in mind probably benefits from
having a ValueError raised when that condition is encountered.
5. This one bugs me a bit. It is nice to have all the factorial
formulas just work and not have a piecewise definition.
BTW, we don't really have a difference of opinion. My mind is open. I
aspire to pick the option that is the best for most users including
students and novice users. The trick in language design is to
anticipate use cases and to understand that people have differing world
views (i.e. it is a perfectly reasonable point-of-view that taking n
things r at a time makes no sense when r is greater than n).
In choosing, there is some bias toward sticking the API as it was
released. Changing horses in midstream always causes a headache for
some user somewhere.
Am still thinking this one through and will let you know in a week or
so. I also want to continue to research into how this is handled in
other libraries and other languages.
Another thought before I forget: The piecewise definition of the choose
function or for binomial coefficients suggests that supporting the r>n
case should be accompanied by supporting the r<0 case.
> 5..
Mathematica returns an empty list.
In[1]:= Permutations[{1,2},{1}]
Out[1]= {{1}, {2}}
In[2]:= Permutations[{1,2},{4}]
Out[2]= {}
In[3]:=
David, thanks for the data point. What does it return for
In[1]:= Permutations[{a, b, c}, {-1}]
Mathematica indicates for the user to define it later. An error.
In[3]:= Permutations[{1,2},{-2}]
Permutations::nninfseq:
Position 2 of Permutations[{1, 2}, {-2}]
must be All, Infinity, a non-negative integer, or a List whose
first
element (required) is a non-negative integer, second element
(optional)
is a non-negative integer or Infinity, and third element (optional)
is a
nonzero integer.
Out[4]= Permutations[{1, 2}, {-2}]
Results.
Got Sage working again. It also returns an empty list for r > n. For r
negative, Combinations returns an empty list and Permutation gives an
error.
sage: Combinations(range(4), 6)
Combinations of [0, 1, 2, 3] of length 6
sage: Combinations(range(4), 6).list()
[]
sage: Permutations(range(4), 6).list()
[]
sage: Combinations(range(4), -1).list()
[]
sage: Permutations(range(4), -1).list()
---------------------------------------------------------------------------
IndexError Traceback (most recent call last)
[... traceback snipped ...]
Data point: Microsoft Excel's PERMUT() and COMBIN() return #NUM! for
r>n or r<0.
I try to "not know" excel. Does it have any other means to represent an
empty set?
Excel is returning the count, not the set itself. So, it could have
chosen to return zero.
The HP32SII also has nCr and nPr functions that return INVALID DATA for
r>n or r<0.
The Combinatorics section of CRC Standard Mathematical Formulae (30th
edition) defines nCr and nPr only for 0 <= r <= n. The same is true in
Harris and Stocker's Handbook of Mathematics and Computational science.
Summary of functions/definitions expected to return a number:
r>n r<0 Source
--------- ---------- ------------------------------
error error MS Excel PERMUT() and COMBIN()
error error HP32SII nPr and nCr
undefined undefined CRC Combinatoric definitions
undefined undefined Handbook of Mathematics and Computational Science
undefined undefined Wolfram:
zero zero
undefined undefined
undefined undefined
zero undefined Knuth's choose function in Concrete Mathematics
zero zero GAP's nrCombinations()
Summary for tools that return the individual subsets:
r>n r<0 Source
--------- ---------- ------------------------------
emptylist error Mathematica
emptylist unknown Magma
emptylist error GAP Combinations
emptylist emptylist GAP Arrangements
emptylist emptylist Sage Combinations
emptylist error Sage Permutations
David, I know the OPs position and Mark's opinion. What is your
recommendation for the r>n case and the r<0 case?
Attached an updated patch which expands the tests and docs.
Handles the r>n case with an empty result.
Leaves the r<0 case as a ValueError.
Am thinking that if we do this, it should be treated as a bug and posted
to 2.6 and 3.0.
I had thought highly of the "mull it over for a week" plan. After a
week we'd decide to follow Stephen Wolfram's lead, which seems to be the
current patch. I haven't yet used the python permutations iterator,
although I used to have a script that solved word JUMBLE puzzles with a
mathematica | spell pipeline. Now I look up words using a sorted
anagram dictionary.
Thanks).
Fixed in r68394
Will forward port in a day or two. | http://bugs.python.org/issue4816?@action=openid_login&provider=myOpenID | CC-MAIN-2017-04 | refinedweb | 2,369 | 64.3 |
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edit :
new question, forked from this thread
Hey @zipit,
Thanks for the detailed explanation about type, will try following it from now on.
Tested FIeldLists implementation and it seems to work very well so far, the only thing I struggle is with "half selected" (bold orange) elements in fieldlists, is there a way to deselect them all like with volumebuilder, where you simply call:
for i in xrange(0, obj.GetListEntryCount()):
obj.SetSelected(i, 0)
Thanks again,
Sandi
hello,
you have to set back the field list like so:
Warning : I discovered that GetSelected is actually bugged and if you set the includeChildren to False, it will crash.
I've opened a bug report for that.
you can use this with children or retrieves the layer using your own function as you can do with an object hierarchy (fieldlayer are BaseList2D)
includeChildren
import c4d
def main():
if op is None:
raise TypeError("no object selected")
data = op.GetDataInstance()
# Retrieves the fieldlist
fl = data.GetCustomDataType(c4d.FIELDS)
if fl is None:
raise ValueError("no field list found")
root = fl.GetLayersRoot()
sel = list()
# Retrieves the selected layers.
fl.GetSelected(sel, True)
for layer in sel:
layer.SetStrength(0.5)
layer.DelBit(c4d.BIT_ACTIVE)
# Sets back the field list to update its content.
op.SetParameter(c4d.FIELDS, fl, c4d.DESCFLAGS_SET_NONE)
c4d.EventAdd()
if __name__=='__main__':
main()
The linked object is still selected, but that reproduce what the "select none" popup menu does.
Cheers,
Manuel
Hi,
you could try your luck with BaseList2D.DelBit(), but I wouldn't hold my breath, since FieldLists are presented in a very specialized GUI gadget. Something like this (I did not try this):
BaseList2D.DelBit()
FieldLists
for layer in get_field_layers(my_fieldlist):
layer.DelBit(c4d.BIT_ACTIVE)
layer.Message(c4d.MSG_UPDATE)
my_fieldlist.Message(c4d.MSG_UPDATE)
c4d.EventAdd()
Cheers
zipit
I've forked the other thread as this is a new question.
I'm not sure what you are talking about "half selected" element. Are you talking about the field object in the object manager ?
A screenshot showing what you mean by that would be apreciate.
@m_magalhaes I am talking about the bold orange Highlight on selected field object when it is not actually selected in the OM but trough the field list
I would like to remove this, deselect everything inside Field list, if possible.
Thanks.
@zipit Thanks for this, I tried, doesn't seem to work with DelBit(), it does change the state, so if I read it back with GetBit() it says false, but it doesn't reflect in OM or AM.
But thanks anyway, this is more a visual thing anyway, would be cool to fix but it works without it too, just more confusing
@m_magalhaes Hey!
Added the code you provided and it works nicely, thanks so much!
Cheers, | https://plugincafe.maxon.net/topic/11832/how-to-deselect-item-in-a-fieldlist | CC-MAIN-2021-31 | refinedweb | 506 | 62.68 |
There are quite a few different conventions for binary datetime, depending on different platforms and protocols. Some of these have severe drawbacks. For example, people using Unix time (seconds since Jan 1, 1970) think that they are safe until near the year 2038. But cases can and do arise where arithmetic manipulations causes serious problems. Consider the computation of the average of two datetimes, for example: if one calculates them with
averageTime = (time1 + time2)/2, there will be overflow even with dates around the present. Moreover, even if these problems don't occur, there is the issue of conversion back and forth between different systems.
Binary datetimes differ in a number of ways: the datatype, the unit, and the epoch (origin). We'll refer to these as time scales. For example:
All of the epochs start at 00:00 am (the earliest possible time on the day in question), and are assumed to be UTC.
The ranges for different datatypes are given in the following table (all values in years). The range of years includes the entire range expressible with positive and negative values of the datatype. The range of years for double is the range that would be allowed without losing precision to the corresponding unit.
These functions implement a universal time scale which can be used as a 'pivot', and provide conversion functions to and from all other major time scales. This datetimes to be converted to the pivot time, safely manipulated, and converted back to any other datetime time scale.
So what to use for this pivot? Java time has plenty of range, but cannot represent .NET
System.DateTime values without severe loss of precision. ICU4C time addresses this by using a
double that is otherwise equivalent to the Java time. However, there are disadvantages with
doubles. They provide for much more graceful degradation in arithmetic operations. But they only have 53 bits of accuracy, which means that they will lose precision when converting back and forth to ticks. What would really be nice would be a
long double (80 bits -- 64 bit mantissa), but that is not supported on most systems.
The Unix extended time uses a structure with two components: time in seconds and a fractional field (microseconds). However, this is clumsy, slow, and prone to error (you always have to keep track of overflow and underflow in the fractional field).
BigDecimal would allow for arbitrary precision and arbitrary range, but we do not want to use this as the normal type, because it is slow and does not have a fixed size.
Because of these issues, we ended up concluding that the .NET framework's
System.DateTime would be the best pivot. However, we use the full range allowed by the datatype, allowing for datetimes back to 29,000 BC and up to 29,000 AD. This time scale is very fine grained, does not lose precision, and covers a range that will meet almost all requirements. It will not handle the range that Java times do, but frankly, being able to handle dates before 29,000 BC or after 29,000 AD is of very limited interest.
Definition in file utmscale.h.
#include "unicode/utypes.h"
Go to the source code of this file. | http://icu.sourcearchive.com/documentation/4.4.1-7/utmscale_8h.html | CC-MAIN-2017-39 | refinedweb | 541 | 63.7 |
Introduction
Here we look at an example of a WCF Service in which we create a service for applying simple calculator functions (like add, subtract, multiply and divide).
Step 1: First we open the Visual Studio.
Here we select the WCF in the Project Type and then we select the WCF Service Library in it. After that, we specify the name of this library to be Calc (which we can define in the Name Section). And then we click on the OK Button.
Step 2: When we click on the Ok Button, the Calc.cs will be opened. In the Solution Explorer, we delete the following files, since we want to create the service from the start.
Step 3: In Calc.cs, first we create the class public and then we create it as a WCF Data Contract. For this we first add the namespace System.Runtime.Serialization. And then we write the following code.
Code
using System.Runtime.Serialization;
namespace Calc
{
[DataContract]
public class Calc
[DataMember]
public double n1;
public double n2;
}
}Step 4: After that we add another class.
Here we name it ICalcService.cs.Step 5: Now we declare as an interface not a class so we change the code like this.
public interface ICalcService
Here we type the following operations:
double Add(double n1, double n2);
double Subtract(double n1, double n2);
double Multiply(double n1, double n2);
double Divide(double n1, double n2);
After that, we delare it as a Service Contract, which is in a different namespace: System.ServiceModel. Now we look at the code:
using System.ServiceModel;
[ServiceContract]
public interface ICalcService
[OperationContract]
double Add(double n1, double n2);
double Subtract(double n1, double n2);
double Multiply(double n1, double n2);
double Divide(double n1, double n2);
}
}Step 6: After that we add another class: CalcService.cs. It is an actual service implementation class, so here we can specify the ICalcService like this.
Code
public class CalcService:ICalcService
}Here we implement an interface by right-clicking and choosing the option Implement Interface Explicitly:
Now we add the ServiceBeahvior like this:[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
It specifies the behavior of our service and InstanceContextMode.Single means it creates a single instace of our service. Now we write the following code in it.
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
public class CalcService:ICalcService;
Step 7: Now we try to run the program; it can not be run since it is not yet completed. Now right-click on the App.config file and select the Edit WCF Configuration option.
After that the following window will be appear.
After that we select the Calc.CalcService in the Configuration option:
After that we click on the Name Option:
After that we click on EndPoints.
And then we click on Empty Name.
Here we click on Contart and again select the Calc.dll.Step 8: Now we run the program.
Step 9: After that we click on Add or any other function. When we click on Add the following window will be appear:
Here we enter values for n1 and n2 and click on the Invoke Button. The result will appear as:
My name is Mahak Gupta. I am a C# Corner MVP.
©2015
C# Corner. All contents are copyright of their authors. | http://www.c-sharpcorner.com/UploadFile/mahakgupta/a-simple-example-of-wcf-service/ | CC-MAIN-2015-35 | refinedweb | 541 | 58.28 |
It opens lots of possibilities, as when it's resolved it has access to the python code being edited (and all the available modules and Pydev APIs).
Some default templates were added already taking advantage of that (see: pytemplate_defaults.py as a reference -- the docstring explains how to create your own templates).
The image below shows the variables created in the defaults (already using Jython scripting -- note that when multiple superclasses are available, the ${superclass} variable enables the user to choose which one to use):
This enabled the print template to work as expected (giving only 'print ' in python 2.x and 'print()' in python 3.x, as it can 'know' which grammar you are using).
To finish, 2 other templates were creating taking advantage of the context:
super : super(MyClass, self).CurrentMethod()
super_raw : MySuperClass.CurrentMethod(self)
If anyone has other 'must have' template suggestions now that this is available, those are very welcome.
On a side note, the current nightly build is pretty stable (and should be the new released version unless there's some critical error lying there found in the next 2-3 days), so, it should be safe to get it to experiment with those.
7 comments:
That's nice.
To add them we need to set in Pydev preferences a folder that holds our extensions files.
Would it be possible to use something like setuptools' entries point to let Pydev disover extension? Can Jython use setuptools?
I must say that I have no idea if Jython can use setuptools (especially because Pydev is currently bound to version 2.1 of Jython -- the latest got too big to be incorporated).
Also, what would be the advantages over the current system? (which I believe is pretty simple to use)
I know this is not help desk, but would this be a way to improve auto-completion (where introspection can't do it) of PyDev?
There are some problems with Django and auto-completion that I would like to fix, even with hardcoded scripts or something ugly if not the neat introspection can handle. Especially when I need to look at the name of the arguments in method, e.g. initializer __init__ of model fields such as:
something = models.CharField([CTRL-Space]...)
I get nothing, nada. I always have to go to look at the the source of CharField.__init__() to know the init parameters, they are neatly listed in there but for some reason PyDev won't show them...
One of my ideas to start fixing auto-completion is to look at the @rtype or :rtype: value in docstring, and assume the output is in that type if possible. This does not help with Django, but with many other well documented modules it would.
I don't really think that'd be the place for improving that kind of introspection...
Those ideas would be very well suited for the Pydev bugtracker (at sourceforge).
See:
Cheers,
Fabio
It would be great to have docstring template according to PEP 257 spec. like this:
def complex(real=0.0, imag=0.0):
"""Form a complex number.
Keyword arguments:
real -- the real part (default 0.0)
imag -- the imaginary part (default 0.0)
"""
if imag == 0.0 and real == 0.0: return complex_zero
Template should build keyword argument list along with default values
Hi, please post feature requests in the sourceforge tracker (otherwise they end up lost in this blog). See:
Please, add ${package} too | http://pydev.blogspot.com/2010/01/templates-on-pydev-with-jython.html?showComment=1264883066432 | CC-MAIN-2015-32 | refinedweb | 574 | 65.12 |
Binary Search Algorithm - C Programming Example
Hakan Torun
・2 min read
A binary search algorithm is a search algorithm that finds the position of searched value within the array. In the binary search algorithm, the element in the middle of the array is checked each time for the searched element to be found. If the middle element is not equal to the searched element, the search is repeated in the other half of the searched element. In this way, the search space is halved at each step.
The binary search algorithm works on sorted arrays. For non-sorted arrays, the array must first be sorted by any sorting algorithm in order to make a binary search.
The steps of binary search algorithm:
1- Select the element in the middle of the array.
2- Compare the selected element to the searched element, if it is equal to the searched element, terminate.
3- If the searched element is larger than the selected element, repeat the search operation in the major part of the selected element.
4- If the searched element is smaller than the selected element, repeat the search in the smaller part of the selected element.
5- Repeat the steps until the smallest index in the search space is less than or equal to the largest index.
For example; 2,3,4,5,6,7,8,9,22,33,45.
The following steps will be followed to find the number 4 with binary search in a sequential array of these numbers.
The middle element of the array is selected as 7 and compared with the searched element 4. The searched element (4) is not equal to the middle element (7), the part at the center of the array which is less than 7.
Our new search array: 2,3,4,5,6.
The middle element of our new search array is 4 and the search is completed.
With binary search algorithm, it is possible to find the searched value to log2N comparisons in an N-element array.
A sample C code will be as follows if we try to implement the binary search algorithm in a sequential array as in the example.
C Example:
#include <stdio.h> int main() { int array[11] = {2,3,4,5,6,7,8,9,22,33,45}; int low = 0; int high = 10; int flag = 0; int s = 4; while(low <= high){ int index = low+(high-low)/2; if(array[index] == s){ flag = 1; printf("Founded: %d \n",index); break; } else if(array[index] < s){ low = index+1; } else{ high = index-1; } } if(flag == 0){ printf("Not Found!\n"); } return 0; } | https://dev.to/hakan/binary-search-algorithm---c-programming-example-47cg | CC-MAIN-2019-35 | refinedweb | 436 | 61.77 |
Currently working on MSI packaging for our software and using WiX tool suite to automate the process. Since it was decided that we don’t want to use patches, I had to implement pseudo-major upgrades for each version. Now, the problem with that is that MSI framework doesn’t really care for version number so much as for the product GUID. In other words, if the version is the same but the product GUID is different (which happens because our build process generates new MSIs every time a module is updated, even if others are not, and the product ID is generated anew with every build), it will run the full uninstall old/install new routine regardless of other factors. This costs extra time during the installation, so I wanted to avoid it if possible.
The idea I had was to write an algorithm that created a unique GUIDs out of a string (or two strings: module/product name and version number). This way I could ensure that the package whose version has not changed will always have the same product GUID, regardless how many times it is rebuilt. The only difficult part was to find a way to make the implementation of said algorithm as simple and stupid as possible.
As I set off, I discovered that Java (my primary programming language at the moment) already has a nifty UUID class. However, it could only create random UUIDs (the universal term describing what Microsoft calls “GUID”) with the static randomUUID() method. Now, there was also nameUUIDFromBytes(), which made the algorithm pathetically easy:
String tempResult = UUID.nameUUIDFromBytes(aSourceString.getBytes()).toString(); System.out.println(tempResult);
However, the problem with that is that it generates Version 3 UUIDs (read more about versions on the Wikipedia) and WiX only accepts Version 4 (like the ones generated by randomUUID(), which are, well, too random). Then I took a look at the standard constructors and saw that there’s only one and it generates a Version 4 GUID out of two Long numbers (basically, a GUID consists of two 64 bit arrays, read two Long numbers: least significant long and most significant long). Yay! Now, where can I get an injective function that would map a string to a particular Long number?
Immediately, I thought of the MD5 hashes but a bit of googling revealed that there is no single pretty string-to-MD5 hashing function in the standard Java libraries. Unwilling to make my own implementation (simple-stupid, remember), however, I soon found the next best thing: the CRC32 class. Now, the beauty of this solution lies in the fact that it’s a standard library class and it’s relatively easy to use:
private CRC32 localCRC32Generator = new CRC32();();
Basically, you initialize the CRC32 instance, update it with a byte array generated from the source string, read the Long value, then reset the instance. The last part is essential if you want to generate identical Longs during the entire runtime.
The rest seemed easy at first:
return UUID(tempApplicationChecksum, tempVersionChecksum).toString();
However, I immediately noticed that the resulting UUIDs had a lot of nulls in them. This is because the return values of CRC32.getValue() are 10 digits long and the 64 bit Long is 20 digits. Hence, half of the numbers (higher registers) are padded with nulls in the UUID. So I thought, how to produce two 20 digit Longs out of two 10 digit Longs. The answer is trivial if you know some math:
Long tempMSBits = tempApplicationChecksum * tempVersionChecksum; Long tempLSBits = tempVersionChecksum * tempVersionChecksum; return UUID(tempMSBits, tempLSBits).toString();
I chose to use tempVersionChecksum as the multiplier in both cases, because it is what actually changes across versions, whereas the tempApplicationChecksum is just there to avoid collisions between product GUIDs of different product packages with the same version. Apropos collisions: I decided that CRC32 has good enough collision resistance for my purposes and the products of the results are distinct enough on such scale.
However, even after that, I was again frustrated by failure. This time, the WiX compiler again claimed that the GUID is invalid. I consulted the Wikipedia again and remembered that the Version 4 GUIDs had several reserved bits, which, of course, are not present in the UUIDs generated by my algorithm thus far. However, that was a minor problem: all I had to do was to wrap the GUID string I got into a StringBuffer, replace the 15th character with a “4” and the 20th, with an “8”, “9”, “A”, or “B”. Actually, it doesn’t matter which of the four characters is in the 20th position, it can even be always the same, but I wrote a small subroutine for additional collision resistance. In the end my class looked like this:
import java.util.UUID; import java.util.zip.CRC32; public class VersionToGuidConverter { private CRC32 localCRC32Generator = new CRC32(); public static void main(String[] args) { VersionToGuidConverter tempConverter = new VersionToGuidConverter(); System.out.println(tempConverter.generateGUID(args[0], args[1])); }(); Long tempMSBits = tempApplicationChecksum * tempVersionChecksum; Long tempLSBits = tempVersionChecksum * tempVersionChecksum; StringBuffer tempUUID = new StringBuffer(new UUID(tempMSBits, tempLSBits).toString()); tempUUID.replace(14, 15, "4"); tempUUID.replace(19, 20, convertSecondReservedCharacter(tempUUID.substring(19, 20))); return tempUUID.toString(); } private String convertSecondReservedCharacter(String aString) { switch (aString.charAt(0) % 4) { case 0: return "8"; case 1: return "9"; case 2: return "a"; case 3: return "b"; default: return aString; } } }
For a cherry tapping, you can add a feature that generates truly random UUIDs (with UUID.randomUUID()) if the Version or Product have a specific value. But that should be easy. Now go and have fun.
Thanks for this! This should be in the UUID by default!
Yeah, it should, but who are we to decide things for the almighty Oracle? 😀
Cool stuff! However, this probably should not be in UUID class by default, as it’s just a hack to get around the below (apparent) defect in WiX. There is no good reason to actually generate type 3 UUIDs that are misrepresented as type 4 UUIDs, unless you are trying to feed a type 3 UUID into a library that for some reason insists on type 4.
“However, the problem with that is that it generates Version 3 UUIDs (read more about versions on the Wikipedia) and WiX only accepts Version 4 (like the ones generated by randomUUID(), which are, well, too random).”
Do you know why WiX is limited to type 4? Is it an accident or intentional?
I am pretty sure it’s intentional because they only wanted to have to support one UUID implementation, with the assumption that the users keep track of their own UUIDs and use patches to update packages. The way I used MSI was dictated more by the specifics of our existing deployment process than any standards considerations. 🙂 | http://blag.koveras.net/2010/12/03/how-to-generate-a-deterministic-guid-from-two-strings-in-java/ | CC-MAIN-2017-26 | refinedweb | 1,128 | 51.28 |
Psyco, the Python Specializing Compiler
Psyco is a Python extension module which can massively speed up the execution of any Python code.
REQUIREMENTS
Psyco works on almost any version of Python (currently 2.2.2 to 2.5). At present it requires a 32-bit architecture, but it is OS-independant. It can only generate machine code for 386-compatible processors, although it includes a slower emulation mode for other (32-bit!) processors.
This program is still and will always be incomplete, but it has been stable for a long time and can give good results.
There are no plans to port Psyco to 64-bit architectures. This would be rather involved. Psyco is only being maintained, not further developed. The development efforts of the author are now focused on PyPy, which includes Psyco-like techniques. ()
Psyco requires Python >= 2.2.2. Support for older versions has been dropped after Psyco 1.5.2.
QUICK INTRODUCTION
To install Psyco, do the usual
python setup.py install
Manually, you can also put the 'psyco' package in your Python search path, e.g. by copying the subdirectory 'psyco' into the directory '/usr/lib/python2.x/site-packages' (default path on Linux).
Basic usage is very simple: add
import psyco psyco.full()
to the beginning of your main script. For basic introduction see:
import psyco help(psyco)
DOCUMENTATION AND LATEST VERSIONS
The current up-to-date documentation is the Ultimate Psyco Guide. If it was not included in this distribution ("psycoguide.ps" or "psycoguide/index.html"), see the doc page:
DEBUG BUILD
To build a version of Psyco that includes debugging checks and/or debugging output, see comments in setup.py. | https://bitbucket.org/arigo/psyco/src/3be29c654536?at=release-1.6 | CC-MAIN-2016-07 | refinedweb | 278 | 51.55 |
C# is a programming language developed by Microsoft. It is a fully object-oriented programming language like Java, and it’s the only component presented by -oriented language. C# is derived from C and C++ languages. It is suitable for developing web-based applications and supports the .NET framework, Microsoft’s development platform.
Want to learn C#? Take a course at Udemy.com.
C# Features
Though C# is the successor of languages like C and C++ with several similarities in comparison, it contains several unique features:
- Boolean Conditions
- Automatic Garbage Collections
- Assembly Versioning
- Properties and Events
- Standard Library
- Easy to use Generics
- Simple Multithreading
- LINQ and Lambda Expressions
- Integration with Windows
What is .NET Framework?
Any language can access the .NET framework as well as communicate with each other using .NET libraries. In addition, it is a component-based model in which a program is broken into numerous individual components where each one offers a particular service. This mechanism is called Microsoft Intermediate Language (MSIL). The most striking feature of .NET framework is the compiler inter-operability by compiling code into an IL that is compatible with other IL modules. Microsoft .NET software provides building, deploying and running web services and other console applications. It consists of three different technologies:
- Common Language Runtime
- Framework Base Classes
- User & Program Interfaces (ASP.NET and Winforms)
Common Language Runtime (CLR) provides runtime environments for languages including C#.
The CLR provides a number of services that include:
- Memory isolation for applications
- Compilation of IL into native executable code.
Hello World with C#
A simple C# program has following parts:
Learn how to work with the C# language at Udemy.com.
- Namespace Declaration
- class
- Class methods
- Class attributes
- Main method
- Statements & Expressions
Example
using System;
namespaceHelloWorld
{
class Hello
{
static void Main()
{
/* it is Hello World in C# */
Console.WriteLine(“Hello World”);
}
}
}
Output
Hello World
- The first line “using System”: In this example, ‘using’ is the keyword used to include the “System” namespace in the program. A program has many ‘using’ statements and is similar to import statement in java or “include” statement in c.
- Namespace declaration: A namespace is a collection of classes. For instance, HelloWorld namespace contains “Hello” class.
- Next is the declaration of the class. The “”Hello” class contains methods definitions and members that are used in the program. Classes can contain any number of functions but there should be only one Main method.
- Next line defines the Main method, which points the compiler to the entry point of the execution of program. All methods and function calls are made from Main method.
- Console.WriteLine() is the method of console class defined inside the System namespace. This causes the text written inside the quotes to get printed on the screen.
- Everything written between /*….*/ is ignored by the compiler and they are known as comments. It helps to improve the readability and helps the user understand the program by mentioning details of tasks at different steps in complex programs.
Points to Note:
- C# is case sensitive language
- All statements must end with semicolon
- The program execution starts at Main method
Compiling and Running The C# Program:
From Visual Studio
- Start visual studio
- From Menu bar choose new project and choose C# template
- Choose Console application. The new project appears in Solution Explorer.
- Write the code and press F5 to compile and run the code
From Command line:
- Write the code in any text editor and save the file with “.cs” extension.
- Open command prompt and move to the directory where the program was saved.
- Type “csc filename” and press enter to compile the code. The executable file will be generated if there are no errors found.
- Type the filename to run the program. The output will be visible on the screen
Example of Command Line Arguments
using System;
namespaceHelloCommandLine
{
class Hello
{
static void Main(string[] args)
{
/* it is Hello World in using Command Line Argument */
Console.Write(“Welcome to Command Line “);
Console.WriteLine(“”+arg[0]);
Console.WriteLine(” “+args[1]);
}
}
}
Notice in this Main method declaration
public static void main(string args[])
Main method is enclosed with the parameter “args”. The parameter is the array of strings also known as “String objects“. Any arguments given in the command line at the time of execution is passed to “args” as its elements. These elements are then accessed by using subscript args[0], args[1] and so on.
If you provide three arguments at the time of execution for instance
thisàargs[0]
isàargs[1]
commandlineàargs[2]
argumentàargs[3]
The only difference between WriteLine() and Write() method is that the latter does not create a line break and therefore the next output will be printed on the same line.
Applications of C#
- Console application
- Windows application
- Developing windows Controls
- Developing ASP.NET projects
- Providing Web Services
- Developing .NET Component library
Framework Base Classes
.NET supplies a library of base classes that help you implement web applications quickly. You can use them by instantiating the program and invoking their methods. The namespace named System includes a lot of functionality.
User and Program Interfaces
.NET provides many tools for managing user applications
- Windows Forms
- Web Forms
- Console Application
- Web Services
- These tools help the user to develop web based and desktop based applications using a wide variety of languages.
Tools Required for C#
- .NET Framework
- Integrated Development Environment: Visual Studio, Visual C# 2010 Express, And Visual Web Developer.
- Windows Operating System: C# can only run on systems that have .NET framework installed.
One thing to note is that .NET framework only works for Windows environment and you cannot run the C# program without .NET framework. Though Mono an open source platform of .NET framework includes C# compiler, it has been developed so that it can run C# program on cross platforms, including Mac OS.
Get to know more about the C# language at Udemy.com. | https://blog.udemy.com/c-sharp-tutorial-2/ | CC-MAIN-2015-18 | refinedweb | 975 | 56.66 |
One of your collaborators has posted a comma-delimited text file online for you to analyze. The file contains dimensions of a series of shrubs (ShrubID, Length, Width, Height) and they need you to determine their volumes. You could do this using a spreadsheet, but the project that you are working on is going to be generating lots of these files so you decide to write a program to automate the process.
The following function will download the text from the web and return it as a list of lists:
def get_file_from_web(url): """Download CSV data from web""" webpage = urllib.urlopen(url) datareader = csv.reader(webpage) data = [] for row in datareader: data.append(row) return data
It requires the use of the urllib and csv modules, so you will need to import those modules before using the function.
Use this function to download the data and then use a for loop to calculate the volumes and return a list of lists where the first item in each sublist contains the ShrubID and the second item contains the volume. There should be one sublist for each ShrubID. Once you have created this list, use another for loop to print out each combination of ShrubID and volume on it’s own line in a string like ‘The volume of shrub a1 is 22.5.’ | http://www.programmingforbiologists.org/exercises/Lists-6/ | CC-MAIN-2019-09 | refinedweb | 222 | 66.88 |
Dear Java architect
I'm new in JMS concept and I have a J2SE application and receive messages from ESB channel in pub/sub model.
However I just wondering how can I implement a load balancing in pub/sub model, as I dun want to all my java instances to process the same thing.
In IBM MQ have a CLONESUPP model which can serve as only one instance of a durable topic subscriber can run at a time and two or more instances of the same durable topic subscriber can run simultaneously, but each instance must run in a separate Java virtual machine (JVM). If I'm not using IBM MQ as my ESB channel then any other suitable solution can satisfy the above issue? Since this is a J2SE application and I have no idea to form a cluster.
I would appreciate any help you can provide!
Thanks in advance
Bonnie
Message Load Balancing (2 messages)
- Posted by: Bonnie Smith
- Posted on: March 16 2006 20:31 EST
Threaded Messages (2)
- Message Load Balancing by Gideon Low on March 17 2006 10:09 EST
- Message Load Balancing by James Strachan on March 20 2006 23:17 EST
Message Load Balancing[ Go to top ]
Bonnie,
- Posted by: Gideon Low
- Posted on: March 17 2006 10:09 EST
- in response to Bonnie Smith
You should consider looking at the more advanced Distributed Caching solutions. Gemstone's GemFire product solves the problem you stated by:
1. Easily creating clusters based on our technology's Distributed System and Group Membership Services. Use multicast for location transparency or TCP/IP with a lookup service if multicast is not available on your network.
2. Automatically load-balancing message distribution from a message source (or sources) into an application cluster (J2EE or J2SE). We use "namespace" instead of "topic", but they implemenation is logicaly equivalent (for example, you can use "dot" notation in subject creation).
3. Giving you the option of statically or dynamically partitioning data distribution (and thus message receipt event firing) within the cluster. You can choose specific primary and backup instances, or let the system dynamically assign these for you.
4. Guaranteeing that a callback event (equivalent of onMsg()) logically fires once and only once accross your cluster. The major advance in our newest product is that event firing is absolutely guaranteed across any failover boundary condition.
5. All HA/Failover and load balancing logic is handled by GemFire, both from the publisher and subscriber/cluster perspective.
So, we take care of clustering, guaranteed messaging, HA/Failover, and load balancing all through one product that's easy to configure and has an intuitive API. There are also many more great features--far to many to list here.
In fairness, you can get some (but not all) of these feature from some of our competitors as well.
Cheers,
Gideon
gideon dot low at gemstone dot com
GemFire-The Enterprise Data Fabric
Message Load Balancing[ Go to top ]
You can't load balance topics via the JMS API; they are not designed for that, but JMS Queues are.
- Posted by: James Strachan
- Posted on: March 20 2006 23:17 EST
- in response to Bonnie Smith
So instead use a single topic subscriber to publish to a queue (or just use a queue instead of the topic) - then have multiple consumers on the queue and you will get load balancing of the messages on the queue to the different consumers.
James
LogicBlaze
Open Source SOA | http://www.theserverside.com/discussions/thread.tss?thread_id=39488 | CC-MAIN-2016-36 | refinedweb | 579 | 55.27 |
21 December 2012 21:07 [Source: ICIS news]
HOUSTON (ICIS)--?xml:namespace>
Given the number of TiO2 customers, the number of companies that could join the lawsuit is huge, according to court documents. At least 700 TiO2 buyers were affected by the alleged price fixing.
The lawsuit was initially filed in February 2010 by Haley Paint in US District Court, Maryland District.
Haley sued DuPont, Huntsman Kronos and Millennium Inorganic Chemicals, accusing them of fixing TiO2 prices from 1 February 2003 to the present.
A fifth TiO2 producer, Tronox, was not named in the lawsuit because, at the time, it was operating under Chapter 11 bankruptcy protection. Tronox has since emerged from bankruptcy protection.
Regardless, Haley still alleged that Tronox cooperated with the other producers.
TiO2 producer Huntsman said "there is absolutely no merit to the case. There was no conspiracy to fix TiO2 prices".
TiO2 producers Millennium Inorganic Chemicals did not immediately respond to a request for comment. Millennium is owned by Cristal Global.
Other producers declined to comment as they typically do not discuss pending litigation.
Altogether, Tronox and the other producers control about 70% of global production capacity, Haley said in its lawsuit. The companies controlled all capacity in
Such command of the market helped the companies fix prices, Haley alleged.
The producers were also helped by the high cost of entering the TiO2 market, Haley alleged. A new plant costs $450m-500m (€342m-380m) and requires three to five years to build.
Haley alleged that the TiO2 industry had many characteristics that made it conducive to price fixing, such as a small number of producers and a product that is similar regardless of who makes it.
In addition, many customers buy TiO2, Haley said. The pigment is a product that makes up a small portion of their costs, and it does not have a practical substitute, Haley alleged.
During the time of the lawsuit, Haley accused the producers of raising prices in spite of flat demand, lower costs and excess capacity
Haley alleged that the TiO2 producers coordinated their price increases through announcements and during industry meetings.
As a result, customers paid higher prices for TiO2 than they would have paid in a competitive market, Haley | http://www.icis.com/Articles/2012/12/21/9626975/us-tio2-price-fixing-suit-gets-class-status-seeks-more-buyers.html | CC-MAIN-2014-42 | refinedweb | 370 | 54.63 |
Archives
Upcoming Functional Programming/F# Talks
Well, I certainly have an ambitious May schedule ahead of me. Most of course will be revolving around functional programming and F# as it seems to be finally catching on. I've been noticing a bunch from the Java and Ruby communities becoming interested in such things as Scala, Haskell, OCaml, Erlang and F#. I was rather heartened by this as some in the Ruby world like here and here coming back to the static world for ways of representing data and functions in different ways. Of course Lisp and Scheme (IronLisp and IronScheme) still manages to eek in the rebirth, but still remains on the outside.
I will be speaking at the Northern Virginia Code Camp on May 17th for a total of two topics:
- Improve your C# with Functional Programming and F# concepts
Learn how .NET 3.5 takes ideas from Functional Programming and how you can apply lessons learned from it and F# respectively.
- Introduction to Functional Programming and F#
Come learn about functional programming, an older paradigm that Object Oriented Programming, and the ideas around it. This talk will cover the basics including high-order functions, functions as values, immutability, currying, pattern matching and more. Learn how to mesh ideas from functional programming with imperative programming in F# and .NET.
So, if you're in the DC area, go ahead and register here and show your support for the community.
Also, I will be taking some time to spend up in Philadelphia this month at the next Philly ALT.NET meeting to also talk about F#. Still ironing out the details on that one in regards to the DC ALT.NET meeting in May. Either way, should be a good time!
Making Spec# a Priority
During ALT.NET Open Spaces, Seattle, I spent a bit of time with Rustan Leino and Mike Barnett from the Spec# team at Microsoft Research. This was to help introduce Design by Contract (DbC) and Spec# to the ALT.NET audience who may not have seen it before through me or Greg Young. I covered it in detail on my old blog here.
Spec# at ALT.NET Open Spaces, Seattle
As I said before I took a bit of time during Saturday to spend some time with the Spec# guys. I spent much of the morning with them in the IronRuby session explaining dynamic languages versus static ones. They had the session at 11:30, the second session of the day, in direct competition with the Functional Programming talk I had planned with Dustin Campbell. Greg was nice enough to record much of the session on a handheld camera and you can find that here. It's not the best quality, but you can understand most of it, so I'm pretty happy.
The things that were covered in this session were:
- Spec# overview
- Non-null Types
- Preconditions
- Postconditions
- Invariants
- Compile-Time checking versus Runtime checking
- Visual Studio Integration
Scott Hanselman also recorded a session with the Spec# guys for Episode 128. This is a much better interview than on DotNetRocks Episode 237 that Rustan did last year. This actually gets into the technical guts of the matter in a much better way, so go ahead and give it a listen. I was fortunate enough to be in the room at the time to listen.
The New Release
Mike and Rustan recently released a new version of Spec# back on April 11th so now Visual Studio 2008 is supported. You must remember though, this is still using the Spec# compiler that's only C# 2.0 compliant. So, anything using lambdas, extension methods, LINQ or anything like that is not supported. As always, you can find the installs here.
As with before, both the Spec# mode (stripped down mode) and C# mode are supported. What's really interesting is the inferred contracts. From an algorithm that Mike and Rustan worked on, they have the ability to scan a method to determine its preconditions and postconditions. It's not perfect, but to have that kind of Intellisense is really powerful.
What you can see is that the GetEnumerator method ensures that the result is new. Keep in mind, result is a keyword which states what the return value is for a method. It also says that the owner of IEnumerator will be the same as before. Object ownership is one of the more difficult things to comprehend with Spec# but equally powerful.
Another concept that's pretty interesting is the ability to make all reference types non-null by default in C# or in Spec# modes. Instead of having to mark your non-null types with an exclamation mark (!), instead you can mark your nullable types with a question mark (?) much as you would with the System.Nullable<T> generic class. All it takes is the flip of a switch in Spec#:
Or in the C# mode:
And then you have all the Spec# goodness.
Why It's Important
So, why have I been harping on this? To be able to express DbC as part of my method signature is extremely important to me. To be able to express my preconditions (what I require), postconditions (what I ensure), my invariants (what state will change) is a pretty powerful concept. Not to mention, to enforce immutability and method purity is also a pretty strong concept, especially in the times of multi-core processing. More on that subject later.
Focus on Behaviors
What Spec# can bring to the table is the ability to knock out a bit of your unit tests. Now, I don't mean all of them, but what about the ones that check for null values? Are they valid if you already put in your method signature to require a non-null value or use the ! symbol to denote a non-null type? Those edge cases aren't really valid anymore. The ability to track your invariants is the same as well as your postconditions. Instead, what that does is frees you up to consider the behaviors of your code, what you should have been testing anyways.
Immutability
Immutability plays a big part in Spec# as well. To some extent, I'll cover more in a Domain Driven Design post, but instead will get some things out of the way here. Eric Lippert, C# team member, has stated that immutable data structures are the way of the future in C# going forward. Spec# can make that move a bit more painless? How you might ask? Well, the ImmutableAttribute lays out that explicitly. Let's do a simple ReadOnlyDictionary in Spec#, taking full advantage of Spec#'s attributes, preconditions and postconditions:
using System;
using System.Collections;
using System.Collections.Generic;
using Microsoft.Contracts;
namespace Microsoft.Samples
{
[Immutable]
public class ReadOnlyDictionary<TKey, TValue> : ICollection<KeyValuePair<TKey!, TValue>> where TKey : class
{
private readonly IDictionary<TKey!, TValue>! dictionary;
public ReadOnlyDictionary(IDictionary<TKey!, TValue>! dictionary)
{
this.dictionary = dictionary;
}
public TValue this[TKey! key]
{
get
requires ContainsKey(key);
{ return dictionary[key]; }
}
[Pure]
public bool ContainsKey(TKey! key)
{
return dictionary.ContainsKey(key);
}
void ICollection<KeyValuePair<TKey!,TValue>>.Add(KeyValuePair<TKey!, TValue> item)
{
throw new NotImplementedException();
}
void ICollection<KeyValuePair<TKey!,TValue>>.Clear()
{
throw new NotImplementedException();
}
[Pure]
public bool Contains(KeyValuePair<TKey!, TValue> item)
{
return dictionary.Contains(item);
}
[Pure]
public void CopyTo(KeyValuePair<TKey!, TValue>[]! array, int arrayIndex)
requires arrayIndex >=0 && arrayIndex < Count;
{
dictionary.CopyTo(array, arrayIndex);
}
[Pure]
public int Count
{
get
ensures result >= 0;
{ return dictionary.Count; }
}
[Pure]
public bool IsReadOnly
{
get
ensures result == true;
{ return true; }
}
[Pure]
bool ICollection<KeyValuePair<TKey!,TValue>>.Remove(KeyValuePair<TKey!, TValue> item)
{
throw new NotImplementedException();
}
[Pure]
public IEnumerator<KeyValuePair<TKey!, TValue>>! GetEnumerator()
{
return dictionary.GetEnumerator();
}
[Pure]
IEnumerator! System.Collections.IEnumerable.GetEnumerator()
{
return dictionary.GetEnumerator();
}
}
}
As you can see, I marked the class itself as immutable. But as well, I removed anything that might change the state of our dictionary, as well as mark things with non-null values. That's a little extra on top, but still very readable. I'll be covering more in the near future as it applies to Domain Driven Design.
Call to Action
So, the call to action is clear, make Spec# a priority to get it in C# going forward. Greg Young has started the campaign, so we need to get it moving!
let Matt = CodeBetter + 1
Joining the CodeBetter Community....
#light
type FullName = string * string
let FullNameToString (name : FullName) =
let first, last = name in
first + " " + last
let blogger = FullNameToString("Matthew", "Podwysocki")
I'm pretty excited to be joining the CodeBetter gang after following for so many years. I want to thank Jeremy Miller, Brendan Tompkins, Dave Laribee, Greg Young and others for welcoming me to the fold. No, this blog won't be going away, but instead will also serve as a host for my posts.
So Who Are You and Why Are You Here?
So, just to introduce myself, I work for Microsoft in the Washington DC area. I'm active in the developer community in whether it be in the .NET space, Ruby, or less mainstream languages (F#, Haskell, OCaml, Lisp, etc). I also run the DC ALT.NET group since the November timeframe of last year and helped plan the latest incarnation in Seattle.
The number one reason I'm here is to help better myself. Deep down, I'm a language geek with any of the aforementioned languages. I'm one of those who strives to learn a language every year, but not just learn it, let it sink in. That's really the key. Sure, I can learn a certain dialect, but it's not quite being a native speaker. That's how I can take those practices back to my other languages to try to apply lessons learned such as functional programming paradigms (pattern matching, currying, first order functions, etc).
I also have a pretty deep interest in TDD/BDD, Domain Driven Design and of course one of Greg Young's topics, messaging. Right now in the world of messaging, I think we're in a pretty important time in the development world when messaging, multi-threaded processing and such is going to be more mainstream and hopefully less hard than it is now.
I'm also a tinkerer at heart. I'm looking at testing frameworks to help make my TDD experiences easier. I'm looking at IoC containers to help make my system just a bit more configurable. I'll look at the tests to see how each one does what it is. That's the fun part about it.
I'm also on the fringe with such topics as Spec# and Design by Contract. I'd love nothing more than to see many of the things being done at Microsoft Research become a bit more mainstream and not just seen as a place where we might see something 10 years down the line. Topics such as Spec#, F# and others have real importance now and it's best to play with them, give them our feedback and such.
So What Do You Want From Me?
Here's the thing, since I'm always looking to better myself, I'll need your help along the way. I value your feedback along the way and hopefully we'll learn from each other. Now that this is out of the way, time for more serious topics...
xUnit.net Goes 1.0 and Unit Testing F#?
ALT.NET Open Spaces Closing Day Recap
In my previous post, I talked about some of the happenings from the day two experience. Day three was only a half day with only two sessions. So, it was best to make the best of times anyhow. Once again, it snowed again, rather heavily at times, so nature's cruel joke on ALT.NET.
Impromptu Sessions
One of the best sessions was an impromptu session with Jeremy Miller on the StoryTeller tool and his future plans for it. If you're not familiar with it, it is a tool used to manage and create automated testing over the FitNesse Dot Net libraries and helps in an acceptance test driven development environment. Anyhow, a number of us managed to corner him at one point during the day and sure enough he had his laptop available. From there, we were able to encourage him to work on it some more as well as learn about where to go from where it is right now. Jeremy covers more about it here. Sometimes these impromtu sessions are some of the more valuable interactions to be had at events such as these.
More Video To Be Had
It seems that almost everyone had a camera at the event. Greg Young and Dave Laribee managed to capture a bit of the sessions on video. That's a great thing because I honestly wish I could have cloned myself and gone to more sessions. Hopefully more of this will be forthcoming. Dave posted Greg Young's fishbowl conversation on Architecture Futures which you can see here.
Other videos that are on this list are from John Lam's IronRuby session, Udi Dahan with ScottGu and Chad Myers talking about Microsoft and Open Source Software and so on. You can find them at the end of Greg's video.
Software Design Has Failed, What Can We Do About It?
Scott Koon, aka LazyCoder, convened with JP Boodhoo a session on how software design has failed us. This turned into a fishbowl conversation as well since there was a lot to be said. The basic points revolved around the large amount of software failures. What causes them? Are they technological issues? People issues? Politics? Many people brought their opinions to bear, and it was interesting that the point that I brought is that at the end of the day, customer satisfaction is the metric that matters. Are we listening to them? In the Agile methodology world, customer satisfaction is the only metric. Yes, we can talk about TDD/BDD, DDD and so on, but are we actually putting software into the hands of the user that they actually want?
I'm not forgetting of course the ideals around mentoring and helping make the team stronger. Those issues are important as well. Do we do pair programming? Do we hold brown bag sessions? All of those suggestions are key to helping grow a stronger team. But, also it helps grow the team as a more cohesive unit that's not afraid to ask questions, pair up and avoid flailing.
F# and Concurrency
Roy Osherove convened a session on concurrency and functional programming as the last topic I was going to attend. When we start to deal with multi-core environments, threading issues come to bear more frequently. Are we utilizing the CPUs to the maximum or are we still just sitting on that one thread, and barely using the machine to its capacity? Those are many of the issues we face. In Software Engineering Radio Episode 14, Ted Neward talks to this very point quite frankly that multi-threaded programming is hard. There are no two ways about it. But, when we talk about functional programming, some of that is solved. Why? Immutability by default is one of the key strong points of FP. Instead, you have to go out of your way to make a value to be mutable. Is this something we'll see in C# 4.0? Spec# has something to say about it. And once again, another topic for discussion. I keep putting these things on my plate...
Anyhow, Harry Pierson and I helped run this session. Harry had some of his parsing code that he has posted on his blog to show off. I think that did the trick well to show some advanced things such as high order functions, pattern matching, anonymous functions and so on. Instead, if you wish to learn more, I'll probably cover it here in some detail, but you can check chapter 13 of Don Syme's "Expert F#" book to learn more in the mean time.
Action Items
Some action items came up from this event that I think are rather important. Because ALT.NET is a community looking to improve itself, there are naturally some things that help. Here are a few that I can think of:
- Keep the conversation going
Just because the conference ended doesn't mean the conversations that started there have to.
- Start a local group
After the session was done, the altdotnet mailing list came alive with people wanting to create that ALT.NET groups like I did in DC, Brian Donahue did in Philly and Jeremy Jarrell did in Pittsburgh.
- Support the community
Ray Houston laid out a challenge for those who use Open Source products to donate to them. This doesn't mean only money, but time as well. Many projects are in need of some assistance, and all it takes is for someone to ask.
- Challenge Assumptions and Bring Change
It was said best during the conference "If you can't change your job, change your job". Don't let these discussions that happened here just stay there. Bring them to your work place, bring change for the better. Question why things are done the way they are.
Wrapping it Up
I'm glad to have been a part of this event in Seattle. It couldn't have been with a better bunch of people who are willing to better themselves, challenge themselves and their assumptions and bring change to the developer community. There was a lot to learn this past weekend and each conversation brought up a new angle. Until next time...
ALT.NET Open Spaces, Seattle Day 2 Recap
In my previous installment of recapping the events from ALT.NET Open Spaces, Seattle, I covered pretty much the opening ceremonies as it were. The weather was definitely interesting the entire weekend. Who would believe that we had snow, hail and rain for most of the time we were there in the latter half of April? Mind you it didn't stick, but if you believe in God, there is something to be said of ALT.NET coming to town....
DC ALT.NET Meeting 4/23/2008 - Jay Flowers and CI Factory
Now that we've somewhat recovered from ALT.NET Open Spaces, Seattle, it's time for another DC ALT.NET meeting. I'm currently finishing up my wrapups for Seattle still and I'm sure I have months worth of material from there. Anyhow, this time Jay Flowers will be talking to us about Continuous Integration and CI Factory which was postponed from last month due to schedule conflicts. As always we have the first hour or whenever the conversation ends for our main topic and the rest is Open Spaces. Food will be served as well.
Below are the details for the meeting:
Time:
4/23/2008 - 7PM-9PM
Location:
2201 Wilson Blvd
Arlington, VA 22201
Parking/Metro:
Best parking on N. Veitch St
Courthouse Metro the best bet
As always you can find out more by joining the mailing list here. Hope to see a great crowd there and to continue some of the great discussions that were held in Seattle. Until next time...
ALT.NET Open Spaces, Seattle Day 1 Recap
ALT.NET Open Spaces, Seattle has come to a close. What a great time it was and it met every expectation if not exceeded them. Currently I'm in the Seattle airport waiting for my flight home which just got re-arranged. Anyhow, I'd like to wrap up my thoughts for the first day of the event.
Setting It Up
I arrived one day early for the event to make sure we were set up appropriately. I was able to meet up with Dave Laribee, Glenn Block, Scott Bellware, Jeremy Miller, Greg Young, Scott C Reynolds, Ray Lewallen, Patrick Smacchia and others. Everyone was already burned out from the MVP Summit, so I wasn't sure how well people would be for the event. But it was great to talk to Sam Gentile and I'm glad he's back in the fold with ALT.NET as he announced earlier last week here.
Even though a lot of people were tired, we had plenty of help to set up for the event. Of course the joke is that "How many ALT.NETers does it take to go to Costco?"...
Kicking It Off
One couldn't ask for a more prepared and outstanding facilitator in Steven "Doc" List. What an amazing job he did to bring the Open Spaces together. The event started with a description of Open Spaces Technology. if you're not familiar with the Open Spaces, Technology Format, here are the four basic principles:
- Whoever comes are the right people
- Whatever happens is the only thing that could have
- Whenever it starts is the right time
- When it's over, it's over
The Sessions
I met with Mike Barnett from the Spec# team who was one of the many people I had invited to this event. Spec# as you may have figured from my blog is a passion of mine. It is one of my goals to publicize it enough and to make sure that people are aware of this wonderful technology that the product teams such as Mads Torgersen and Anders Hejlsberg notice. Anyhow, Mike went up and announced a session on Spec# and static verification. I'll cover more of that in subsequent posts again. Start your letter writing campaigns now!
Dustin Campbell also was in attendance and he and I chatted about F# and doing a session on functional programming and F#. It was going to be a great session, but unfortunately when the schedule was finalized, I couldn't possibly attend the Spec# and functional programming and F# talk. I was a little disappointed by that, but luckily Roy Osherove suggested a talk about "Concurrency and Functional Programming" which I was more than willing and able to help out on. I also pulled Harry Pierson, the new Program Manager for IronPython to help in such a session.
Since John Lam wasn't in attendance that night, I volunteered him for a session on IronRuby and the DLR which he was more than happy to oblige. We scheduled that for the first session on Saturday. I'll cover each of these in detail in subsequent posts.
The Fishbowl
From there, we went to a fishbowl style conversation in which there are a number of chairs in the middle of the room. There must be all but one of the chairs filled at any given time. Any person may in turn come and take a seat and another person must leave to keep the balance. The discussion started with Scott Hanselman, Ted Neward, Charlie Calvert and Martin Fowler talking about the Polyglot Programmer. Ted Neward couldn't be there for the whole event, unfortunately as he was also doing No Fluff Just Stuff this weekend as well with Venkat Subramaniam, Neal Ford and others. Luckily I got some time to talk to Ted about some F# related items as well as his upcoming trip to Reston, VA for No Fluff Just Stuff next weekend. So, if you're in the area and interested in seeing Ted and Venkat, that's the place to go! But anyways, the event was great and a lot of people pitched in. There are so many to name, I'd just run out of space.
To Be Continued....
Off to Seattle and ALT.NET Open Spaces, Seattle
Well, the day has finally come where I'm heading to ALT.NET Open Spaces, Seattle. It's been a long time of planning for this day with all the other guys mentioned on the site. The weather's not looking so great with a possibility of snow on Saturday. Not looking forward to that part as I'm leaving sunny, beautiful Washington DC where it is around 75F or so right now.
I hope to be live blogging much of the event, well as much as I can. I you're on Twitter, you can follow me at mattpodwysocki. Looking forward to seeing everyone there!
NOVARUG with Dave Thomas (PragDave) Recap
Last night I attended the Northern Virginia Ruby Users Group (NovaRUG) meeting in Reston last night with Dave Thomas (PragDave) and Chad Fowler. It was a completely packed house and the temperatures were a bit hight in the room, but it was well worth the sweating to attend.
Paul Barry presented first on Merb and gave a really good demonstration of some of the capabilities in comparison to Ruby on Rails. If you're not familiar with Merb, it is a lightweight Model View Controller framework written in Ruby. It was written by Ezra Zygmuntowicz in response to trying and giving up on making Ruby on Rails thread safe. You can find his presentation materials here.
It was mentioned that there will be a Ruby conference in the Northern Virginia area upcoming I'd like to see if we can get some IronRuby in there instead of all those Java guys with JRuby. We'll see what happens, but for right now, everything seems to be in flux. Stay tuned!
Next up, Dave Thomas talked about the Ruby object model with a very good presentation. Below you can find some of my pictures I took from the event. Forgive the quality of the images, but you can tell that it was a crowded place! Anyhow, it was a really good talk about the object model, how the scoping of self and the resolution of classes and methods are done deep down in Ruby. It was an excellent presentation and I was definitely excited by his passion for the community and the technology.
First we have Dave talking about the inheritance chain of Ruby objects.
Then here's Dave talking about the method resolution.
I had a chance to chat with Dave afterwards on F# as he has been looking into OCaml lately, where F# got most of its functionality from. It's his hope that F# succeeds and I ultimately think it will. So, I told him to give it a try. Anyhow, it was a great night and good to reach out to the community. The DC area has a pretty rich community of .NET, Ruby and Java programmers that's really refreshing to see. Until next time...
Metaprogramming in F#
Tonight I will be heading to the Northern Virginia Ruby Users Group (NoVARUG) meeting tonight with Dave Thomas (PragDave) talking about metaprogramming in Ruby. Should be a great time and I'm sure it will be full tonight. For those interested in some introduction to metaprogramming in Ruby, here's a good link to help get you started.
Metaprogramming in F#?
One of the many things that has interested me in F# is that it was originally written as a language to write other languages. This of course leads me to a discussion of F# and metaprogramming. Is it a fit? There are a couple of links well worth visiting and then at a future date, we'll come back to the subject.
Before the links, most of the language oriented stuff comes from quotations. Quotations are a little block of code which turns a particular piece of code into an expression tree. This language tree can then be transformed, optimized and even compiled into different languages. There are two types of these quotations, raw and typed. Typed Quotations contain static typing information whereas the raw do not. For a good introduction to these, check out Tomas Petricek's post here.
- Leveraging Meta-Programming Components with F# - Don Syme
Talks about F# with Quotations and LINQ expressions for expressing metaprogramming in F#
- F# metaprogramming and classes - Tomas Petricek
Talks about Class Quotations and basic metaprogramming capabilities in F# and its limitations
Adventures in F# - F# 101 Part 8 (Mutables and Reference Cells)
class Program
ALT.NET on DotNetRocks and the Community
Dave Laribee and Jeremy Miller recently recorded an episode on DotNetRocks and was just posted today. Episode 333 "It's the ALT.NET Show" can be found here. It's a great show that explains ALT.NET for those who may not really know what it is outside of some of the arguments on the altdotnet mailing list. This includes discussions on open source frameworks, agile practices, refactoring and so on..
CMAP Code Camp Wrap Up - Dependency Injection and IoC Containers
I really enjoyed speaking at this past weekend's CMAP Code Camp. I hope you all enjoyed my presentation on "Loosen Your Dependencies with Dependency Injection and Inversion of Control Containers". It was a great discussion to have with everyone and I like to learn there as much as I teach.
I also enjoyed teaming up with Scott Allen on his "A Gentle Introduction to Mocking" where we talked about mocks versus stubs, test pattens and mock frameworks such as Rhino Mocks and Moq. Hopefully we'll be doing some more ping-pong sessions in the future.
If you note, I my code uses the following products in order to get it to run:
- ASP.NET MVC Preview 2
- xUnit.net
- Castle Windsor
- StructureMap
- Unity Application Block
- Unity Community Contributions
Unity Community Contributions and Interception
public delegate IMethodReturn InovkeHandlerDelegate(IMethodInvocation call,
GetNextHandlerDelegate getNext);
public delegate InovkeHandlerDelegate GetNextHandlerDelegate();
public interface IInterceptionHandler
{
IMethodReturn Invoke(IMethodInvocation call,
GetNextHandlerDelegate getNext);
}
}
xUnit.net RC3 Just Released
Well, Brad Wilson and Jim Newkirk must really be busy lately. After I talked about the release of xUnit.net RC2, just today, Brad announced the release of RC3. As always, you can find the latest bits here. This fixes a number of bugs and adds CruiseControl.NET and ASP.NET MVC Preview 2 support as well in addition to the Resharper 3.1 and TestDriven.NET support. For more information about it, check out Brad's post here. More or less, they are feature complete for version 1.0 and the only that I think really is needed at this point is a decent GUI runner and that's well acknowledged as something they are working on. Visual Studio integration would be nice as well...RockNUG appearance, all tests for my demos were using xUnit.net, so I am actively using it right now and will be for my CMAP Code Camp appearance this weekend. However, I did not show the GUI runner because, well, it's not there yet, and instead, the console runner works just fine, thank you. So, go ahead and pick up the latest bits and give the team feedback!
For my other posts in this series, check them out here:
One last note regarding Brad, he was recently interviewed by Scott Swigart and Sean Campbell over at How Software Is Built and gives some interesting insights in the open source world inside and outside Microsoft and his contributions to it. Very good interview and well worth the time to read.
RockNUG IoC Container Presentation Wrapup
I want to thank the fine folks at the Rockville .NET Users Group (RockNUG) and Dean Fiala for giving me the opportunity to speak last night. It was a record crowd last night, so I'm glad that people were interested in Loose Coupling, Design Patterns, Test Driven Development, Behavior Driven Development and Inversion of Control containers. I hope everyone got some good information, and if not interested in using containers, design patterns and such, at least know they exist and have their use. Based on the feedback I've already received, it was warming and why I like presenting at user groups, so that both of us can learn.
NoVARUG Meeting April 16th - Dave Thomas (PragDave)
The Northern Virginia Ruby Users Group (NoVARUG) will be holding their next meeting next week with a special speaker in Dave Thomas (PragDave). Dave is in town teaching Advanced Rails Studio in Reston and will be kind enough to come talk about the Ruby Object model and how it facilitates metaprogramming.
The details are as follows:
Subject:
Dave Thomas - The Ruby Object Model and Metaprogramming
Date:
April 16th, 2008 - 7-9PM
Location:
FGM Inc
12021 Sunset Hills Road
Suite 400
Reston, VA 20190
Hope to see a good crowd there! I know I'm very interested in this subject and hope to dive deeper soon. That reminds me I need to do some of metaprogramming in F# as well.
Unity 1.0 Released into the Wild
As Chris Tavares mentioned in his blog, Unity 1.0 has been released a couple of days earlier than the April 7th release date mentioned by Grigori Melnik earlier. Scott Densmore also announced this as well as working on porting the inteception from ObjectBuilder2 which I talked about earlier in some of my Unity and IoC containers posts. Looking forward to that post as we've shared some emails on the subject.
Would You Like To Know More?
For those looking for my posts on the matter, I've covered it quite extensively with the comparison to other IoC containers as well as IoC containers in general:
- IoC and Unity - Configuration Changes for the Better
Covers the latest configuration changes to allow for better constructor injection
- IoC and Unity - The Basics and Inteception
Covers the basics of an IoC container and inteception techniques
- IoC Container, Unity and Breaking Changes Galore
Covers the breaking changes made from the old Unity drop to the new one
- IoC Containers, Unity and ObjectBuilder2 - The Saga Continues
Managing instances and parameter mapping resolution
- IoC and the Unity Application Block Once Again
Setter Injection versus Constructor Injection and PostSharp4Unity
- IoC and the Unity Application Block - Going Deeper
Constructor Injection and comparing Unity with Castle Windsor
- IoC and the Unity Application Block
Covering ObjectBuilder and Unity Application Block
Anyhow, if interesting in more Unity content, check out David Hayden's Unity IoC and MVC screencast as well as others on the subject here.
Speaking of which, I'm going to be a busy man indeed with my upcoming speaking schedule on IoC containers, not necessarily Unity in particular, but all of them, the background and decoupling your applications. Here is the complete schedule for this month:
- RockNUG - April 9th
- CMAP Code Camp - April 12th
- CMAP Architecture SIG - April 15th
Relooking at xUnit.net RC2
using MVC_APPLICATION_NAMESPACE.Controllers; // This using directive needs to point to the namespace of your MVC project
Adventures in F# - F# 101 Part 7 (Creating Types)
#light
let coin = "heads", "tails"
let c1, _ = coin
let _, c2 = coin
print_string c1
print_string c2
Covering NUnit 2.4.7
#light
) | http://weblogs.asp.net/podwysocki/archive/2008/04?PageIndex=2 | CC-MAIN-2015-27 | refinedweb | 5,781 | 63.7 |
Swift version: 5.1
PDFKit makes it easy to watermark PDFs as they are rendered, for example to add “FREE SAMPLE” over pages. It takes six steps, five of which are trivial and one which involves a little Core Graphics heavy lifting.
Let’s get the easy stuff out of the way:
PDFPage.
import PDFKitto the top of the new file.
PDFViewand make the
ViewControllerclass conform to the
PDFDocumentDelegateprotocol.
pdfView.document = document) then insert this directly before:
document.delegate = self. That means the document will ask your view controller what class it should use to render pages.
SampleWatermarkclass for its pages.
Add this method to your view controller now:
func classForPage() -> AnyClass { return SampleWatermark.self }
What we’ve just done is create a new
PDFPage subclass that will handle watermark rendering, then tell our
PDFDocument to use it for all pages. We haven’t given the
SampleWatermark class any code yet, which means it will look just like a regular page – we’re going to fix that now.
When doing custom PDF rendering there are a few things to know:
super.draw(), your content will appear behind the page content. That might be what you want, but we’ll be doing the opposite here.
We’re going to write the words “FREE SAMPLE” in red, centered near the top of each page using a bold font. Add this method to SampleWatermark.swift:
override func draw(with box: PDFDisplayBox, to context: CGContext) { super.draw(with: box, to: context) let string: NSString = "FREE SAMPLE" let attributes: [NSAttributedString.Key: Any] = [.foregroundColor: UIColor.red, .font: UIFont.boldSystemFont(ofSize: 32)] let stringSize = string.size(withAttributes: attributes) UIGraphicsPushContext(context) context.saveGState() let pageBounds = bounds(for: box) context.translateBy(x: (pageBounds.size.width - stringSize.width) / 2, y: pageBounds.size.height) context.scaleBy(x: 1.0, y: -1.0) string.draw(at: CGPoint(x: 0, y: 55), withAttributes: attributes) context.restoreGState() UIGraphicsPopContext() }
If everything went well you should now see “FREE SAMPLE” emblazoned across every page of your PDF. – learn more in my book Advanced iOS: Volume Two
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.
Link copied to your pasteboard. | https://www.hackingwithswift.com/example-code/libraries/how-to-watermark-pdfs-inside-a-pdfview | CC-MAIN-2020-16 | refinedweb | 363 | 59.7 |
31 August 2011 05:13 [Source: ICIS news]
By Wong Lei Lei
?xml:namespace>
PG producers’ attempt to hike prices is being met with strong resistance from buyers, they said.
Spot prices for industrial grade PG (PGI) in northeast (NE) Asia and southeast (SE) Asia have held steady throughout August at $1,750-1,800/tonne (€1,208-1,242/tonne) CFR (cost and freight) SE/NE Asia basis, while PO prices rose by more than $100/tonne from end-July to $2,030-2,090/tonne CFR China on 26 August, according to ICIS.
Bearish demand in the downstream sector capped PG prices’ movement.
Production at the unsaturated polyester resins (UPR) industry - the main PGI consumer in China and most parts of Asia – has stayed low since June, translating to much lower demand for PGI, market sources said. UPR is used in the manufacture of fibreglass.
“The unsaturated polyester resins [plants in
Margins have been squeezed so thin for PGI producers, that a major north Asian maker stopped producing the material.
“PGI prices are so low now even though
The producer is currently limiting itself to producing pharmaceutical grade PG (PG USP), which continues to enjoy good demand.
“The PG USP demand from buyers is steady, despite the current weak global economy and lacklustre PGI market, as PG USP is used in the food and pharmaceutical sectors that have relatively stable demands,” said another producer.
PG USP spot prices were assessed at $2,050-2,100/tonne CFR NE Asia, largely unchanged for the whole of August, according to ICIS.
( | http://www.icis.com/Articles/2011/08/31/9488601/asia-pg-to-stay-weak-in-september-on-sustained-low-demand.html | CC-MAIN-2014-52 | refinedweb | 261 | 55.58 |
This blog was updated on a semi-daily basis by Joey during the year of work concentrating on the git-annex assistant that was funded by his kickstarter campaign.
Post-kickstarter work will instead appear on the devblog. However, this page's RSS feed will continue to work, so you don't have to migrate your RSS reader.
Spent a while tracking down a bug that causes a crash on OSX when setting up an XMPP account. I managed to find a small test case that reliably crashes, and sent it off to the author of the haskell-gnutls bindings, which had one similar segfault bug fixed before with a similar test case. Fingers crossed..
Just finished tracking down a bug in the Android app that caused its terminal to spin and consume most CPU (and presumably a lot of battery). I introduced this bug when adding the code to open urls written to a fifo, due to misunderstanding how java objects are created, basically. This bug is bad enough to do a semi-immediate release for; luckily it's just about time for a release anyway with other improvements, so in the next few days..
Have not managed to get a recent ghc-android to build so far.
Guilhem fixed some bugs in
git annex unused.
Today was a day off, really. However, I have a job running to try to build get a version of ghc-android that works on newer Android releases.
Also, guilhem's
git annex unused speedup patch landed. The results are
extrordinary -- speedups on the order of 50 to 100 times faster should
not be uncommon. Best of all (for me), it still runs in constant memory!
After a couple days plowing through it, my backlog is down to 30 messages from 150. And most of what's left is legitimate bugs and todo items.
Spent a while today on an ugly file descriptor leak in the assistant's local pairing listener. This was an upstream bug in the network-multicast library, so while I've written a patch to fix it, the fix isn't quite deployed yet. The file descriptor leak happens when the assistant is running and there is no network interface that supports multicast. I was able to reproduce it by just disconnecting from wifi.
Meanwhile, guilhem has been working on patches that promise to massively
speed up
git annex unused! I will be reviewing them tonight.
Made some good progress on the backlog today. Fixed some bugs, applied some patches. Noticing that without me around, things still get followed up on, to a point, for example incomplete test cases for bugs get corrected so they work. This is a very good thing. Community!
I had to stop going through the backlog when I got to one message from
Anarcat mentioning quvi. That turns
out to be just what is needed to implement the often-requested feature
of
git-annex addurl supporting YouTube and other similar sites. So I
spent the rest of the day making that work. For example:
% git annex addurl --fast '' addurl Star_Wars_X_Wing__Seth_Green__Clare_Grant__and_Mike_Lamond_Join_Wil_on_TableTop_SE2E09.webm ok
Yes, that got the video title and used it as the filename, and yes,
I can commit this file and run
git annex get later, and it will be
able to go download the video! I can even use
git annex fsck --fast
to make sure YouTube still has my videos. Awesome.
The great thing about quvi is it takes the url to a video webpage, and returns an url that can be used to download the actual video file. So it simplifies ugly flash videos as far out of existence as is possible. However, since the direct url to the video file may not keep working for long. addurl actually records the page's url, with an added indication that quvi should be used to get it.
Back home. I have some 170 messages of backlog to attend to. Rather than digging into that on my first day back, I spent some time implementing some new features.
git annex import has grown three options that help managing importing of
duplicate files in different ways. I started work on that last week, but
didn't have time to find a way to avoid the
--deduplicate option
checksumming each imported file twice. Unfortunately, I have still not
found a way I'm happy with, so it works but is not as efficient as it could
be.
git annex mirror is a new command suggested to me by someone at DebConf
(they don't seem to have filed the requested todo). It arranges for two
repositories to contain the same set of files, as much as possible (when
numcopies allows). So for example,
git annex mirror --to otherdrive
will make the otherdrive remote have the same files present and not present
as the local repository.
I am thinking about expanding
git annex sync with an option to also sync
data. I know some find it confusing that it only syncs the git metadata
and not the file contents. That still seems to me to be the best and most
flexible behavior, and not one I want to change in any case since
it would be most unexpected if
git annex sync downloaded a lot of stuff
you don't want. But I can see making
git annex sync --data download
all the file contents it can, as well as uploading all available file
contents to each remote it syncs with. And
git annex sync --data --auto
limit that to only the preferred content. Although perhaps
these command lines are too long to be usable?
With the campaign more or less over, I only have a little over a week before it's time to dive into the first big item on the roadmap. Hope to be through the backlog by then.
Wow, 11 days off! I was busy with first dentistry and then DebConf.
Yesterday I visited CERN and
got to talk with some of their IT guys about how they manage their tens of
petabytes of data. Interested to hear they also have the equivilant of a
per-subdirectory annex.numcopies setting. OTOH, they have half a billion
more files than git's index file is likely to be able to scale to support.
Pushed a release out today despite not having many queued changes. Also, I got git-annex migrated to Debian testing, and so was also able to update the wheezy backport to a just 2 week old version.
Today is also the last day of the campaign!
There has been a ton of discussion about git-annex here at DebConf, including 3 BoF sessions that mostly focused on it, among other git stuff. Also, RichiH will be presenting his "Gitify Your Life" talk on Friday; you can catch it on the live stream.
I've also had a continual stream of in-person bug and feature requests. (Mostly features.) These have been added to the wiki and I look forward to working on that backlog when I get home.
As for coding, I am doing little here, but I do have a branch cooking that
adds some options to
git annex import to control handling of duplicate
files.
Made two big improvements to the Windows port, in just a few hours. First, got gpg working, and encrypted special remotes work on Windows. Next, fixed a permissions problem that was breaking removing files from directory special remotes on Windows. (Also cleaned up a lot of compiler warnings on Windows.)
I think I'm almost ready to move the Windows port from alpha to beta status. The only really bad problem that I know of with using it is that due to a lack of locking, it's not safe to run multiple git-annex commands at the same time in Windows.
Got the release out, with rather a lot of fiddling to fix broken builds on various platforms.
Also released a backport to Debian stable. This backport has the assistant, although without WebDAV support. Unfortunately it's an old version from May, since ghc transitions and issues have kept newer versions out of testing so far. Hope that will clear up soon (probably by dropping haskell support for s390x), and I can update it to a newer version. If nothing else it allows using direct mode with Debian stable.
Pleased that the git-cat-files bug was quickly fixed by Peff and has already been pulled into Junio's release tree!
This evening, I've added an interface around the new improved
git check-ignore in git 1.8.4. The assistant can finally honor
.gitignore
files!
Today was a nice reminder that there are no end of bugs lurking in filename handling code.
First, fixed a bug that prevented git-annex from adding filenames starting with ":", because that is a special character to git.
Second, discovered that git 1.8.4 rc0 has changed
git-cat-file --batch in
a way that makes it impossible to operate on filenames containing spaces.
This is, IMHO, a reversion, so hopefully my
bug report will get it fixed.
Put in a workaround for that, although using the broken version of git with a direct mode repository with lots of spaces in file or directory names is going to really slow down git-annex, since it often has to fork a new git cat-file process for each file.
Release day tomorrow..
Turns out ssh-agent is the cause of the unknown UUID bug! I got a tip
about this from a user, and was quickly able to reproduce the bug that had
eluded me so long. Anyone who has run
ssh-add and is using ssh-agent
would see the bug.
It was easy enough to fix as it turns out. Just need to set IdentitiesOnly in .ssh/config where git-annex has set up its own IdentityFile to ensure that its special purpose ssh key is used rather than whatever key the ssh-agent has loaded into it. I do wonder why ssh behaves this way -- why would I set an IdentityFile for a host if I didn't want ssh to use it?
Spent the rest of the day cleaning up after the bug. Since this affects so many people, I automated the clean up process. The webapp will detect repositories with this problem, and the user just has to click to clean up. It'll then correct their .ssh/config and re-enable the repository.
Back to bug squashing. Fixed several, including a long-standing problem on OSX that made the app icon seem to "bounce" or not work. Followed up on a bunch more.
The 4.20130723 git-annex release turns out to have broken support for
running on crippled filesystems (Android, Windows).
git annex sync will
add dummy symlinks to the annex as if they were regular files, which is
not good!
Recovery instructions
I've updated the Android and Windows builds and recommend an immediate upgrade.
Will make a formal release on Friday.
Spent some time improving the test suite on Windows, to catch this bug,
and fix a bug that was preventing it from testing
git annex sync on
Windows.
I am getting very frustrated with this "unknown UUID" problem that a dozen
people have reported. So far nobody has given me enough information to
reproduce the problem. It seems to have something to do with
git-annex-shell not being found on the remote system that has been either
local paired with or is being used as a ssh server, but I don't yet
understand what. I have spent hours today trying various scenarios to break
git-annex and get this problem to happen.
I certainly can improve the webapp's behavior when a repository's UUID is not known. The easiest fix would be to simply not display such repositories. Or there could be a UI to try to get the UUID. But I'm more interested in fixing the core problem than putting in a UI bandaid.
Technically offtopic, but did a fun side project today:
Worked on 3 interesting bugs today. One I noticed myself while doing tests with adding many thousands of files yesterday. Assistant was delaying making a last commit of the batch of files, and would only wake up and commit them after a further change was made. Turns out this bug was introduced in April while improving commit batching when making very large commits. I seem to remember someone mentioning this problem at some point, but I have not been able to find a bug report to close.
Also tried to reproduce ?this bug. Frustrating, because I'm quite sure I have made changes that will avoid it happening again, but since I still don't know what the root cause was, I can't let it go.
The last bug is ?non-repos in repositories list (+ other weird output) from git annex status and is a most strange thing. Still trying to get a handle on multiple aspects of it.
Also various other bug triage. Down to only 10 messages in my git-annex folder. That included merging about a dozen bugs about local pairing, that all seem to involve git-annex-shell not being found in path. Something is up with that..
The big news: Important behavior change in
git annex dropunused. Now it
checks, just like
git annex drop, that it's not dropping the last copy of
the file. So to lose data, you have to use
--force. This continues the
recent theme of making git-annex hold on more tenaciously to old data, and
AFAIK it was the last place data could be removed without
--force.
Also a nice little fix to
git annex unused so it doesn't identify
temporary files as unused if they're being used to download a file.
Fixing it was easy thanks to all the transfer logs and locking
infrastucture built for the assistant.
Fixed a bug in the assistant where even though syncing to a network remote was disabled, it would still sync with it every hour, or whenever a network connection was detected.
Working on some direct mode scalability problems when thousands of the identical files are added. Fixing this may involvie replacing the current simple map files with something more scalable like a sqllite database.
While tracking that down, I also found a bug with adding a ton of files in indirect mode, that could make the assistant stall. Turned out to be a laziness problem. (Worst kind of Haskell bug.) Fixed.
Today's sponsor is my sister, Anna Hess, who incidentially just put the manuscript of her latest ebook in the family's annex prior to its publication on Amazon this weekend.
Seems I forgot why I was using debian stable chroots to make the autobuilds: Lots of people still using old glibc version. Had to rebuild the stable chroots that I had upgraded to unstable. Wasted several hours.. I was able to catch up on recent traffic in between.
Was able to reproduce a bug where
git annex initremote hung with some
encrypted special remotes. Turns out to be a deadlock when it's not built
with the threaded GHC runtime. So I've forced that runtime to be used.
Got the release out.
I've been working on fleshing out the timeline for the next year. Including a fairly detailed set of things I want to do around disaster recovery in the assistant.
No release today after all. Unexpected bandwidth failure. Maybe in a few days..
Got unannex and uninit working in direct mode. This is one of the more subtle parts of git-annex, and took some doing to get it right. Surprisingly, unannex in direct mode actually turns out to be faster than in indirect mode. In direct mode it doesn't have to immediately commit the unannexing, it can just stage it to be committed later.
Also worked on the ssh connection caching code. The perrennial problem with that code is that the fifo used to communicate with ssh has a small limit on its path, somewhere around 100 characters. This had caused problems when the hostname was rather long. I found a way to avoid needing to be able to reverse back from the fifo name to the hostname, and this let me take the md5sum of long hostnames, and use that shorter string for the fifo.
Also various other bug followups.
Campaign is almost to 1 year!
git!
Succeeded fixing a few bugs today, and followed up on a lot of other ones..
Fixed checking when content is present in a non-bare repository accessed via http.
My changes a few days ago turned out to make uninit leave hard links behind in .git/annex. Luckily the test suite caught this bug, and it was easily fixed by making uninit delete objects with 2 or more hard links at the end.
Theme today seems to be fun with exceptions.
Fixed an uncaught exception that could crash the assistant's Watcher thread if just the right race occurred.
Also fixed it to not throw an exception if another process is
already transferring a file. What this means is that if you run multiple
git annex get processes on the same files, they'll cooperate in each
picking their own files to get and download in parallel. (Also works for
copy, etc.) Especially useful when downloading from an encrypted remote,
since often one process will be decrypting a file while the other is
downloading the next file. There is still room for improvement here;
a -jN option could better handle ensuring N downloads ran concurrently, and
decouple decryption from downloading. But it would need the output layer to
be redone to avoid scrambled output. (All the other stuff to make parallel
git-annex transfers etc work was already in place for a long time.)
Campaign update: Now funded for nearly 10 months, and aiming for a year..
Surprise! I'm running a new crowdfunding campaign, which I hope will fund several more months of git-annex development.
Please don't feel you have to give, but if you do decide to, give
generously.
I'm accepting both Paypal and Bitcoin (via CoinBase.com),
and have some rewards that you might enjoy.
I came up with two lists of things I hope this campaign will fund. These are by no means complete lists. First, some general features and development!
- Use deltas to reduce bandwidth needed to transfer modified versions of files.
Secondly, some things to improve security:
-.
It will also, of course, fund ongoing bugfixing, support, etc.
Been keeping several non-coding balls in the air recently, two of which landed today.
First, Rsync.net is offering a discount to all git-annex users, at one third their normal price. "People using git-annex are clueful and won't be a big support burden for us, so it's a win-win." The web app will be updated offer the discount when setting up a rsync.net repository.
Secondly, I've recorded an interview today for the Git Minutes podcast, about git-annex. Went well, looking forward to it going up, probably on Monday.
Got the release out, after fixing test suite and windows build breakage. This release has all the features on the command line side (--all, --unused, etc), but several bugfixes on the assistant side, and a lot of Windows bug fixes.
I've spent this evening adding icons to git-annex on Linux. Even got the Linux standalone tarball to automatically install icons.
Two gpg fixes today. The OSX Mtn Lion builds were pulling in a build of gpg that wanted a gpg-agent to be installed in /usr/local or it wouldn't work. I had to build my own gpg on OSX to work around this. I am pondering making the OSX dmg builds pull down the gpg source and build their own binary, so issues on the build system can't affect it. But would really rather not, since maintaining your own version of every dependency on every OS is hard (pity about there still being so many OS's without sane package management).
On Android, which I have not needed to touch for a month, gpg was built with --enable-minimal, which turned out to not be necessary and was limiting the encryption algorythms included, and led to interoperability problems for some. Fixed that gpg build too.
Also fixed an ugly bug in the webapp when setting up a rsync repository.
It would configure
~/.ssh/authorized_keys on the server to force
git-annex-shell to be run. Which doesn't work for rsync. I didn't notice
this before because it doesn't affect ssh servers that already have a ssh
setup that allows accessing them w/o a password.
Spent a while working on a bug that can occur in a non-utf8 locale when using special characters in the directory name of a ssh remote. I was able to reproduce it, but have not worked out how to fix it; encoding issues like this are always tricky.
Added something to the walkthrough to help convince people that yes, you can use tags and branches with git-annex just like with regular git. One of those things that is so obvious to the developer writing the docs that it's hard to realize it will be a point of concern.
Seems like there is a release worth of changes already, so I plan to push it out tomorrow.
Actually spread out over several days..
I think I have finally comprehensively dealt with all the wacky system
misconfigurations that can make
git commit complain and refuse to commit.
The last of these is a system with a FQDN that doesn't have a dot in it.
I personally think git should just use the hostname as-is in the email
address for commits here -- it's better to be robust. Indeed, I think it
would make more sense if
git commit never failed, unless it ran out of
disk or the repo is corrupt. But anyway,
git-annex
init will now detect when the commit fails because of this and put a
workaround in place.
Fixed a bug in
git annex addurl --pathdepth when the url's path was
shorter than the amount requested to remove from it.
Tracked down a bug that prevents git-annex from working on a system with an old linux kernel. Probably the root cause is that the kernel was built without EVENTFD support. Found a workaround to get a usable git-annex on such a system is to build it without the webapp, since that disables the threaded runtime which triggered the problem.
Dealt with a lot of Windows bugs. Very happy that it's working well enough
that some users are reporting bugs on it in Windows, and with enough detail
that I have not needed to boot Windows to fix them so far.
I've felt for a while that git-annex needed better support for managing the contents of past versions of files that are stored in the annex. I know some people get confused about whether git-annex even supports old versions of files (it does, but you should use indirect mode; direct mode doesn't guarantee old versions of files will be preserved).
So today I've worked on adding command-line power for managing past
versions: a new
--all option.
So, if you want to copy every version of every file in your repository to
an archive, you can run
git annex copy --all --to archive.
Or if you've got a repository on a drive that's dying, you can run
git annex copy --all --to newdrive, and then on the new drive, run
git
annex fsck --all to check all the data.
In a bare repository,
--all is default, so you can run
git annex get
inside a bare repository and it will try to get every version of every file
that it can from the remotes.
The tricky thing about
--all is that since it's operating on objects and
not files, it can't check
.gitattributes settings, which are tied to the
file name. I worried for a long time that adding
--all would make
annex.numcopies settings in those files not be honored, and that this would
be a Bad Thing. The solution turns out to be simple: I just didn't
implement
git annex drop --all! Dropping is the only action that needs to
check numcopies (move can also reduce the number of copies, but explicitly
bypasses numcopies settings).
I also added an
--unused option. So if you have a repository that has
been accumulating history, and you'd like to move all file contents not
currently in use to a central server, you can run
git annex unused; git
annex move --unused --to origin
Spent too many hours last night tracking down a bug that caused the webapp
to hang when it got built with the new yesod 1.2 release. Much of that time
was spent figuring out that yesod 1.2 was causing the problem. It turned out to
be a stupid typo in my yesod compatability layer.
liftH = liftH in
Haskell is an infinite loop, not the stack overflow you get in most
languages.
Even though it's only been a week since the last release, that was worth pushing a release out for, which I've just done. This release is essentially all bug fixes (aside from the automatic ionice and nicing of the daemon).
This website is now available over https. Perhaps more importantly, all the links to download git-annex builds are https by default.
The success stories list is getting really
nice. Only way it could possibly be nicer is if you added your story! Hint.
Came up with a fix for the gnucash hard linked file problem that makes the assistant notice the files gnucash writes. This is not full hard link support; hard linked files still don't cleanly sync around. But new hard links to files are noticed and added, which is enough to support gnucash.
Spent around 4 hours on reproducing and trying to debug ?Hanging on install on Mountain lion. It seems that recent upgrades of the OSX build machine led to this problem. And indeed, building with an older version of Yesod and Warp seems to have worked around the problem. So I updated the OSX build for the last release. I will have to re-install the new Yesod on my laptop and investigate further -- is this an OSX specific problem, or does it affect Linux? Urgh, this is the second hang I've encountered involving Warp..
Got several nice success stories, but I don't
think I've seen yours yet.
Please post!
Got caught up on a big queue of messages today. Mostly I hear from people when git-annex is not working for them, or they have a question about using it. From time to time someone does mention that it's working for them.
We have 4 or so machines all synching with each other via the local network thing. I'm always amazed when it doesn't just explode
Due to the nature of git-annex, a lot of people can be using it without anyone knowing about it. Which is great. But these little success stories can make all the difference. It motivates me to keep pounding out the development hours, it encourages other people to try it, and it'd be a good thing to be able to point at if I tried to raise more funding now that I'm out of Kickstarter money.
I'm posting my own success story to my main blog: git annex and my mom
If you have a success story to share, why not blog about it, microblog it, or just post a comment here, or even send me a private message. Just a quick note is fine. Thanks!
Going through the bug reports and questions today, I ended up fixing three separate bugs that could break setting up a repo on a remote ssh server from the webapp.
Also developed a minimal test case for some gnucash behavior that prevents the watcher from seeing files it writes out. I understand the problem, but don't have a fix for that yet. Will have to think about it. (A year ago today, my blog featured the first release of the watcher.)
Pushed out a release today. While I've somewhat ramped down activity this month with the Kickstarter period over and summer trips and events ongoing, looking over the changelog I still see a ton of improvements in the 20 days since the last release.
Been doing some work to make the assistant daemon be more
nice. I don't
want to nice the whole program, because that could make the web interface
unresponsive. What I am able to do, thanks to Linux violating POSIX, is to
nice certain expensive operations, including the startup scan and the daily
sanity check. Also, I put in a call to
ionice (when it's available)
when
git annex assistant --autostart is run, so the daemon's
disk IO will be prioritized below other IO. Hope this keeps it out of your
way while it does its job.
One of my Windows fixes yesterday got the test suite close to sort of working on Windows, and I spent all day today pounding on it. Fixed numerous bugs, and worked around some weird Windows behaviors -- like recursively deleting a directory sometimes fails with a permission denied error about a file in it, and leaves behind an empty directory. (What!?) The most important bug I fixed caused CR to leak into files in the git-annex branch from Windows, during a union merge, which was not a good thing at all.
At the end of the day, I only have 6 remaining failing test cases on
Windows. Half of them are some problem where running
git annex sync
from the test suite stomps on PATH somehow and prevents xargs from working.
The rest are probably real bugs in the directory (again something to do
with recursive directory deletion, hmmm..), hook, and rsync
special remotes on Windows. I'm punting on those 6 for now, they'll be
skipped on Windows.
Should be worth today's pain to know in the future when I break something that I've oh-so-painfully gotten working on Windows.
Yay, I fixed the Handling of files inside and outside archive directory at the same time bug! At least in direct mode, which thanks to its associated files tracking knows when a given file has another file in the repository with the same content. Had not realized the behavior in direct mode was so bad, or the fix so relatively easy. Pity I can't do the same for indirect mode, but the problem is much less serious there.
That was this weekend. Today, I nearly put out a new release (been 2 weeks since the last one..), but ran out of time in the end, and need to get the OSX autobuilder fixed first, so have deferred it until Friday.
However, I did make some improvements today.
Added an
annex.debug git config setting, so debugging can
be turned on persistently. People seem to expect that to happen when
checking the checkbox in the webapp, so now it does.
Fixed 3 or 4 bugs in the Windows port. Which actually, has users now, or at least one user. It's very handy to actually get real world testing of that port.
Today I got to deal with bugs on Android (busted use of
cp among other
problems), Windows (fixed a strange hang when adding several files), and
Linux (
.desktop files suck and Wine ships a particularly nasty one).
Pretty diverse!
Did quite a lot of research and thinking on XMPP encryption yesterday, but
have not run any code yet (except for trying out a D-H exchange in
ghci).
I have listed several options on the XMPP page.
Planning to take a look at Handling of files inside and outside archive directory at the same time tomorrow; maybe I can come up with a workaround to avoid it behaving so badly in that case.
Got caught up on my backlog yesterday.
Part of adding files in direct mode involved removing write permission from them temporarily. That turned out to cause problems with some programs that open a file repeatedly, and was generally against the principle that direct mode files are always directly available. Happily, I was able to get rid of that without sacrificing any safety.
Improved syncing to bare repositories. Normally syncing pushes to a synced/master branch, which is good for non-bare repositories since git does not allow pushing to the currently checked out branch. But for bare repositories, this could leave them without a master branch, so cloning from them wouldn't work. A funny thing is that git does not really have any way to tell if a remote repository is bare or not. Anyway, I did put in a fix, at the expense of pushing twice (but the git data should only be transferred once anyway).
Slowly getting through the bugs that were opened while I was on vacation and then I'll try to get to all the comments. 60+ messages to go.
Got git-annex working better on encfs, which does not support hard links in paranoid mode. Now git-annex can be used in indirect mode, it doesn't force direct mode when hard links are not supported.
Made the Android repository setup special case generate a .gitignore file to ignore thumbnails. Which will only start working once the assistant gets .gitignore support.
Been thinking today about encrypting XMPP traffic, particularly git push data. Of course, XMPP is already encrypted, but that doesn't hide it from those entities who have access to the XMPP server or its encryption key. So adding client-to-client encryption has been on the TODO list all along.
OTR would be a great way to do it. But I worry that the confirmation steps OTR uses to authenticate the recipient would make the XMPP pairing UI harder to get through.
Particularly when pairing your own devices over XMPP, with several devices involved, you'd need to do a lot of cross-confirmations. It would be better there, I think, to just use a shared secret for authentication. (The need to enter such a secret on each of your devices before pairing them would also provide a way to use different repositories with the same XMPP account, so 2birds1stone.)
Maybe OTR confirmations would be ok when setting up sharing with a friend. If OTR was not used there, and it just did a Diffie-Hellman key exchange during the pairing process, it could be attacked by an active MITM spoofing attack. The attacker would then know the keys, and could decrypt future pushes. How likely is such an attack? This goes far beyond what we're hearing about. Might be best to put in some basic encryption now, so we don't have to worry about pushes being passively recorded on the server. Comments appreciated.
Today marks 1 year since I started working on the git-annex assistant. 280 solid days of work!
As a background task here at the beach I've been porting git-annex to yesod 1.2. Finished it today, earlier than expected, and also managed to keep it building with older versions. Some tricks kept the number of ifdefs reasonably low.
Landed two final changes before the release..
First, made git-annex detect if any of the several long-running git process
it talks to have died, and, if yes, restart them. My stress test is reliably
able to get at least
git cat-file to crash, and while I don't know why (and
obviously should follow up by getting a core dump and stack trace of it),
the assistant needs to deal with this to be robust.
Secondly, wrote rather a lot of Java code to better open the web browser
when the Android app is started. A thread listens for URLs to be written to
a FIFO. Creating a FIFO from fortran^Wjava code is .. interesting. Glad to
see the back of the
am command; it did me no favors.
AFK
Winding down work for now, as I prepare for a week at the beach starting in 2 days. That will be followed by a talk about git-annex at SELF2013 in Charlotte NC on June 9th.
Bits & pieces today.
Want to get a release out RSN, but I'm waiting for the previous release to finally reach Debian testing, which should happen on Saturday. Luckily I hear the beach house has wifi, so I will probably end up cutting the release from there. Only other thing I might work on next week is updating to yesod 1.2.
Yeah, Java hacking today. I have something that I think should deal with the ?Android app permission denial on startup problem. Added a "Open WebApp" item to the terminal's menu, which should behave as advertised. This is available in the Android daily build now, if your device has that problem.
I was not able to get the escape sequence hack to work. I had no difficulty modifying the terminal to send an intent to open an url when it received a custom escape sequence. But sending the intent just seemed to lock up the terminal for a minute without doing anything. No idea why. I had to propigate a context object in to the terminal emulator through several layers of objects. Perhaps that doesn't really work despite what I read on stackoverflow.
Anyway, that's all I have time to do. It would be nice if I, or some other interested developer who is more comfortable with Java, could write a custom Android frontend app, that embedded a web browser widget for the webapp, rather than abusing the terminal this way. OTOH, this way does provide the bonus of a pretty good terminal and git shell environment for Android to go with git-annex.
The fuzz testing found a file descriptor leak in the XMPP git push code. The assistant seems to hold up under fuzzing for quite a while now.
Have started trying to work around some versions of Android not letting
the
am command be used by regular users to open a web browser on an URL.
Here is my current crazy plan: Hack the terminal emulator's title setting
code, to get a new escape sequence that requests an URL be opened. This
assumes I can just use
startActivity() from inside the app and it will
work. This may sound a little weird, but it avoids me needing to set up a
new communications channel from the assistant to the Java app. Best of all,
I have to write very little Java code. I last wrote Java code in 1995, so
writing much more is probably a good thing to avoid.
Fuzz tester has found several interesting bugs that I've now fixed. It's even found a bug in my fixes. Most of the problems the fuzz testing has found have had to do with direct mode merges, and automatic merge conflict resoltion. Turns out the second level of automatic merge conflict resolution (where the changes made to resolve a merge conflict themselves turn out conflict in a later merge) was buggy, for example.
So, didn't really work a lot today -- was not intending to work at all actually -- but have still accomplished a lot.
(Also, Tobias contributed dropboxannex .. I'll be curious to see what the use case for that is, if any!)
Got caught up on some bug reports yesterday. The main one was odd behavior of the assistant when the repository was in manual mode. A recent change to the preferred content expression caused it. But the expression was not broken. The problem was in the parser, which got the parentheses wrong in this case. I had to mostly rewrite the parser, unfortunately. I've tested the new one fairly extensively -- on the other hand this bug lurked in the old parser for several years (this same code is used for matching files with command-line parameters).
Just as I finished with that, I noticed another bug. Turns out git-cat-file doesn't reload the index after it's started. So last week's changes to make git-annex check the state of files in the index won't work when using the assistant. Luckily there was an easy workaround for this.
Today I finished up some robustness fixes, and added to the test suite checks for preferred content expressions, manual mode, etc.
I've started a stress test, syncing 2 repositories over XMPP, with the fuzz tester running in each to create lots of changes to keep in sync.
The Android app should work on some more devices now, where hard linking to busybox didn't work. Now it installs itself using symlinks.
Pushed a point release so
cabal install git-annex works again. And,
I'm really happy to see that the 4.20130521 release has autobuilt on all
Debian architectures, and will soon be replacing the old 3.20120629 version
in testing. (Well, once a libffi transition completes..)
TobiasTheMachine has done it again: googledriveannex
I spent most of today building a fuzz tester for the assistant.
git annex
fuzztest will (once you find the special runes to allow it to run) create
random files in the repository, move them around, delete them, move
directory trees around, etc. The plan is to use this to run some long
duration tests with eg, XMPP, to make sure the assistant keeps things
in shape after a lot of activity. It logs in machine-readable format,
so if it turns up a bug I may even be able to use it to reproduce the same
bug (fingers crossed).
I was able to use QuickCheck to generate random data for some parts of the fuzz tester. (Though the actual file names it uses are not generated using QuickCheck.) Liked this part:
instance Arbitrary FuzzAction where arbitrary = frequency [ (100, FuzzAdd <$> arbitrary) , (10, FuzzDelete <$> arbitrary) , (10, FuzzMove <$> arbitrary <*> arbitrary) , (10, FuzzModify <$> arbitrary) , (10, FuzzDeleteDir <$> arbitrary) , (10, FuzzMoveDir <$> arbitrary <*> arbitrary) , (10, FuzzPause <$> arbitrary) ]
Tobias has been busy again today, creating a flickrannex special remote! Meanwhile, I'm thinking about providing a ?more complete interface so that special remote programs not written in Haskell can do some of the things the hook special remote's simplicity doesn't allow.
Finally realized last night that the main problem with the XMPP push code was an inversion of control. Reworked it so now there are two new threads, XMPPSendpack and XMPPReceivePack, each with their own queue of push initiation requests, that run the pushes. This is a lot easier to understand, probably less buggy, and lets it apply some smarts to squash duplicate actions and pick the best request to handle next.
Also made the XMPP client send pings to detect when it has been disconnected from the server. Currently every 120 seconds, though that may change. Testing showed that without this, it did not notice (for at least 20 minutes) when it lost routing to the server. Not sure why -- I'd think the TCP connections should break and this throw an error -- but this will also handle any idle disconnection problems that some XMPP servers might have.
While writing that, I found myself writing this jem using async, which has a comment much longer than the code, but basically we get 4 threads that are all linked, so when any dies, all do.
pinger `concurrently` sender `concurrently` receiver
Anyway, I need to run some long-running XMPP push tests to see if I've really ironed out all the bugs.
Got the bugfix release out.
Tobias contributed megaannex, which allows using mega.co.nz as a special remote. Someone should do this with Flickr, using filr. I have improved the hook special remote to make it easier to create and use reusable programs like megaannex.
But, I am too busy rewriting lots of the XMPP code to join in the special remote fun. Spent all last night staring at protocol traces and tests, and came to the conclusion that it's working well at the basic communication level, but there are a lot of bugs above that level. This mostly shows up as one side refusing to push changes made to its tree, although it will happily merge in changes sent from the other side.
The NetMessanger code, which handles routing messages to git commands and queuing other messages, seems to be just wrong. This is code I wrote in the fall, and have basically not touched since. And it shows. Spent 4 hours this morning rewriting it. Went all Erlang and implemented message inboxes using STM. I'm much more confident it won't drop messages on the floor, which the old code certainly did do sometimes.
Added a check to avoid unnecessary pushes over XMPP. Unfortunately, this required changing the protocol in a way that will make previous versions of git-annex refuse to accept any pushes advertised by this version. Could not find a way around that, but there were so many unnecessary pushes happening (and possibly contributing to other problems) that it seemed worth the upgrade pain.
Will be beating on XMPP a bit more. There is one problem I was seeing
last night that I cannot reproduce now. It may have been masked or even
fixed by these changes, but I need to verify that, or put in a workaround.
It seemed that sometimes this code in
runPush would run the setup
and the action, but either the action blocked forever, or an exception
got through and caused the cleanup not to be run.
r <- E.bracket_ setup cleanup <~> a
Worked on several important bug fixes today. One affects automatic merge confict resolution, and can case data loss in direct mode, so I will be making a release with the fix tomorrow.
Practiced TDD today, and good thing too. The new improved test suite turned up a really subtle bug involving the git-annex branch vector clocks-ish code, which I also fixed.
Also, fixes to the OSX autobuilds. One of them had a broken gpg, which is now fixed. The other one is successfully building again. And, I'm switching the Linux autobuilds to build against Debian stable, since testing has a new version of libc now, which would make the autobuilds not work on older systems. Getting an amd64 chroot into shape is needing rather a lot of backporting of build dependencies, which I already did for i386.
Today I had to change the implementation of the Annex monad. The old one turned out to be buggy around exception handling -- changes to state recorded by code that ran in an exception handler were discarded when it threw an exception. Changed from a StateT monad to a ReaderT with a MVar. Really deep-level change, but it went off without a hitch!
Other than that it was a bug catch up day. Almost entirely caught up once more.
git-annex is now autobuilt for Windows on the same Jenkins farm that builds msysgit. Thanks for Yury V. Zaytsev for providing that! Spent about half of today setting up the build.
Got the test suite to pass in direct mode, and indeed in direct mode
on a FAT file system. Had to fix one corner case in direct mode
git annex
add. Unfortunately it still doesn't work on Android; somehow
git clone
of a local repository is broken there. Also got the test suite to build,
and run on Windows, though it fails pretty miserably.
Made a release.
I am firming up some ideas for post-kickstarter. More on that later.
In the process of setting up a Windows autobuilder, using the same jenkins installation that is used to autobuild msysgit.
Laid some groundwork for porting the test suite to Windows, and getting it
working in direct mode. That's not complete, but even starting to run the
test suite in direct mode and looking at all the failures (many of them
benign, like files not being symlinks) highlighted something
I have been meaning to look into for quite a while: Why, in direct mode,
git-annex doesn't operate on data staged in the index, but requires you
commit changes to files before it'll see them. That's an annoying
difference between direct and indirect modes.
It turned out that I introduced this behavior back on
January 5th, working around a nasty
bug I didn't understand. Bad Joey, should have root caused the bug at the
time! But the commit says I was stuck on it for hours, and it was
presenting as if it was a bug in
git cat-file itself, so ok. Anyway,
I quickly got to the bottom of it today, fixed the underlying bug (which
was in git-annex, not git itself), and got rid of the workaround and its
undesired consequences. Much better.
The test suite is turning up some other minor problems with direct mode. Should have found time to port it earlier.
Also, may have fixed the issue that was preventing GTalk from working on Android. (Missing DNS library so it didn't do SRV lookups right.)
The?
Spent some time today to get caught up on bug reports and website traffic. Fixed a few things.
Did end up working on Windows for a while too. I got
git annex drop
working. But nothing that moves content quite works yet..
I've run into a stumbling block with
rsync. It thinks that
C:\repo is a path on a ssh server named "C". Seems I will need to translate
native windows paths to unix-style paths when running rsync.
It's remarkable that a bad decision made in 1982 can cause me to waste an
entire day in 2013. Yes,
/ vs
\ fun time. Even though I long ago
converted git-annex to use the haskell
</> operator wherever it builds
up paths (which transparently handles either type of separator), I still
spent most of today dealing with it. Including some libraries I use that
get it wrong. Adding to the fun is that git uses
/ internally, even on
Windows, so Windows separated paths have to be converted when being fed
into git.
Anyway,
git annex add now works on Windows. So does
git annex find,
and
git annex whereis, and probably most query stuff.
Today was very un-fun and left me with a splitting headache, so I will certainly not be working on the Windows port tomorrow.
After working on it all day, git-annex now builds on Windows!
Even better,
git annex init works. So does
git annex status, and
probably more. Not
git annex add yet, so I wasn't able to try much more.
I didn't have to add many stubs today, either. Many of the missing Windows features were only used in code paths that made git-annex faster, but I could fall back to a slower code path on Windows.
The things that are most problimatic so far:
- POSIX file locking. This is used in git-annex in several places to make it safe when multiple git-annex processes are running. I put in really horrible dotfile type locking in the Windows code paths, but I don't trust it at all of course.
- There is, apparently, no way to set an environment variable in Windows from Haskell. It is only possible to set up a new process' environment before starting it. Luckily most of the really crucial environment variable stuff in git-annex is of this latter sort, but there were a few places I had to stub out code that tries to manipulate git-annex's own environment.
The
windows branch has a diff of 2089 lines. It add 88 ifdefs to the code
base. Only 12 functions are stubbed out on Windows. This could be so much
worse.
Next step: Get the test suite to build. Currently ifdefed out because it
uses some stuff like
setEnv and
changeWorkingDirectory that I don't know
how to do in Windows yet.
Set up my Windows development environment. For future reference, I've installed:
- haskell platform for windows
- cygwin
- gcc and a full C toolchain in cygwin
- git from upstream (probably git-annex will use this)
- git in cygwin (the other git was not visible inside cygwin)
- vim in cygwin
- vim from upstream, as the cygwin vim is not very pleasant to use
- openssh in cygwin (seems to be missing a ssh server)
- rsync in cygwin
- Everything that
cabal install git-annexis able to install successfully.
This includes all the libraries needed to build regular git-annex, but not the webapp. Good start though.
Result basically feels like a linux system that can't decide which way slashes in paths go. :P I've never used Cygwin before (I last used a Windows machine in 2003 for that matter), and it's a fairly impressive hack.
Fixed up git-annex's configure program to run on Windows (or, at least, in Cygwin), and have started getting git-annex to build.
For now, I'm mostly stubbing out functions that use unix stuff. Gotten the first 44 of 300 source files to build this way.
Once I get it to build, if only with stubs, I'll have a good idea about all the things I need to find Windows equivilants of. Hopefully most of it will be provided by.
So that's the plan. There is a possible shortcut, rather than doing a full port. It seems like it would probably not be too hard to rebuild ghc inside Cygwin, and the resulting ghc would probably have a full POSIX emulation layer going through cygwin. From ghc's documentation, it looks like that's how ghc used to be built at some point in the past, so it would probably not be too hard to build it that way. With such a cygwin ghc, git-annex would probably build with little or no changes. However, it would be a git-annex targeting Cygwin, and not really a native Windows port. So it'd see Cygwin's emulated POSIX filesystem paths, etc. That seems probably not ideal for most windows users.. but if I get really stuck I may go back and try this method.
It all came together for Android today. Went from a sort of working app to a fully working app!
- rsync.net works.
- Box.com appears to work -- at least it's failing with the same timeout I get on my linux box here behind the firewall of dialup doom.
- XMPP is working too!
These all needed various little fixes. Like loading TLS certificates from where they're stored on Android, and ensuring that totally crazy file permissions from Android (----rwxr-x for files?!) don't leak out into rsync repositories. Mostly though, it all just fell into place today. Wonderful..
The Android autobuild is updated with all of today's work, so try it out.
Fixed a nasty bug that affects at least some FreeBSD systems. It misparsed
the output of
sha256, and thought every file had a SHA256 of "SHA256".
Added multiple layers of protection against checksum programs not having
the expected output format.
Lots more building and rebuilding today of Android libs than I wanted to do. Finally have a completly clean build, which might be able to open TCP connections. Will test tomorrow.
In the meantime, I fired up the evil twin of my development laptop. It's identical, except it runs Windows.
I installed the Haskell Platform for Windows on it, and removed some of the bloatware to free up disk space and memory for development. While a rather disgusting experience, I certainly have a usable Haskell development environment on this OS a lot faster than I did on Android! Cabal is happily installing some stuff, and other stuff wants me to install Cygwin.
So, the clock on my month of working on a Windows port starts now. Since I've already done rather a lot of ground work that was necessary for a Windows port (direct mode, crippled filesystem support), and for general sanity and to keep everything else from screeching to a halt, I plan to only spend half my time messing with Windows over the next 30 days.
Put in a fix for
getprotobyname apparently not returning anything for
"tcp" on Android. This might fix all the special remotes there, but I don't
know yet, because I have to rebuild a lot of Haskell libraries to try it.
So, I spent most of today writing a script to build all the Haskell libraries for Android from scratch, with all my patches.
This seems a very auspicious day to have finally gotten the Android app doing something useful! I've fixed the last bugs with using it to set up a remote ssh server, which is all I need to make my Android tablet sync photos I take with a repository on my laptop.
I set this up entirely in the GUI, except for needing to switch to the terminal twice to enter my laptop's password.
How fast is it? Even several minute long videos transfer before I can
switch from the camera app to the webapp. To get this screenshot with it in
the process of syncing, I had to take a dozen pictures in a minute. Nice
problem to have.
Have fun trying this out for yourself after tonight's autobuilds. But a
warning: One of the bugs I fixed today had to be fixed in
git-annex-shell,
as run on the ssh server that the Android connects to. So the Android app
will only work with ssh servers running a new enough version of git-annex.
Worked on geting git-annex into Debian testing, which is needed before the wheezy backport can go in. Think I've worked around most of the issues that were keeping it from building on various architectures.
Caught up on some bug reports and fixed some of them.
Created a backport of the latest git-annex release for Debian 7.0 wheezy. Needed to backport a dozen haskell dependencies, but not too bad. This will be available in the backports repository once Debian starts accepting new packages again. I plan to keep the backport up-to-date as I make new releases.
The cheap Android tablet I bought to do this last Android push with came pre-rooted from the factory. This may be why I have not seen this bug: ?Android app permission denial on startup. If you have Android 4.2.2 or a similar version, your testing would be helpful for me to know if this is a widespread problem. I have an idea about a way to work around the problem, but it involves writing Java code, and probably polling a file, ugh.
Got S3 support to build for Android. Probably fails to work due to the same network stack problems affecting WebDAV and Jabber.
Got removable media mount detection working on Android. Bionic has an
amusing stub for
getmntent that prints out "FIX ME! implement
getmntent()". But,
/proc/mounts is there, so I just parse it.
Also enabled the app's
WRITE_MEDIA_STORAGE permission to allow
access to removable media. However, this didn't seem to do anything.
Several fixes to make the Android webapp be able to set up repositories on
remote ssh servers. However, it fails at the last hurdle with what
looks like a
git-annex-shell communication problem. Almost there..
There's a new page Android that documents using git-annex on Android in detail.
The Android app now opens the webapp when a terminal window is opened. This is good enough for trying it out easily, but far from ideal.
Fixed an EvilSplicer bug that corrupted newlines in the static files served by the webapp. Now the icons in the webapp display properly, and the javascript works.
Made the startup screen default to
/sdcard/annex for the repository
location, and also have a button to set up a camera repository. The camera
repository is put in the "source" preferred content group, so it will only
hang onto photos and videos until they're uploaded off the Android device.
Quite a lot of other small fixes on Android. At this point I've tested the following works:
- Starting webapp.
- Making a repository, adding files.
- All the basic webapp UI.
However, I was not able to add any remote repository using only the webapp, due to some more problems with the network stack.
- Jabber and Webdav don't quite work ("getProtocolByname: does not exist (no such protocol name: tcp)").
- SSH server fails. ("Network/Socket/Types.hsc:(881,3)-(897,61): Non-exhaustive patterns in case") I suspect it will work if I disable the DNS expansion code.
So, that's the next thing that needs to be tackled.
If you'd like to play with it in its current state, I've updated the Android builds to incorporate all my work so far.
I fixed what I thought was keeping the webapp from working on Android, but
then it started segfaulting every time it was started. Eventually I
determined this segfault happened whenever haskell code called
getaddrinfo. I don't know why. This is particularly weird since I had
a demo web server that used
getaddrinfo working way back in
day 201 real Android wrapup. Anyway, I worked around it by not using
getaddrinfo on Android.
Then I spent 3 hours stuck, because the webapp seemed to run, but
nothing could connect to the port it was on. Was it a firewall? Was
the Haskell threaded runtime's use of
accept() broken? I went all the way
down to the raw system calls, and back, only to finally notice I had
netstat
available on my Android. Which showed it was not listening to the port I
thought it was!
Seems that
ntohs and
htons are broken somehow. To get the
screenshot, I fixed up the port manually. Have a build running that
should work around the issue.
Anyway, the webapp works on Android!
Pushed out a release today. Looking back over April, I'm happy with it as a bug fix and stabilization month. Wish I'd finished the Android app in April, but let's see what happens tomorrow.
Recorded part of a screencast on using Archive.org, but
recordmydesktop
lost the second part. Grr. Will work on that later.
Took 2 days in a row off, because I noticed I have forgotten to do that since February, or possibly earlier, not counting trips. Whoops!
Also, I was feeling overwhelmed with the complexity of fixing XMPP to not be buggy when there are multiple separate repos using the same XMPP account. Let my subconscious work on that, and last night it served up the solution, in detail. Built it today.
It's only a partial solution, really. If you want to use the same XMPP account for multiple separate repositories, you cannot use the "Share with your other devices" option to pair your devices. That's because XMPP pairing assumes all your devices are using the same XMPP account, in order to avoid needing to confirm on every device each time you add a new device. The UI is clear about that, and it avoids complexity, so I'm ok with that.
But, if you want to instead use "Share with a friend", you now can use the same XMPP account for as many separate repositories as you like. The assistant now ignores pushes from repositories it doesn't know about. Before, it would merge them all together without warning.
While I was testing that, I think I found out the real reason why XMPP
pushes have seemed a little unreliable. It turns out to not be an XMPP
issue at all! Instead, the merger was simply not always
noticing when
git receive-pack updated a ref, and not merging it into
master. That was easily fixed.
Adam Spiers has been getting a
.gitignore query interface suitable for
the assistant to use into
git, and he tells me it's landed in
I should soon check that out and get the assistant using it. But first,
Android app!
Turns out my old Droid has such an old version of Android (2.2) that it doesn't work with any binaries produced by my haskell cross-compiler. I think it's using a symbol not in its version of libc. Since upgrading this particular phone is a ugly process and the hardware is dying anyway (bad USB power connecter), I have given up on using it, and ordered an Android tablet instead to use for testing. Until that arrives, no Android. Bah. Wanted to get the Android app working in April.
Instead, today I worked on making the webapp require less redundant password entry when adding multiple repositories using the same cloud provider. This is especially needed for the Internet Archive, since users will often want to have quite a few repositories, for different IA items. Implemented it for box.com, and Amazon too.
Francois Marier has built an Ubuntu PPA for git-annex, containing the current version, with the assistant and webapp. It's targeted at Precise, but I think will probably also work with newer releases.
Probably while I'm waiting to work on Android again, I will try to improve the situation with using a single XMPP account for multiple repositories. Spent a while today thinking through ways to improve the design, and have some ideas.
Quiet day. Only did minor things, like adding webapp UI for changing the
directory used by Internet Archive remotes, and splitting out an
enableremote command from
initremote.
My Android development environment is set up and ready to go on my Motorola Droid. The current Android build of git-annex fails to link at run time, so my work is cut out for me. Probably broke something while enabling XMPP?
Very productive & long day today, spent adding a new feature to the webapp: Internet Archive support!
git-annex already supported using archive.org via its S3 special remotes, so this is just a nice UI around that.
How does it decide which files to publish on archive.org? Well, the item has a unique name, which is based on the description field. Any files located in a directory with that name will be uploaded to that item. (This is done via a new preferred content expression I added.)
So, you can have one repository with multiple IA items attached, and sort files between them however you like. I plan to make a screencast eventually demoing that.
Another interesting use case, once the Android webapp is done, would be add a repository on the DCIM directory, set the archive.org repository to prefer all content, and bam, you have a phone or tablet that auto-publishes and archives every picture it takes.
Another nice little feature added today is that whenever a file is uploaded
to the Internet Archive, its public url is automatically recorded, same
as if you'd ran
git annex addurl. So any users who can clone your
repository can download the files from archive.org, without needing any
login or password info. This makes the Internet Archive a nice way to
publish the large files associated with a public git repository.
Working on assistant's performance when it has to add a whole lot of files (10k to 100k).
Improved behavior in several ways, including fixing display of the alert in the webapp when the default inotify limit of 8192 directories is exceeded.
Created a new TList data type, a transactional DList. Much nicer implementation than the TChan based thing it was using to keep track of the changes, although it only improved runtime and memory usage a little bit. The way that this is internally storing a function in STM and modifying that function to add items to the list is way cool.
Other tuning seems to have decreased the time it would take to import 100k files from somewhere in the range of a full day (too long to wait to see), to around 3.5 hours. I don't know if that's good, but it's certainly better.
There seem to be a steady state of enough bug reports coming in that I can work on them whenever I'm not working on anything else. As I did all day today.
This doesn't bother me if the bug reports are of real bugs that I can reproduce and fix, but I'm spending a lot of time currently following up to messages and asking simple questions like "what version number" and "can I please see the whole log file". And just trying to guess what a vague problem report means and read people's minds to get to a definite bug with a test case that I can then fix.
I've noticed the overall quality of bug reports nosedive over the past several months. My guess is this means that git-annex has found a less technical audience. I need to find something to do about this.
With that whining out of the way ... I fixed a pretty ugly bug on FAT/Android today, and I am 100% caught up on messages right now!
Got the OSX autobuilder back running, and finally got a OSX build up for the 4.20130417 release. Also fixed the OSX app build machinery to handle rpath.
Made the assistant (and
git annex sync) sync with git remotes that have
annex-ignore set. So,
annex-ignore is only used to prevent using
the annex of a remote, not syncing with it. The benefit of this change
is that it'll make the assistant sync the local git repository with
a git remote that is on a server that does not have git-annex installed.
It can even sync to github.
Worked around more breakage on misconfigured systems that don't have GECOS information.
... And other bug fixes and bug triage.
Ported all the C libraries needed for XMPP to Android. (gnutls, libgcrypt, libgpg-error, nettle, xml2, gsasl, etc). Finally got it all to link. What a pain.
Bonus: Local pairing support builds for Android now, seems recent changes to the network library for WebDAV also fixed it.
Today was not a work day for me, but I did get a chance to install git-annex in real life while visiting. Was happy to download the standalone Linux tarball and see that it could be unpacked, and git-annex webapp started just by clicking around in the GUI. And in very short order got it set up.
I was especially pleased to see my laptop noticed this new repository had appeared on the network via XMPP push, and started immediately uploading files to my rsync.net transfer repository so the new repository could get them.
Did notice that the standalone tarball neglected to install a FDO menu file. Fixed that, and some other minor issues I noticed.
I also got a brief chance to try the Android webapp. It fails to start;
apparently
getaddrinfo doesn't like the flags passed to it and is
failing. As failure modes go, this isn't at all bad. I can certainly work
around it with some hardcoded port numbers, but I want to fix it the right
way. Have ordered a replacement battery for my dead phone so I can use it
for Android testing.
Got WebDAV enabled in the Android build. Had to deal with some system calls not available in Android's libc.
New poll: Android default directory
Finished the last EvilSplicer tweak and other fixes to make the Android webapp build without any hand-holding.
Currently setting up the Android autobuilder to include the webapp in its builds. To make this work I had to set up a new chroot with all the right stuff installed.
Investigated how to make the Android webapp open a web browser when run.
As far as I can tell (without access to an Android device right now),
am start -a android.intent.action.VIEW -d should do
it.
Seems that git 1.8.2 broke the assistant. I've put in a fix but have not yet tested it.
Late last night, I successfully built the full webapp for Android!
That was with several manual modifications to the generated code, which I still need to automate. And I need to set up the autobuilder properly still. And I need to find a way to make the webapp open Android's web browser to URL. So it'll be a while yet until a package is available to try. But what a milestone!
The point I was stuck on all day yesterday was generated code that looked like this:
(toHtml (\ u_a2ehE -> urender_a2ehD u_a2ehE [] (CloseAlert aid)))));
That just couldn't type check at all. Most puzzling. My best guess is that
u_a2ehE is the dictionary GHC passes internally to make a typeclass work,
which somehow leaked out and became visible. Although
I can't rule out that I may have messed something up in my build environment.
The EvilSplicer has a hack in it that finds such code and converts it to
something like this:
(toHtml (flip urender_a2ehD [] (CloseAlert aid)))));
I wrote some more about the process of the Android port in my personal blog: Template Haskell on impossible architectures
Release day today. The OSX builds are both not available yet for this release, hopefully will come out soon.
Several bug fixes today, and got mostly caught up on recent messages. Still have a backlog of two known bugs that I cannot reproduce well enough to have worked on, but I am thinking I will make a release tomorrow. There have been a lot of changes in the 10 days since the last release.
I am, frustratingly, stuck building the webapp on Android with no forward progress today (and last night) after such a productive day yesterday.
The expanded Template Haskell code of the webapp fails to compile, whereever type safe urls are used.
Assistant/WebApp/Types.hs:95:63: Couldn't match expected type `Route WebApp -> t2' with actual type `Text' The function `urender_a1qcK' is applied to three arguments, but its type `Route WebApp -> [(Text, Text)] -> Text' has only two In the expression: urender_a1qcK u_a1qcL [] LogR In the first argument of `toHtml', namely `(\ u_a1qcL -> urender_a1qcK u_a1qcL [] LogR)'
My best guess is this is a mismatch between the versions of yesod (or other libraries) used for the native and cross compiled ghc's. So I've been slowly trying to get a fully matched set of versions in between working on bugs.
Back to really working toward an Android webapp now. I have been improving the EvilSplicer, and the build machinery, and build environment all day. Slow but steady progress.
First milestone of the day was when I got
yesod-form to build with all
Template Haskell automatically expanded by the EvilSplicer. (With a few
manual fixups where it's buggy.)
At this point the Android build with the webapp enabled successfully builds several files containing Yesod code.. And I suspect I am very close to getting a first webapp build for Android.
Fixed a bug where the locked down ssh key that the assistant sets up to access the annex on a remote server was being used by ssh by default for all logins to that server.
That should not have happened. The locked down key is written to a filename
that ssh won't use at all, by default. But, I found code in gnome-keyring
that watches for
~/.ssh/*.pub to appear, and automatically adds all such
keys to the keyring. In at least some cases, probably when it has no other
key, it then tells ssh to go ahead and use that key. Astounding.
To avoid this, the assistant will store its keys in
~/.ssh/annex/
~/.ssh/git-annex/ instead. gnome-keyring does not look there (verified in
the source). If you use gnome-keyring and have set up a repository on a
remote server with the assistant, I'd recommend moving the keys it set up
and editing
~/.ssh/config to point to their new location.
gnome-keyring is not the only piece of software that has a bad interaction with git-annex. I've been working on a bug that makes git-annex fail to authenticate to ejabberd. ejabberd 2.1.10 got support for SCRAM-SHA-1, but its code violates the RFC, and chokes on an address attribute that the haskell XMPP library provides. I hope to get this fixed in ejabberd.
Also did some more work on the Evil Splicer today, integrating it into the
build of the Android app, and making it support incremental building.
Improved its code generation, and am at the milestone where it creates
valid haskell code for the entire
Assistant/WebApp/Types.hs file,
where Template Haskell expands 2 lines into 2300 lines of code!
Spent today bulding the Evil Splicer, a program that parses
ghc -ddump-splices
output, and uses it to expand Template Haskell splices in source code.
I hope to use this crazy hack to get the webapp working on Android.
This was a good opportunity to use the Parsec library for parsing the ghc output. I've never really used it before, but found it quite nice to work with. The learning curve, if you already know monads and applicatives, is about 5 minutes. And instead of ugly regular expressions, you can work with nice code that's easily composable and refactorable. Even the ugly bits come out well:
{- All lines of the splice result will start with the same - indent, which is stripped. Any other indentation is preserved. -} i <- lookAhead indent result <- unlines <$> many1 (string i >> restOfLine)
Anyway, it works.. sorta. The parser works great! The splices that ghc outputs are put into the right places in the source files, and formatted in a way that ghc is able to build. Often though, they contain code that doesn't actually build as-is. I'm working to fix up the code to get closer to buildable.
Meanwhile, guilhem has made ssh connection caching work for rsync special
remotes! It's very nice to have another developer working on git-annex.
Felt like spending my birthday working on git-annex. Thanks again to everyone who makes it possible for me to work on something I care about every day.
Did some work on
git annex addurl today. It had gotten broken in direct
mode (I think by an otherwise good and important bugfix). After fixing
that, I made it interoperate with the webapp. So if you have the webapp
open, it will display progress bars for downloads being run by
git annex
addurl.
This enhancement meshes nicely with a FlashGot script Andy contributed, which lets you queue up downloads into your annex from a web browser. Andy described how to set it up in this tip.
(I also looked briefly into ways to intercept a drag and drop of a link into the webapp and make it lauch a download for you. It doesn't seem that browsers allow javascript to override their standard behavior of loading links that are dropped into them. Probably good to prevent misuse, but it would be nice here...)
Also, I think I have fixed the progress bars displayed when downloading a file from an encrypted remote. I did this by hooking up existing download progress metering (that was only being used to display a download percentage in the console) into the location log, so the webapp can use it. So that was a lot easier than it could have been, but still a pretty large patch (500+ lines). Haven't tested this; should work.
Short day because I spent 3 hours this morning explaining free software and kickstarter to an accountant. And was away until 3 pm, so how did I get all this done‽
Eliot pointed out that shutting down the assistant could leave transfers
running. This happened because
git annex transferkeys is a separate
process, and so it was left to finish up any transfer that was in
process. I've made shutdown stop all transfers that the
assistant started. (Other paired computers could still be connecting to
make transfers even when the assistant is not running, and those are not
affected.)
Added sequence numbers to the XMPP messages used for git pushes. While
these numbers are not used yet, they're available for debugging, and will
help me determine if packets are lost or come out of order. So if you have
experienced problems with XMPP syncing sometimes failing, run tonight's
build of the assistant with
--debug (or turn on debugging in the webapp
configuration screen), and send me a log by email to
debuglogs201204@joeyh.name
Changed the way that autobuilds and manual builds report their version number. It now includes the date of the last commit, and the abbreviated commit ID, rather than being some random date after the last release.
Frederik found a bug using the assistant on a FAT filesystem. It didn't properly handle the files that git uses to stand-in for symlinks in that situation, and annexed those files. I've fixed this, and even moving around symlink stand-in files on a FAT filesystem now results in correct changes to symlinks being committed.
Did.
Developed a way to run the webapp on a remote or headless computer.
The webapp can now be started on a remote or headless computer, just
specify
--listen=address to make it listen on an address other than
localhost. It'll print out the URL to open to access it.
This doesn't use HTTPS yet, because it'd need to generate a certificate, and even if it generated a self-signed SSL certificate, there'd be no easy way for the browser to verify it and avoid a MITM.
So
--listen is a less secure but easier option; using ssh to forward
the webapp's port to the remote computer is more secure.
(I do have an idea for a way to do this entirely securely, making the webapp set up the ssh port forwarding, which I have written down in webapp.. but it would be rather complicated to implement.)
Made the webapp rescan for transfers after it's been used to change a repository's group. Would have been easy, but I had to chase down a cache invalidation bug.
Finally fixed the bug causing repeated checksumming when a direct mode file contains duplicate files. I may need to add some cleaning of stale inode caches eventually.
Meanwhile, Guilhem made
git annex initremote use higher quality entropy,
with
--fast getting back to the old behavior of urandom quality entropy.
The assistant doesn't use high quality entropy since I have no way to
prompt when the user would need to generate more. I did have a fun idea to
deal with this: Make a javascript game, that the user can play while
waiting, which would generate enropy nicely. Maybe one day..
Also made a small but significant change to ?archive directory handling.
Now the assistant syncs files that are in
archive directories like any
other file, until they reach an archive repository. Then they get dropped
from all the clients. This way, users who don't set up archive repositories
don't need to know about this special case, and users who do want to use
them can, with no extra configuration.
After recent changes, the preferred content expression for transfer repositories is becoming a bit unweidly, at 212 characters. Probably time to add support for macros..
(not (inallgroup=client and copies=client:2) and (((exclude=*/archive/* and exclude=archive/*) or (not (copies=archive:1 or copies=smallarchive:1))) or (not copies=semitrusted+:1))) or (not copies=semitrusted+:1)
Still, it's pretty great how much this little language lets me express, so easily.
Made a release today. Releasing has sure gotten easier with all the autobuilds to use!
I am now using git-annex to share files with my mom. Here's how the webapp looks for our family's repository. Soon several of us will be using this repository.
We're using XMPP and rsync.net, so pretty standard setup much like shown in my last screencast.
Real-world deployments help find bugs, and I found a few:
If you're running the webapp in
w3mon a remote computer to set it up, some forms are lacking submit buttons. This must be a issue with Bootstrap, or HTML5, I guess. I switched to
lynxand it offers a way to submit forms that lack an explicit button.
Progress bars for downloads from encrypted rsync repos don't update during the actual download, but only when gpg is decrypting the downloaded file.
XMPP pushes sometimes fail still. Especially when your mom's computer is saturating its limited outgoing network connection uploading hundreds of photos. I have not yet determined if this is a packet loss/corruption issue, or if the XMPP messages are getting out of order. My gut feeling is it's the latter, in which can I can fix this pretty easily by adding sequence numbers and some buffering for out of order packets. Or perhaps just make it retry failed pushes when this happens.
Anyway, I found it was useful to set up a regular git repository on a server to suppliment the git pushes over XMPP. It's helpful to have such a git repository anyway, so that clients can push to there when the other client(s) are not online to be pushed to directly over XMPP.
Got caught up on bug reports and made some bug fixes.
The one bug I was really worried about, a strange file corruption problem on Android, turned out not to be a bug in git-annex. (Nor is it a bug that will affect regular users.)
The only interesting bug fixed was a mixed case hash directory name collision when a repository is put on a VFAT filesystem (or other filesystem with similar semantics). I was able to fix that nicely; since such a repository will be in crippled filesystem mode due to other limitations of the filesystem, and so won't be using symlinks, it doesn't need to use the mixed case hash directory names.
Last night, finished up the repository removal code, and associated UI tweaks. It works very well.
Will probably make a release tomorrow.
Getting.
The xmpp screencast is at long last done!
Fixed a bug that could cause the assistant to unstage files from git sometimes. This happened because of a bad optimisation; adding a file when it's already present and unchanged was optimised to do nothing. But if the file had just been removed, and was put back, this resulted in the removal being staged, and the add not being staged. Ugly bug, although the assistant's daily sanity check automatically restaged the files.
Underlying that bug was a more important problem: git-annex does not always update working tree files atomically. So a crash at just the wrong instant could cause a file to be deleted from the working tree. I fixed that too; all changes to files in the working tree should now be staged in a temp file, which is renamed into place atomically.
Also made a bunch of improvements to the dashboard's transfer display, and to the handling of the underlying transfer queue.
Both the assistant and
git annex drop --auto refused to drop files from
untrusted repositories. Got that fixed.
Finally recorded the xmpp pairing screencast. In one perfect take, which
somehow
recordmydesktop lost the last 3 minutes of.
Argh! Anyway I'm editing it now, so, look for that screencast soon.
The goals for April poll results are in.
- There have been no votes at all for working on cloud remotes. Seems that git-annex supports enough cloud remotes already.
- A lot of people want the Android webapp port to be done, so I will probably spend some time on that this month.
- Interest in other various features is split. I am surprised how many want git-remote-gcrypt, compared to the features that would make syncing use less bandwidth. Doesn't git push over xmpp cover most of the use cases where git-remote-gcrypt would need to be used with the assistant?
- Nearly as many people as want features, want me to work on bug fixing and polishing what's already there. So I should probably continue to make screencasts, since they often force me to look at things with fresh eyes and see and fix problems. And of course, continue working on bugs as they're reported.
- I'm not sure what to make of the 10% who want me to add direct mode support. Since direct mode is already used by default, perhaps they want me to take time off?
(I certainly need to fix the ?Direct mode keeps re-checksuming duplicated files bug, and one other direct mode bug I discovered yesterday.)
I've posted a poll: goals for April
Today added UI to the webapp to delete repositories, which many users have requested. It can delete the local repository, with appropriate cautions and sanity checks:
More likely, you'll use it to remove a remote, which is done with no muss and no fuss, since that doesn't delete any data and the remote can always be added back if you change your mind.
It also has an option to fully delete the data on a remote. This doesn't actually delete the remote right away. All it does is marks the remote as untrusted[1], and configures it to not want any content. This causes all the content on it to be sucked off to whatever other repositories can hold it.
I had to adjust the preferred content expressions to make that work. For example, when deleting an archive drive, your local (client) repository does not normally want to hold all the data it has in "archive" directories. With the adjusted preferred content expressions, any data on an untrusted or dead repository is wanted. An interesting result is that once a client repository has moved content from an untrusted remote, it will decide it doesn't want it anymore, and shove it out to any other remote that will accept it. Which is just the behavior we want. All it took to get all this behavior is adding "or (not copies=semitrusted:1)" to the preferred content expressions!
For most special remotes, just sucking the data from them is sufficient to pretty well delete them. You'd want to delete an Amazon bucket or glacier once it's empty, and git repositories need to be fully deleted. Since this would need unique code for each type of special remote, and it would be code that a) deletes possibly large quantities of data with no real way to sanity check it and b) doesn't get run and tested very often; it's not something I'm thrilled about fully automating. However, I would like to make the assistant detect when all the content has been sucked out of a remote, and pop up at least a message prompting to finish the deletion. Future work.
[1] I really, really wanted to mark it dead, but letting puns drive code is probably a bad idea. I had no idea I'd get here when I started developing this feature this morning.. Honest!
Built a feature for power users today.
annex.largefiles can be
configured to specify what files
git annex add and the assistant should
put into the annex. It uses the same syntax as preferred content,
so arbitrarily complex expressions can be built.
For example, a game written in C with some large data files could include only 100kb or larger files, that are not C code:
annex.largefiles = largerthan=100kb and not (include=*.c or include=*.h)
The assistant will commit small files to git directly!
git annex add, being a lower level tool, skips small files
and leaves it up to you to
git add them as desired.
It's even possible to tell the assistant that no file is too large to be
committed directly to git.
git config annex.largefiles 'exclude=*'
The result should be much like using SparkleShare or dvcs-autosync.
Also today, made the remote ssh server checking code in the webapp deal with servers where the default shell is csh or some other non-POSIX shell.
Went out and tried for the second time to record a screencast demoing
setting up syncing between two computers using just Jabber and a cloud
remote. I can't record this one at home, or viewers would think git-annex
was crazy slow, when it's just my dialup.
But once again I encountered
bugs, and so I found myself working on progress bars today, unexpectedly.
Seems there was confusion in different parts of the progress bar code about whether an update contained the total number of bytes transferred, or the delta of bytes transferred since the last update. One way this bug showed up was progress bars that seemed to stick at 0% for a long time. Happened for most special remotes, although not for rsync or git remotes. In order to fix it comprehensively, I added a new BytesProcessed data type, that is explicitly a total quantity of bytes, not a delta. And checked and fixed all the places that used a delta as that type was knitted into the code.
(Note that this doesn't necessarily fix every problem with progress bars. Particularly, buffering can now cause progress bars to seem to run ahead of transfers, reaching 100% when data is still being uploaded. Still, they should be a lot better than before.)
I've just successfully run through the Jabber + Cloud remote setup process again, and it seems to be working great now. Maybe I'll still get the screencast recorded by the end of March.
Back from my trip. Spent today getting caught up.
Didn't do much while I was away. Pushed out a new release on Saturday.
Made
git annex usage display nicer.
Fixed some minor webapp bugs today. The interesting bug was a race that sometimes caused alerts or other notifications to be missed and not be immediately displayed if they occurred while a page was loading. You sometimes had to hit reload to see them, but not anymore!
Checked if the
push.default=simple change in upcoming git release will
affect git-annex. It shouldn't affect the assistant, or
git annex sync,
since they always list all branches to push explicitly. But if you
git push
manually, when the default changes that won't include the git-annex branch
in the push any longer.
Was!
I've been running some large transfers with the assistant, and looking at ways to improve performance. (I also found and fixed a zombie process leak.)
One thing I noticed is that the assistant pushes changes to the git-annex location log quite frequently during a batch transfer. If the files being transferred are reasonably sized, it'll be pushing once per file transfer. It would be good to reduce the number of pushes, but the pushes are important in some network topologies to inform other nodes when a file gets near to them, so they can get the file too.
Need to see if I can find a smart way to avoid some of the pushes. For example, if we've just downloaded a file, and are queuing uploads of the file to a remote, we probably don't need to push the git-annex branch to the remote.
Another performance problem is that.
I'd prefer to wait on doing that until I'm able to use Fay to generate Javascript from Haskell, because it would be much more pleasant.. will see.
Also a performance problem when performing lots of transfers, particularly
of small files, is that the assistant forks off a
git annex transferkey
for each transfer, and that has to in turn start up several git commands.
Today I have been working to change that, so the assistant maintains a
pool of transfer processes, and dispatches each transfer it wants to make
to a process from the pool. I just got all that to build, although untested
so far, in the
transferpools branch.
Triaged some of the older bugs and was able to close a lot of them.
Should mention that I will be in Boston this weekend, attending
LibrePlanet 2013.
Drop by and find me, I'll have git-annex stickers!
Did some UI work on the webapp. Minor stuff, but stuff that needed to be fixed up. Like inserting zero-width spaces into filenames displayed in it so very long filenames always get reasonably wrapped by the browser. (Perhaps there's a better way to do that with CSS?)
Is what I planned to do on git-annex today. Instead I fixed several bugs, but I'm drawing the line at blogging. Oops.
A long time ago I made Remote be an instance of the Ord typeclass, with an implementation that compared the costs of Remotes. That seemed like a good idea at the time, as it saved typing.. But at the time I was still making custom Read and Show instances too. I've since learned that this is not a good idea, and neither is making custom Ord instances, without deep thought about the possible sets of values in a type.
This Ord instance came around and bit me when I put Remotes into a Set, because now remotes with the same cost appeared to be in the Set even if they were not. Also affected putting Remotes into a Map. I noticed this when the webapp got confused about which Remotes were paused.
Rarely does a bug go this deep. I've fixed it comprehensively, first removing the Ord instance entirely, and fixing the places that wanted to order remotes by cost to do it explicitly. Then adding back an Ord instance that is much more sane. Also by checking the rest of the Ord (and Eq) instances in the code base (which were all ok).
While doing that, I found lots of places that kept remotes in Maps and Sets. All of it was probably subtly broken in one way or another before this fix, but it would be hard to say exactly how the bugs would manifest.
Also fought some with Google Talk today. Seem to be missing presence messages sometimes. Ugh. May have fixed it, but I've thought that before..
Made --debug include a sanitized dump of the XMPP protocol.
Made UI changes to encourage user to install git-annex on the server when adding a ssh server, rather than just funneling them through to rsync.
Fixed UI glitches in XMPP username/password prompt.
Switched all forms in the webapp to use POST, to avoid sensitive information leaking on the url bar.
Added an incremental backup group. Repositories in this group only want files that have not been backed up somewhere else yet.
I've reworked the UI of the webapp's dashboard. Now the repository list is included, above the transfers. I found I was spending a lot of time switching between the dashboard and repository list, so might as well combine them into a single screen. Yesod's type safe urls and widgets made this quite easy to do, despite it being a thousand line commit. Liking the result ... Even though it does make all my screencasts dated.
Rest of my time was spent on XMPP pairing UI. Using the same pages for both pairing with a friend and for self-pairing was confusing, so now the two options are split.
Now every time an XMPP git push is received or sent, it checks if there's a cloud repository configured, which is needed to send the contents of files. If not, it'll display this alert. Hopefully this will be enough to get users fully set up.
At this point I'm finally happy enough with the XMPP pairing + cloud repository setup process to film a screencast of it. As soon as I have some time & bandwidth someplace quiet. Expect one by the end of the month.
Fighting with javascript all day and racing to get a release out. Unstuck the OSX and Android autobuilders. Got drag and drop repository list reordering working great. Tons of changes in this release!
Also put up a new podcast.
Got the assistant to check again, just before starting a transfer, if the remote still wants the object. This should be all that's needed to handle the case where there is a transfer remote on the internet somewhere, and a locally paired client on the LAN. As long as the paired repository has a lower cost value, it will be sent any new file first, and if that is the only client, the file will not be sent to the transfer remote at all.
But.. locally paired repos did not have a lower cost set, at all. So I made their cost be set to 175 when they're created. Anyone who already did local pairing should make sure the Repositories list shows locally paired repositories above transfer remotes.
Which brought me to needing an easy way to reorder that list of remotes, which I plan to do by letting the user drag and drop remotes around, which will change their cost accordingly. Implementing that has two pain points:
Often a lot of remotes will have the same default cost value. So how to insert a remote in between two that have cost 100? This would be easy if git-annex didn't have these cost numbers, and instead just had an ordered list of remotes.. but it doesn't. Instead, dragging remotes in the list will sometimes need to change the costs of others, to make room to insert them in. It's BASIC renumbering all over again. So I wrote some code to do this with as little bother as possible.
Drag and drop means javascript. I got the basics going quickly with jquery-ui, only to get stuck for over an hour on some CSS issue that made lines from the list display all weird while being dragged. It is always something like this with javascript..
So I've got these 2 peices working, and even have the AJAX call firing, but it's not quite wired up just yet. Tomorrow.
Last night, revamped the web site, including making a videos page, which includes a new screencast introducing the git-annex assistant.
Worked on improving my Haskell development environment in vim.
hdevtools is an excellent but tricky thing to get working. Where before
it took around 30 seconds per compile for me to see type errors,
I now see them in under a second each time I save, and can also look up
types of any expression in the file. Since programming in Haskell is
mostly driven by reacting to type errors
this should speed me up a lot,
although it's not perfect. Unfortunatly, I got really caught up in tuning
my setup, and only finished doing that at 5:48 am.
Disasterously late this morning, fixed the assistant's
~/.ssh/git-annex-shell wrapper so it will work when the ssh key does
not force a command to be run. Also made the webapp behave better
when it's told to create a git repository that already exists.
After entirely too little sleep, I found a puzzling bug where copying files to a local repo fails once the inode cache has been invalidated. This turned out to involve running a check in the state monad of the wrong repository. A failure mode I'd never encountered before.
Only thing I had brains left to do today was to record another screencast, which is rendering now...
Got renaming fully optimised in the assistent in direct mode. I even got it to work for whole directory renames. I can drag files around all day in the file manager and the assistant often finishes committing the rename before the file manager updates. So much better than checksumming every single renamed file! Also, this means the assistant makes just 1 commit when a whole directory is renamed.
Last night I added a feature to
git annex status. It can now be asked to
only show the status of a single directory, rather than the whole annex.
All the regular file filtering switches work, so some neat commands
are possible. I like
git annex status . --in foo --not --in bar to see
how much data is in one remote but not another.
This morning, an important thought about ?smarter flood filling, that will avoid unnecessary uploads to transfer remotes when all that's needed to get the file to its destination is a transfer over the LAN. I found an easy way to make that work, at least in simple cases. Hoping to implement it soon.
Less fun, direct mode turns out to be somewhat buggy when files with
duplicate content are in the repository. Nothing fails, but
git annex
sync will re-checksum files each time it's run in this situation, and the
assistant will re-checksum files in certian cases. Need to work on this
soon too.
Trying to record screencasts demoing the assistant is really helping me see things that need to be fixed.
Got the version of the haskell TLS library in Debian fixed, backporting some changes to fix a botched security fix that made it reject all certificates. So WebDAV special remotes will work again on the next release.
Fixed some more problems around content being dropped when files are moved to archive directories, and gotten again when files are moved out.
Fixed some problems around USB drives. One was a real jaw-dropping bug: "git annex drop --from usbdrive" when the drive was not connected still updated the location log to indicate it did not have the file anymore! (Thank goodness for fsck..)
I've noticed that moving around files in direct mode repos is inneficient, because the assistant re-checksums the "new" file. One way to avoid that would be to have a lookup table from (inode, size, mtime) to key, but I don't have one, and would like to avoid adding one.
Instead, I have a cunning plan to deal with this heuristically. If the assistant can notice a file was removed and another file added at the same time, it can compare the (inode, size, mtime) to see if it's a rename, and avoid the checksum overhead.
The first step to getting there was to make the assistant better at batching together delete+add events into a single rename commit. I'm happy to say I've accomplished that, with no perceptable delay to commits.
And so we waited. Tick-tock, blink-blink, thirty seconds stretched themselves out one by one, a hole in human experience. -- The Bug
I think I've managed to fully track down the ?webapp hang. It is, apparently, a bug in the Warp web server's code intended to protect against the Slowloris attack. It assumes, incorrectly, that a web browser won't reuse a connection it's left idle for 30 seconds. Some bad error handling keeps a connection open with no thread to service it, leading to the hang.
Have put a 30 minute timeout into place as a workaround, and, unless a web browser sits on an idle connection for a full 30 minutes and then tries to reuse it, this should be sufficient.
I was chasing that bug, quietly, for 6 months. Would see it now and then, but not be able to reproduce it or get anywhere with analysis. I had nearly given up. If you enjoy stories like that, read Ellen Ullman's excellent book The Bug.
To discover that between the blinks of the machine’s shuttered eye—going on without pause or cease; simulated, imagined, but still not caught—was life.
Fixed the last XMPP bug I know of. Turns out it was not specific to XMPP at all; the assistant could forget to sync with any repository on startup under certain conditions.
Also fixed bugs in
git annex add and in the glob matching, and some more.
I've been working on some screencasts. More on them later.. But while doing them I found a perfect way to reliably reproduce the webapp hang that I've been chasing for half a year, and last saw at my presentation in Australia. Seems the old joke about bugs only reproducible during presentations is literally true here!
I have given this bug its ?own page at last, and have a tcpdump of it happening and everything. Am working on an hypotheses that it might be caused by Warp's slowloris attack prevention code being falsely triggered by the repeated hits the web browser makes as the webapp's display is updated.
More XMPP fixes. The most important change is that it now stores important messages, like push requests, and (re)sends them when a buddy's client sends XMPP presence. This makes XMPP syncing much more robust, all the clients do not need to already be connected when messages are initially sent, but can come and go. Also fixed a bug preventing syncing from working immediately after XMPP pairing. XMPP seems to be working well now; I only know of one minor bug.
Yesterday was all bug fixes, nothing to write about really.
Today I've been working on getting XMPP remotes to sync more reliably. I left some big holes when I stopped work on it in November:
- The assistant did not sync with XMPP remotes when it started up.
- .. Or when it detected a network reconnection.
- There was no way to trigger a full scan for transfers after receiving a push from an XMPP remote.
The asynchronous nature of git push over XMPP complicated doing this, but I've solved all 3 issues today.
Tracked down the bug that's been eluding me for days. It was indeed a race, and could result in a file being transferred into a direct mode repository and ending up in indirect mode. Was easy to fix once understood, just needed to update the direct mode mapping before starting the transfer.
While I was in there, I noticed another potential race, also in direct mode, where the watcher could decide to rewrite a symlink to fix its target, and at just the wrong time direct mode content could arrive in its place, and so get deleted. Fixed that too.
Seems likely there are some other direct mode races. I spent quite a while hammering on dealing with the indirect mode races with the assistant originally.
Next on my list is revisiting XMPP.
Verified that git push over XMPP works between multiple repositories that are sharing the same XMPP account. It does.
Seeing the XMPP setup process with fresh eyes, I found several places wording could be improved. Also, when the user goes in and configures (or reconfigures) an XMPP account, the next step is to do pairing, so it now redirects directly to there.
Next I need to make XMPP get back into sync after a network disconnection or when the assistant is restarted. This currently doesn't happen until a XMPP push is received due to a new change being made.
back burner: yesod-pure
Last night I made a yesod-pure branch, and did some exploratory conversion away from using Hamlet, of the Preferences page I built yesterday.
I was actually finding writing pure Blaze worked better than Hamlet, at first. Was able to refactor several things into functions that in Hamlet are duplicated over and over in my templates, and built some stuff that makes rendering type safe urls in pure Blaze not particularly ungainly. For example, this makes a submit button and a cancel button that redirects to another page:
buttons = toWidget $ \redir -> "Save Preferences" <>|<> redir ConfigurationR []
The catch is how to deal with widgets that need to be nested inside other html. It's not possible to do this both cleanly and maximally efficiently, with Blaze. For max efficiency, all the html before the widget should be emitted, and then the widget run, and then all html after it be emitted. To use Blaze, it would have to instead generate the full html, then split it around the widget, and then emit the parts, which is less efficient, doesn't stream, etc.
I guess that's the core of what Hamlet does; it allows a clean representation and due to running TH at build time, can convert this into an efficient (but ugly) html emitter.
So, I may give up on this experiment. Or I may make the webapp less than maximally fast at generating html and go on with it. After all, these sorts of optimisations are mostly aimed at high-volume websites, not local webapps.
Stuck on a bug or two, I instead built a new Preferences page:
The main reason I wanted that was to allow enabling debug logging at runtime. But I've also wanted to expose annex.diskreserve and annex.numcopies settings to the webapp user. Might as well let them control whether it auto-starts too.
Had some difficulty deciding where to put this. It could be considered additional configuration for the local repository, and so go in the local repository edit form. However, this stuff can only be configured for local repositories, and not remotes, and that same form is used to edit remotes, which would lead to inconsistent UI and complicate the code. Also, it might grow to include things not tied to any repository, like choice of key/value backends. So, I put the preferences on their own page.
Also, based on some useful feedback from testing the assistant with a large number of files, I made the assistant disable git-gc auto packing in repositories it sets up. (Like fsck, git-gc always seems to run exactly when you are in a hurry.) Instead, it'll pack at most once a day, and with a rather higher threshold for the number of loose objects.
I got yesod-pure fully working on Android...
As expected, this involved manually splicing some template haskell. I'm now confident I can port the git-annex webapp to Android this way, and that it will take about a week. Probably will start on that in a month or so. If anyone has some spare Android hardware they'd like to loan me, possibly sooner. (Returning loaner Asus Transformer tomorrow; thanks Mark.) Although I'm inclined to let the situation develop; we may just get a ghc-android that supports TH..
Also:
- Fixed several bugs in the Android installation process.
- Committed patches for all Haskell libraries I've modified to the git-annex git repo.
- Ran the test suite on Android. It found a problem; seems
git cloneof a local repository is broken in the Android environment.
Non-Android:
- Made the assistant check every hour if logs have grown larger than a megabyte, and rotate them to avoid using too much disk space.
- Avoided noise in log about typechanged objects when running git commit in direct mode repositories. Seems
git commithas no way to shut that up, so I had to /dev/null it.
- When run with
--debug, the assistant now logs more information about why it transfers or drops objects.
- Found and fixed a case where moving a file to an archive directory would not cause its content to be dropped.
- Working on a bug with the assistant where moving a file out of an archive directory in direct mode sometimes ends up with a symlink rather than a proper direct mode file. Have not gotten to the bottom of it entirely, but it's a race, and I think the race is between the direct mode mapping being updated, and the file being transferred.
Seems I am not done with the Android porting just yet after all. One more porting day..
Last night I managed to get all of Yesod to build for Android. I even successfully expanded some Template Haskell used in yesod-form. And am fairly confident I could manually expand all the TH in there, so it's actually useable without TH. Most of the TH is just commented out for now.
However, programs using Yesod didn't link; lots of missing symbols. I have been fighting to fix those all day today.
Finally, I managed to build the yesod-pure demo server,
and I have a working web server on Android! It listens for requests, it logs
them correctly, and it replies to requests. I did cripple yesod's routing
code in my hack-n-slash port of it, so it fails to display any pages,
but never has "Internal Server Error" in a web browser been such a sweet
sight.
At this point, I estimate about 1 or 2 weeks work to get to an Android webapp. I'd need to:
- More carefully port Yesod, manually expanding all Template Haskell as I went, rather than commenting it all out like I did this time.
- Either develop a tool to automatically expand Hamlet TH splices (preferred; seems doable), or convert all the webapp's templates to not use Hamlet.
I've modified 38 Haskell libraries so far to port them to Android. Mostly small hacks, but eep this is a lot of stuff to keep straight.
As well as making a new release, I rewrote most of the Makefile, so that it uses cabal to build git-annex. This avoids some duplication, and most importantly, means that the Makefile can auto-detect available libraries rather than needing to juggle build flags manually. Which was becoming a real pain.
I had avoided doing this before because cabal is slow for me on my little netbook. Adding ten seconds to every rebuild really does matter! But I came up with a hack to let me do incremental development builds without the cabal overhead, by intercepting and reusing the ghc command that cabal runs.
There was also cabal "fun" to get the Android build working with cabal.
And more fun involving building the test suite. For various reasons, I
decided to move the test suite into the git-annex binary. So you can run
git annex test at any time, any place, and it self-tests. That's a neat
trick I've seen one or two other programs do, and probably the nicest thing
to come out of what was otherwise a pretty yak shaving change that involved
babysitting builds all day.
An Android autobuilder is now set up to run nightly. At this point I don't see an immediate way to getting the webapp working on Android, so it's best to wait a month or two and see how things develop in Haskell land. So I'm moving on to other things.
Today:
- Fixed a nasty regression that made
*not match files in subdirectories. That broke the preferred content handling, among other things. I will be pushing out a new release soon.
- As a last Android thing (for now), made the Android app automatically run
git annex assistant --autostart, so you can manually set up an assistant-driven repository on Android, listing the repository in
.config/git-annex/autostart
- Made the webapp display any error message from
git initif it fails. This was the one remaining gap in the logging. One reason it could fail is if the system has a newer git in use, and
~/.gitconfigis configured with some options the older git bundled with git-annex doesn't like.
- Bumped the major version to 4, and annex.version will be set to 4 in new direct mode repositories. (But version 3 is otherwise still used, to avoid any upgrade pain.) This is to prevent old versions that don't understand direct mode from getting confused. I hope direct mode is finally complete, too, after the work to make it work on crippled filesystems this month.
- Misc other bugfixes etc. Backlog down to 43.
Wrote..
Set up an autobuilder for the linux standalone binaries. Did not get an Android autobuilder set up yet, but I did update the Android app with recent improvements, so upgrade.
Investigated further down paths to getting the webapp built for Android.
Since recent ghc versions support ghci and thus template haskell on arm, at least some of the time, I wonder what's keeping the ghc-android build from doing so? It might be due to it being a cross compiler. I tried recompiling it with the stage 2, native compiler enabled. While I was able to use that ghc binary on Android, it refused to run --interactive, claiming it was not built with that enabled. Don't really understand the ghc build system, so might have missed something.
Maybe I need to recompile ghc using the native ghc running on Android. But that would involve porting gcc and a lot of libraries and toolchain stuff to Android.
yesod-pure is an option, and I would not mind making all the code changes to use it, getting rid of template haskell entirely. (Probably around 1 thousand lines of code would need to be written, but most of it would be trivial conversion of hamlet templates.)
Question is, will yesod install at all without template haskell? Not easily.
vector,
monad-logger,
aeson,
shakespeare,
shakespeare-css,
shakespeare-js,
shakespeare-i18n,
hamletall use TH at build time. Hacked them all to just remove the TH parts.
The hack job on
yesod-corewas especially rough, involving things like 404 handlers. Did get it to build tho!
Still a dozen packages before I can build yesod, and then will try building this yesod-pure demo.
So it seems the Android app works pretty well on a variety of systems. Only report of 100% failure so far is on Cyanogenmod 7.2 (Android 2.3.7).
Worked today on some of the obvious bugs.
- Turns out that getEnvironment is broken on Android, returning no environment, which explains the weird git behavior where it complains that it cannot determine the username and email (because it sees no USER or HOST), and suggests setting them in the global git config (which it ignores, because it sees no HOME). Put in a work around for this that makes
git annex initmore pleasant, and opened a bug report on ghc-android.
- Made the Android app detect when it's been upgraded, and re-link all the commands, etc.
- Fixed the bug that made
git-annex assistanton Android re-add all existing files on startup.
- Enabled a few useful things in busybox. Including vi.
- Replaced the service notification icon with one with the git-annex logo.
- Made the terminal not close immediately when the shell exits, which should aid in debugging of certain types of crashes.
I want to set up an autobuilder for Android, but to do that I need to
install all the haskell libraries on my server. Since getting them built
for Android involved several days of hacking the first time, this will
be an opportunity to make sure I can replicate that. Hopefully in less time.
Well, it's built. Real Android app for git-annex.
When installed, this will open a terminal in which you have access to git-annex and all the git commands and busybox commands as well. No webapp yet, but command line users should feel right at home.
Please test it out, at least as far as installing it, opening the terminal,
and checking that you can run
git annex; I've only been able to test on
one Android device so far. I'm especially keen to know if it works with
newer versions of Android than 4.0.3. (I know it only supports arm based
Android, no x86 etc.) Please comment if you tried it.
Building this went mostly as planned, although I had about 12 builds of the app in the middle which crashed on startup with no error message ora logs. Still, it took only one day to put it all together, and I even had time to gimp up a quick icon. (Better icons welcome.)
Kevin thinks that my space-saving hack won't work on all Androiden, and he
may be right. If the
lib directory is on a different filesystem on some
devices, it will fail. But I used it for now anyhow. Thanks to the hack,
the 7.8 mb compressed .apk file installs to use around 23 mb of disk space.
Tomorrow: Why does
git-annex assistant on Android re-add all existing
files on startup?
Today's work:
- Fixed
git annex addof a modified file in direct mode.
- Fixed bugs in the inode sentinal file code added yesterday.
With some help from Kevin Boone, I now understand how KBOX works and how to use similar techniques to build my own standalone Android app that includes git-annex.
Kevin is using a cute hack; he ships a tarball and some other stuff as (pseudo-)library files (
libfoo.so), which are the only files the Android package manager deigns to install. Then the app runs one of these, which installs the programs.
This avoids needing to write Java code that extracts the programs from one of its assets and writes it to an executable file, which is the canonical way to do this sort of thing. But I noticed it has a benefit too (which KBOX does not yet exploit). Since the pseudo-library file is installed with the X bit set, if it's really a program, such as busybox or git-annex, that program can be run without needing to copy it to an executable file. This can save a lot of disk space. So, I'm planning to include all the binaries needed by git-annex as these pseudo-libraries.
- Got the Android Terminal Emulator to build. I will be basing my first git-annex Android app on this, since a terminal is needed until there's a webapp.
- Wasted several hours fighting with
Android.mkfiles to include my pseudo shared library. This abuse of Makefiles by the NDK is what CDBS wants to grow up to be.. or is it the other way around? Anyway, it sucks horribly, and I finally found a way to do it without modifying the file at all. Ugh.
- At this point, I can build a
git-annex.apkfile containing a
libgit-annex.so, and a
libbusybox.so, that can both be directly run. The plan from here is to give git-annex the ability to auto-install itself, and the other pseudo-libraries, when it's run as
libgit-annex.so.
Felt spread thin yesterday, as I was working on multiple things concurrently & bouncing around as compiles finished. Been working to get openssh to build for Android, which is quite a pain, starting with getting openssl to build and then dealing with the Cyanogenmod patches, some of which are necessary to build on Android and some of which break builds outside Cyanogenmod. At the same time was testing git-annex on Android. Found and fixed several more portability bugs while doing that. And on the back burner I was making some changes to the webapp..
(Forgot to commit my blog post yesterday too..)
Today, that all came together.
- When adding another local repository in the webapp, it now allows you to choose whether it should be combined with your current repository, or kept separate. Several people had requested a way to add local clones with the webapp, for various reasons, like wanting a backup repository, or wanting to make a repository on a NFS server, and this allows doing that.
More porting fun. FAT filesystems and other things used on Android can get all new inode numbers each time mounted. Made git-annex use a sentinal file to detect when this has happened, since in direct mode it compares inodes. (As a bonus this also makes copying direct mode repositories between filesystems work.)
Got openssh building for Android. Changed it to use $HOME/.ssh rather than trusting pwent.
Got git-annex's ssh connection caching working on Android. That needs a place where it can create a socket. When the repository is on a crippled filesystem, it instead puts the socket in a temporary directory set up on the filesystem where the git-annex program resides.
With ssh connection caching, transferring multiple files off my Android tablet screams! I was seeing 6.5 megabytes transferred per second, sustained over a whole month's worth of photos.
Next problem:
git annex assistant on Android is for some reason crashing
with a segfault on startup. Especially odd since
git annex watch works.
I'm so close to snap-photo-and-it-syncs-nirvana, but still so far away...
Pushed out a release yesterday mostly for a bug fix. I have to build git-annex 5 times now when releasing. Am wondering if I could get rid of the Linux 64 bit standalone build. The 32 bit build should run ok on 64 bit Linux systems, since it has all its own 32 bit libraries. What I really need to do is set up autobuilders for Linux and Android, like we have for OSX.
Today, dealt with all code that creates or looks at symlinks. Audited every bit of it, and converted all relevant parts to use a new abstraction layer that handles the pseudolink files git uses when core.symlinks=false. This is untested, but I'm quite happy with how it turned out.
Where next for Android? I want to spend a while testing command-line git-annex. After I'm sure it's really solid, I should try to get the webapp working, if possible.
I've heard rumors that Ubuntu's version of ghc somehow supports template haskell on arm, so I need to investigate that. If I am unable to get template haskell on arm, I would need to either wait for further developments, or try to expand yesod's template haskell to regular haskell and then build it on arm, or I could of course switch away from hamlet (using blaze-html instead is appealing in some ways) and use yesod in non-template-haskell mode entirely. One of these will work, for sure, only question is how much pain.
After getting the webapp working, there's still the issue of bundling it all up in an Android app that regular users can install.
Finished crippled filesystem support, except for symlink handling.
This was straightforward, just got lsof working in that mode, made
migrate copy key contents, and adapted the rsync special remote to
support it. Encrypted rsync special remotes have no more overhead on
crippled filesystems than normally. Un-encrypted rsync special remotes
have some added overhead, but less than encrypted remotes. Acceptable
for now.
I've now successfully run the assistant on a FAT filesystem.
Git handles symlinks on crippled filesystems by setting
core.symlinks=false and checking them out as files containing the link
text. So to finish up crippled filesystem support, git-annex needs to
do the same whenever it creates a symlink, and needs to read file contents
when it normally reads a symlink target.
There are rather a lot of calls to
createSymbolicLink,
readSymbolicLink,
getSymbolicLinkStatus,
isSymbolicLink, and
isSymLink
in the tree; only ones that are used in direct mode
need to be converted. This will take a while.
Checking whether something is a symlink, or where it points is especially tricky. How to tell if a small file in a git working tree is intended to be a symlink or not? Well, it can look at the content and see if it makes sense as a link text pointing at a git-annex key. As long as the possibility of false positives is ok. It might be possible, in some cases, to query git to verify if the object stored for that file is really a symlink, but that won't work if the file has been renamed, for example.
Converted some of the most commonly used symlink code to handle this.
Much more to do, but it basically works; I can
git annex get and
git
annex drop on FAT, and it works.
Unfortunately, got side-tracked when I discovered that the last release introduced a bug in direct mode. Due to the bug, "git annex get file; git annex drop file; git annex get file" would end up with the file being an indirect mode symlink to the content, rather than a direct mode file. No data loss, but not right. So, spent several hours fixing that reversion, which was caused by me stupidly fixing another bug at 5 am in the morning last week.. and I'll probably be pushing out another release tomorrow with the fix.
There are at least three problems with using git-annex
on
/sdcard on Android, or on a FAT filesystem, or on (to a first
approximation) Windows:
- symlinks
- hard links
- unix permissions
So, I've added an
annex.crippledfilesystem setting.
git annex init now
probes to see if all three are supported, and if not, enables that, as well
as direct mode.
In crippled filesystem mode, all the permissions settings are skipped. Most of them are only used to lock down content in the annex in indirect mode anyway, so no great loss.
There are several uses of hard links, most of which can be dealt with by making copies. The one use of permissions and hard links I absolutely needed to deal with was that they're used to lock down a file as it's being ingested into the annex. That can't be done on crippled filesystems, so I made it instead check the metadata of the file before and after to detect if it changed, the same way direct mode detects when files are modified. This is likely better than the old method anyway.
The other reason files are hardlinked while they're being ingested is that this allows running lsof on a single directory of files that are in the process of being added, to detect if anything has them open for write. I still need to adjust the lsof check to work in crippled filesystem mode. It seems this won't make it much slower to run lsof on the whole repository.
At this point, I can use git-annex with a repository on
/sdcard or a FAT
filesystem, and at least
git annex add works.
Still several things on the TODO list before crippled filesystem mode is
complete. The only one I'm scared about is making
git merge do something
sane when it wants to merge two trees full of symlinks, and the filesystem
doesn't let it create a symlink..
Ported all the utilities git-annex needs to run on Android: git, rsync, gnupg, dropbear (ssh client), busybox. Built a Makefile that can download, patch, and cross build these from source.
While all the utilities work, dropbear doesn't allow git-annex to use ssh connection caching, which is rather annoying especially since these systems tend to be rather slow and take a while to start up ssh connections. I'd sort of like to try to get openssh's client working on Android instead. Don't know how realistic that is.
Dealt with several parts of git-annex that assumed
/bin/sh exists,
so it instead uses
/system/bin/sh on Android. Also adapted
runshell
for Android.
Now I have a 8 mb compressed tarball for Android. Uncompressed it's 25 mb. This includes a lot of git and busybox commands that won't be used, so it could be trimmed down further. 16 mb of it is git-annex itself.
Instructions for using the Android tarball
This is for users who are rather brave, not afraid of command line and keyboard usage. Good first step.
I'm now successfully using git-annex at the command line on Android.
git annex watch works too.
For now, I'm using a git repository under
/data, which is on a real,
non-cripped filesystem, so symlinks work there.
There's still the issue of running without any symlinks on
/mnt/sdcard.
While direct mode gets most of the way, it still uses symlinks in a few
places, so some more work will be needed there. Also, git-annex uses hard
links to lock down files, which won't work on cripped filesystems.
Besides that, there's lots of minor porting, but no big show-stoppers currently.. Some of today's porting work:
Cross-compiled git for Android. While the Terminal IDE app has some git stuff, it's not complete and misses a lot of plumbing commands git-annex uses. My git build needs some tweaks to be relocatable without setting
GIT_EXEC_PATH, but it works.
Switched git-annex to use the Haskell glob library, rather than PCRE. This avoids needing libpcre, which simplifies installation on several platforms (including Android).
Made git-annex's
configurehardcode some settings when cross-compiling for Android, rather than probing the build system.
Android's built-in
lsofdoesn't support the -F option to use a machine-readable output format. So wrote a separate lsof output parser for the standard lsof output format. Unfortunatly, Android's lsof does not provide any information about where a file is open for read or write, so for safety, git-annex has to assume any file that's open might be written to, and avoid annexing it. It might be better to provide my own lsof eventually.
Thanks to hhm, who pointed me at KBOX, I have verified that I can build haskell programs that work on Android.
After hacking on it all day, I've succeeded in making an initial build of git-annex for Android. It links! It runs!
Which is not to say it's usable yet; for one thing I need to get a port of git before it can do anything useful. (Some of the other things git-annex needs, like ssh and sha256sum, are helpfully provided by KBOX.)
Next step will be to find or built a git port for Android. I know there's one in the "Terminal IDE" app. Once I can use git-annex at the command line on Android, I'll be able to test it out some (I can also port the test suite program and run it on Android), and get a feeling for what is needed to get the port to a usable command-line state.
And then on to the webapp, and an Android app, I suppose. So far, the port doesn't include the webapp, but does include the assistant. The webapp needs ghci/template haskell for arm. A few people have been reporting they have that working, but I don't yet.
Have been working on getting all the haskell libraries git-annex uses built with the android cross compiler. Difficulties so far are libraries that need tweaks to work with the new version of ghc, and some that use cabal in ways that break cross compilation. Haskell's network library was the last and most challenging of those.
At this point, I'm able to start trying to build git-annex for android. Here's the first try!
joey@gnu:~/src/git-annex>cabal install -w $HOME/.ghc-android-14-arm-linux-androideabi-4.7/bin/arm-unknown-linux-androideabi-ghc --with-ghc-pkg=$HOME/.ghc-android-14-arm-linux-androideabi-4.7/bin/arm-unknown-linux-androideabi-ghc-pkg --with-ld=$HOME/.ghc-android-14-arm-linux-androideabi-4.7/bin/arm-linux-androideabi-ld --flags="-Webapp -WebDAV -XMPP -S3 -Dbus" Resolving dependencies... Configuring git-annex-3.20130207... Building git-annex-3.20130207... Preprocessing executable 'git-annex' for git-annex-3.20130207... on the commandline: Warning: -package-conf is deprecated: Use -package-db instead Utility/libdiskfree.c:28:26: fatal error: sys/statvfs.h: No such file or directory compilation terminated.
Should not be far from a first android build now..
While I already have Android "hello world" executables to try, I have not yet been able to run them. Can't seem to find a directory I can write to on the Asus Transformer, with a filesystem that supports the +x bit. Do you really have to root Android just to run simple binaries? I'm crying inside.
It seems that the blessed Android NDK way would involve making a Java app, that pulls in a shared library that contains the native code. For haskell, the library will need to contain a C shim that, probably, calls an entry point to the Haskell runtime system. Once running, it can use the FFI to communicate back to the Java side, probably. The good news is that CJ van den Berg, who already saved my bacon once by developing ghc-android, tells me he's hard at work on that very thing.
In the meantime, downloaded the Android SDK. Have gotten it to build a
.apk package from just javascript code, and managed to do it without
using eclipse (thank god). Will need this later, but for now want to wash
my brain out with soap after using it.
Have not tried to run my static binary on Android yet, but I'm already working on a plan B in case that doesn't work. Yesterday I stumbled upon, a ghc cross-compiler for Android that uses the Android native development kit. It first appeared on February 4th. Good timing!
I've gotten it to build and it emits arm executables, that seem to use the Android linker. So that's very promising indeed.
I've also gotten cabal working with it, and have it chewing through installing git-annex's build dependencies.
Also made a release today, this is another release that's mostly bugfixes, and a few minor features. Including one bug fixed at 6 am this morning, urk.
I think I will probably split my days between working on Android porting and other git-annex development.
I need an Android development environment. I briefly looked into rooting the Asus Transformer so I could put a Debian chroot on it and build git-annex in there, but this quickly devolved to the typical maze of forum posts all containing poor instructions and dead links. Not worth it.
Instead, I'm doing builds on my Sheevaplug, and once I have a static armel binary, will see what I need to do to get it running on Android.
Fixed building with the webapp disabled, was broken by recent improvements. I'll be building without the webapp on arm initially, because ghci/template haskell on arm is still getting sorted out. (I tried ghc 7.6.2 and ghci is available, but doesn't quite work.)
From there, I got a binary built pretty quickly (well, it's arm, so not too
quickly). Then tried to make it static by appending
-optl-static -optl-pthread to the ghc command line.
This failed with a bunch of errors:
/usr/lib/gcc/arm-linux-gnueabi/4.6/../../../arm-linux-gnueabi/libxml2.a(nanohttp.o): In function `xmlNanoHTTPMethodRedir': (.text+0x2128): undefined reference to `inflateInit2_' /usr/lib/gcc/arm-linux-gnueabi/4.6/../../../arm-linux-gnueabi/libxml2.a(xzlib.o): In function `xz_decomp': (.text+0x36c): undefined reference to `lzma_code' ...
Disabling DBUS and (temporarily) XMPP got around that.
Result!
joey@leech:~/git-annex>ldd tmp/git-annex not a dynamic executable joey@leech:~/git-annex>ls -lha tmp/git-annex -rwxr-xr-x 1 joey joey 18M Feb 6 16:23 tmp/git-annex*
Next: Copy binary to Android device, and watch it fail in some interesting way.
Repeat.
Also more bug triage this morning...
Got the pre-commit hook to update direct mode mappings.
Uses
git diff-index HEAD to find out what's changed. The only
tricky part was detecting when
HEAD doesn't exist yet. Git's
plumbing is deficient in this area. Anyway, the mappings get updated
much better now.
Fixed a wacky bug where
git annex uninit behaved badly on a filesystem
that does not support hardlinks.
Got fairly far along in my triage of my backlog, looking through everything that happened after January 23rd. Still 39 or so items to look at.
There have been several reports of problems with ssh password prompts.
I'm beginning to think the assistant may need to prompt for the password
when setting up a ssh remote. This should be handled by
ssh-askpass or
similar, but some Linux users probably don't have it installed, and there
seems to be no widely used OSX equivalent.
Fixed several bugs today, all involving (gasp) direct mode.
The tricky one involved renaming or deleting files in direct mode. Currently nothing removes the old filename from the direct mode mapping, and this could result in the renamed or deleted file unexpectedly being put back into the tree when content is downloaded.
To deal with this, it now assumes that direct mode mappings may be out of
date compared to the tree, and does additional checks to catch
inconsistencies. While that works well enough for the assistant,
I'd also like to make the
pre-commit hook update the mappings for files
that are changed. That's needed to handle things like
git mv.
Back from Australia. Either later today or tomorrow I'll dig into the messages I was not able to get to while traveling, and then the plan is to get into the Android port.
Video of my LCA2013 git-annex talk is now available. I have not watched it yet, hope it turned out ok despite some technical difficulties!
Not!
Hacking on a bus to Canberra for LCA2013, I made the webapp's UI for pausing syncing to a repository also work for the local repository. This pauses the watcher thread. (There's also an annex.autocommit config setting for this.)
Ironically, this didn't turn out to the use the thread manager I built yesterday. I am not sure that a ThreadKilled exception would never be masked in the watcher thread. (There is some overly broad exception handling in git-annex that dates to back before I quite understood haskell exceptions.)
Got back to hacking today, and did something I've wanted to do for some time. Made all the assistant's threads be managed by a thread manager. This allows restarting threads if they crash, by clicking a button in the webapp. It also will allow for other features later, like stopping and starting the watcher thread, to pause the assistant adding local files.
I added the haskell async library as a dependency, which made this pretty easy to implement. The only hitch is that async's documentation is not clear about how it handles asyncronous exceptions. It took me quite a while to work out why the errors I'd inserted into threads to test were crashing the whole program rather than being caught!
15 hours in a plane with in-seat power. Ok, time for some new features!
Added two new repository groups.
"manual" can be used to avoid the assistant downloading any file contents
on its own. It'll still upload and otherwise sync data. To download files,
you can use
git annex get while the assistant is running. You can also
drop files using the command line.
"source" is for repositories that are the source of new files, but don't need to retain a copy once the file has been moved to another repository. A camera would be a good example.
Ok, those were easy features to code; I suck at being productive on planes. Release coming up with those, once I find enough bandwidth here in AU.
On Friday, worked on several bugs in direct mode mapping code. Fixed it to not crash on invalid unicode in filenames. Dealt with some bugs when mappings were updated in subdirectories of the repository.
Those bugs could result in inconsistent mapping files, so today I
made
fsck check mapping files for consistency.
Leaving for Australia tomorrow, but I also hope to get another bugfix release out before my flight leaves. Then will be on vacation for several days, more or less. Then at Linux Conf Australia, where there will be a git-annex presentation on February 1st.
BTW, I've lined up my Android development hardware for next month. I will be using an Asus Transformer, kindly lent to me by Mark H. This has the advantage of having a real keyboard, and running the (currently) second most widely used version of Android, 4.0.x. I have already experienced frustration getting photos off the thing and into my photo annex; the file manager is the worst I've seen since the 80's. I understand why so many want an Android port!
Interestingly, its main user filesystem is a FUSE mount point on
/sdcard
backed by an ext4 filesystem on
/data that a regular user is not allowed
to access. Whatever craziness this entails does not support symlinks.
When I wasn't dealing with the snowstorm today, I was fixing more bugs. Rather serious bugs.
One actually involved corruption to git-annex's location tracking info, due to a busted three-way merge. Takes an unusual set of circumstances for that bug to be triggered, which is why it was not noticed before now. Also, since git-annex is designed to not trust its location tracking info, and recover from it becoming inconsistent, someone could have experienced the bug and not really noticed it. Still it's a serious problem and I'm in debt to user a-or-b for developing a good test case that let me reproduce it and fix it. (Also added to the test suite.) ?This is how to make a perfect bug report
Another bug made
git add; git commit cause data loss in direct mode.
I was able to make that not lose data, although it still does something
that's unlikely to be desired, unless the goal is to move a file from an
annexed direct mode file to having its entire contents stored in git.
Also found a bug with sync's automatic resolution of git conflicts. It
failed when two repositories both renamed a file to different names.
I had neglected to explicitly
git rm the old file name, which is
necessary to resolve such a conflict.
Only one bug fix today, but it was a doozie. It seems that gpg2 has an incompatability with the gpg 1.x that git-annex was written for, that causes large numbers of excess passphrase prompts, when it's supposed to be using a remote's symmetric encryption key. Adding the --batch parameter fixed this.
I also put together a page listing related software to git-annex.
I've also updated direct mode's documentation, about when it's safe to
use direct mode. The intuition I've developed about direct mode is that if
you don't need full versioning of files (with the ability to get back old
versions), direct mode is fine and safe to use. If you want full
versioning, it's best to not use direct mode. Or a reasonable compromise is
to
git annex untrust the direct mode repository and set up a backup remote.
With this compromise, only if you edit a file twice in a row might the old
version get lost before it can be backed up.
Of course, it would be possible to make direct mode fully version preserving, but it'd have to back up every file in the repository locally to do so. Going back to two local copies of every file, which is part of git that git-annex happily avoids. Hmm, it might be possible to only back up a file locally until it reaches the backup remote..
I've noticed people have some problems getting me logs when there'a a bug, so I worked on improving the logging of the assistant.
While the assistant logged to
.git/annex/daemon.log when started as a
daemon, when the webapp ran it didn't log there. It's somewhat tricky to
make the webapp redirect messages to the log, because it may start a web
browser that wants to write to the console. Took some file descriptor
juggling, but I made this work. Now the log is even used when the assistant
is started for the first time in a newly created repository. So, we have
total log coverage.
Next, I made a simple page in the webapp to display the accumulated logs.
It does not currently refresh as new things are logged. But it's easier
for me to tell users to click on
Current Repository -> View log than
ask for them to look for the daemon.log file.
Finally, I made all the webapp's alerts also be written to the log.
Also did the requisite bug fixes.
Fixed a goodly amount of bugs today.
The most interesting change was that in direct mode, files using the same key are no longer hardlinked, as that could cause a surprising behavior if modifying one, where the other would also change.
Made a release, which is almost entirely bug fixes. Debian amd64 build
included this time.
I've finished making direct mode file transfers safe. The last piece of the
puzzle was making
git-annex-shell recv-key check data it's received from
direct mode repositories. This is a bit expensive, but avoids adding
another round-trip to the protocol. I might revisit this later, this was
just a quick fix.
The poll was quite useful. Some interesting points:
- 14% have been reading this blog, and rightly don't trust direct mode to be safe. Which is why I went ahead with a quick fix to make it safe.
- 6% want an Ubuntu PPA. I don't anticipate doing this myself, but if anyone who develops for Ubuntu wants to put together a PPA with a newer version, I can help you pick the newer haskell packages you'll need from Debian, etc.
- 9% just need me to update the amd64 build in Debian sid. I forgot to include it in the last release, and the Debian buildds cannot currently autobuild git-annex due to some breakage in the versions of haskell libraries in unstable. Hopefully I'll remember to include an amd64 build in my next release.
And lots of other interesting stuff, I have a nice new TODO list now.
This month's theme is supposed to be fixing up whatever might prevent users from using the assistant. To that end, I've posted an open-ended poll, what is preventing me from using git-annex assistant. Please go fill it out so I can get an idea of how many people are using the assistant, and what needs to be done to get the rest of you, and your friends and family able to use it.
In the meantime, today I fixed several bugs that were recently reported in the webapp and assistant. Getting it working as widely as possible, even on strange IPv6 only systems, and with browsers that didn't like my generated javascript code is important, and fits right into this month's theme. I'm happy to see lots of bugs being filed, since it means more users are trying the assistant out.
Also continued work on making direct mode transfers safe. All transfers to local git remotes (wish I had a better phrase!) are now safe in direct mode. Only uploading from a direct mode repository over ssh to another git repository is still potentially unsafe.
Well underway on making direct mode transfers roll back when the file is modified while it's transferred.
As expected, it was easy to do for all the special remotes ... Except for bup, which does not allow deleting content. For bup it just removes the git ref for the bad content, and relies on bup's use of git delta compression to keep space use sane.
The problem is also handled by
git-annex-shell sendkey.
But not yet for downloads from other git repositories. Bit stuck on that.
Also: A few minor bug fixes.
I was up at the crack of dawn wrestling 100 pound batteries around for 3 hours and rewiring most of my battery bank, so today is a partial day... but a day with power, which is always nice.
Did some design work on finally making transfers of files from direct mode repositories safe, even if a file is modified as it's being uploaded. This seems easily doable for special remotes; git to git repository transfers are harder, but I think I see how to do it without breaking backwards compatability.
(An unresolved problem is that a temp file would be left behind when a transfer failed due to a file being changed. What would really be nice to do is to use that temp file as the rsync basis when transferring the new version of a file. Although this really goes beyond direct mode, and into deltas territory.)
Made fsck work better in direct mode repositories. While it's expected for files to change at any time in direct mode, and so fsck cannot complain every time there's a checksum mismatch, it is possible for it to detect when a file does not seem to have changed, then check its checksum, and so detect disk corruption or other data problems.
Also dealt with several bug reports. One really weird one involves
git
cat-file failing due to some kind of gpg signed data in the git-annex
branch. I don't understand that at all yet.
(Posted a day late.)
Got
git annex add (and
addurl) working in direct mode. This allowed me
to make
git annex sync in direct mode no longer automatically add new
files.
It's also now safe to mix direct mode annexed files with regular files in
git, in the same repository. Might have been safe all along, but I've
tested it, and it certainly works now. You just have to be careful to not
use
git commit -a to commit changes to such files, since that'll also
stage the entire content of direct mode files.
Made a minor release for these recent changes and bugfixes. Recommended if you're using direct mode. Had to chase down a stupid typo I made yesterday that caused fsck to infinite loop if it found a corrupted file. Thank goodness for test suites.
Several bugfixes from user feedback today.
Made the assistant detect misconfigured systems where git will fail to commit because it cannot determine the user's name or email address, and dummy up enough info to get git working. It makes sense for git and git-annex to fail at the command line on such a misconfigured system, so the user can fix it, but for the assistant it makes sense to plow on and just work.
I found a big gap in direct mode -- all the special remotes expected to find content in the indirect mode location when transferring to the remote. It was easy to fix once I noticed the problem. This is a big enough bug that I will be making a new release in a day or so.
Also, got fsck working in direct mode. It doesn't check as many things as in indirect mode, because direct mode files can be modified at any time. Still, it's usable, and useful.
There was a typo in cabal file that broke building the assistant on OSX. This didn't affect the autobuilds of the app, but several users building by hand reported problems. I made a new minor release fixing that typo, and also a resouce leak bug.
Got a restart UI working after all. It's a hack though. It opens a new tab for the new assistant instance, and as most web browsers don't allow javascript to close tabs, the old tab is left open. At some point I need to add a proper thread manager to the assistant, which the restart code could use to kill the watcher and committer threads, and then I could do a clean restart, bringing up the new daemon and redirecting the browser to it.
Found a bug in the assistant in direct mode -- the expensive transfer scan
didn't queue uploads needed to sync to other repos in direct mode, although
it did queue downloads. Fixing this laid some very useful groundwork for
making more commands support direct mode, too. Got stuck for a long time
dealing with some very strange
git-cat-file behavior while making this
work. Ended up putting in a workaround.
After that, I found that these commands work in direct mode, without needing any futher changes!
git annex find
git annex whereis
git annex copy
git annex move
git annex drop
git annex log
Enjoy! The only commands I'd like to add to this are
fsck,
add,
and
addurl...
Installed a generator, so I'll have more power and less hibernation.
Added UI in the webapp to shut down the daemon. Would like to also have restart UI, but that's rather harder to do, seems it'd need to start another copy of the webapp (and so, of the assistant), and redirect the browser to its new url. ... But running two assistants in the same repo at the same time isn't good. Anyway, users can now use the UI to shut it down, and then use their native desktop UI to start it back up.
Spiffed up the control menu. Had to stop listing other local repositories in the menu, because there was no way to notice when a new one was added (without checking a file on every page load, which is way overkill for this minor feature). Instead added a new page that lists local repositories it can switch to.
Released the first git-annex with direct mode today. Notably, the assistant enables direct mode in repositories it creates. All builds are updated to 3.20130102 now.
My plan for this month is to fix whatever things currently might be preventing you from using the git-annex assistant. So bugfixes and whatever other important gaps need to be filled, but no major new feature developments.
A few final bits and pieces of direct mode. Fixed a few more bugs in the assistant. Made all git-annex commands that don't work at all, or only partially work in direct mode, refuse to run at all. Also, some optimisations.
I'll surely need to revisit direct mode later and make more commands
support it;
fsck and
add especially.
But the only thing I'd like to deal with before I make a release with direct
mode is the problem of files being able to be modified while they're
being transferred, which can result in data loss.
Short day today, but I spent it all on testing the new FSEvents code, getting it working with the assistant in direct mode. This included fixing its handling of renaming, and various other bugs.
The assistant in direct mode now seems to work well on OSX. So I made the assistant default to making direct mode repositories on OSX.
That'll presumably flush out any bugs.
More importantly,
it let me close several OSX-specific bugs to do with interactions between
git-annex's symlinks and OSX programs that were apparently written under the
misprehension that it's a user-mode program's job to manually follow symlinks.
Of course, defaulting to direct mode also means users can just modify files as they like and the assistant will commit and sync the changed files. I'm waiting to see if direct mode becomes popular enough to make it the default on all OS's.
Investigated using the OSX fsevents API to detect when files are modified, so they can be committed when using direct mode. There's a haskell library and even a sample directory watching program. Initial tests look good...
Using fsevents will avoid kqueue's problems with needing enough file descriptors to open every subdirectory. kqueue is a rather poor match for git-annex's needs, really. It does not seem to provide events for file modifications at all, unless every file is individually opened. While I dislike leaving the BSD's out, they need a better interface to be perfectly supported by git-annex, and kqueue will still work for indirect mode repositories.
Got the assistant to use fsevents. It seems to work well!
The only problem I know of is that it doesn't yet handle whole directory renames. That should be easy to fix later.
Over Christmas, I'm working on making the assistant support direct mode. I like to have a fairly detailed plan before starting this kind of job, but in this case, I don't. (Also I have a cold so planning? Meh.) This is a process of seeing what's broken in direct mode and fixing it. I don't know if it'll be easy or hard. Let's find out..
First, got direct mode adding of new files working. This was not hard, all the pieces I needed were there. For now, it uses the same method as in indirect mode to make sure nothing can modify the file while it's being added.
An unexpected problem is that in its startup scan, the assistant runs
git add --updateto detect and stage any deletions that happened while it was not running. But in direct mode that also stages the full file contents, so can't be used. Had to switch to using git plumbing to only stage deleted files. Happily this also led to fixing a bug; deletions were not always committed at startup when using the old method; with the new method it can tell when there are deletions and trigger a commit.
Next, got it to commit when direct mode files are modified. The Watcher thread gets a inotify event when this happens, so that was easy. (Although in doing that I had to disable a guard in direct mode that made annexed files co-exist with regular in-git files, so such mixed repositories probably won't work in direct mode yet.)
However, naughty kqueue is another story, there are no kqueue events for file modifications. So this won't work on OSX or the BSDs yet. I tried setting some more kqueue flags in hope that one would make such events appear, but no luck. Seems I will need to find some other method to detect file modifications, possibly an OSX-specific API.
Another unexpected problem: When an assistant receives new files from one of its remotes, in direct mode it still sets up symlinks to the content. This was because the Merger thread didn't use the
synccommand's direct mode aware merge code.. so fixed that.
Finally there was some direct mode bookeeping the assistant has to get right. For example, when a file is modified, the old object has to be looked up, and be marked as not locally present any longer. That lookup relies on the already running
git cat-file --batch, so it's not as fast as it could be, if I kept a local cache of the mapping between files and objects. But it seems fast enough for now.
At this point the assistant seems to work in direct mode on Linux! Needs more testing..
Finished getting automatic merge conflict resolution working in direct mode. Turned out I was almost there yesterday, just a bug in a filename comparison needed to be fixed.
Fixed a bug where the assistant dropped a file after transferring it, despite the preferred content settings saying it should keep its copy of the file. This turned out to be due to it reading the transfer info incorrectly, and adding a "\n" to the end of the filename, which caused the preferred content check to think it wasn't wanted after all. (Probably because it thought 0 copies of the file were wanted, but I didn't look into this in detail.)
Worked on my test suite, particularly more QuickCheck tests. I need to use QuickCheck more, particularly when I've pairs of functions, like encode and decode, that make for easy QuickCheck properties.
Got merging working in direct mode!
Basically works as outlined yesterday, although slightly less clumsily.
Since there was already code that ran
git diff-tree to update the
associated files mappings after a merge, I was able to adapt that same code
to also update the working tree.
An important invariant for direct mode merges is that they should never
cause annexed objects to be dropped. So if a file is deleted by a merge,
and was a direct mode file that was the only place in the working copy
where an object was stored, the object is moved into
.git/annex/objects.
This avoids data loss and any need to re-transfer objects after a merge.
It also makes renames and other move complex tree manipulations always end
up with direct mode files, when their content was present.
Automatic merge conflict resoltion doesn't quite work right yet in direct mode.
Direct mode has landed in the
master branch, but I still consider it
experimental, and of course the assistant still needs to be updated to
support it.
As winter clouds set in, I have to ration my solar power and have been less active than usual.
It seems that the OSX 10.8.2
git init hanging issue has indeed been
resolved, by building the app on 10.8.2. Very good news! Autobuilder setup is
in progress.
Finally getting stuck in to direct mode git-merge handling. It's
not possible to run
git merge in a direct mode tree, because it'll
see typechanged files and refuse to do anything.
So the only way to use
git merge, rather than writing my own merge engine,
is to use
--work-tree to make it operate in a temporary work tree directory
rather than the real one.
When it's run this way, any new, modified, or renamed files will be added
to the temp dir, and will need to be moved to the real work tree.
To detect deleted files, need to use
git ls-files --others, and
look at the old tree to see if the listed files were in it.
When a merge conflict occurs, the new version of the file will be in the temp directory, and the old one in the work tree. The normal automatic merge conflict resolution machinery should work, with just some tweaks to handle direct mode.
Fixed a bug in the kqueue code that made the assistant not notice when a
file was renamed into a subdirectory. This turned out to be because the
symlink got broken, and it was using
stat on the file. Switching to
lstat fixed that.
Improved installation of programs into standalone bundles. Now it uses the programs detected by configure, rather than a separate hardcoded list. Also improved handling of lsof, which is not always in PATH.
Made a OSX 10.8.2 build of the app, which is nearly my last gasp attempt
at finding a way around this crazy
git init spinning problem with Jimmy's
daily builds are used with newer OSX versions. Try it here:
Mailed out the Kickstarter T-shirt rewards today, to people in the US. Have to fill out a bunch of forms before I can mail the non-US ones.
Built
git annex direct and
git annex indirect to toggle back and forth
between direct mode. Made
git annex status show if the repository is in
direct mode. Now only merging is needed for direct mode to be basically
usable.
I can do a little demo now. Pay attention to the "@" ls shows at the end of symlinks.
joey@gnu:~/tmp/bench/rdirect>ls myfile@ otherfile@ joey@gnu:~/tmp/bench/rdirect>git annex find otherfile # So, two files, only one present in this repo. joey@gnu:~/tmp/bench/rdirect>git annex direct commit # On branch master # Your branch is ahead of 'origin/master' by 7 commits. # nothing to commit (working directory clean) ok direct myfile ok direct otherfile ok direct ok joey@gnu:~/tmp/bench/rdirect>ls myfile@ otherfile # myfile is still a broken symlink because we don't have its content joey@gnu:~/tmp/bench/rdirect>git annex get myfile get myfile (from origin...) ok (Recording state in git...) joey@gnu:~/tmp/bench/rdirect>ls myfile otherfile joey@gnu:~/tmp/bench/rdirect>echo "look mom, no symlinks" >> myfile joey@gnu:~/tmp/bench/rdirect>git annex sync add myfile (checksum...) ok commit (Recording state in git...) [master 0e8de9b] git-annex automatic sync ... ok joey@gnu:~/tmp/bench/rdirect>git annex indirect commit ok indirect myfile ok indirect otherfile ok indirect ok joey@gnu:~/tmp/bench/rdirect>ls myfile@ otherfile@
I'd like
git annex direct to set the repository to untrusted, but
I didn't do it. Partly because having
git annex indirect set it back to
semitrusted seems possibly wrong -- the user might not trust a repo even in
indirect mode. Or might fully trust it. The docs will encourage users to
set direct mode repos to untrusted -- in direct mode you're operating
without large swathes of git-annex's carefully constructed safety net.
(When the assistant later uses direct mode, it'll untrust the repository
automatically.)
Yesterday I cut another release. However, getting an OSX build took until 12:12 pm today because of a confusion about the location of lsof on OSX. The OSX build is now available, and I'm looking forward to hearing if it's working!
Today I've been working on making
git annex sync commit in direct mode.
For this I needed to find all new, modified, and deleted files, and I also
need the git SHA from the index for all non-new files. There's not really
an ideal git command to use to query this. For now I'm using
git ls-files --others --stage, which works but lists more files than I
really need to look at. It might be worth using one of the Haskell libraries
that can directly read git's index.. but for now I'll stick with
ls-files.
It has to check all direct mode files whose content is present, which means
one stat per file (on top of the stat that git already does), as well as one
retrieval of the key per file (using the single
git cat-file process that
git-annex talks to).
This is about as efficient as I can make it, except that unmodified
annexed files whose content is not present are listed due to --stage,
and so it has to stat those too, and currently also feeds them into
git add.
The assistant will be able to avoid all this work, except once at startup.
Anyway, direct mode committing is working!
For now,
git annex sync in direct mode also adds new files. This because
git annex add doesn't work yet in direct mode.
It's possible for a direct mode file to be changed during a commit, which would be a problem since committing involves things like calculating the key and caching the mtime/etc, that would be screwed up. I took care to handle that case; it checks the mtime/etc cache before and after generating a key for the file, and if it detects the file has changed, avoids committing anything. It could retry, but if the file is a VM disk image or something else that's constantly modified, commit retrying forever would not be good.
For
git annex sync to be usable in direct mode, it still needs
to handle merging. It looks like I may be able to just enhance the automatic
conflict resolution code to know about typechanged direct mode files.
The other missing piece before this can really be used is that currently
the key to file mapping is only maintained for files added locally, or
that come in via
git annex sync. Something needs to set up that mapping
for files present when the repo is initally cloned. Maybe the thing
to do is to have a
git annex directmode command that enables/disables
direct mode and can setup the the mapping, as well as any necessary unlocks
and setting the trust level to untrusted.
Made
git annex sync update the file mappings in direct mode.
To do this efficiently, it uses
git diff-tree to find files that are
changed by the sync, and only updates those mappings. I'm rather happy
with this, as a first step to fully supporting sync in direct mode.
Finished the overhaul of the OSX app's library handling. It seems to work well, and will fix a whole class of ways the OSX app could break.
Fixed a bug in the preferred content settings for backup repositories, introduced by some changes I made to preferred content handling 4 days ago.
Fixed the Debian package to build with WebDAV support, which I forgot to turn on before.
Planning a release tomorrow.
Got object sending working in direct mode. However, I don't yet have a reliable way to deal with files being modified while they're being transferred. I have code that detects it on the sending side, but the receiver is still free to move the wrong content into its annex, and record that it has the content. So that's not acceptable, and I'll need to work on it some more. However, at this point I can use a direct mode repository as a remote and transfer files from and to it.
Automated updating of the cached mtime, etc data. Next I need to automate
generation of the key to filename mapping files. I'm thinking that I'll make
git annex sync do it. Then, once I get committing and
merging working in direct mode repositories (which is likely to be a
good week's worth of work), the workflow for using these repositories
will be something like this:
git config annex.direct true git annex sync # pulls any changes, merges, updates maps and caches git annex get # modify files git annex sync # commits and pushes changes
And once I get direct mode repositories working to this degree at the command line, I can get on with adding support to the assistant.
Also did some more work today on the OSX app. Am in the middle of getting it to modify the binaries in the app to change the paths to the libraries they depend on. This will avoid the hacky environment variable it is currently using, and make runshell a much more usable environment. It's the right way to do it. (I can't believe I just said RPATH was the right way to do anything.)
In the middle of this, I discovered, which does the same type of thing.
Anyway, I have to do some crazy hacks to work around short library name fields in executables that I don't want to have to be specially rebuilt in order to build the webapp. Like git.
Started laying the groundwork for desymlink's direct mode. I got rather far!
A git repo can be configured with
annex.direct and all actions that
transfer objects to it will replace the symlinks with regular files.
Removing objects also works (and puts back a broken symlink),
as does checking if an object is present, which even detects if a file
has been modified.
So far, this works best when such a direct mode repository is used as a git remote of another repository. It is also possible to run a few git-annex commands, like "get" in a direct mode repository, though others, like "drop" won't work because they rely on the symlink to map back to the key.
Direct mode relies on map files existing for each key in the repository, that tell what file(s) use it. It also relies on cache files, that contain the last known mtime, size, and inode of the file. So far, I've been setting these files up by hand.
The main thing that's missing is support for transferring objects from direct mode repositories. There's no single place I can modify to support that (like I could for the stuff mentioned above), and also it's difficult to do safely, since files could be modified at any time.
So it'll need to quarantine files, to prevent a modified version from
getting sent out. I could either do this by copying the file, or by
temporarily
git annex locking it. Unsure which choice would be less
annoying..
Also did some investigation with Jimmy of the OSX app git-config hang. Seems to be some kind of imcompatability between the 10.7 autobuilder and 10.8. Next step is probably to try to build on 10.8. Might also be worth trying, although my own scripts do more or less the same thing to build the app.
Biding my time while desymlink gells in my head..
Fixed a bug in the assistant's local pairing that rejected ssh keys with a period in the comment.
Fixed a bug in the assistant that made it try to drop content from remotes that didn't have it, and avoided a drop failure crashing a whole assistant thread.
Made --auto behave better when preferred content is set.
Looked into making the transfer queue allow running multiple transfers at the same time, ie, one per remote. This seems to essentially mean splitting the queue into per remote queues. There are some complexities, and I decided not to dive into working through it right now, since it'd be a distraction from thinking about desymlink. Will revisit it later.
Allow specifying a port when setting up a ssh remote.
While doing that, noticed that the assistant fails to transfer files to sync to a ssh remote that was just added. That got broken while optimising reconnecting with a remote; fixed it.
One problem with the current configurators for remotes is they have a lot of notes and text to read at the top. I've worked on cut that down somewhat, mostly by adding links and help buttons next to fields in the form.
I also made each form have a check box controlling whether encryption is enabled. Mostly as a way to declutter the text at the top, which always had to say encryption is enabled.
I have a fairly well worked out design for desymlink. Will wait a few days to work on it to let it jell.
Made the webapp show runtime errors on a prettified page that includes version info, a bug reporting link, etc.
Dealt with a bad interaction between required fields and the bootstrap modals displayed when submitting some configuration forms. This was long, complex, and had lots of blind alleys. In the end, I had to derive new password and text fields in yesod that don't set the required attribute in the generated html.
Yesterday, I woke up and realized I didn't know what I needed to work on in git-annex. Added a poll, Android to help me decide what major thing to work on next.
More flailing at the OSX monster. (A species of gelatinous cube?) Current fun seems to involve git processes spinning if git-annex was started without a controlling TTY. I'm befuddled by this.
Made the S3 and Glacier configurators have a list of regions, rather than requiring a the region's code be entered correctly. I could not find a list of regions, or better, an API to get a list, so I'll have to keep updating as Amazon adds services in new regions.
Spent some time trying to get WebDAV to work with livedrive.com. It doesn't like empty PROPPATCH. I've developed a change to the haskell DAV library that will let me avoid this problem.
Just filling in a few remaining bits and pieces from this month's work.
- Made the assistant periodically check glacier-cli for archives that are ready, and queue downloads of them.
- The box.com configurator defaults to embedding the account info, allowing one-click enabling of the repository. There's a check box to control this.
- Fix some bugs with how the standalone images run git-annex.
- Included ssh in the standalone images.
- Various other bug fies.
I had planned to do nothing today; I can't remember the last time I did that. Twas not to be; instead I had to make a new release to fix a utterly stupid typo in the rsync special remote. I'm also seeing some slightly encouraging signs of the OSX app being closer to working and this release has a further fix toward that end; unsetting all the environment variables before running the system's web browser.
New release today, the main improvements in this one being WebDAV, Box.com, and Amazon glacier support. release notes
Collected together all the OSX problem reports into one place at ?OSX, to make it easier to get an overview of them.
Did some testing of the OSX standalone app and found that it was missing
some libraries. It seems some new libraries it's using themselves depend on
other libraries, and
otool -L doesn't recursively resolve this.
So I converted the simplistic shell script it was using to install libraries into a haskell progream that recursively adds libraries until there are no more to add. It's pulling in quite a lot more libraries now. This may fix some of the problems that have been reported with the standalone app; I don't really know since I can only do very limited testing on OSX.
Still working on getting the standalone builds for this release done, should be done by the end of today.
Also found a real stinker of a bug in
dirContentsRecursive, which was
just completely broken, apparently since day 1. Fixing that has certainly
fixed buggy behavior of
git annex import. It seems that the other
user of it, the transfer log code, luckily avoided the deep directory
trees that triggered the bug.
Got progress bars working for glacier. This needed some glacier-cli changes, which Robie helpfully made earlier.
Spent some hours getting caught up and responding to bug reports, etc.
Spent a while trying to make git-annex commands that fail to find any matching files to act on print a useful warning message, rather than the current nothing. Concluded this will be surprisingly hard to do, due to the multiple seek passes some commands perform. Update: Thought of a non-invasive and not too ugly way to do this while on my evening walk, and this wart is gone.
Added a configurator for Glacier repositories to the webapp. That was the last cloud repository configurator that was listed in the webapp and wasn't done. Indeed, just two more repository configurators remain to be filled in: phone and NAS.
By default, Glacier repositories are put in a new "small archive" group. This makes only files placed in "archive" directories be sent to Glacier (as well as being dropped from clients), unlike the full archive group which archives all files. Of course you can change this setting, but avoiding syncing all data to Glacier seemed like a good default, especially since some are still worried about Glacier's pricing model.
Fixed several bugs in the handling of archive directories, and the webapp makes a toplevel archive directory when an archive remote is created, so the user can get on with using it.
Made the assistant able to drop local files immediately after transferring them to glacier, despite not being able to trust glacier's inventory. This was accomplished by making the transferrer, after a successful upload, indicate that it trusts the remote it just uploaded to has the file, when it checks if the file should be dropped.
Only thing left to do for glacier is to make the assistant retry failed downloads from it after 4 hours, or better, as soon as they become available.
Got.
Changed how the directory and webdav special remotes store content. The new method uses less system calls, is more robust, and leaves any partially transferred key content in a single tmp directory, which will make it easier to clean that out later.
Also found & fixed a cute bug in the directory special remote when the chunksize is set to a smaller value than the ByteString chunk size, that caused it to loop forever creating empty files.
Added an embedcreds=yes option when setting up special remotes. Will put UI for it into the webapp later, but rather than work on that tomorrow, I plan to work on glacier.
Unexpectedly today, I got progress displays working for uploads via WebDAV.
The roadblock had been that the interface of for uploading to S3 and WebDAV
is something like
ByteString -> IO a. Which doesn't provide any hook to
update a progress display as the ByteString is consumed.
My solution to this was to create a
hGetContentsObserved, that's similar
to
hGetContents, but after reading each 64kb chunk of data from the
Handle to populate the ByteString, it runs some observing action. So when
the ByteString is streamed, as each chunk is consumed, the observer
runs. I was able to get this to run in constant space, despite not having
access to some of the ByteString internals that
hGetContents is built
with.
So, a little scary, but nice. I am curious if there's not a better way to solve this problem hidden in a library somewhere. Perhaps it's another thing that conduit solves somehow? Because if there's not, my solution probably deserves to be put into a library. Any Haskell folk know?
Used above to do progress displays for uploads to S3. Also did progress display to console on download from S3. Now very close to being done with progressbars. Finally. Only bup and hook remotes need progress work.
Reworked the core crypto interface, to better support streaming data through gpg. This allowed fixing both the directory and webdav special remotes to not buffer whole files in memory when retrieving them as chunks from the remote.
Spent some time dealing with API changes in Yesod and Conduit. Some of them annoyingly gratuitous.
I needed an easy day, and I got one. Configurator in the webapp for Box.com came together really quickly and easily, and worked on the first try.
Also filed a bug on the Haskell library that is failing on portknox.com's SSL certificate. That site is the only OwnCloud provider currently offering free WebDAV storage. Will hold off on adding OwnCloud to the webapp's cloud provider lists until that's fixed.
Worked on webdav special remotes all day.
- Got encryption working, after fixing an amusing typo that made
initremotefor webdav throw away the encryption configuration and store files unencrypted.
- Factored out parts of the directory special remote that had to do with file chunking, and am using that for webdav. This refactoring was painful.
At this point, I feel the webdav special remote works better than the old davfs2 + directory special remote hack. While webdav doesn't yet have progress info for uploads, that info was pretty busted anyway with davfs2 due to how it buffers files. So ... I've merged webdav into master!
Tomorrow, webapp configurators for Box.com and any other webdav supporting sites I can turn up and get to work..
A while ago I made git-annex not store login credentials in git for special remotes, when it's only encrypting them with a shared cipher. The rationalle was that you don't want to give everyone who gets ahold of your git repo (which includes the encryption key) access to your passwords, Amazon S3 account, or whatever. I'm now considering adding a checkbox (or command-line flag) that allows storing the login credentials in git, if the user wants to. While using public key crypto is the real solution (and is fully supported by git-annex (but not yet configurable in the webapp)), this seems like a reasonable thing to do in some circumstances, like when you have a Box.com account you really do want to share with the people who use the git repo.
Two releases of the Haskell DAV library today. First release had my changes from yesterday. Then I realized I'd also need support for making WebDAV "collections" (subdirectories), and sent Clint a patch for that too, as well as a patch for querying DAV properties, and that was 0.2. Got it into Debian unstable as well. Should have everything I'll need now.
The webdav special remote is now working! Still todo: Encryption support, progress bars, large file chunking, and webapp configurators. But already, it's a lot nicer than the old approach of using davfs2, which was really flakey and slow with large data volumes.
I did notice, though, that uploading a 100 mb file made the process use 100 mb of memory. This is a problem I've struggled with earlier with S3, the Haskell http libraries are prevented from streaming data by several parts of the protocol that cause the data to be accessed more than once. I guess this won't be a problem for DAV though, since it'll probably be chunking files anyway.
Mailed out all my Kickstarter USB key rewards, and ordered the T-shirts too.
Read up on WebDAV, and got the haskell library working. Several hours were wasted by stumbling over a bug in the library, that requires a carefully crafted XML document to prevent. Such a pity about things like DAV (and XMPP) being designed back when people were gung-ho about XML.. but we're stuck with them now.
Now I'm able to send and receive files to box.com using the library. Trying to use an OwnCloud server, though, I get a most strange error message, which looks to be coming from deep in the HTTPS library stack: "invalid IV length"
The haskell DAV library didn't have a way to delete files. I've added one and sent off a patch.
Roughed in a skeleton of a webdav special remote. Doesn't do anything yet. Will soon.
Factored out a Creds module from parts of the S3 special remote and XMPP support, that all has to do with credentials storage. Using this for webdav creds storage too.
Will also need to factor out the code that's currently in the directory special remote, for chunking of files.
PS: WebDAV, for all its monstrously complicated feature set, lacks one obvious feature: The ability to check how much free space is available to store files. Eyeroll.
Dealt with post-release feedback deluge. There are a couple weird bugs that I don't understand yet. OSX app is still not working everywhere.
Got the list of repositories in the webapp to update automatically when repositories are added, including when syncing with a remote causes repositories to be discovered.
I need a plan for the rest of the month. It feels right to focus on more cloud storage support. Particularly because all the cloud providers supported so far are ones that, while often being best of breed, also cost money. To finish up the cloud story, need support for some free ones.
Looking at the results of the prioritizing special remotes poll, I suspect that free storage is a large part of why Google Drive got so many votes. Soo, since there is not yet a Haskell library for Google Drive, rather than spending a large chunk of time writing one, I hope to use a Haskell WebDAV library that my friend Clint recently wrote. A generic WebDAV special remote in git-annex will provide much better support for box.com (which has 5 to 50 gb free storage), as well as all the OwnCloud providers, at least one of which provides 5 gb free storage.
If I have time left this month after doing that, I'd be inclined to do Amazon Glacier. People have already gotten that working with git-annex, but a proper special remote should be better/easier, and will allow integrating support for it into the assistant, which should help deal with its long retrieval delays. And since, if you have a lot of data archived in Glacier, you will only want to pull out a few files at a time, this is another place besides mobile phones where a partial content retrieval UI is needed. Which is on the roadmap to be worked on next month-ish. Synergy, here I come. I hope.
Cut a new release today. It's been nearly a month since the last one, and a large number of improvements.. Be sure to read the release notes if upgrading. All the standalone builds are updated already.
I hope I'm nearly at the end of this XMPP stuff after today. Planning a new release tomorrow.
Split up the local pairing and XMPP pairing UIs, and wrote a share with a friend walkthrough.
Got the XMPP push code to time out if expected data doesn't arrive within 2 minutes, rather than potentially blocking other XMPP push forever if the other end went away.
I pulled in the Haskell async library for this, which is yes, yet another library, but one that's now in the haskell platform. It's worth it, because of how nicely it let me implement IO actions that time out.
runTimeout :: Seconds -> IO a -> IO (Either SomeException a) runTimeout secs a = do runner <- async a controller <- async $ do threadDelaySeconds secs cancel runner cancel controller `after` waitCatch runner
This would have been 20-50 lines of gnarly code without async, and I'm sure I'll find more uses for async in the future.
Discovered that the XMPP push code could deadlock, if both clients started a push to the other at the same time. I decided to fix this by allowing each client to run both one push and one receive-pack over XMPP at the same time.
Prevented the transfer scanner from trying to queue transfers to XMPP remotes.
Made XMPP pair requests that come from the same account we've already paired with be automatically accepted. So once you pair with one device, you can easily add more.
I got full-on git-annex assistant syncing going over XMPP today!
How well does it work? Well, I'm at the cabin behind a dialup modem. I have
two repos that can only communicate over XMPP. One uses my own XMPP server,
and the other uses a Google Talk account. I make a file in one repo, and
switch windows to the other, and type
ls, and the file (not its content
tho..) has often already shown up. So, it's about as fast as syncing over
ssh, although YMMV.
Refactored the git push over XMPP code rather severely. It's quite a lot cleaner now.
Set XMPP presence priority to a negative value, which will hopefully prevent git-annex clients that share a XMPP account with other clients from intercepting chat messages. Had to change my XMPP protocol some to deal with this.
Some webapp UI work. When showing the buddy list, indicate which buddies are already paired with.
After XMPP pairing, it now encourages setting up a shared cloud repository.
I still need to do more with the UI after XMPP pairing, to help the paired users configure a shared cloud transfer remote. Perhaps the thing to do is for the ConfigMonitor to notice when a git push adds a new remote, and pop up an alert suggesting the user enable it. Then one user can create the repository, and the other one enable it.
I.
I've finished building the XMMP side of git push over XMPP. Now I only have to add code to trigger these pushes. And of course, fix all the bugs, since none of this has been tested at all.
Had to deal with some complications, like handling multiple clients that all want to push at the same time. Only one push is handled at a time; messages for others are queued. Another complication I don't deal with yet is what to do if a client stops responding in the middle of a push. It currently will wait forever for a message from the client; instead it should time out.
Jimmy got the OSX builder working again, despite my best attempts to add dependencies and break it.
Laying.
Spent about 5 hours the other night in XMPP hell. At every turn Google Talk exhibited behavior that may meet the letter of the XMPP spec (or not), but varies between highly annoying and insane.
By "insane", I mean this: If a presence message is directed from one client to another client belonging to that same user, randomly leaking that message out to other users who are subscribed is just a security hole waiting to happen.
Anyway, I came out of that with a collection of hacks that worked, but I didn't like. I was using directed presence for buddy-to-buddy pairing, and an IQ message hack for client-to-client pairing.
Today I got chat messages working instead, for both sorts of pairing. These chat messages have an empty body, which should prevent clients from displaying them, but they're sent directed to only git-annex clients anyway.
And XMPP pairing 100% works now! Of course, it doesn't know how to git pull over XMPP yet, but everything else works.
Here's a real
.git/config generated by the assistant after XMPP pairing.
[remote "joey"] url = fetch = +refs/heads/*:refs/remotes/joey/* annex-uuid = 14f5e93e-1ed0-11e2-aa1c-f7a45e662d39 annex-xmppaddress = joey@kitenet.net
Fixed a typo that led to an infinite loop when adding a ssh git repo with the assistant. Only occurred when an absolute directory was specified, which is why I didn't notice it before.
Security fix: Added a
GIT_ANNEX_SHELL_DIRECTORY environment variable that
locks down git-annex-shell to operating in only a single directory. The
assistant sets that in ssh
authorized_keys lines it creates. This
prevents someone you pair with from being able to access any other git or
git-annex repositories you may have.
Next up, more craziness. But tomorrow is Nov 6th, so you in the US already knew that..
Reworked my XMPP code, which was still specific to push notification, into a more generic XMPP client, that's based on a very generic NetMessager class, that the rest of the assistant can access without knowing anything about XMPP.
Got pair requests flowing via XMPP ping, over Google Talk! And when the webapp receives a pair request, it'll pop up an alert to respond. The rest of XMPP pairing should be easy to fill in from here.
To finish XMPP pairing, I'll need git pull over XMPP, which is nontrivial, but I think I know basically how to do. And I'll need some way to represent an XMPP buddy as a git remote, which is all that XMPP pairing will really set up.
It could be a git remote using an
xmpp:user@host URI for the git url, but
that would confuse regular git to no end (it'd think it was a ssh host),
and probably need lots of special casing in the parts of git-annex that
handle git urls too. Or it could be a git remote without an url set, and
use another config field to represent the XMPP data. But then git wouldn't
think it was a remote at all, which would prevent using "git pull
xmppremote" at all, which I'd like to be able to use when implementing git
pull over XMPP.
Aha! The trick seems to be to leave the url unset in git config, but temporarily set it when pulling:
GIT_SSH=git-annex git git -c remote.xmppremote.url=xmpp:client pull xmppremote
Runs git-annex with "xmpp git-upload-pack 'client'".. Just what I need.
Got the XMPP client maintaining a list of buddies, including tracking which clients are present and away, and which clients are recognised as other git-annex assistant clients. This was fun, it is almost all pure functional code, which always makes me happy.
Started building UI for XMPP pairing. So far, I have it showing a list of buddies who are also running git-annex (or not). The list even refreshes in real time as new buddies come online.
Did a lot of testing, found and fixed 4 bugs with repository setup configurators. None of them were caused by the recent code reworking.
Finished working the new assistant monad into all the assistant's code. I've changed 1870 lines of code in the past two days. It feels like more. While the total number of lines of code has gone up by around 100, the actual code size has gone down; the monad allowed dropping 3.4 kilobytes of manual variable threading complications. Or around 1% of a novel edited away, in other words.
I don't seem to have broken anything, but I'm started an extensive test of all the assistant and webapp. So far, the bugs I've found were not introduced by my monadic changes. Fixed several bugs around adding removable drives, and a few other minor bugs. Plan to continue testing tomorrow.
Spent most of the past day moving the assistant into a monad of its own that encapsulates all the communications channels for its threads. This involved modifiying nearly every line of code in the whole assistant.
Typical change:
handleConnection threadname st dstatus scanremotes pushnotifier = do reconnectRemotes threadname st dstatus scanremotes (Just pushnotifier) =<< networkRemotes st handleConnection = reconnectRemotes True =<< networkRemotes
So, it's getting more readable..
Back in day 85 more foundation work, I wrote:
I suspect, but have not proven, that the assistant is able to keep repos arranged in any shape of graph in sync, as long as it's connected (of course) and each connection is bi-directional. [And each node is running the assistant.]
After today's work, many more graph topologies can be kept in sync -- the assistant now can keep repos in sync that are not directly connected, but must go through a central transfer point, which does not run the assistant at all. Major milestone!
To get that working, as well as using XMPP push notifications, it turned out to need to be more agressive about pushing out changed location log information. And, it seems, that was the last piece that was missing. Although I narrowly avoided going down a blind alley involving sending transfer notifications over XMPP. Luckily, I came to my senses.
This month's focus was the cloud, and the month is almost done. And now the assistant can, indeed be used to sync over the cloud! I would have liked to have gotten on to implementing Amazon Glacier or Google Drive support, but at least the cloud fundamentals are there.
Now that I have XMPP support, I'm tending toward going ahead and adding XMPP pairing, and git push over XMPP. This will open up lots of excellent use cases.
So, how to tunnel git pushes over XMPP? Well,
GIT_SHELL can be set to
something that intercepts the output of
git-send-pack and
git-receive-pack, and that data can be tunneled through XMPP to connect
them. Probably using XMPP ping.
(XEP-0047: In-Band Bytestreams would be the right way ...
but of course Google Talk doesn't support that extension.)
XMPP requires ugly encoding that will bloat the data, but the data quantities are fairly small to sync up a few added or moved files (of course, we'll not be sending file contents over XMPP). Pairing with an large git repository over XMPP will need rather more bandwidth, of course.
Continuing to flail away at this XMPP segfault, which turned out not to be fixed by bound threads. I managed to make a fairly self-contained and small reproducible test case for it that does not depend on the network. Seems the bug is gonna be either in the Haskell binding for GNUTLS, or possibly in GNUTLS itself.
Update: John was able to fix it using my testcase! It was a GNUTLS credentials object that went out of scope and got garbage collected. I think I was seeing the crash only with the threaded runtime because it has a separate garbage collection thread.
Arranged for the XMPP thread to restart when network connections change, as well as when the webapp configures it.
Added an alert to nudge users to enable XMPP. It's displayed after adding a remote in the cloud.
So, the first stage of XMPP is done. But so far all it does is push notification. Much more work to do here.
Built a SRV lookup library that can use either
host or ADNS.
Worked on DBUS reconnection some more; found a FD leak in the dbus library, and wrote its long-suffering author, John Millikin (also the XMPP library author, so I've been bothering him a lot lately), who once again came through with a quick fix.
Built a XMPP configuration form, that tests the connection to the server. Getting the wording right on this was hard, and it's probably still not 100% right.
Pairing over XMPP is something I'm still thinking about. It's contingent on tunneling git over XMPP (actually not too hard), and getting a really secure XMPP connection (needs library improvements, as the library currently accepts any SSL certificate).
Had to toss out my XMPP presence hack. Turns out that, at least in Google Talk, presence info is not sent to clients that have marked themselves unavailable, and that means the assistant would not see notifications, as it was nearly always marked unavailable as part of the hack.
I tried writing a test program that uses XMPP personal eventing, only to find that Google Talk rejected my messages. I'm not 100% sure my messages were right, but I was directly copying the example in the RFC, and prosody accepted them. I could not seem to get a list of extensions out of Google Talk either, so I don't know if it doesn't support personal eventing, or perhaps only supports certian specific types of events.
So, plan C... using XMPP presence extended content. The assistant generates a presence message tagged "xa" (Extended Away), which hopefully will make it not seem present to clients. And to that presence message, I add my own XML element:
<git-annex
This is all entirely legal, and not at all a hack. (Aside from this not really being presence info.) Isn't XML fun?
And plan C works, with Google Talk, and prosody. I've successfully gotten push notifications flowing over XMPP!
Spent some hours dealing with an unusual probolem: git-annex started segfaulting intermittently on startup with the new XMPP code.
Haskell code is not supposed to segfault..
I think this was probably due to not using a bound thread for XMPP, so if haskell's runtime system recheduled its green thread onto a different OS thread during startup, when it's setting up TLS, it'd make gnuTLS very unhappy.
So, fixed it to use a bound thread. Will wait and see if the crash is gone.
Re-enabled DBUS support, using a new version of the library that avoids the memory leak. Will need further changes to the library to support reconnecting to dbus.
Next will be a webapp configuration UI for XMPP. Various parts of the webapp will direct the user to set up XMPP, when appropriate, especially when the user sets up a cloud remote.
To make XMPP sufficiently easy to configure, I need to check SRV records to
find the XMPP server, which is an unexpected PITA because
getaddrinfo
can't do that. There are several haskell DNS libraries that I could use for
SRV, or I could use the
host command:
host -t SRV _xmpp-client._tcp.gmail.com
Built out the XMPP push notifier; around 200 lines of code.
Haven't tested it yet, but it just might work. It's in the
xmpp branch
for now.
I decided to send the UUID of the repo that was pushed to, otherwise peers would have to speculatively pull from every repo. A wrinkle in this is that not all git repos have a git-annex UUID. So it might notify that a push was sent to an unidentified repo, and then peers need to pull from every such repo. In the common case, there will only be one or a few such repos, at someplace like at github that doesn't support git-annex. I could send the URL, but there's no guarantee different clients have the same URLs for a git remote, and also sending the URL leaks rather more data than does a random UUID.
Had a bit of a scare where it looked like I couldn't use the haskell
network-protocol-xmpp package together with the
mtl package that
git-annex already depends on. With help from #haskell I found the way
to get them co-existing, by using the PackageImports extension. Whew!
Need to add configuration of the XMPP server to use in the webapp, and
perhaps also a way to create
.git/annex/creds/notify-xmpp from the
command line.
Time to solve the assistant's cloud notification problem. This is really the last big road-bump to making it be able to sync computers across the big, bad internet.
So, IRC still seems a possibility, but I'm going to try XMPP first. Since Google Talk uses XMPP, it should be easy for users to get an account, and it's also easy to run your own XMPP server.
Played around with the Haskell XMPP library. Clint helpfully showed me an example of a simple client, which helped cut through that library's thicket of data types. In short order I had some clients that were able to see each other connecting to my personal XMPP server. On to some design..
I want to avoid user-visible messages. (dvcs-autosync also uses XMPP, but I checked the code and it seems to send user-visible messages, so I diverge from its lead here.) This seems very possible, only a matter of finding the right way to use the protocol, or an appropriate and widely deployed extension. The only message I need to send with XMPP, really, is "I have pushed to our git repo". One bit of data would do; being able to send a UUID of the repo that did the update would be nice.
I'd also like to broadcast my notification to a user's buddies. dvcs-autosync sends only self-messages, but that requires every node have the same XMPP account configured. While I want to be able to run in that mode, I also want to support pairs of users who have their own XMPP accounts, that are buddied up in XMPP.
To add to the fun, the assistant's use of XMPP should not make that XMPP account appear active to its buddies. Users should not need a dedicated XMPP account for git-annex, and always seeming to be available when git-annex is running would not be nice.
The first method I'm trying out is to encode the notification data inside a XMPP presence broadcast. This should meet all three requirements. The plan is two send two presence messages, the first marks the client as available, and the second as unavailable again. The "id" attribute will be set to some value generated by the assistant. That attribute is allowed on presence messages, and servers are required to preserve it while the client is connected. (I'd only send unavailable messages, but while that worked when I tested it using the prosody server, with google talk, repeated unavailable messages were suppressed. Also, google talk does not preserve the "id" attribute of unavailable presence messages.)
If this presence hackery doesn't work out, I could try XEP-0163: Personal Eventing Protocol. But I like not relying on any extensions.
Added yet another thread, the ConfigMonitor. Since that thread needs to run code to reload cached config values from the git-annex branch when files there change, writing it also let me review where config files are cached, and I found that every single config file in the git-annex branch does get cached, with the exception of the uuid.log. So, added a cache for that, and now I'm more sanguine about yesterday's removal of the lower-level cache, because the only thing not being cached is location log information.
The ConfigMonitor thread seems to work, though I have not tested it extensively. The assistant should notice and apply config changes made locally, as well as any config changes pushed in from remotes. So, for example, if you add a S3 repo in the webapp, and are paired with another computer, that one's webapp will shortly include the new repo in its list. And all the preferred content, groups, etc settings will propigate over and be used as well.
Well ... almost. Seems nothing causes git-annex branch changes to be pushed, until there's some file change to sync out.
Got preferred content checked when files are moved around. So, in repositories in the default client group, if you make a "archive" directory and move files to it, the assistant will drop their content (when possible, ie when it's reached an archive or backup). Move a file out of an archive directory, and the assistant will get its content again. Magic.
Found an intractable bug, obvious in retrospect, with the git-annex branch read cache, and had to remove that cache. I have not fully determined if this will slow down git-annex in some use cases; might need to add more higher-level caching. It was a very minimal cache anyway, just of one file.
Removed support for "in=" from preferred content expressions. That was problimatic in two ways. First, it referred to a remote by name, but preferred content expressions can be evaluated elsewhere, where that remote doesn't exist, or a different remote has the same name. This name lookup code could error out at runtime. Secondly, "in=" seemed pretty useless, and indeed counterintuitive in preferred content expressions. "in=here" did not cause content to be gotten, but it did let present content be dropped. Other uses of "in=" are better handled by using groups.
In place of "in=here", preferred content expressions can now use "present", which is useful if you want to disable automatic getting or dropping of content in some part of a repository. Had to document that "not present" is not a good thing to use -- it's unstable. Still, I find "present" handy enough to put up with that wart.
Realized last night that the code I added to the TransferWatcher to check preferred content once a transfer is done is subject to a race; it will often run before the location log gets updated. Haven't found a good solution yet, but this is something I want working now, so I did put in a quick delay hack to avoid the race. Delays to avoid races are never a real solution, but sometimes you have to TODO it for later.
Been thinking about how to make the assistant notice changes to configuration in the git-annex branch that are merged in from elsewhere while it's running. I'd like to avoid re-reading unchanged configuration files after each merge of the branch.
The most efficient way would be to reorganise the git-annex branch, moving
config files into a configs directory, and logs into a logs directory. Then it
could
git ls-tree git-annex configs and check if the sha of the configs
directory had changed, with git doing minimal work
(benchmarked at 0.011 seconds).
Less efficiently, keep the current git-annex branch layout, and
use:
git ls-tree git-annex uuid.log remote.log preferred-content.log group.log trust.log
(benchmarked at 0.015 seconds)
Leaning toward the less efficient option, with a rate limiter so it doesn't try more often than once every minute. Seems reasonable for it to take a minute for config changes take effect on remote repos, even if the assistant syncs file changes to them more quickly.
Got unwanted content to be dropped from the local repo, as well as remotes when doing the expensive scan. I kept the scan a single pass for now, need to revisit that later to drop content before transferring more. Also, when content is downloaded or uploaded, this can result in it needing to be dropped from somewhere, and the assistant handles that too.
There are some edge cases with hypothetical, very weird preferred content expressions, where the assistant won't drop content right away. (But will later in the expensive scan.) Other than those, I think I have nearly all content dropping sorted out. The only common case I know of where unwanted content is not dropped by the assistant right away is when a file is renamed (eg, put in a "Trash" directory).
In other words, repositories put into the transfer group will now work as described, only retaining content as long as is needed to distribute it to clients. Big milestone!
I released git-annex an unprecidented two times yesterday, because just after the first release, I learned of a another zombie problem. Turns out this zombie had existed for a while, but it was masked by zombie reaping code that I removed recently, after fixing most of the other zombie problems. This one, though, is not directly caused by git-annex. When rsync runs ssh, it seems to run two copies, and one is left unwaited on as a zombie. Oddly, this only happens when rsync's stdout is piped into git-annex, for progress bar handling. I have not source-dived rsync's code to get to the bottom of this, but I put in a workaround.
I did get to the bottom of yesterday's runaway dbus library. Got lucky and found the cause of the memory leak in that library on the first try, which is nice since each try involved logging out of X. I've been corresponding with its author, and a fix will be available soon, and then git-annex will need some changes to handle dbus reconnection.
For the first time, I'm starting to use the assistant on my own personal git-annex repo. The preferred content and group settings let me configure it use the complex system of partial syncing I need. For example, I have this configured for my sound files, keeping new podcasts on a server until they land somewhere near me. And keeping any sound files that I've manually put on my laptop, and syncing new podcasts, but not other stuff.
# (for my server) preferred-content 87e06c7a-7388-11e0-ba07-03cdf300bd87 = include=podcasts/* and (not copies=nearjoey:1) # (for my laptop) preferred-content 0c443de8-e644-11df-acbf-f7cd7ca6210d = exclude=*/out/* and (in=here or (include=podcasts/*))
Found and fixed a bug in the preferred content matching code, where if the assistant was run in a subdirectory of the repo, it failed to match files correctly.
More bugfixes today. The assistant now seems to have enough users that they're turning up interesting bugs, which is good. But does keep me too busy to add many more bugs^Wcode.
The fun one today made it bloat to eat all memory when logging out of a Linux desktop. I tracked that back to a bug in the Haskell DBUS library when a session connection is open and the session goes away. Developed a test case, and even profiled it, and sent it all of to the library's author. Hopefully there will be a quick fix, in the meantime today's release has DBUS turned off. Which is ok, it just makes it a little bit slower to notice some events.
I was mostly working on other things today, but I did do some bug fixing.
The worst of these is a bug introduced in 3.20121009 that breaks
git-annex-shell configlist. That's pretty bad for using git-annex
on servers, although you mostly won't notice unless you're just getting
started using a ssh remote, since that's when it calls configlist.
I will be releasing a new version as soon as I have bandwidth (tomorrow).
Also made the standalone Linux and OSX binaries build with ssh connection caching disabled, since they don't bundle their own ssh and need to work with whatever ssh is installed.
Did a fair amount of testing and bug fixing today.
There is still some buggy behavior around pausing syncing to a remote, where transfers still happen to it, but I fixed the worst bug there.
Noticed that if a non-bare repo is set up on a removable drive, its file tree will not normally be updated as syncs come in -- because the assistant is not running on that repo, and so incoming syncs are not merged into the local master branch. For now I made it always use bare repos on removable drives, but I may want to revisit this.
The repository edit form now has a field for the name of the repo,
so the ugly names that the assistant comes up with for ssh remotes
can be edited as you like.
git remote rename is a very nice thing.
Changed the preferred content expression for transfer repos to this: "not (inallgroup=client and copies=client:2)". This way, when there's just one client, files on it will be synced to transfer repos, even though those repos have no other clients to transfer them to. Presumably, if a transfer repo is set up, more clients are coming soon, so this avoids a wait. Particularly useful with removable drives, as the drive will start being filled as soon as it's added, and can then be brought to a client elsewhere. The "2" does mean that, once another client is found, the data on the transfer repo will be dropped, and so if it's brought to yet another new client, it won't have data for it right away. I can't see way to generalize this workaround to more than 2 clients; the transfer repo has to start dropping apparently unwanted content at some point. Still, this will avoid a potentially very confusing behavior when getting started.
I need to get that dropping of non-preferred content to happen still. Yesterday, I did some analysis of all the events that can cause previously preferred content to no longer be preferred, so I know all the places I have to deal with this.
The one that's giving me some trouble is checking in the transfer scan. If it checks for content to drop at the same time as content to transfer, it could end up doing a lot of transfers before dropping anything. It'd be nicer to first drop as much as it can, before getting more data, so that transfer remotes stay as small as possible. But the scan is expensive, and it'd also be nice not to need two passes.
Switched the OSX standalone app to use
DYLD_ROOT_PATH.
This is the third
DYLD_* variable I've tried; neither
of the other two worked in all situations. This one may do better.
If not, I may be stuck modifying the library names in each executable
using
install_name_tool
(good reference for doing that).
As far as I know, every existing dynamic library lookup system is broken
in some way other other; nothing I've seen about OSX's so far
disproves that rule.
Fixed a nasty utf-8 encoding crash that could occur when merging the git-annex branch. I hope I'm almost done with those.
Made git-annex auto-detect when a git remote is on a sever like github that doesn't support git-annex, and automatically set annex-ignore.
Finished the UI for pausing syncing of a remote. Making the syncing actually stop still has some glitches to resolve.
Bugfixes all day.
The most amusing bug, which I just stumbled over randomly on my own,
after someone on IRC yesterday was possibly encountering the same issue,
made
git annex webapp go into an infinite memory-consuming loop on
startup if the repository it had been using was no longer a valid git
repository.
Then there was the place where HOME got unset, with also sometimes amusing results.
Also fixed several build problems, including a threaded runtime hang in the test suite. Hopefully the next release will build on all Debian architectures again.
I'll be cutting that release tomorrow. I also updated the linux prebuilt tarballs today.
Hmm, not entirely bugfixes after all. Had time (and power) to work on the repository configuration form too, and added a check box to it that can be unchecked to disable syncing with a repository. Also, made that form be displayed after the webapp creates a new repository.
today
Came up with four groups of repositories that it makes sense to define standard preferred content expressions for.
preferredContent :: StandardGroup -> String preferredContent ClientGroup = "exclude=*/archive/*" preferredContent TransferGroup = "not inallgroup=client and " ++ preferredContent ClientGroup preferredContent ArchiveGroup = "not copies=archive:1" preferredContent BackupGroup = "" -- all content is preferred
preferred content has the details about these groups, but as I was writing those three preferred content expressions, I realized they are some of the highest level programming I've ever done, in a way.
Anyway, these make for a very simple repository configuration UI:
yesterday (forgot to post this)
Got the assistant honoring preferred content settings. Although so far that only determines what it transfers. Additional work will be needed to make content be dropped when it stops being preferred.
Added a "configure" link next to each repository on the repository config page. This will go to a form to allow setting things like repository descriptions, groups, and preferred content settings.
Cut a release.
Preferred content control is wired up to
--auto and working for
get,
copy, and
drop. Note that
drop --from remote --auto drops files that
the remote's preferred content settings indicate it doesn't want;
likewise
copy --to remote --auto sends content that the remote does want.
Also implemented
smallerthan,
largerthan, and
ingroup limits,
which should be everything needed for the scenarios described in
transfer control.
Dying to hook this up to the assistant, but a cloudy day is forcing me to curtail further computer use.
Also, last night I developed a patch for the hS3 library, that should let
git-annex upload large files to S3 without buffering their whole content in
memory. I have a
s3-memory-leak in git-annex that uses the new API I
developed. Hopefully hS3's maintainer will release a new version with that
soon.
Fixed the assistant to wait on all the zombie processes that would sometimes pile up. I didn't realize this was as bad as it was.
Zombies and git-annex have been a problem since I started developing it, because back then I made some rather poor choices, due to barely knowing how to write Haskell. So parts of the code that stream input from git commands don't clean up after them properly. Not normally a problem, because git-annex reaps the zombies after each file it processes. But this reaping is not thread-safe; it cannot be used in the assistant.
If I were starting git-annex today, I'd use one of the new Haskell things like Conduits, that allow for very clean control over finalization of resources. But switching it to Conduits now would probably take weeks of work; I've not yet felt it was worthwhile. (Also it's not clear Conduits are the last, best thing.)
For now, it keeps track of the pids it needs to wait on, and all the code run by the assistant is zombie-free. However, some code for fsck and unused that I anticipate the assistant using eventually still has some lurking zombies.
Solved the issue with preferred content expressions and dropping that I mentioned yesterday. My solution was to add a parameter to specify a set of repositories where content should be assumed not to be present. When deciding whether to drop, it can put the current repository in, and then if the expression fails to match, the content can be dropped.
Using yesterday's example "(not copies=trusted:2) and (not in=usbdrive)", when the local repo is one of the 2 trusted copies, the drop check will see only 1 trusted copy, so the expression matches, and so the content will not be dropped.
I've not tested my solution, but it type checks. :P I'll wire it up to
get/drop/move --auto tomorrow and see how it performs.
Would preferred content expressions be more readble if they were inverted (becoming content filtering expressions)?
- "(not copies=trusted:2) and (not in=usbdrive)" becomes "copies=trusted:2 or in=usbdrive"
- "smallerthan=10mb and include=.mp3 and exclude=junk/" becomes "largerthan=10mb or exclude=.mp3" or include=junk/"
- "(not group=archival) and (not copies=archival:1)" becomes "group=archival or copies=archival:1"
1 and 3 are improved, but 2, less so. It's a trifle weird for "include" to mean "include in excluded content".
The other reason not to do this is that currently the expressions
can be fed into
git annex find on the command line, and it'll come
back with the files that would be kept.
Perhaps a middle groud is to make "dontwant" be an alias for "not". Then we can write "dontwant (copies=trusted:2 or in=usbdrive)"
A user told me this:
I can confirm that the assistant does what it is supposed to do really well. I just hooked up my notebook to the network and it starts syncing from notebook to fileserver and the assistant on the fileserver also immediately starts syncing to the [..] backup
That makes me happy, it's the first quite so real-world success report I've heard.
Started implementing transfer control. Although I'm currently calling the configuration for it "preferred content expressions". (What a mouthful!)
I was mostly able to reuse the Limit code (used to handle parameters like --not --in otherrepo), so it can already build Matchers for preferred content expressions in my little Domain Specific Language.
Preferred content expressions can be edited with
git annex vicfg, which
checks that they parse properly.
The plan is that the first place to use them is not going to be inside the
assistant, but in commands that use the
--auto parameter, which will use
them as an additional constraint, in addition to the numcopies setting
already used. Once I get it working there, I'll add it to the assistant.
Let's say a repo has a preferred content setting of "(not copies=trusted:2) and (not in=usbdrive)"
git annex get --autowill get files that have less than 2 trusted copies, and are not in the usb drive.
git annex drop --autowill drop files that have 2 or more trusted copies, and are not in the usb drive (assuming numcopies allows dropping them of course).
git annex copy --auto --to thatreporun from another repo will only copy files that have less than 2 trusted copies. (And if that was run on the usb drive, it'd never copy anything!)
There is a complication here.. What if the repo with that preferred content
setting is itself trusted? Then when it gets a file, its number of
trusted copies increases, which will make it be dropped again.
This is a nuance that the numcopies code already deals with, but it's much harder to deal with it in these complicated expressions. I need to think about this; the three ideas I'm working on are:
- Leave it to whoever/whatever writes these expressions to write ones that avoid such problems. Which is ok if I'm the only one writing pre-canned ones, in practice..
- Transform expressions into ones that avoid such problems. (For example, replace "not copies=trusted:2" with "not (copies=trusted:2 or (in=here and trusted=here and copies=trusted:3))"
- Have some of the commands (mostly drop I think) pretend the drop has already happened, and check if it'd then want to get the file back again.
Not a lot of programming today; I spent most of the day stuffing hundreds of envelopes for this Kickstarter thing you may have heard of. Some post office is going to be very surprised with all the international mail soon.
That said, I did write 184 lines of code. (Actually rather a lot, but it was mostly pure functional code, so easy to write.) That pops up your text editor on a file with the the trust and group configurations of repositories, that's stored in the git-annex branch. Handy for both viewing that stuff all in one place, and changing it.
The real reason for doing that is to provide a nice interface for editing transfer control expressions, which I'll be adding next.
Today I revisited something from way back in day 7 bugfixes.
Back then, it wasn't practical to run
git ls-files on every
file the watcher noticed, to check if it was already in git. Revisiting
this, I found I could efficiently do that check at the same point it checks
lsof. When there's a lot of files being added, they're batched up at that
point, so it won't be calling
git ls-files repeatedly.
Result: It's safe to mix use of the assistant with files stored in git
in the normal way. And it's safe to mix use of
git annex unlock with
the assistant; it won't immediately re-lock files. Yay!
Also fixed a crash in the committer, and made
git annex status display
repository groups.
Been thinking through where to store the transfer control expressions.
Since repositories need to know about the transfer controls of other
remotes, storing them in
.git/config isn't right. I thought it might be
nice to configure the expressions in
.gitattributes, but it seems the
file format doesn't allow complicated multi-word attributes. Instead,
they'll be stored in the git-annex branch.
Spent a lot of time this weekend thinking about/stuck on the cloud notification problem. Currently IRC is looking like the best way for repositories to notify one-another when changes are made, but I'm not sure about using that, and not ready to start on it.
Instead, laid some groundwork for transfer control today. Added some simple commands to manage groups of repositories, and find files that are present in repositories in a group. I'm not completely happy with the syntax for that, and need to think up some good syntax to specify files that are present in all repositories in a group.
The plan is to have the assistant automatically guess at groups to put new repositories it makes in (it should be able to make good guesses), as well as have an interface to change them, and an interface to configure transfer control using these groups (and other ways of matching files). And, probably, some canned transfer control recipes for common setups.
Collected up the past week's work and made a release today. I'm probably back to making regular releases every week or two.
I hear that people want the git-annex assistant to be easy to install without messing about building it from source..
on OSX
So Jimmy and I have been working all week on making an easily installed OSX app of the assistant. This is a .dmz file that bundles all the dependencies (git, etc) in, so it can be installed with one click.
It seems to basically work. You can get it here.
Unfortunatly, the ?pasting into annex on OSX bug resurfaced while testing this.. So I can't really recommend using it on real data yet.
Still, any testing you can do is gonna be really helpful. I'm squashing OSX bugs right and left.
on Linux
First of all, the git-annex assistant is now available in Debian unstable, and in Arch Linux's AUR. Proper packages.
For all the other Linux distributions, I have a workaround. It's a big hack, but it seems to work.. at least on Debian stable.
I've just put up a linux standalone tarball, which has no library dependencies apart from glibc, and doesn't even need git to be installed on your system.
on FreeBSD
The FreeBSD port has been updated to include the git-annex assistant too..
Various bug fixes, and work on the OSX app today:
- Avoid crashing when ssh-keygen fails due to not being able to parse
authorized_keys.. seems a lot of people have crufty unparsable
authorized_keysfiles.
- On OSX, for some reason the webapp was failing to start sometimes due to bind failing with EINVAL. I don't understand why, as that should only happen if the socket is already bound, which it should not as it's just been created. I was able to work around this by retrying with a new socket when bind fails.
- When setting up
authorized_keysto let
git-annex-shellbe run, it had been inserting a perl oneliner into it. I changed that to instead call a
~/.ssh/git-annex-shellwrapper script that it sets up. The benefits are it no longer needs perl, and it's less ugly, and the standalone OSX app can modify the wrapper script to point to wherever it's installed today (people like to move these things around I guess).
- Made the standalone OSX app set up autostarting when it's first run.
- Spent rather a long time collecting the licenses of all the software that will be bundled with the standalone OSX app. Ended up with a file containing 3954 lines of legalese. Happily, all the software appears redistributable, and free software; even the couple of OSX system libraries we're bundling are licensed under the APSL.
Amazon S3 was the second most popular choice in the prioritizing special remotes poll, and since I'm not sure how I want to support phone/mp3 players, I did it first.
So I added a configurator today to easily set up an Amazon S3 repository. That was straightforward and didn't take long since git-annex already supported S3.
The hard part, of course, is key distribution. Since the webapp so far can only configure the shared encryption method, and not fullblown gpg keys, I didn't feel it would be secure to store the S3 keys in the git repository. Anyone with access to that git repo would have full access to S3 ... just not acceptable. Instead, the webapp stores the keys in a 600 mode file locally, and they're not distributed at all.
When the same S3 repository is enabled on another computer, it prompts for keys then too. I did add a hint about using the IAM Management Console in this case -- it should be possible to set up users in IAM who can only access a single bucket, although I have not tried to set that up.
Also, more work on the standalone OSX app.
Mostly took a break from working on the assistant today. Instead worked on adding incremental fsck to git-annex. Well, that will be something that assistant will use, eventually, probably.
Jimmy and I have been working on a self-contained OSX app for using the assistant, that doesn't depend on installing git, etc. More on that once we have something that works.
Just released git-annex 3.20120924, which includes beta versions of the assistant and webapp. Read the ?errata, then give it a try!
I've uploaded it to Haskell's cabal, and to Debian unstable, and hope my helpers for other distributions will update them soon. (Although the additional dependencies to build the webapp may take a while on some.) I also hope something can be done to make a prebuilt version available on OSX soonish.
I've decided to license the webapp under the AGPL. This should not impact normal users of it, and git-annex can be built without the webapp as a pure GPL licensed program. This is just insurance to prevent someone turning the webapp into a propritary web-only service, by requiring that anyone who does so provide the source of the webapp.
Finally wrapped up progress bars; upload progress is now reported in all situations.
After all that, I was pleased to find a use for the progress info, beyond displaying it to the user. Now the assistant uses it to decide whether it makes sense to immediately retry a failed transfer. This should make it work nicely, or at least better, with flaky network or drives.
The webapp crashed on startup when there was no
~/.gitconfig.
Guess all of us who have tried it so far are actual git users,
but I'm glad I caught this before releasing the beta.
Jimmy Tang kindly took on making a OS X .app directory for git-annex.
So it now has an icon that will launch the webapp.
I'm getting lots of contributors to git-annex all of a sudden. I've had 3 patches this weekend, and 2 of them have been to Haskell code. Justin Azoff is working on ?incremental fsck, and Robie Basak has gotten Amazon Glacier working using the hook special remote.
Started doing some design for transfer control. I will start work on this after releasing the first beta.
Short day today, but I again worked only on progress bars.
- Added upload progress tracking for the directory special remote.
- Some optimisations.
- Added a
git annex-shell transferkeycommand. This isn't used yet, but the plan is to use it to feed back information about how much of a file has been sent when downloading it. So that the uploader can display a progress bar. This method avoids needing to parse the rsync protocol, which is approximately impossible without copying half of rsync. Happily, git-annex's automatic ssh connection caching will make the small amount of data this needs to send be efficiently pipelined over the same ssh connection that rsync is using.
I probably have less than 10 lines of code to write to finish up
progressbars for now. Looking forward to getting that behind me, and on
to something more interesting. Even doing mail merge to print labels to
mail out Kickstarter rewards is more interesting than progress bars at this
point.
Worked more on upload progress tracking. I'm fairly happy with its state now:
It's fully implemented for rsync special remotes.
Git remotes also fully support it, with the notable exception of file uploads run by
git-annex-shell recvkey. That runs
rsync --server --sender, and in that mode, rsync refuses to output progress info. Not sure what to do about this case. Maybe I should write a parser for the rsync wire protocol that can tell what chunk of the file is being sent, and shim it in front of the rsync server? That's rather hardcore, but it seems the best of a bad grab bag of options that include things like
LD_PRELOADhacks.
Also optimised the rsync progress bar reader to read whole chunks of data rather than one byte at a time.
Also got progress bars to actually update in the webapp for uploads.
This turned out to be tricky because kqueue cannot be used to detect when existing files have been modified. (One of kqueue's worst shortcomings vs inotify.) Currently on kqueue systems it has to poll.
I will probably upload add progress tracking to the directory special remote, which should be very easy (it already implements its own progress bars), and leave the other special remotes for later. I can add upload progress tracking to each special remote when I add support for configuring it in the webapp.
Putting together a shortlist of things I want to sort out before the beta.
- Progress bars for file uploads.
- No mocked up parts in the webapp's UI. Think I implemented the last of those yesterday, although there are some unlinked repository configuration options.
- The basic watching functionality, should work reliably. There are some known scalability issues with eg, kqueue on OSX that need to be dealt with, but needn't block a beta.
- Should keep any configuration of repositories that can be set up using the webapp in sync whenever it's possible to do so. I think that'll work after the past few days work.
- Should be easy to install and get running. Of course part of the point of the beta release is to get it out there, on Hackage, in Debian unstable, and in the other places that git-annex packagers put it. As to getting it running, the autostart files and menu items look good on Linux. The OSX equivilants still need work and testing.
- No howlingly bad bugs. ?This bug is the one I'm most concerned with currently. OTOH, ?watcher commits unlocked files can be listed in the errata.
So I worked on progress bars for uploads today. Wrote a nice little parser for rsync's progress output, that parses arbitrary size chunks, returning any unparsable part. Added a ProgressCallback parameter to all the backends' upload methods. Wrote a nasty thing that intercepts rsync's output, currently a character at a time (horrible, but rsync doesn't output that much, so surprisingly acceptable), and outputs it and parses it. Hooked all this up, and got it working for uploads to git remotes. That's 1/10th of the total ways uploads can happen that have working progress bars. It'll take a while to fill in the rest..
Turns out I was able to easily avoid the potential upload loops that would occur if each time a repo receives a download, it queues uploads to the repos it's connected to. With that done. I suspect, but have not proven, that the assistant is able to keep repos arranged in any shape of graph in sync, as long as it's connected (of course) and each connection is bi-directional. That's a good start .. or at least a nice improvement from only strongly connected graphs being kept in sync.
Eliminated some empty commits that would be made sometimes, which is a nice optimisation.
I wanted to get back to some UI work after this week's deep dive into the internals. So I filled in a missing piece, the repository switcher in the upper right corner. Now the webapp's UI allows setting up different repositories for different purposes, and switching between them.
Implemented deferred downloads. So my example from yesterday of three repositories in a line keep fully in sync now!
I punted on one problem while doing it. It might be possible to get a really big list of deferred downloads in some situation. That all lives in memory. I aim for git-annex to always have a constant upper bound on memory use, so that's not really acceptable. I have TODOed a reminder to do something about limiting the size of this list.
I also ran into a nasty crash while implementing this, where two threads were trying to do things to git HEAD at the same time, and so one crashed, and in a way I don't entirely understand, that crash took down another thread with a BlockedIndefinitelyOnSTM exception. I think I've fixed this, but it's bothersome that this is the second time that modifications to the Merger thread have led to a concurrency related crash that I have not fully understood.
My guess is that STM can get confused when it's retrying, and the thread that was preventing it from completing a transaction crashes, because it suddenly does not see any other references to the TVar(s) involved in the transaction. Any GHC STM gurus out there?
Still work to be done on making data transfers to keep fully in sync in all circumstances. One case I've realized needs work occurs when a USB drive is plugged in. Files are downloaded from it to keep the repo in sync, but the repo neglects to queue uploads of those files it just got out to other repositories it's in contact with. Seems I still need to do something to detecting when a successful download is done, and queue uploads.
Syncing works well when the graph of repositories is strongly connected. Now I'm working on making it work reliably with less connected graphs.
I've been focusing on and testing a doubly-connected list of repositories,
such as:
A <-> B <-> C
I was seeing a lot of git-annex branch push failures occuring in this line of repositories topology. Sometimes was is able to recover from these, but when two repositories were trying to push to one-another at the same time, and both failed, both would pull and merge, which actually keeps the git-annex branch still diverged. (The two merge commits differ.)
A large part of the problem was that it pushed directly into the git-annex
branch on the remote; the same branch the remote modifies. I changed it to
push to
synced/git-annex on the remote, which avoids most push failures.
Only when A and C are both trying to push into
B/synced/git-annex at the
same time would one fail, and need to pull, merge, and retry.
With that change, git syncing always succeeded in my tests, and without needing any retries. But with more complex sets of repositories, or more traffic, it could still fail.
I want to avoid repeated retries, exponential backoffs, and that kind of thing. It'd probably be good enough, but I'm not happy with it because it could take arbitrarily long to get git in sync.
I've settled on letting it retry once to push to the synced/git-annex and synced/master branches. If the retry fails, it enters a fallback mode, which is guaranteed to succeed, as long as the remote is accessible.
The problem with the fallback mode is it uses really ugly branch names.
Which is why Joachim Breitner and I originally decided on making
git annex
sync use the single
synced/master branch, despite the potential for
failed syncs. But in the assistant, the requirements are different,
and I'm ok with the uglier names.
It does seem to make sense to only use the uglier names as a fallback,
rather than by default. This preserves compatability with
git annex sync,
and it allows the assistant to delete fallback sync branches after it's
merged them, so the ugliness is temporary.
Also worked some today on a bug that prevents C from receiving files added to A.
The problem is that file contents and git metadata sync independantly. So C will probably receive the git metadata from B before B has finished downloading the file from A. C would normally queue a download of the content when it sees the file appear, but at this point it has nowhere to get it from.
My first stab at this was a failure. I made each download of a file result in uploads of the file being queued to every remote that doesn't have it yet. So rather than C downloading from B, B uploads to C. Which works fine, but then C sees this download from B has finished, and proceeds to try to re-upload to B. Which rejects it, but notices that this download has finished, so re-uploads it to C...
The problem with that approach is that I don't have an event when a download succeeds, just an event when a download ends. Of course, C could skip uploading back to the same place it just downloaded from, but loops are still possible with other network topologies (ie, if D is connected to both B and C, there would be an upload loop 'B -> C -> D -> B`). So unless I can find a better event to hook into, this idea is doomed.
I do have another idea to fix the same problem. C could certainly remember that it saw a file and didn't know where to get the content from, and then when it receives a git push of a git-annex branch, try again.
Started today doing testing of syncing, and found some bugs and things
it needs to do better. But was quickly sidetracked when I noticed that
transferkey was making a commit to the git-annex branch for every file it
transferred, which is too slow and bloats history too much.
To fix that actually involved fixing a long-standing annoyance; that
read-only git-annex commands like
whereis sometimes start off with
"(Recording state in git)", when the journal contains some not yet
committed changes to the git-annex branch. I had to carefully think
through the cases to avoid those commits.
As I was working on that, I found a real nasty lurking bug in the git-annex
branch handling. It's unlikely to happen unless
annex.autocommit=false is
set, but it could occur when two git-annex processes race one another just
right too. The root of the bug is that
git cat-file --batch does not
always show changes made to the index after it started. I think it does
in enough cases to have tricked me before, but in general it can't be
trusted to report the current state of the index, but only some past state.
I was able to fix the bug, by ensuring that changes being made to the branch are always visible in either the journal or the branch -- never in the index alone.
Hopefully something less low-level tomorrow..!
It's possible for one git annex repository to configure a special remote that it makes sense for other repositories to also be able to use. Today I added the UI to support that; in the list of repositories, such repositories have a "enable" link.
To enable pre-existing rsync special remotes, the webapp has to do the same
probing and ssh key setup that it does when initially creating them.
Rsync.net is also handled as a special case in that code. There was one
ugly part to this.. When a rsync remote is configured in the webapp,
it uses a mangled hostname like "git-annex-example.com-user", to
make ssh use the key it sets up. That gets stored in the
remote.log, and so
the enabling code has to unmangle it to get back to the real hostname.
Based on the still-running ?prioritizing special remotes poll, a lot of people want special remote support for their phone or mp3 player. (As opposed to running git-annex on an Android phone, which comes later..) It'd be easy enough to make the webapp set up a directory special remote on such a device, but that makes consuming some types of content on the phone difficult (mp3 players seem to handle them ok based on what people tell me). I need to think more about some of the ideas mentioned in android for more suitable ways of storing files.
One thing's for sure: You won't want the assistant to sync all your files to your phone! So I also need to start coming up with partial syncing controls. One idea is for each remote to have a configurable matcher for files it likes to receive. That could be only mp3 files, or all files inside a given subdirectory, or all files not in a given subdirectory. That means that when the assistant detects a file has been moved, it'll need to add (or remove) a queued transfer. Lots of other things could be matched on, like file size, number of copies, etc. Oh look, I have a beautiful library I wrote earlier that I can reuse!
I've changed the default backend used by git-annex from SHA256 to SHA256E. Including the filename extension in the key is known to make repositories more usable on things like MP3 players, and I've recently learned it also avoids Weird behavior with OS X Finder and Preview.app.
I thought about only changing the default in repositories set up by the assistant, but it seemed simpler to change the main default. The old backend is really only better if you might have multiple copies of files with the same content that have different extensions.
Fixed the socket leak in pairing that eluded me earlier.
I've made a new polls page, and posted a poll: prioritizing special remotes
Tons of pairing work, which culminated today in pairing fully working for the very first time. And it works great! Type something like "my hovercraft is full of eels" into two git annex webapps on the same LAN and the two will find each other, automatically set up ssh keys, and sync up, like magic. Magic based on math.
- Revert changes made to
authorized_keyswhen the user cancels a pairing response. Which could happen if the machine that sent the pairing request originally is no longer on the network.
- Some fixes to handle lossy UDP better. Particularly tricky at the end of the conversation -- how do both sides reliably know when a conversation is over when it's over a lossy wire? My solution is just to remember some conversatons we think are over, and keep saying "this conversation is over" if we see messages in that conversation. Works.
- Added a UUID that must be the same in related pairing messages. This has a nice security feature: It allows detection of brute-force attacks to guess the shared secret, after the first wrong guess! In which case the pairing is canceled and a warning printed.
- That led to a thorough security overview, which I've added to the pairing page. Added some guards against unusual attacks, like console poisioning attacks. I feel happy with the security of pairing now, with the caveats that only I have reviewed it (and reviewing your own security designs is never ideal), and that the out-of-band shared secret communication between users is only as good as they make it.
- Found a bug in Yesod's type safe urls. At least, I think it's a bug. Worked around it.
- Got very stuck trying to close the sockets that are opened to send multicast pairing messages. Nothing works, down to and including calling C
close(). At the moment I have a socket leak.
I need to understand the details of multicast sockets better to fix this. Emailed the author of the library I'm using for help.
Alerts can now have buttons, that go to some url when clicked. Yay.
Implementing that was a PITA, because Yesod really only wants its type-safe urls to be rendered from within its Handler monad. Which most things that create alerts are not. I managed to work around Yesod's insistence on this only by using a MVar to store the pure function that Yesod uses internally. That function can only be obtained once the webapp is running.
Fixed a nasty bug where using gpg would cause hangs. I introduced this back when I was reworking all the code in git-annex that runs processes, so it would work with threading. In the process a place that had forked a process to feed input to gpg was lost. Fixed it by spawning a thread to feed gpg. Luckily I have never released a version of git-annex with that bug, but the many users who are building from the master branch should update.
Made alerts be displayed while pairing is going on, with buttons to cancel pairing or respond to a pairing request.
About.
Started reading about ZeroMQ with the hope that it could do some firewall traversal thing, to connect mutually-unroutable nodes. Well, it could, but it'd need a proxy to run on a server both can contact, and lots of users won't have a server to run that on. The XMPP approach used by dvcs-autosync is looking like the likeliest way for git-annex to handle that use case.
However, ZeroMQ did point in promising directions to handle another use case I need to support: Local pairing. In fairly short order, I got ZeroMQ working over IP Multicast (PGM), with multiple publishers sending messages that were all seen by multiple clients on the LAN (actually the WAN; works over OpenVPN too). I had been thinking about using Avahi/ZeroConf for discovery of systems to pair with, but ZeroMQ is rather more portable and easy to work with.
Unfortunatly, I wasn't able to get ZeroMQ to behave reliably enough.
It seems to have some timeout issues the way I'm trying to use it,
or perhaps its haskell bindings are buggy? Anyway, it's really overkill
to use PGM when all I need for git-annex pairing discovery is lossy
UDP Multicast. Haskell has a simple
network-multicast library for that,
and it works great.
With discovery out of the way (theoretically), the hard part about pairing is going to be verifying that the desired repository is being paired with, and not some imposter. My plan to deal with this involves a shared secret, that can be communicated out of band, and HMAC. The webapp will prompt both parties to enter the same agreed upon secret (which could be any phrase, ideally with 64 bytes of entropy), and will then use it as the key for HMAC on the ssh public key. The digest will be sent over the wire, along with the ssh public key, and the other side can use the shared secret to verifiy the key is correct.
The other hard part about pairing will be finding the best address to use for git, etc to connect to the other host. If MDNS is available, it's ideal, but if not the pair may have to rely on local DNS, or even hard-coded IPs, which will be much less robust. Or, the assistant could broadcast queries for a peer's current IP address itself, as a poor man's MDNS.
All right then! That looks like a good week's worth of work to embark on.
Slight detour to package the haskell network-multicast library and upload to Debian unstable.
Roughed out a data type that models the whole pairing conversation, and can be serialized to implement it. And a state machine to run that conversation. Not yet hooked up to any transport such as multicast UDP.
- On OSX, install a launcher plist file, to run the assistant on login, and a
git-annex-webapp.commandfile in the desktop. This is not tested yet.
- Made the webapp display alerts when the inotify/kqueue layer has a warning message.
- Handle any crashes of each of the 15 or so named threads by displaying an alert. (Of course, this should never happen.)
Now finished building a special configurator for rsync.net. While this is just a rsync remote to git-annex, there are some tricky bits to setting up the ssh key using rsync.net's restricted shell. The configurator automates that nicely. It took about 3 hours of work, and 49 lines of rsync.net specific code to build this.
Thanks to rsync.net who heard of my Kickstarter and gave me a really nice free lifetime account. BTW guys, I wish your restricted shell supported '&&' in between commands, and returned a nonzero exit status when the command fails. This would make my error handling work better.
I've also reworked the repository management page. Nice to see those configurators start to fill in!
Decided to only make bare git repos on remote ssh servers. This configurator is aimed at using a server somewhere, which is probably not going to be running the assistant. So it doesn't need a non-bare repo, and there's nothing to keep the checked out branch in a non-bare repo up-to-date on such a server, anyway. For non-bare repos on locally accessible boxes, the pairing configurator will be the thing to use, instead of this one.
Note: While the remote ssh configurator works great, and you could even have the assistant running on multiple computers and use it to point them all at the same repo on a server, the assistant does not yet support keeping such a network topology in sync. That needs some of the ideas in cloud to happen, so clients can somehow inform each other when there are changes. Until that happens, the assistant polls only every 30 minutes, so it'll keep in sync with a 30 minute delay.
This configurator can also set up encryped rsync special remotes. Currently it always encrypts them, using the shared cipher mode of git-annex's encryption. That avoids issues with gpg key generation and distribution, and was easy to get working.
I feel I'm in a good place now WRT adding repository configurator wizards to the webapp. This one took about 2.5 days, and involved laying some groundwork that will be useful for other repository configurators. And it was probably one of the more complex ones.
Now I should be able to crank out configurators for things like Amazon S3, Bup, Rsync.net, etc fairly quickly. First, I need to do a beta release of the assistant, and start getting feedback from my backers to prioritize what to work on.
Got ssh probing implemented. It checks if it can connect to the server, and probes the server to see how it should be used.
Turned out to need two ssh probes. The first uses the system's existing ssh configuration, but disables password prompts. If that's able to get in without prompting for a password, then the user must have set that up, and doesn't want to be bothered with password prompts, and it'll respect that configuration.
Otherwise, it sets up a per-host ssh key, and configures a hostname alias
in
~/.ssh/config to use that key, and probes using that.
Configuring ssh this way is nice because it avoids changing ssh's
behavior except when git-annex uses it, and it does not open up the server
to arbitrary commands being run without password.
--
Next up will be creating the repositories. When there's a per-host key,
this will also involve setting up
authorized_keys, locking down the ssh
key to only allow running git-annex-shell or rsync.
I decided to keep that separate from the ssh probing, even though it means the user will be prompted twice for their ssh password. It's cleaner and allows the probing to do other checks -- maybe it'll later check the amount of free disk space -- and the user should be able to decide after the probe whether or not to proceed with making the repository.
Today I built the UI in the webapp to set up a ssh or rsync remote.
This is the most generic type of remote, and so it's surely got the most complex description. I've tried to word it as clearly as I can; suggestions most appreciated. Perhaps I should put in a diagram?
The idea is that this will probe the server, using ssh. If
git-annex-shell
is available there, it'll go on to set up a full git remote. If not, it'll
fall back to setting up a rsync special remote. It'll even fall all the way
back to using
rsync:// protocol if it can't connect by ssh. So the user
can just point it at a server and let it take care of the details,
generally.
The trickiest part of this will be authentication, of course. I'm relying
on ssh using
ssh-askpass to prompt for any passwords, etc, when there's
no controlling terminal. But beyond passwords, this has to deal with ssh
keys.
I'm planning to make it check if you have a ssh key configured already. If you do, it doesn't touch your ssh configuration. I don't want to get in the way of people who have a manual configuration or are using MonkeySphere.
But for a user who has never set up a ssh key, it will prompt asking if
they'd like a key to be set up. If so, it'll generate a key and configure
ssh to only use it with the server.. and as part of its ssh probe, that key
will be added to
authorized_keys.
(Obviously, advanced users can skip this entirely;
git remote add
ssh://... still works..)
Also today, fixed more UI glitches in the transfer display. I think I have them all fixed now, except for the one that needs lots of javascript to be written to fix it.
Amusingly, while I was working on UI glitches, it turned out that all the fixes involved 100% pure code that has nothing to do with UI. The UI was actually just exposing bugs.
For example, closing a running transfer had a bug that weirdly reordered the queue. This turned out to be due to the transfer queue actually maintaining two versions of the queue, one in a TChan and one a list. Some unknown bugs caused these to get out of sync. That was fixed very handily by deleting the TChan, so there's only one copy of the data.
I had only been using that TChan because I wanted a way to block while the queue was empty. But now that I'm more comfortable with STM, I know how to do that easily using a list:
getQueuedTransfer q = atomically $ do sz <- readTVar (queuesize q) if sz < 1 then retry -- blocks until size changes else ...
Ah, the times before STM were dark times indeed. I'm writing more and more STM code lately, building up more and more complicated and useful transactions. If you use threads and don't know about STM, it's a great thing to learn, to get out of the dark ages of dealing with priority inversions, deadlocks, and races.
Short day today.
- Worked on fixing a number of build failures people reported.
- Solved the problem that was making transfer pause/resume not always work. Although there is another bug where pausing a transfer sometimes lets another queued transfer start running.
- Worked on getting the assistant to start on login on OSX.
More work on the display and control of transfers.
- Hide redundant downloads from the transfer display. It seemed simplest to keep the behavior of queuing downloads from every remote that has a file, rather than going to some other data structure, but it's clutter to display those to the user, especially when you often have 7 copies of each file, like I do.
- When canceling a download, cancel all other queued downloads of that key too.
- Fixed unsettting of the paused flag when resuming a paused transfer.
- Implemented starting queued transfers by clicking on the start button.
- Spent a long time debugging why pausing, then resuming, and then pausing a transfer doesn't successfully pause it the second time. I see where the code is seemingly locking up in a
throwTo, but I don't understand why that blocks forever. Urgh..
Got the webapp's progress bars updating for downloads. Updated progressbars with all the options for ways to get progress info. For downloads, it currently uses the easy, and not very expensive, approach of periodically polling the sizes of files that are being downloaded.
For uploads, something more sophisticated will be called for..
The webapp really feels alive now that it has progress bars!
It's done! The assistant branch is merged into master.
Updated the assistant page with some screenshots and instructions for using it.
Made some cosmetic fixes to the webapp.
Fixed the transferrer to use
~/.config/git-annex/program
to find the path to git-annex when running it. (There are ways to find the
path of the currently running program in unux, but they all suck, so I'm
avoiding them this way.)
Read some OSX launchd documentation, and it seems it'd be pretty easy to get the assistant to autostart on login on OSX. If someone would like to test launchd files for me, get in touch.
AKA: Procrastinating really hard on those progress bars.
Almost done with the data transfer code.. Today I filled in some bits and peices.
Made the expensive transfer scan handle multiple remotes in one pass. So on startup, it only runs once, not N times. And when reconnecting to the network, when a remote has changed, it scans all network remotes in one pass, rather than making M redundant passes.
Got syncing with special remotes all working. Pretty easy actually. Just had to avoid doing any git repo push/pull with them, while still queueing data transfers.
It'll even download anything it can from the web special remote. To support that, I added generic support for readonly remotes; it'll only download from those and not try to upload to them.
(Oh, and I properly fixed the nasty
GIT_INDEX_FILE environment variable
problem I had the other day.)
I feel I'm very close to being able to merge the assistant branch into master now. I'm reasonably confident the data transfer code will work well now, and manage to get things in sync eventually in all circumstances. (Unless there are bugs.) All the other core functionality of the assistant and webapp is working. The only think I might delay because of is the missing progressbars in the webapp .. but that's a silly thing to block the merge on.
Still, I might spend a day and get a dumb implementation of progress bars for downloads working first (progress bars for uploads are probably rather harder). I'd spend longer on progress bars, but there are so many more exciting things I'm now ready to develop, like automatic configurators for using your git annex with Amazon S3, rsync.net, and the computer across the room..!
Working toward getting the data syncing to happen robustly, so a bunch of improvements.
- Got unmount events to be noticed, so unplugging and replugging a removable drive will resume the syncing to it. There's really no good unmount event available on dbus in kde, so it uses a heuristic there.
- Avoid requeuing a download from a remote that no longer has a key.
- Run a full scan on startup, for multiple reasons, including dealing with crashes.
Ran into a strange issue: Occasionally the assistant will run
git-annex
copy and it will not transfer the requested file. It seems that
when the copy command runs
git ls-files, it does not see the file
it's supposed to act on in its output.
Eventually I figured out what's going on: When updating the git-annex
branch, it sets
GIT_INDEX_FILE, and of course environment settings are
not thread-safe! So there's a race between threads that access
the git-annex branch, and the Transferrer thread, or any other thread
that might expect to look at the normal git index.
Unfortunatly, I don't have a fix for this yet.. Git's only interface for
using a different index file is
GIT_INDEX_FILE. It seems I have a lot of
code to tear apart, to push back the setenv until after forking every git
command.
Before I figured out the root problem, I developed a workaround for the
symptom I was seeing. I added a
git-annex transferkey, which is
optimised to be run by the assistant, and avoids running
git ls-files, so
avoids the problem. While I plan to fix this environment variable problem
properly,
transferkey turns out to be so much faster than how it was
using
copy that I'm going to keep it.
Implemented everything I planned out yesterday: Expensive scans are only done once per remote (unless the remote changed while it was disconnected), and failed transfers are logged so they can be retried later.
Changed the TransferScanner to prefer to scan low cost remotes first, as a crude form of scheduling lower-cost transfers first.
A whole bunch of interesting syncing scenarios should work now. I have not tested them all in detail, but to the best of my knowledge, all these should work:
- Connect to the network. It starts syncing with a networked remote. Disconnect the network. Reconnect, and it resumes where it left off.
- Migrate between networks (ie, home to cafe to work). Any transfers that can only happen on one LAN are retried on each new network you visit, until they succeed.
One that is not working, but is soooo close:
- Plug in a removable drive. Some transfers start. Yank the plug. Plug it back in. All necessary transfers resume, and it ends up fully in sync, no matter how many times you yank that cable.
That's not working because of an infelicity in the MountWatcher. It doesn't notice when the drive gets unmounted, so it ignores the new mount event.
Woke up this morning with most of the design for a smarter approach to syncing in my head. (This is why I sometimes slip up and tell people I work on this project 12 hours a day..)
To keep the current
assistant branch working while I make changes
that break use cases that are working, I've started
developing in a new branch,
assistant-wip.
In it, I've started getting rid of unnecessary expensive transfer scans.
First optimisation I've done is to detect when a remote that was
disconnected has diverged its
git-annex branch from the local branch.
Only when that's the case does a new transfer scan need to be done, to find
out what new stuff might be available on that remote, to have caused the
change to its branch, while it was disconnected.
That broke a lot of stuff. I have a plan to fix it written down in syncing. It'll involve keeping track of whether a transfer scan has ever been done (if not, one should be run), and recording logs when transfers failed, so those failed transfers can be retried when the remote gets reconnected.
Today, added a thread that deals with recovering when there's been a loss of network connectivity. When the network's down, the normal immediate syncing of changes of course doesn't work. So this thread detects when the network comes back up, and does a pull+push to network remotes, and triggers scanning for file content that needs to be transferred.
I used dbus again, to detect events generated by both network-manager and wicd when they've sucessfully brought an interface up. Or, if they're not available, it polls every 30 minutes.
When the network comes up, in addition to the git pull+push, it also currently does a full scan of the repo to find files whose contents need to be transferred to get fully back into sync.
I think it'll be ok for some git pulls and pushes to happen when moving to a new network, or resuming a laptop (or every 30 minutes when resorting to polling). But the transfer scan is currently really too heavy to be appropriate to do every time in those situations. I have an idea for avoiding that scan when the remote's git-annex branch has not changed. But I need to refine it, to handle cases like this:
- a new remote is added
- file contents start being transferred to (or from it)
- the network is taken down
- all the queued transfers fail
- the network comes back up
- the transfer scan needs to know the remote was not all in sync before #3, and so should do a full scan despite the git-annex branch not having changed
Doubled the ram in my netbook, which I use for all development. Yesod needs rather a lot of ram to compile and link, and this should make me quite a lot more productive. I was struggling with OOM killing bits of chromium during my last week of development.
As I prepare to dive back into development, now is a good time to review what I've built so far, and how well I'm keeping up with my planned roadmap.
I started working two and a half months ago, so am nearing the end of the three months I originally asked to be funded for on Kickstarter.
I've built much of what I planned to build in the first three months -- inotify is done (and kqueue is basically working, but needs scalability work), local syncing is done, the webapp works, and I've built some of the first configurators. It's all functional in a narrow use case involving syncing to removable drives.
progressbars still need to be dealt with, and network syncing needs to be revisited soon, so that I can start building easy configurators for further use cases, like using the cloud, or another machine on the local network.
I think I'm a little behind my original schedule, but not too bad, and at the same time, I think I've built things rather more solidly than I expected them to be at this point. I'm particularly happy with how well the inotify code works, no matter what is thrown at it, and how nice the UI in the webapp is shaping up to be.
I also need to get started on fulfilling my Kickstarter rewards, and I was happy to spend some time in the airport working on the main blocker toward that, a lack of a scalable git-annex logo, which is needed for printing on swag.
Turns out that inkscape has some amazing bitmap tracing capabilities. I was able to come up with this scalable logo in short order, it actually took longer to add back the colors, as the tracer generated a black and white version.
With that roadblock out of the way, I am moving toward ordering large quantities of usb drives, etc.
Actually did do some work on the webapp today, just fixing a bug I noticed in a spare moment. Also managed a bit in the plane earlier this week, implementing resuming of paused transfers. (Still need to test that.)
But the big thing today was dinner with one of my major Kickstarter backers, and as it turned out, "half the Haskell community of San Francisco" (3 people). Enjoyed talking about git-annex and haskell with them.
I'm looking forward to getting back home and back to work on Monday..
Unexpectedly managed a mostly productive day today.
Went ahead with making the assistant run separate
git-annex processes for
transfers. This will currently fail if git-annex is not installed in PATH.
(Deferred dealing with that.)
To stop a transfer, the webapp needs to signal not just the git-annex process, but all its children. I'm using process groups for this, which is working, but I'm not extremely happy with.
Anyway, the webapp's UI can now be used for stopping transfers, and it wasn't far from there to also implementing pausing of transfers.
Pausing a transfer is actually the same as stopping it, except a special signal is sent to the transfer control thread, which keeps running, despite the git-annex process having been killed, waits for a special resume signal, and restarts the transfer. This way a paused transfer continues to occupy a transfer slot, which prevents other queued transfers from running. This seems to be the behavior that makes sense.
Still need to wire up the webapp's button for starting a transfer. For a paused transfer, that will just need to resume it. I have not decided what the button should do when used on a transfer that is queued but not running yet. Maybe it forces it to run even if all transfer slots are already in use? Maybe it stops one of the currently running transfers to free up a slot?
Probably won't be doing any big coding on the git-annex assistant in the upcoming week, as I'll be traveling and/or slightly ill enough that I can't fully get into flow.
There was a new Yesod release this week, which required minor changes to make the webapp build with it. I managed to keep the old version of Yesod also supported, and plan to keep that working so it can be built with the version of Yesod available in, eg, Linux distributions. TBD how much pain that will involve going forward.
I'm mulling over how to support stopping/pausing transfers. The problem is that if the assistant is running a transfer in one thread, and the webapp is used to cancel it, killing that thread won't necessarily stop the transfer, because, at least in Haskell's thread model, killing a thread does not kill processes started by the thread (like rsync).
So one option is to have the transfer thread run a separate git-annex process, which will run the actual transfer. And killing that process will stop the transfer nicely. However, using a separate git-annex process means a little startup overhead for each file transferred (I don't know if it'd be enough to matter). Also, there's the problem that git-annex is sometimes not installed in PATH (wish I understood why cabal does that), which makes it kind of hard for it to run itself. (It can't simply fork, sadly. See past horrible pain with forking and threads.)
The other option is to change the API for git-annex remotes, so that
their
storeKey and
retrieveKeyFile methods return a pid of the program
that they run. When they do run a program.. not all remotes do. This
seems like it'd make the code in the remotes hairier, and it is also asking
for bugs, when a remote's implementation changes. Or I could go
lower-level, and make every place in the utility libraries that forks a
process record its pid in a per-thread MVar. Still seems to be asking for
bugs.
Oh well, at least git-annex is already crash-safe, so once I figure out
how to kill a transfer process, I can kill it safely.
A bit under the weather, but got into building buttons to control running and queued transfers today. The html and javascript side is done, with each transfer now having a cancel button, as well as a pause/start button.
Canceling queued transfers works. Canceling running transfers will need some more work, because killing a thread doesn't kill the processes being run by that thread. So I'll have to make the assistant run separate git-annex processes for transfers, that can be individually sent signals.
Nothing flashy today; I was up all night trying to download photos taken by a robot lowered onto Mars by a skycrane.
Some work on alerts. Added an alert when a file transfer succeeds or fails. Improved the alert combining code so it handles those alerts, and simplified it a lot, and made it more efficient.
Also made the text of action alerts change from present to past tense when
the action finishes. To support that I wrote a fun data type, a
TenseString
that can be rendered in either tense.
Spent yesterday and today making the WebApp handle adding removable drives.
While it needs more testing, I think that it's now possible to use the WebApp for a complete sneakernet usage scenario.
- Start up the webapp, let it make a local repo.
- Add some files, by clicking to open the file manager, and dragging them in.
- Plug in a drive, and tell the webapp to add it.
- Wait while files sync..
- Take the drive to another computer, and repeat the process there.
No command-line needed, and files will automatically be synced between two or more computers using the drive.
Sneakernet is only one usage scenario for the git-annex assistant, but I'm really happy to have one scenario 100% working!
Indeed, since the assistant and webapp can now actually do something
useful, I'll probably be merging them into
master soon.
Details follow..
So, yesterday's part of this was building the configuration page to add a removable drive. That needs to be as simple as possible, and it currently consists of a list of things git-annex thinks might be mount points of removable drives, along with how much free space they have. Pick a drive, click the pretty button, and away it goes..
(I decided to make the page so simple it doesn't even ask where you want to put the directory on the removable drive. It always puts it in a "annex" directory. I might add an expert screen later, but experts can always set this up themselves at the command line too.)
I also fought with Yesod and Bootstrap rather a lot to make the form look good. Didn't entirely succeed, and had to file a bug on Yesod about its handling of check boxes. (Bootstrap also has a bug, IMHO; its drop down lists are not always sized wide enough for their contents.)
Ideally this configuration page would listen for mount events, and refresh its list. I may add that eventually; I didn't have a handy channel it could use to do that, so defferred it. Another idea is to have the mount event listener detect removable drives that don't have an annex on them yet, and pop up an alert with a link to this configuration page.
Making the form led to a somewhat interesting problem: How to tell if a mounted
filesystem is a removable drive, or some random thing like
/proc or
a fuse filesystem. My answer, besides checking that the user can
write to it, was various heuristics, which seem to work ok, at least here..
sane Mntent { mnt_dir = dir, mnt_fsname = dev } {- We want real disks like /dev/foo, not - dummy mount points like proc or tmpfs or - gvfs-fuse-daemon. -} | not ('/' `elem` dev) = False {- Just in case: These mount points are surely not - removable disks. -} | dir == "/" = False | dir == "/tmp" = False | dir == "/run/shm" = False | dir == "/run/lock" = False
Today I did all the gritty coding to make it create a git repository on the removable drive, and tell the Annex monad about it, and ensure it gets synced.
As part of that, it detects when the removable drive's filesystem doesn't support symlinks, and makes a bare repository in that case. Another expert level config option that's left out for now is to always make a bare repository, or even to make a directory special remote rather than a git repository at all. (But directory special remotes cannot support the sneakernet use case by themselves...)
Another somewhat interesting problem was what to call the git remotes that it sets up on the removable drive and the local repository. Again this could have an expert-level configuration, but the defaults I chose are to use the hostname as the remote name on the removable drive, and to use the basename of the mount point of the removable drive as the remote name in the local annex.
Originally, I had thought of this as cloning the repository to the drive.
But, partly due to luck, I started out just doing a
git init to make
the repository (I had a function lying around to do that..).
And as I worked on it some more, I realized this is not as simple as a clone. It's a bi-directional sync/merge, and indeed the removable drive may have all the data already in it, and the local repository have just been created. Handling all the edge cases of that (like, the local repository may not have a "master" branch yet..) was fun!
Today I added a "Files" link in the navbar of the WebApp. It looks like a regular hyperlink, but clicking on it opens up your desktop's native file manager, to manage the files in the repository!
Quite fun to be able to do this kind of thing from a web page.
Made
git annex init (and the WebApp) automatically generate a description
of the repo when none is provided.
Also worked on the configuration pages some. I don't want to get ahead of myself by diving into the full configuration stage yet, but I am at least going to add a configuration screen to clone the repo to a removable drive.
After that, the list of transfers on the dashboard needs some love. I'll probably start by adding UI to cancel running transfers, and then try to get drag and drop reordering of transfers working.
Now installing git-annex automatically generates a freedesktop.org .desktop
file, and installs it, either system-wide (root) or locally (user). So
Menu -> Internet -> Git Annex will start up the web app.
(I don't entirely like putting it on the Internet menu, but the Accessories menu is not any better (and much more crowded here), and there's really no menu where it entirely fits.)
I generated that file by writing a generic library to deal with freedesktop.org desktop files and locations. Which seemed like overkill at the time, but then I found myself continuing to use that library. Funny how that happens.
So, there's also another .desktop file that's used to autostart the
git-annex assistant daemon when the user logs into the desktop.
This even works when git-annex is installed to the ugly non-PATH location
.cabal/bin/git-annex by Cabal! To make that work, it records the path
the binary is at to a freedesktop.org data file, at install time.
That should all work in Gnome, KDE, XFCE, etc. Not Mac OSX I'm guessing...
Also today, I added a sidebar notification when the assistant notices new files. To make that work well, I implemented merging of related sidebar action notifications, so the effect is that there's one notification that collectes a list of recently added files, and transient notifications that show up if a really big file is taking a while to checksum.
I'm pleased that the notification interface is at a point where I was able to implement all that, entirely in pure functional code.
Based on the results of yesterday's poll, the WebApp defaults to
~/Desktop/annex when run in the home directory. If there's no
Desktop
directory, it uses just
~/annex. And if run from some other place than
the home directory, it assumes you want to use cwd. Of course, you can
change this default, but I think it's a good one for most use cases.
My work today has all been on making one second of the total lifetime
of the WebApp work. It's the very tricky second in between clicking on
"Make repository" and being redirected to a WebApp running in your new
repository. The trickiness involves threads, and MVars, and
multiple web servers, and I don't want to go into details here.
I'd rather forget.
Anyway, it works; you can run "git annex webapp" and be walked right
through to having a usable repository! Now I need to see about adding
that to the desktop menus, and making "git annex webapp", when run a second
time, remembering where your repository is. I'll use
~/.config/git-annex/repository for storing that.
Started work on the interface displayed when the webapp is started with no existing git-annex repository. All this needs to do is walk the user through setting up a repository, as simply as possible.
A tricky part of this is that most of git-annex runs in the Annex monad, which requires a git-annex repository. Luckily, much of the webapp does not run in Annex, and it was pretty easy to work around the parts that do. Dodged a bullet there.
There will, however, be a tricky transition from this first run webapp, to a normally fully running git-annex assistant and webapp. I think the first webapp will have to start up all the normal threads once it makes the repository, and then redirect the user's web browser to the full webapp.
Anyway, the UI I've made is very simple: A single prompt, for the directory where the repository should go. With, eventually, tab completion, sanity checking (putting the repository in "/" is not good, and making it all of "$HOME" is probably unwise).
Ideally most users will accept the default, which will be something
like
/home/username/Desktop/Annex, and be through this step in seconds.
Suggestions for a good default directory name appreciated.. Putting it on a folder that will appear on the desktop seems like a good idea, when there's a Desktop directory. I'm unsure if I should name it something specific like "GitAnnex", or something generic like "Synced".
Time for the first of probably many polls!
What should the default directory name used by the git-annex assistant be?
Annex (38%)
GitAnnex (14%)
~/git-annex/ (2%)
Synced (20%)
AutoSynced (0%)
Shared (2%)
something lowercase! (20%)
CowboyNeal (2%)
Annexbox (2%)
Total votes: 50
(Note: This is a wiki. You can edit this page to add your own poll options!)
Lots of WebApp UI improvements, mostly around the behavior when displaying alert messages. Trying to make the alerts informative without being intrusively annoying, think I've mostly succeeded now.
Also, added an intro display. Shown is the display with only one repo; if there are more repos it also lists them all.
Some days I spend 2 hours chasing red herrings (like "perhaps my JSON ajax calls arn't running asynchronoously?") that turn out to be a simple one-word typo. This was one of them.
However, I did get the sidebar displaying alert messages, which can be easily sent to the user from any part of the assistant. This includes transient alerts of things it's doing, which disappear once the action finishes, and long-term alerts that are displayed until the user closes them. It even supports rendering arbitrary Yesod widgets as alerts, so they can also be used for asking questions, etc.
Time for a screencast!
Focus today was writing a notification broadcaster library. This is a way to send a notification to a set of clients, any of which can be blocked waiting for a new notification to arrive. A complication is that any number of clients may be be dead, and we don't want stale notifications for those clients to pile up and leak memory.
It took me 3 tries to find the solution, which turns out to be head-smackingly simple: An array of SampleVars, one per client.
Using SampleVars means that clients only see the most recent notification, but when the notification is just "the assistant's state changed somehow; display a refreshed rendering of it", that's sufficient.
First use of that was to make the thread that woke up every 10 minutes and checkpointed the daemon status to disk also wait for a notification that it changed. So that'll be more current, and use less IO.
Second use, of course, was to make the WebApp block long polling clients until there is really a change since the last time the client polled.
To do that, I made one change to my Yesod routes:
-/status StatusR GET +/status/#NotificationId StatusR GET
Now I find another reason to love Yesod, because after doing that,
I hit "make".. and fixed the type error. And hit make.. and fixed
the type error. And then it just freaking worked! Html was generated with
all urls to /status including a
NotificationId, and the handler for
that route got it and was able to use it:
{- Block until there is an updated status to display. -} b <- liftIO $ getNotificationBroadcaster webapp liftIO $ waitNotification $ notificationHandleFromId b nid
And now the WebApp is able to display transfers in realtime!
When I have both the WebApp and
git annex get running on the same screen,
the WebApp displays files that git-annex is transferring about as fast
as the terminal updates.
The progressbars still need to be sorted out, but otherwise the WebApp is a nice live view of file transfers.
I also had some fun with Software Transactional Memory. Now when the assistant moves a transfer from its queue of transfers to do, to its map of transfers that are currently running, it does so in an atomic transaction. This will avoid the transfer seeming to go missing (or be listed twice) if the webapp refreshes at just the wrong point in time. I'm really starting to get into STM.
Next up, I will be making the WebApp maintain a list of notices, displayed on its sidebar, scrolling new notices into view, and removing ones the user closes, and ones that expire. This will be used for displaying errors, as well as other communication with the user (such as displaying a notice while a git sync is in progress with a remote, etc). Seems worth doing now, so the basic UI of the WebApp is complete with no placeholders.
The webapp now displays actual progress bars, for the actual transfers that the assistant is making! And it's seriously shiny.
Yes, I used Bootstrap. I can see why so many people are using it, that the common complaint is everything looks the same. I spent a few hours mocking up the transfer display part of the WebApp using Bootstrap, and arrived at something that doesn't entirely suck remarkably quickly.
The really sweet thing about Bootstrap is that when I resized my browser to the shape of a cell phone, it magically redrew the WebApp like so:
To update the display, the WebApp uses two techniques. On noscript browsers, it just uses a meta refresh, which is about the best I can do. I welcome feedback; it might be better to just have an "Update" button in this case.
With javascript enabled, it uses long polling, done over AJAX. There are some other options I considered, including websockets, and server-sent events. Websockets seem too new, and while there's a WAI module supporting server-sent events, and even an example of them in the Yesod book, the module is not packaged for Debian yet. Anyway, long polling is the most widely supported, so a good starting place. It seems to work fine too, I don't really anticipate needing the more sophisticated methods.
(Incidentially, this's the first time I've ever written code that uses AJAX.)
Currently the status display is rendered in html by the web server, and just updated into place by javascript. I like this approach since it keeps the javascript code to a minimum and the pure haskell code to a maximum. But who knows, I may have to switch to JSON that gets rendered by javascript, for some reason, later on.
I was very happy with Yesod when I managed to factor out a general purpose widget that adds long-polling and meta-refresh to any other widget. I was less happy with Yesod when I tried to include jquery on my static site and it kept serving up a truncated version of it. Eventually worked around what's seemingly a bug in the default WAI middleware, by disabling that middleware.
Also yesterday I realized there were about 30 comments stuck in moderation on this website. I thought I had a feed of those, but obviously I didn't. I've posted them all, and also read them all.
Next up is probably some cleanup of bugs and minor todos. Including
figuring out why
watch has started to segfault on OSX when it was
working fine before.
After that, I need to build a way to block the long polling request until the DaemonStatus and/or TransferQueue change from the version previously displayed by the WebApp. An interesting concurrency problem..
Once I have that working, I can reduce the current 3 second delay between refreshes to a very short delay, and the WebApp will update in near-realtime as changes come in.
After an all-nighter, I have
git annex webapp launching a WebApp!
It doesn't do anything useful yet, just uses Yesod to display a couple of hyperlinked pages and a favicon, securely.
The binary size grew rather alarmingly, BTW.
Indeed, it's been growing
for months..
-rwxr-xr-x 1 root root 9.4M Jul 21 16:59 git-annex-no-assistant-stripped -rwxr-xr-x 1 joey joey 12M Jul 25 20:54 git-annex-no-webapp-stripped -rwxr-xr-x 1 joey joey 17M Jul 25 20:52 git-annex-with-webapp-stripped
Along the way, some Not Invented Here occurred:
I didn't use the yesod scaffolded site, because it's a lot of what seems mostly to be cruft in this use case. And because I don't like code generated from templates that people are then expected to edit. Ugh. That's my least favorite part of Yesod. This added some pain, since I had to do everything the hard way.
I didn't use wai-handler-launch because:
- It seems broken on IPv6 capable machines (it always opens though it apparently doesn't always listen there.. I think it was listening on my machine's ipv6 address instead. I know, I know; I should file a bug about this..)
- It always uses port 4587, which is insane. What if you have two webapps?
- It requires javascript in the web browser, which is used to ping the server, and shut it down when the web browser closes (which behavior is wrong for git-annex anyway, since the daemon should stay running across browser closes).
- It opens the webapp on web server startup, which is wrong for git-annex; instead the command
git annex webappwill open the webapp, after
git annex assistantstarted the web server.
Instead, I rolled my own WAI webapp laucher, that binds to any free port
on localhost, It does use
xdg-open to launch the web browser,
like wai-handler-launch (or just
open on OS X).
Also, I wrote my own WAI logger, which logs using System.Log.Logger,
instead of to stdout, like
runDebug does.
The webapp only listens for connections from localhost, but that's
not sufficient "security". Instead, I added a secret token to
every url in the webapp, that only
git annex webapp knows about.
But, if that token is passed to
xdg-open on its command line,
it will be briefly visible to local attackers in the parameters of
xdg-open.. And if the web browser's not already running, it'll run
with it as a parameter, and be very visible.
So instead, I used a nasty hack. On startup, the assistant
will create a html file, readably only by the user, that redirects
the user to the real site url. Then
git annex webapp will run
xdg-open on that file.
Making Yesod check the
auth= parameter (to verify that the secret token
is right) is when using Yesod started to pay off. Yesod has a simple
isAuthorized method that can be overridden to do your own authentication
like this.
But Yesod really started to shine when I went to add the
auth= parameter
to every url in the webapp. There's a
joinPath method can can be used
to override the default url builder. And every type-safe url in the
application goes through there, so it's perfect for this.
I just had to be careful to make it not add
auth= to the url for the
favicon, which is included in the "Permission Denied" error page. That'd be
an amusing security hole..
Next up: Doing some AJAX to get a dynamic view of the state of the daemon,
including currently running transfers, in the webapp. AKA stuff I've never
done before, and that, unlike all this heavy Haskell Yesod, scares me.
Milestone:!
Made the MountWatcher update state for remotes located in a drive that gets mounted. This was tricky code. First I had to make remotes declare when they're located in a local directory. Then it has to rescan git configs of git remotes (because the git repo mounted at a mount point may change), and update all the state that a newly available remote can affect.
And it works: I plug in a drive containing one of my git remotes, and the assistant automatically notices it and syncs the git repositories.
But, data isn't transferred yet. When a disconnected remote becomes connected, keys should be transferred in both directions to get back into sync.
To that end, added Yet Another Thread; the TransferScanner thread will scan newly available remotes to find keys, and queue low priority transfers to get them fully in sync.
(Later, this will probably also be used for network remotes that become available when moving between networks. I think network-manager sends dbus events it could use..)
This new thread is missing a crucial peice, it doesn't yet have a way to find the keys that need to be transferred. Doing that efficiently (without scanning the whole git working copy) is Hard. I'm considering design possibilities..
I made the MountWatcher only use dbus if it sees a client connected to dbus that it knows will send mount events, or if it can start up such a client via dbus. (Fancy!) Otherwise it falls back to polling. This should be enough to support users who manually mount things -- if they have gvfs installed, it'll be used to detect their manual mounts, even when a desktop is not running, and if they don't have gvfs, they get polling.
Also, I got the MountWatcher to work with KDE. Found a dbus event that's
emitted when KDE mounts a drive, and this is also used. If anyone with
some other desktop environment wants me to add support for it, and it uses
dbus, it should be easy: Run
dbus-monitor, plug in a drive, get
it mounted, and send me a transcript.
Of course, it'd also be nice to support anything similar on OSX that can provide mount event notifications. Not a priority though, since the polling code will work.
Some OS X fixes today..
- Jimmy pointed out that my
getmntentcode broke the build on OSX again. Sorry about that.. I keep thinking Unix portability nightmares are a 80's thing, not a 2010's thing. Anyway, adapted a lot of hackish C code to emulate
getmntenton BSD systems, and it seems to work. (I actually think the BSD interface to this is saner than Linux's, but I'd rather have either one than both, sigh..)
- Kqueue was blocking all the threads on OSX. This is fixed, and the assistant seems to be working on OSX again.
I put together a preliminary page thanking everyone who contributed to the git-annex Kickstarter. thanks The wall-o-names is scary crazy humbling.
Improved
--debug mode for the assistant, now every thread says whenever
it's doing anything interesting, and also there are timestamps.
Had been meaning to get on with syncing to drives when they're mounted, but got sidetracked with the above. Maybe tomorrow. I did think through it in some detail as I was waking up this morning, and think I have a pretty good handle on it.
Really productive day today, now that I'm out of the threaded runtime tarpit!
First, brought back
--debug logging, better than before! As part of that, I
wrote some 250 lines of code to provide a IMHO more pleasant interface to
System.Process (itself only 650 lines of code) that avoids all the
low-level setup, cleanup, and tuple unpacking. Now I can do things like
write to a pipe to a process, and ensure it exits nonzero, this easily:
withHandle StdinHandle createProcessSuccess (proc "git" ["hash-object", "--stdin"]) $ \h -> hHutStr h objectdata
My interface also makes it easy to run nasty background processes, reading their output lazily.
lazystring <- withHandle StdoutHandle createBackgroundProcess (proc "find" ["/"]) hGetContents
Any true Haskellers are shuddering here, I really should be using conduits or pipes, or something. One day..
The assistant needs to detect when removable drives are attached, and sync with them. This is a reasonable thing to be working on at this point, because it'll make the currently incomplete data transfer code fully usable for the sneakernet use case, and firming that up will probably be a good step toward handing other use cases involving data transfer over the network, including cases where network remotes are transientely available.
So I've been playing with using dbus to detect mount events. There's a very nice Haskell library to use dbus.
This simple program will detect removable drives being mounted, and works on Xfce (as long as you have automounting enabled in its configuration), and should also work on Gnome, and, probably, KDE:
{-# LANGUAGE OverloadedStrings #-} import Data.List (sort) import DBus import DBus.Client import Control.Monad main = do client <- connectSession listen client mountadded $ \s -> putStrLn (show s) forever $ getLine -- let listener thread run forever where mountadded = matchAny { matchInterface = Just "org.gtk.Private.RemoteVolumeMonitor" , matchMember = Just "MountAdded" }
(Yeah... "org.gtk.Private.RemoteVolumeMonitor". There are so
many things wrong with that string. What does gtk have to do with
mounting a drive? Why is it Private? Bleagh. Should I only match
the "MountAdded" member and not the interface? Seems everyone who does
this relies on google to find other people who have cargo-culted it,
or just runs
dbus-monitor and picks out things.
There seems to be no canonical list of events. Bleagh.)
Spent a while shaving a yak of needing a
getmntent interface in Haskell.
Found one in a hsshellscript library; since that library is not packaged
in Debian, and I don't really want to depend on it, I extracted just
the mtab and fstab parts of it into a little library in git-annex.
I've started putting together a MountWatcher thread. On systems without
dbus (do OSX or the BSDs have dbus?), or if dbus is not running, it polls
/etc/mtab every 10 seconds for new mounts. When dbus is available,
it doesn't need the polling, and should notice mounts more quickly.
Open question: Should it still poll even when dbus is available? Some of us
like to mount our own drives, by hand and may have automounting disabled. It'd
be good if the assistant supported that. This might need a
annex.no-dbus setting, but I'd rather avoid needing such manual
configuration.
One idea is to do polling in addition to dbus, if
/etc/fstab contains
mount points that seem to be removable drives, on which git remotes lives.
Or it could always do polling in addition to dbus, which is just some extra
work. Or, it could try to introspect dbus to see if mount events will
be generated.
The MountWatcher so far only detects new mounts and prints out what happened. Next up: Do something in response to them.
This will involve manipulating the Annex state to belatedly add the Remote on the mount point.. tricky. And then, for Git Remotes, it should pull/push the Remote to sync git data. Finally, for all remotes, it will need to queue Transfers of file contents from/to the newly available Remote.
Beating my head against the threaded runtime some more. I can reproduce
one of the hangs consistently by running 1000 git annex add commands
in a loop. It hangs around 1% of the time, reading from
git cat-file.
Interestingly,
git cat-file is not yet running at this point --
git-annex has forked a child process, but the child has not yet exec'd it.
Stracing the child git-annex, I see it stuck in a futex. Adding tracing,
I see the child never manages to run any code at all.
This really looks like the problem is once again in MissingH, which uses
forkProcess. Which happens to come with a big warning about being very
unsafe, in very subtle ways. Looking at the C code that the newer
process
library uses when sparning a pipe to a process, it messes around with lots of
things; blocking signals, stopping a timer, etc. Hundreds of lines of C
code to safely start a child process, all doing things that MissingH omits.
That's the second time I've seemingly isolated a hang in the GHC threaded runtime to MissingH.
And so I've started converting git-annex to use the new
process library,
for running all its external commands. John Goerzen had mentioned
process
to me once before when I found a nasty bug in MissingH, as the cool new
thing that would probably eliminate the
System.Cmd.Utils part of MissingH,
but I'd not otherwise heard much about it. (It also seems to have the
benefit of supporting Windows.)
This is a big change and it's early days, but each time I see a hang, I'm
converting the code to use
process, and so far the hangs have just gone
away when I do that.
Hours later... I've converted all of git-annex to use
process.
In the er, process, the
--debug switch stopped printing all the commands
it runs. I may try to restore that later.
I've not tested everything, but the test suite passes, even when using the threaded runtime. MILESTONE
Looking forward to getting out of these weeds and back to useful work..
Hours later yet.... The
assistant branch in git now uses the threaded
runtime. It works beautifully, using proper threads to run file transfers
in.
That should fix the problem I was seeing on OSX yesterday. Too tired to test it now.
--
Amazingly, all the assistant's own dozen or so threads and thread synch variables etc all work great under the threaded runtime. I had assumed I'd see yet more concurrency problems there when switching to it, but it all looks good. (Or whatever problems there are are subtle ones?)
I'm very relieved. The threaded logjam is broken! I had been getting increasingly worried that not having the threaded runtime available would make it very difficult to make the assistant perform really well, and cause problems with the webapp, perhaps preventing me from using Yesod.
Now it looks like smooth sailing ahead. Still some hard problems, but it feels like with inotify and kqueue and the threaded runtime all dealt with, the really hard infrastructure-level problems are behind me.
Back home and laptop is fixed.. back to work.
Warmup exercises:
Went in to make it queue transfers when a broken symlink is received, only to find I'd already written code to do that, and forgotten about it. Heh. Did check that the git-annex branch is always sent first, which will ensure that code always knows where to transfer a key from. I had probably not considered this wrinkle when first writing the code; it worked by accident.
Made the assistant check that a remote is known to have a key before queueing a download from it.
Fixed a bad interaction between the
git annex mapcommand and the assistant.
Tried using a modified version of
MissingH that doesn't use
HSLogger
to make git-annex work with the threaded GHC runtime. Unfortunatly,
I am still seeing hangs in at least 3 separate code paths when
running the test suite. I may have managed to fix one of the hangs,
but have not grokked what's causing the others.
I now have access to a Mac OSX system, thanks to Kevin M. I've fixed some portability problems in git-annex with it before, but today I tested the assistant on it:
Found a problem with the kqueue code that prevents incoming pushes from being noticed.
The problem was that the newly added git ref file does not trigger an add event. The kqueue code saw a generic change event for the refs directory, but since the old file was being deleted and replaced by the new file, the kqueue code, which already had the old file in its cache, did not notice the file had been replaced.
I fixed that by making the kqueue code also track the inode of each file. Currently that adds the overhead of a stat of each file, which could be avoided if haskell exposed the inode returned by
readdir. Room to optimise this later...
Also noticed that the kqueue code was not separating out file deletions from directory deletions. IIRC Jimmy had once mentioned a problem with file deletions not being noticed by the assistant, and this could be responsible for that, although the directory deletion code seems to handle them ok normally. It was making the transfer watching thread not notice when any transfers finished, for sure. I fixed this oversight, looking in the cache to see if there used to be a file or a directory, and running the appropriate hook.
Even with these fixes, the assistant does not yet reliably transfer file contents on OSX. I think the problem is that with kqueue we're not guaranteed to get an add event, and a deletion event for a transfer info file -- if it's created and quickly deleted, the code that synthensizes those events doesn't run in time to know it existed. Since the transfer code relies on deletion events to tell when transfers are complete, it stops sending files after the first transfer, if the transfer ran so quickly it doesn't get the expected events.
So, will need to work on OSX support some more...
Managed to find a minimal, 20 line test case for at least one of the ways git-annex was hanging with GHC's threaded runtime. Sent it off to haskell-cafe for analysis. thread
Further managed to narrow the bug down to MissingH's use of logging code, that git-annex doesn't use. bug report. So, I can at least get around this problem with a modified version of MissingH. Hopefully that was the only thing causing the hangs I was seeing!
I didn't plan to work on git-annex much while at DebConf, because the conference always prevents the kind of concentration I need. But I unexpectedly also had to deal with three dead drives and illness this week.
That said, I have been trying to debug a problem with git-annex and Haskell's threaded runtime all week. It just hangs, randomly. No luck so far isolating why, although I now have a branch that hangs fairly reliably, and in which I am trying to whittle the entire git-annex code base (all 18 thousand lines!) into a nice test case.
This threaded runtime problem doesn't affect the assistant yet, but if I want to use Yesod in developing the webapp, I'll need the threaded runtime, and using the threaded runtime in the assistant generally would make it more responsive and less hacky.
Since this is a task I can work on without much concentration, I'll probably keep beating on it until I return home. Then I need to spend some quality thinking time on where to go next in the assistant.
Spent most of the day making file content transfers robust. There were lots of bugs, hopefully I've fixed most of them. It seems to work well now, even when I throw a lot of files at it.
One of the changes also sped up transfers; it no longer roundtrips to the
remote to verify it has a file. The idea here is that when the assistant is
running, repos should typically be fairly tightly synced to their remotes
by it, so some of the extra checks that the
move command does are
unnecessary.
Also spent some time trying to use ghc's threaded runtime, but continue to be baffled by the random hangs when using it. This needs fixing eventually; all the assistant's threads can potentially be blocked when it's waiting on an external command it has run.
Also changed how transfer info files are locked. The lock file is now separate from the info file, which allows the TransferWatcher thread to notice when an info file is created, and thus actually track transfers initiated by remotes.
I'm fairly close now to merging the
assistant branch into
master.
The data syncing code is very brute-force, but it will work well enough
for a first cut.
Next I can either add some repository network mapping, and use graph analysis to reduce the number of data transfers, or I can move on to the webapp. Not sure yet which I'll do. It's likely that since DebConf begins tomorrow I'll put off either of those big things until after the conference.
My laptop's SSD died this morning. I had some work from yesterday committed to the git repo on it, but not pushed as it didn't build. Luckily I was able to get that off the SSD, which is now a read-only drive -- even mounting it fails with fsck write errors.
Wish I'd realized the SSD was dying before the day before my trip to Nicaragua.. Getting back to a useful laptop used most of my time and energy today.
I did manage to fix transfers to not block the rest of the assistant's threads. Problem was that, without Haskell's threaded runtime, waiting on something like a rsync command blocks all threads. To fix this, transfers now are run in separate processes.
Also added code to allow multiple transfers to run at once. Each transfer
takes up a slot, with the number of free slots tracked by a
QSemN.
This allows the transfer starting thread to block until a slot frees up,
and then run the transfer.
This needs to be extended to be aware of transfers initiated by remotes.
The transfer watcher thread should detect those starting and stopping
and update the
QSemN accordingly. It would also be nice if transfers
initiated by remotes would be delayed when there are no free slots for them
... but I have not thought of a good way to do that.
There's a bug somewhere in the new transfer code, when two transfers are queued close together, the second one is lost and doesn't happen. Would debug this, but I'm spent for the day.
So as not to bury the lead, I've been hard at work on my first day in Nicaragua, and the git-annex assistant fully syncs files (including their contents) between remotes now !!
Details follow..
Made the committer thread queue Upload Transfers when new files are added to the annex. Currently it tries to transfer the new content to every remote; this inefficiency needs to be addressed later.
Made the watcher thread queue Download Transfers when new symlinks appear that point to content we don't have. Typically, that will happen after an automatic merge from a remote. This needs to be improved as it currently adds Transfers from every remote, not just those that have the content.
This was the second place that needed an ordered list of remotes to talk to. So I cached such a list in the DaemonStatus state info. This will also be handy later on, when the webapp is used to add new remotes, so the assistant can know about them immediately.
Added YAT (Yet Another Thread), number 15 or so, the transferrer thread that waits for transfers to be queued and runs them. Currently a naive implementation, it runs one transfer at a time, and does not do anything to recover when a transfer fails.
Actually transferring content requires YAT, so that the transfer action can run in a copy of the Annex monad, without blocking all the assistant's other threads from entering that monad while a transfer is running. This is also necessary to allow multiple concurrent transfers to run in the future.
This is a very tricky piece of code, because that thread will modify the git-annex branch, and its parent thread has to invalidate its cache in order to see any changes the child thread made. Hopefully that's the extent of the complication of doing this. The only reason this was possible at all is that git-annex already support multiple concurrent processes running and all making independent changes to the git-annex branch, etc.
After all my groundwork this week, file content transferring is now fully working!
In a series of airport layovers all day. Since I woke up at 3:45 am, didn't feel up to doing serious new work, so instead I worked through some OSX support backlog.
git-annex will now use Haskell's SHA library if the
sha256sum
command is not available. That library is slow, but it's guaranteed to be
available; git-annex already depended on it to calculate HMACs.
Then I decided to see if it makes sense to use the SHA library
when adding smaller files. At some point, its slower implementation should
win over needing to fork and parse the output of
sha256sum. This was
the first time I tried out Haskell's
Criterion benchmarker,
and I built this simple benchmark in short order.
import Data.Digest.Pure.SHA import Data.ByteString.Lazy as L import Criterion.Main import Common testfile :: FilePath testfile = "/tmp/bar" -- on ram disk main = defaultMain [ bgroup "sha256" [ bench "internal" $ whnfIO internal , bench "external" $ whnfIO external ] ] internal :: IO String internal = showDigest . sha256 <$> L.readFile testfile external :: IO String external = pOpen ReadFromPipe "sha256sum" [testfile] $ \h -> fst . separate (== ' ') <$> hGetLine h
The nice thing about benchmarking in Airports is when you're running a benchmark locally, you don't want to do anything else with the computer, so can alternate people watching, spacing out, and analizing results.
100 kb file:
benchmarking sha256/internal mean: 15.64729 ms, lb 15.29590 ms, ub 16.10119 ms, ci 0.950 std dev: 2.032476 ms, lb 1.638016 ms, ub 2.527089 ms, ci 0.950 benchmarking sha256/external mean: 8.217700 ms, lb 7.931324 ms, ub 8.568805 ms, ci 0.950 std dev: 1.614786 ms, lb 1.357791 ms, ub 2.009682 ms, ci 0.950
75 kb file:
benchmarking sha256/internal mean: 12.16099 ms, lb 11.89566 ms, ub 12.50317 ms, ci 0.950 std dev: 1.531108 ms, lb 1.232353 ms, ub 1.929141 ms, ci 0.950 benchmarking sha256/external mean: 8.818731 ms, lb 8.425744 ms, ub 9.269550 ms, ci 0.950 std dev: 2.158530 ms, lb 1.916067 ms, ub 2.487242 ms, ci 0.950
50 kb file:
benchmarking sha256/internal mean: 7.699274 ms, lb 7.560254 ms, ub 7.876605 ms, ci 0.950 std dev: 801.5292 us, lb 655.3344 us, ub 990.4117 us, ci 0.950 benchmarking sha256/external mean: 8.715779 ms, lb 8.330540 ms, ub 9.102232 ms, ci 0.950 std dev: 1.988089 ms, lb 1.821582 ms, ub 2.181676 ms, ci 0.950
10 kb file:
benchmarking sha256/internal mean: 1.586105 ms, lb 1.574512 ms, ub 1.604922 ms, ci 0.950 std dev: 74.07235 us, lb 51.71688 us, ub 108.1348 us, ci 0.950 benchmarking sha256/external mean: 6.873742 ms, lb 6.582765 ms, ub 7.252911 ms, ci 0.950 std dev: 1.689662 ms, lb 1.346310 ms, ub 2.640399 ms, ci 0.950
It's possible to get nice graphical reports out of Criterion, but this is clear enough, so I stopped here. 50 kb seems a reasonable cutoff point.
I also used this to benchmark the SHA256 in Haskell's Crypto package. Surprisingly, it's a lot slower than even the Pure.SHA code. On a 50 kb file:
benchmarking sha256/Crypto collecting 100 samples, 1 iterations each, in estimated 6.073809 s mean: 69.89037 ms, lb 69.15831 ms, ub 70.71845 ms, ci 0.950 std dev: 3.995397 ms, lb 3.435775 ms, ub 4.721952 ms, ci 0.950
There's another Haskell library, SHA2, which I should try some time.
Starting to travel, so limited time today.
Yet Another Thread added to the assistant, all it does is watch for changes to transfer information files, and update the assistant's map of transfers currently in progress. Now the assistant will know if some other repository has connected to the local repo and is sending or receiving a file's content.
This seemed really simple to write, it's just 78 lines of code. It worked
100% correctly the first time.
But it's only so easy because I've got
this shiny new inotify hammer that I keep finding places to use in the
assistant.
Also, the new thread does some things that caused a similar thread (the merger thread) to go into a MVar deadlock. Luckily, I spent much of day 19 investigating and fixing that deadlock, even though it was not a problem at the time.
So, good.. I'm doing things right and getting to a place where rather nontrivial features can be added easily.
--
Next up: Enough nonsense with tracking transfers... Time to start actually transferring content around!
Well, sometimes you just have to go for the hack. Trying to find a way
to add additional options to git-annex-shell without breaking backwards
compatibility, I noticed that it ignores all options after
--, because
those tend to be random rsync options due to the way rsync runs it.
So, I've added a new class of options, that come in between, like
-- opt=val opt=val ... --
The parser for these will not choke on unknown options, unlike normal getopt. So this let me add the additional info I needed to pass to git-annex-shell to make it record transfer information. And if I need to pass more info in the future, that's covered too.
It's ugly, but since only git-annex runs git-annex-shell, this is an ugliness only I (and now you, dear reader) have to put up with.
Note to self: Command-line programs are sometimes an API, particularly if designed to be called remotely, and so it makes sense consider whether they are, and design expandability into them from day 1.
Anyway, we now have full transfer tracking in git-annex! Both sides of a transfer know what's being transferred, and from where, and have the info necessary to interrupt the transfer.
Also did some basic groundwork, adding a queue of transfers to perform, and adding to the daemon's status information a map of currently running transfers.
Next up: The daemon will use inotify to notice new and deleted transfer info files, and update its status info.
Worked today on two action items from my last blog post:
- on-disk transfers in progress information files (read/write/enumerate)
- locking for the files, so redundant transfer races can be detected, and failed transfers noticed
That's all done, and used by the
get,
copy, and
move subcommands.
Also, I made
git-annex status use that information to display any
file transfers that are currently in progress:
joey@gnu:~/lib/sound/misc>git annex status [...] transfers in progress: downloading Vic-303.mp3 from leech
(Webapp, here we come!)
However... Files being sent or received by
git-annex-shell don't yet
have this transfer info recorded. The problem is that to do so,
git-annex-shell will need to be run with a
--remote= parameter. But
old versions will of course fail when run with such an unknown parameter.
This is a problem I last faced in December 2011 when adding the
--uuid=
parameter. That time I punted and required the remote
git-annex-shell be
updated to a new enough version to accept it. But as git-annex gets more widely
used and packaged, that's becoming less an option. I need to find a real
solution to this problem.
Today is a planning day. I have only a few days left before I'm off to
Nicaragua for DebConf, where I'll only
have smaller chunks of time without interruptions. So it's important to get
some well-defined smallish chunks designed that I can work on later. See
bulleted action items below (now moved to syncing. Each
should be around 1-2 hours unless it turns out to be 8 hours...
First, worked on writing down a design, and some data types, for data transfer tracking (see syncing page). Found that writing down these simple data types before I started slinging code has clarified things a lot for me.
Most importantly, I realized that I will need to modify
git-annex-shell
to record on disk what transfers it's doing, so the assistant can get that
information and use it to both avoid redundant transfers (potentially a big
problem!), and later to allow the user to control them using the web app.
While eventually the user will be able to use the web app to prioritize transfers, stop and start, throttle, etc, it's important to get the default behavior right. So I'm thinking about things like how to prioritize uploads vs downloads, when it's appropriate to have multiple downloads running at once, etc.
Random improvements day..
Got the merge conflict resolution code working in
git annex assistant.
Did some more fixes to the pushing and pulling code, covering some cases I missed earlier.
Git syncing seems to work well for me now; I've seen it recover from a variety of error conditions, including merge conflicts and repos that were temporarily unavailable.
There is definitely a MVar deadlock if the merger thread's inotify event handler tries to run code in the Annex monad. Luckily, it doesn't currently seem to need to do that, so I have put off debugging what's going on there.
Reworked how the inotify thread runs, to avoid the two inotify threads in the assistant now from both needing to wait for program termination, in a possibly conflicting manner.
Hmm, that seems to have fixed the MVar deadlock problem.
Been thinking about how to fix ?watcher commits unlocked files. Posted some thoughts there.
It's about time to move on to data syncing. While eventually that will need to build a map of the repo network to efficiently sync data over the fastest paths, I'm thinking that I'll first write a dumb version. So, two more threads:
Uploads new data to every configured remote. Triggered by the watcher thread when it adds content. Easy; just use a
TSetof Keys to send.
Downloads new data from the cheapest remote that has it. Could be triggered by the merger thread, after it merges in a git sync. Rather hard; how does it work out what new keys are in the tree without scanning it all? Scan through the git history to find newly created files? Maybe the watcher triggers this thread instead, when it sees a new symlink, without data, appear.
Both threads will need to be able to be stopped, and restarted, as needed to control the data transfer. And a lot of other control smarts will eventually be needed, but my first pass will be to do a straightforward implementation. Once it's done, the git annex assistant will be basically usable.
Worked on automatic merge conflict resolution today. I had expected to be able to use git's merge driver interface for this, but that interface is not sufficient. There are two problems with it:
- The merge program is run when git is in the middle of an operation that locks the index. So it cannot delete or stage files. I need to do both as part of my conflict resolution strategy.
- The merge program is not run at all when the merge conflict is caused by one side deleting a file, and the other side modifying it. This is an important case to handle.
So, instead, git-annex will use a regular
git merge, and if it fails, it
will fix up the conflicts.
That presented its own difficulty, of finding which files in the tree
conflict.
git ls-files --unmerged is the way to do that, but its output
is a quite raw form:
120000 3594e94c04db171e2767224db355f514b13715c5 1 foo 120000 35ec3b9d7586b46c0fd3450ba21e30ef666cfcd6 3 foo 100644 1eabec834c255a127e2e835dadc2d7733742ed9a 2 bar 100644 36902d4d842a114e8b8912c02d239b2d7059c02b 3 bar
I had to stare at the rather impenetrable documentation for hours and write a lot of parsing and processing code to get from that to these mostly self explanatory data types:
data Conflicting v = Conflicting { valUs :: Maybe v , valThem :: Maybe v } deriving (Show) data Unmerged = Unmerged { unmergedFile :: FilePath , unmergedBlobType :: Conflicting BlobType , unmergedSha :: Conflicting Sha } deriving (Show)
Not the first time I've whined here about time spent parsing unix command
output, is it?
From there, it was relatively easy to write the actual conflict cleanup
code, and make
git annex sync use it. Here's how it looks:
$ ls -1 foo.png bar.png $ git annex sync commit # On branch master nothing to commit (working directory clean) ok merge synced/master CONFLICT (modify/delete): bar.png deleted in refs/heads/synced/master and modified in HEAD. Version HEAD of bar.png left in tree. Automatic merge failed; fix conflicts and then commit the result. bar.png: needs merge (Recording state in git...) [master 0354a67] git-annex automatic merge conflict fix ok $ ls -1 foo.png bar.variant-a1fe.png bar.variant-93a1.png
There are very few options for ways for the conflict resolution code to name conflicting variants of files. The conflict resolver can only use data present in git to generate the names, because the same conflict needs to be resolved the same everywhere.
So I had to choose between using the full key name in the filenames produced when resolving a merge, and using a shorter checksum of the key, that would be more user-friendly, but could theoretically collide with another key. I chose the checksum, and weakened it horribly by only using 32 bits of it!
Surprisingly, I think this is a safe choice. The worst that can happens if such a collision happens is another conflict, and the conflict resolution code will work on conflicts produced by the conflict resolution code! In such a case, it does fall back to putting the whole key in the filename: "bar.variant-SHA256-s2550--2c09deac21fa93607be0844fefa870b2878a304a7714684c4cc8f800fda5e16b.png"
Still need to hook this code into
git annex assistant.
Not much available time today, only a few hours.
Main thing I did was fixed up the failed push tracking to use a better data
structure. No need for a queue of failed pushes, all it needs is a map of
remotes that have an outstanding failed push, and a timestamp. Now it
won't grow in memory use forever anymore.
Finding the right thread mutex type for this turned out to be a bit of a challenge. I ended up with a STM TMVar, which is left empty when there are no pushes to retry, so the thread using it blocks until there are some. And, it can be updated transactionally, without races.
I also fixed a bug outside the git-annex assistant code. It was possible to crash git-annex if a local git repository was configured as a remote, and the repository was not available on startup. git-annex now ignores such remotes. This does impact the assistant, since it is a long running process and git repositories will come and go. Now it ignores any that were not available when it started up. This will need to be dealt with when making it support removable drives.
I released a version of git-annex over the weekend that includes the
git
annex watch command. There's a minor issue installing it from cabal on
OSX, which I've fixed in my tree. Nice timing: At least the watch command
should be shipped in the next Debian release, which freezes at the end of
the month.
Jimmy found out how kqueue blows up when there are too many directories to keep all open. I'm not surprised this happens, but it's nice to see exactly how. Odd that it happened to him at just 512 directories; I'd have guessed more. I have plans to fork watcher programs that each watch 512 directories (or whatever the ulimit is), to deal with this. What a pitiful interface is kqueue.. I have not thought yet about how the watcher programs would communicate back to the main program.
Back on the assistant front, I've worked today on making git syncing more robust. Now when a push fails, it tries a pull, and a merge, and repushes. That ensures that the push is, almost always, a fast-forward. Unless something else gets in a push first, anyway!
If a push still fails, there's Yet Another Thread, added today, that will wake up after 30 minutes and retry the push. It currently keeps retrying every 30 minutes until the push finally gets though. This will deal, to some degree, with those situations where a remote is only sometimes available.
I need to refine the code a bit, to avoid it keeping an ever-growing queue of failed pushes, if a remote is just dead. And to clear old failed pushes from the queue when a later push succeeds.
I also need to write a git merge driver that handles conflicts in the tree.
If two conflicting versions of a file
foo are saved, this would merge
them, renaming them to
foo.X and
foo.Y. Probably X and Y are the
git-annex keys for the content of the files; this way all clones will
resolve the conflict in a way that leads to the same tree. It's also
possible to get a conflict by one repo deleting a file, and another
modifying it. In this case, renaming the deleted file to
foo.Y may
be the right approach, I am not sure.
I glanced through some Haskell dbus bindings today. I belive there are dbus events available to detect when drives are mounted, and on Linux this would let git-annex notice and sync to usb drives, etc.
Syncing works! I have two clones, and any file I create in the first is immediately visible in the second. Delete that file from the second, and it's immediately removed from the first.
Most of my work today felt like stitching existing limbs onto a pre-existing
monster. Took the committer thread, that waits for changes and commits them,
and refashioned it into a pusher thread, that waits for commits and pushes
them. Took the watcher thread, that watches for files being made,
and refashioned it into a merger thread, that watches for git refs being
updated. Pulled in bits of the
git annex sync command to reanimate this.
It may be a shambling hulk, but it works.
Actually, it's not much of a shambling hulk; I refactored my code after
copying it.
I think I'm up to 11 threads now in the new
git annex assistant command, each with its own job, and each needing
to avoid stepping on the other's toes. I did see one MVar deadlock error
today, which I have not managed to reproduce after some changes. I think
the committer thread was triggering the merger thread, which probably
then waited on the Annex state MVar the committer thread had held.
Anyway, it even pushes to remotes in parallel, and keeps track of remotes it failed to push to, although as of yet it doesn't do any attempt at periodically retrying.
One bug I need to deal with is that the push code assumes any change made to the remote has already been pushed back to it. When it hasn't, the push will fail due to not being a fast-forward. I need to make it detect this case and pull before pushing.
(I've pushed this work out in a new
assistant branch.)
Pondering syncing today. I will be doing syncing of the git repository first, and working on syncing of file data later.
The former seems straightforward enough, since we just want to push all changes to everywhere. Indeed, git-annex already has a sync command that uses a smart technique to allow syncing between clones without a central bare repository. (Props to Joachim Breitner for that.)
But it's not all easy. Syncing should happen as fast as possible, so changes show up without delay. Eventually it'll need to support syncing between nodes that cannot directly contact one-another. Syncing needs to deal with nodes coming and going; one example of that is a USB drive being plugged in, which should immediately be synced, but network can also come and go, so it should periodically retry nodes it failed to sync with. To start with, I'll be focusing on fast syncing between directly connected nodes, but I have to keep this wider problem space in mind.
One problem with
git annex sync is that it has to be run in both clones
in order for changes to fully propagate. This is because git doesn't allow
pushing changes into a non-bare repository; so instead it drops off a new
branch in
.git/refs/remotes/$foo/synced/master. Then when it's run locally
it merges that new branch into
master.
So, how to trigger a clone to run
git annex sync when syncing to it?
Well, I just realized I have spent two weeks developing something that can
be repurposed to do that! Inotify can watch for changes to
.git/refs/remotes, and the instant a change is made, the local sync
process can be started. This avoids needing to make another ssh connection
to trigger the sync, so is faster and allows the data to be transferred
over another protocol than ssh, which may come in handy later.
So, in summary, here's what will happen when a new file is created:
- inotify event causes the file to be added to the annex, and immediately committed.
- new branch is pushed to remotes (probably in parallel)
- remotes notice new sync branch and merge it
- (data sync, TBD later)
- file is fully synced and available
Steps 1, 2, and 3 should all be able to be accomplished in under a second.
The speed of
git push making a ssh connection will be the main limit
to making it fast. (Perhaps I should also reuse git-annex's existing ssh
connection caching code?)
... I'm getting tired of kqueue.
But the end of the tunnel is in sight. Today I made git-annex handle files that are still open for write after a kqueue creation event is received. Unlike with inotify, which has a new event each time a file is closed, kqueue only gets one event when a file is first created, and so git-annex needs to retry adding files until there are no writers left.
Eventually I found an elegant way to do that. The committer thread already wakes up every second as long as there's a pending change to commit. So for adds that need to be retried, it can just push them back onto the change queue, and the committer thread will wait one second and retry the add. One second might be too frequent to check, but it will do for now.
This means that
git annex watch should now be usable on OSX, FreeBSD, and
NetBSD! (It'll also work on Debian kFreeBSD once lsof is ported to it.)
I've meged kqueue support to
master.
I also think I've squashed the empty commits that were sometimes made.
Incidentally, I'm 50% through my first month, and finishing inotify was the first half of my roadmap for this month. Seem to be right on schedule.. Now I need to start thinking about syncing.
Good news! My beta testers report that the new kqueue code works on OSX.
At least "works" as well as it does on Debian kFreeBSD. My crazy
development strategy of developing on Debian kFreeBSD while targeting Mac
OSX is vindicated.
So, I've been beating the kqueue code into shape for the last 12 hours, minus a few hours sleep.
First, I noticed it was seeming to starve the other threads. I'm using
Haskell's non-threaded runtime, which does cooperative multitasking between
threads, and my C code was never returning to let the other threads run.
Changed that around, so the C code runs until SIGALARMed, and then that
thread calls
yield before looping back into the C code. Wow, cooperative
multitasking.. I last dealt with that when programming for Windows 3.1!
(Should try to use Haskell's -threaded runtime sometime, but git-annex
doesn't work under it, and I have not tried to figure out why not.)
Then I made a single commit, with no testing, in which I made the kqueue code maintain a cache of what it expects in the directory tree, and use that to determine what files changed how when a change is detected. Serious code. It worked on the first go. If you were wondering why I'm writing in Haskell ... yeah, that's why.
And I've continued to hammer on the kqueue code, making lots of little
fixes, and at this point it seems almost able to handle the changes I
throw at it. It does have one big remaining problem; kqueue doesn't tell me
when a writer closes a file, so it will sometimes miss adding files. To fix
this, I'm going to need to make it maintain a queue of new files, and
periodically check them, with
lsof, to see when they're done being
written to, and add them to the annex. So while a file is being written
to,
git annex watch will have to wake up every second or so, and run
lsof ... and it'll take it at least 1 second to notice a file's complete.
Not ideal, but the best that can be managed with kqueue.
Followed my plan from yesterday, and wrote a simple C library to interface
to
kqueue, and Haskell code to use that library. By now I think I
understand kqueue fairly well -- there are some very tricky parts to the
interface.
But... it still didn't work. After building all this, my code was failing the same way that the haskell kqueue library failed yesterday. I filed a bug report with a testcase.
Then I thought to ask on #haskell. Got sorted out in quick order! The
problem turns out to be that haskell's runtime has a periodic SIGALARM,
that is interrupting my kevent call. It can be worked around with
+RTS -V0,
but I put in a fix to retry to kevent when it's interrupted.
And now
git-annex watch can detect changes to directories on BSD and OSX!
Note: I said "detect", not "do something useful in response to". Getting
from the limited kqueue events to actually staging changes in the git repo
is going to be another day's work. Still, brave FreeBSD or OSX users
might want to check out the
watch branch from git and see if
git annex watch will at least say it sees changes you make to your
repository.
I've been investigating how to make
git annex watch work on
FreeBSD, and by extension, OSX.
One option is kqueue, which works on both operating systems, and allows very basic monitoring of file changes. There's also an OSX specific hfsevents interface.
Kqueue is far from optimal for
git annex watch, because it provides even
less information than inotify (which didn't really provide everything I
needed, thus the lsof hack). Kqueue doesn't have events for files being
closed, only an event when a file is created. So it will be difficult for
git annex watch to know when a file is done being written to and can be
annexed. git annex will probably need to run lsof periodically to check when
recently added files are complete. (hsevents shares this limitation)
Kqueue also doesn't provide specific events when a file or directory is
moved. Indeed, it doesn't provide specific events about what changed at
all. All you get with kqueue is a generic "oh hey, the directory you're
watching changed in some way", and it's up to you to scan it to work out
how. So git annex will probably need to run
git ls-tree --others
to find changes in the directory tree. This could be expensive with large
trees. (hsevents has per-file events on current versions of OSX)
Despite these warts, I want to try kqueue first, since it's more portable than hfsevents, and will surely be easier for me to develop support for, since I don't have direct access to OSX.
So I went to a handy Debian kFreeBSD porter box, and tried some kqueue stuff to get a feel for it. I got a python program that does basic directory monitoring with kqueue to work, so I know it's usable there.
Next step was getting kqueue working from Haskell. Should be easy, there's a Haskell library already. I spent a while trying to get it to work on Debian kFreeBSD, but ran into a problem that could be caused by the Debian kFreeBSD being different, or just a bug in the Haskell library. I didn't want to spend too long shaving this yak; I might install "real" FreeBSD on a spare laptop and try to get it working there instead.
But for now, I've dropped down to C instead, and have a simple C program that can monitor a directory with kqueue. Next I'll turn it into a simple library, which can easily be linked into my Haskell code. The Haskell code will pass it a set of open directory descriptors, and it'll return the one that it gets an event on. This is necessary because kqueue doesn't recurse into subdirectories on its own.
I've generally had good luck with this approach to adding stuff in Haskell; rather than writing a bit-banging and structure packing low level interface in Haskell, write it in C, with a simpler interface between C and Haskell.
A rather frustrating and long day coding went like this:
1-3 pm
Wrote a single function, of which all any Haskell programmer needs to know is its type signature:
Lsof.queryDir :: FilePath -> IO [(FilePath, LsofOpenMode, ProcessInfo)]
When I'm spending another hour or two taking a unix utility like lsof and parsing its output, which in this case is in a rather complicated machine-parsable output format, I often wish unix streams were strongly typed, which would avoid this bother.
3-9 pm
Six hours spent making it defer annexing files until the commit thread wakes up and is about to make a commit. Why did it take so horribly long? Well, there were a number of complications, and some really bad bugs involving races that were hard to reproduce reliably enough to deal with.
In other words, I was lost in the weeds for a lot of those hours...
At one point, something glorious happened, and it was always making exactly one commit for batch mode modifications of a lot of files (like untarring them). Unfortunately, I had to lose that gloriousness due to another potential race, which, while unlikely, would have made the program deadlock if it happened.
So, it's back to making 2 or 3 commits per batch mode change. I also have a buglet that causes sometimes a second empty commit after a file is added. I know why (the inotify event for the symlink gets in late, after the commit); will try to improve commit frequency later.
9-11 pm
Put the capstone on the day's work, by calling lsof on a directory full of hardlinks to the files that are about to be annexed, to check if any are still open for write.
This works great! Starting up
git annex watch when processes have files
open is no longer a problem, and even if you're evil enough to try having
multiple processes open the same file, it will complain and not annex it
until all the writers close it.
(Well, someone really evil could turn the write bit back on after git annex
clears it, and open the file again, but then really evil people can do
that to files in
.git/annex/objects too, and they'll get their just
deserts when
git annex fsck runs. So, that's ok..)
Anyway, will beat on it more tomorrow, and if all is well, this will finally go out to the beta testers.
git merge watch_
My cursor has been mentally poised here all day, but I've been reluctant to merge watch into master. It seems solid, but is it correct? I was able to think up a lot of races it'd be subject to, and deal with them, but did I find them all?
Perhaps I need to do some automated fuzz testing to reassure myself. I looked into using genbackupdata to that end. It's not quite what I need, but could be moved in that direction. Or I could write my own fuzz tester, but it seems better to use someone else's, because a) laziness and b) they're less likely to have the same blind spots I do.
My reluctance to merge isn't helped by the known bugs with files that are
either already open before
git annex watch starts, or are opened by two
processes at once, and confuse it into annexing the still-open file when one
process closes it.
I've been thinking about just running
lsof on every file as it's being
annexed to check for that, but in the end,
lsof is too slow. Since its
check involves trawling through all of /proc, it takes it a good half a
second to check a file, and adding 25 seconds to the time it takes to
process 100 files is just not acceptable.
But an option that could work is to run
lsof after a bunch of new files
have been annexed. It can check a lot of files nearly as fast as a single
one. In the rare case that an annexed file is indeed still open, it could
be moved back out of the annex. Then when its remaining writer finally
closes it, another inotify event would re-annex it.
Since last post, I've worked on speeding up
git annex watch's startup time
in a large repository.
The problem was that its initial scan was naively staging every symlink in
the repository, even though most of them are, presumably, staged correctly
already. This was done in case the user copied or moved some symlinks
around while
git annex watch was not running -- we want to notice and
commit such changes at startup.
Since I already had the
stat info for the symlink, it can look at the
ctime to see if the symlink was made recently, and only stage it if so.
This sped up startup in my big repo from longer than I cared to wait (10+
minutes, or half an hour while profiling) to a minute or so. Of course,
inotify events are already serviced during startup, so making it scan
quickly is really only important so people don't think it's a resource hog.
First impressions are important.
But what does "made recently" mean exactly? Well, my answer is possibly
over engineered, but most of it is really groundwork for things I'll need
later anyway. I added a new data structure for tracking the status of the
daemon, which is periodically written to disk by another thread (thread #6!)
to
.git/annex/daemon.status Currently it looks like this; I anticipate
adding lots more info as I move into the syncing stage:
lastRunning:1339610482.47928s scanComplete:True
So, only symlinks made after the daemon was last running need to be expensively staged on startup. Although, as RichiH pointed out, this fails if the clock is changed. But I have been planning to have a cleanup thread anyway, that will handle this, and other potential problems, so I think that's ok.
Stracing its startup scan, it's fairly tight now. There are some repeated
getcwd syscalls that could be optimised out for a minor speedup.
Added the sanity check thread. Thread #7! It currently only does one sanity check per day, but the sanity check is a fairly lightweight job, so I may make it run more frequently. OTOH, it may never ever find a problem, so once per day seems a good compromise.
Currently it's only checking that all files in the tree are properly staged
in git. I might make it
git annex fsck later, but fscking the whole tree
once per day is a bit much. Perhaps it should only fsck a few files per
day? TBD
Currently any problems found in the sanity check are just fixed and logged. It would be good to do something about getting problems that might indicate bugs fed back to me, in a privacy-respecting way. TBD
I also refactored the code, which was getting far too large to all be in one module.
I have been thinking about renaming
git annex watch to
git annex assistant,
but I think I'll leave the command name as-is. Some users might
want a simple watcher and stager, without the assistant's other features
like syncing and the webapp. So the next stage of the
roadmap will be a different command that also runs
watch.
At this point, I feel I'm done with the first phase of inotify. It has a couple known bugs, but it's ready for brave beta testers to try. I trust it enough to be running it on my live data.
Kickstarter is over. Yay!
Today I worked on the bug where
git annex watch turned regular files
that were already checked into git into symlinks. So I made it check
if a file is already in git before trying to add it to the annex.
The tricky part was doing this check quickly. Unless I want to write my
own git index parser (or use one from Hackage), this check requires running
git ls-files, once per file to be added. That won't fly if a huge
tree of files is being moved or unpacked into the watched directory.
Instead, I made it only do the check during
git annex watch's initial
scan of the tree. This should be OK, because once it's running, you
won't be adding new files to git anyway, since it'll automatically annex
new files. This is good enough for now, but there are at least two problems
with it:
- Someone might
git mergein a branch that has some regular files, and it would add the merged in files to the annex.
- Once
git annex watchis running, if you modify a file that was checked into git as a regular file, the new version will be added to the annex.
I'll probably come back to this issue, and may well find myself directly querying git's index.
I've started work to fix the memory leak I see when running
git annex
watch in a large repository (40 thousand files). As always with a Haskell
memory leak, I crack open Real World Haskell's chapter on profiling.
Eventually this yields a nice graph of the problem:
So, looks like a few minor memory leaks, and one huge leak. Stared at this for a while and trying a few things, and got a much better result:
I may come back later and try to improve this further, but it's not bad memory usage. But, it's still rather slow to start up in such a large repository, and its initial scan is still doing too much work. I need to optimize more..
Since my last blog, I've been polishing the
git annex watch command.
First, I fixed the double commits problem. There's still some extra
committing going on in the
git-annex branch that I don't understand. It
seems like a shutdown event is somehow being triggered whenever
a git command is run by the commit thread.
I also made
git annex watch run as a proper daemon, with locking to
prevent multiple copies running, and a pid file, and everything.
I made
git annex watch --stop stop it.
Then I managed to greatly increase its startup speed. At startup, it generates "add" events for every symlink in the tree. This is necessary because it doesn't really know if a symlink is already added, or was manually added before it starter, or indeed was added while it started up. Problem was that these events were causing a lot of work staging the symlinks -- most of which were already correctly staged.
You'd think it could just check if the same symlink was in the index. But it can't, because the index is in a constant state of flux. The symlinks might have just been deleted and re-added, or changed, and the index still have the old value.
Instead, I got creative.
We can't trust what the index says about the
symlink, but if the index happens to contain a symlink that looks right,
we can trust that the SHA1 of its blob is the right SHA1, and reuse it
when re-staging the symlink. Wham! Massive speedup!
Then I started running
git annex watch on my own real git annex repos,
and noticed some problems.. Like it turns normal files already checked into
git into symlinks. And it leaks memory scanning a big tree. Oops..
I put together a quick screencast demoing
git annex watch.
While making the screencast, I noticed that
git-annex watch was spinning
in strace, which is bad news for powertop and battery usage. This seems to
be a GHC bug also affecting Xmonad. I
tried switching to GHC's threaded runtime, which solves that problem, but
causes git-annex to hang under heavy load. Tried to debug that for quite a
while, but didn't get far. Will need to investigate this further..
Am seeing indications that this problem only affects ghc 7.4.1; in
particular 7.4.2 does not seem to have the problem.
After a few days otherwise engaged, back to work today.
My focus was on adding the committing thread mentioned in day 4 speed. I got rather further than expected!
First, I implemented a really dumb thread, that woke up once per second,
checked if any changes had been made, and committed them. Of course, this
rather sucked. In the middle of a large operation like untarring a tarball,
or
rm -r of a large directory tree, it made lots of commits and made
things slow and ugly. This was not unexpected.
So next, I added some smarts to it. First, I wanted to stop it waking up every second when there was nothing to do, and instead blocking wait on a change occurring. Secondly, I wanted it to know when past changes happened, so it could detect batch mode scenarios, and avoid committing too frequently.
I played around with combinations of various Haskell thread communications
tools to get that information to the committer thread:
MVar,
Chan,
QSem,
QSemN. Eventually, I realized all I needed was a simple channel
through which the timestamps of changes could be sent. However,
Chan
wasn't quite suitable, and I had to add a dependency on
Software Transactional Memory,
and use a
TChan. Now I'm cooking with gas!
With that data channel available to the committer thread, it quickly got some very nice smart behavior. Playing around with it, I find it commits instantly when I'm making some random change that I'd want the git-annex assistant to sync out instantly; and that its batch job detection works pretty well too.
There's surely room for improvement, and I made this part of the code be an entirely pure function, so it's really easy to change the strategy. This part of the committer thread is so nice and clean, that here's the current code, for your viewing pleasure:
{- Decide if now is a good time to make a commit. - Note that the list of change times has an undefined order. - - Current strategy: If there have been 10 commits within the past second, - a batch activity is taking place, so wait for later. -} shouldCommit :: UTCTime -> [UTCTime] -> Bool shouldCommit now changetimes | len == 0 = False | len > 4096 = True -- avoid bloating queue too much | length (filter thisSecond changetimes) < 10 = True | otherwise = False -- batch activity where len = length changetimes thisSecond t = now `diffUTCTime` t <= 1
Still some polishing to do to eliminate minor inefficiencies and deal with more races, but this part of the git-annex assistant is now very usable, and will be going out to my beta testers soon!
Only had a few hours to work today, but my current focus is speed, and I
have indeed sped up parts of
git annex watch.
One thing folks don't realize about git is that despite a rep for being
fast, it can be rather slow in one area: Writing the index. You don't
notice it until you have a lot of files, and the index gets big. So I've
put a lot of effort into git-annex in the past to avoid writing the index
repeatedly, and queue up big index changes that can happen all at once. The
new
git annex watch was not able to use that queue. Today I reworked the
queue machinery to support the types of direct index writes it needs, and
now repeated index writes are eliminated.
... Eliminated too far, it turns out, since it doesn't yet ever flush that queue until shutdown! So the next step here will be to have a worker thread that wakes up periodically, flushes the queue, and autocommits. (This will, in fact, be the start of the syncing phase of my roadmap!) There's lots of room here for smart behavior. Like, if a lot of changes are being made close together, wait for them to die down before committing. Or, if it's been idle and a single file appears, commit it immediately, since this is probably something the user wants synced out right away. I'll start with something stupid and then add the smarts.
(BTW, in all my years of programming, I have avoided threads like the nasty bug-prone plague they are. Here I already have three threads, and am going to add probably 4 or 5 more before I'm done with the git annex assistant. So far, it's working well -- I give credit to Haskell for making it easy to manage state in ways that make it possible to reason about how the threads will interact.)
What about the races I've been stressing over? Well, I have an ulterior
motive in speeding up
git annex watch, and that's to also be able to
slow it down. Running in slow-mo makes it easy to try things that might
cause a race and watch how it reacts. I'll be using this technique when
I circle back around to dealing with the races.
Another tricky speed problem came up today that I also need to fix. On
startup,
git annex watch scans the whole tree to find files that have
been added or moved etc while it was not running, and take care of them.
Currently, this scan involves re-staging every symlink in the tree. That's
slow! I need to find a way to avoid re-staging symlinks; I may use
git
cat-file to check if the currently staged symlink is correct, or I may
come up with some better and faster solution. Sleeping on this problem.
Oh yeah, I also found one more race bug today. It only happens at startup and could only make it miss staging file deletions.
Today I worked on the race conditions, and fixed two of them. Both
were fixed by avoiding using
git add, which looks at the files currently
on disk. Instead,
git annex watch injects symlinks directly into git's
index, using
git update-index.
There is one bad race condition remaining. If multiple processes have a file open for write, one can close it, and it will be added to the annex. But then the other can still write to it.
Getting away from race conditions for a while, I made
git annex watch
not annex
.gitignore and
.gitattributes files.
And, I made it handle running out of inotify descriptors. By default,
/proc/sys/fs/inotify/max_user_watches is 8192, and that's how many
directories inotify can watch. Now when it needs more, it will print
a nice message showing how to increase it with
sysctl.
FWIW, DropBox also uses inotify and has the same limit. It seems to not
tell the user how to fix it when it goes over. Here's what
git annex
watch will say:
Too many directories to watch! (Not watching ./dir4299) Increase the limit by running: echo fs.inotify.max_user_watches=81920 | sudo tee -a /etc/sysctl.conf; sudo sysctl -p
Last night I got
git annex watch to also handle deletion of files.
This was not as tricky as feared; the key is using
git rm --ignore-unmatch,
which avoids most problematic situations (such as a just deleted file
being added back before git is run).
Also fixed some races when
git annex watch is doing its startup scan of
the tree, which might be changed as it's being traversed. Now only one
thread performs actions at a time, so inotify events are queued up during
the scan, and dealt with once it completes. It's worth noting that inotify
can only buffer so many events .. Which might have been a problem except
for a very nice feature of Haskell's inotify interface: It has a thread
that drains the limited inotify buffer and does its own buffering.
Right now,
git annex watch is not as fast as it could be when doing
something like adding a lot of files, or deleting a lot of files.
For each file, it currently runs a git command that updates the index.
I did some work toward coalescing these into one command (which
git annex
already does normally). It's not quite ready to be turned on yet,
because of some races involving
git add that become much worse
if it's delayed by event coalescing.
And races were the theme of today. Spent most of the day really
getting to grips with all the fun races that can occur between
modification happening to files, and
git annex watch. The inotify
page now has a long list of known races, some benign, and several,
all involving adding files, that are quite nasty.
I fixed one of those races this evening. The rest will probably involve
moving away from using
git add, which necessarily examines the file
on disk, to directly shoving the symlink into git's index.
BTW, it turns out that
dvcs-autosync has grappled with some of these same
races:
I hope that
git annex watch will be in a better place to deal with them,
since it's only dealing with git, and with a restricted portion of it
relevant to git-annex.
It's important that
git annex watch be rock solid. It's the foundation
of the git annex assistant. Users should not need to worry about races
when using it. Most users won't know what race conditions are. If only I
could be so lucky!
First day of Kickstarter funded work!
Worked on inotify today. The
watch branch in git now does a pretty
good job of following changes made to the directory, annexing files
as they're added and staging other changes into git. Here's a quick
transcript of it in action:
joey@gnu:~/tmp>mkdir demo joey@gnu:~/tmp>cd demo joey@gnu:~/tmp/demo>git init Initialized empty Git repository in /home/joey/tmp/demo/.git/ joey@gnu:~/tmp/demo>git annex init demo init demo ok (Recording state in git...) joey@gnu:~/tmp/demo>git annex watch & [1] 3284 watch . (scanning...) (started) joey@gnu:~/tmp/demo>dd if=/dev/urandom of=bigfile bs=1M count=2 add ./bigfile 2+0 records in 2+0 records out 2097152 bytes (2.1 MB) copied, 0.835976 s, 2.5 MB/s (checksum...) ok (Recording state in git...) joey@gnu:~/tmp/demo>ls -la bigfile lrwxrwxrwx 1 joey joey 188 Jun 4 15:36 bigfile -> .git/annex/objects/Wx/KQ/SHA256-s2097152--e5ced5836a3f9be782e6da14446794a1d22d9694f5c85f3ad7220b035a4b82ee/SHA256-s2097152--e5ced5836a3f9be782e6da14446794a1d22d9694f5c85f3ad7220b035a4b82ee joey@gnu:~/tmp/demo>git status -s A bigfile joey@gnu:~/tmp/demo>mkdir foo joey@gnu:~/tmp/demo>mv bigfile foo "del ./bigfile" joey@gnu:~/tmp/demo>git status -s AD bigfile A foo/bigfile
Due to Linux's inotify interface, this is surely some of the most subtle, race-heavy code that I'll need to deal with while developing the git annex assistant. But I can't start wading, need to jump off the deep end to make progress!
The hardest problem today involved the case where a directory is moved outside of the tree that's being watched. Inotify will still send events for such directories, but it doesn't make sense to continue to handle them.
Ideally I'd stop inotify watching such directories, but a lot of state would need to be maintained to know which inotify handle to stop watching. (Seems like Haskell's inotify API makes this harder than it needs to be...)
Instead, I put in a hack that will make it detect inotify events from directories moved away, and ignore them. This is probably acceptable, since this is an unusual edge case.
The notable omission in the inotify code, which I'll work on next, is staging deleting of files. This is tricky because adding a file to the annex happens to cause a deletion event. I need to make sure there are no races where that deletion event causes data loss. | http://git-annex.branchable.com/design/assistant/blog/ | CC-MAIN-2014-35 | refinedweb | 64,994 | 71.85 |
This notebook will provide an introduction to the peewee ORM. We will use an in-memory SQLite database, but peewee comes with support for Postgresql and MySQL as well.
In this notebook we will get familiar with writing and executing queries with peewee.
It is my hope that after reading this notebook you will:
To get peewee:
pip install peewee
from peewee import * database = SqliteDatabase(':memory:') # Create a database instance.
Models are a 1-to-1 mapping to database tables, and each "field" maps to a column on the table. There are lots of field types suitable for storing various types of data. peewee handles converting between “pythonic” values those used by the database, so you don’t have to worry about it.
class Person(Model): name = CharField() birthday = DateField() is_relative = BooleanField() class Meta: database = database # this model uses the in-memory database we just created
class Pet(Model): owner = ForeignKeyField(Person, related_name='pets') name = CharField() animal_type = CharField() class Meta: database = database # use the in-memory database
# Let's create the tables now that the models are defined. Person.create_table() Pet.create_table()
# Let’s store some people to the database, and then we’ll give them some pets. from datetime import date uncle_bob = Person(name='Bob', birthday=date(1960, 1, 15), is_relative=True) uncle_bob.save() # bob is now stored in the database
# We can shorten this by calling `Model.create`. grandma = Person.create(name='Grandma', birthday=date(1935, 3, 1), is_relative=True) herb = Person.create(name='Herb', birthday=date(1950, 5, 5), is_relative=False)
# We can make updates and re-save to the database. grandma.name = 'Grandma L.' grandma.save()
# Now we have stored 3 people in the database. Let’s give them some pets. # Grandma doesn’t like animals in the house, so she won’t have any, but Herb has a lot of pets. gets sick and dies. We need to remove him from the database. herb_mittens.delete_instance() # he had a great life
1
# You might notice that it printed “1” – whenever you call Model.delete_instance() it will return the number of # rows removed from the database.
# Uncle Bob decides that too many animals have been dying at Herb’s house, so he adopts Fido. herb_fido.owner = uncle_bob herb_fido.save() bob_fido = herb_fido # rename our variable for clarity
# Let's retrieve Grandma's record from the database. grandma = Person.select().where(Person.name == 'Grandma L.').get() print grandma.name
Grandma L.
# We can also use the following shortcut: grandma = Person.get(Person.name == 'Grandma L.') print grandma.name
Grandma L.
# Let's list all the people in the database. for person in Person.select(): print person.name, '- is relative?', person.is_relative
Bob - is relative? True Grandma L. - is relative? True Herb - is relative? False
# Now let's list all the people and their pets. for person in Person.select(): print person.name, person.pets.count(), 'pets' for pet in person.pets: print ' ', pet.name, pet.animal_type
Bob 2 pets Kitty cat Fido dog Grandma L. 0 pets Herb 1 pets Mittens Jr cat
# List all the cats and their owner's name. for pet in Pet.select().where(Pet.animal_type == 'cat'): print pet.name, 'owned by', pet.owner.name
Kitty owned by Bob Mittens Jr owned by Herb
# This one will be a little more interesting and introduces the concept of joins. #
Kitty Fido
# Use `order_by` to sort the list. for pet in Pet.select().where(Pet.owner == uncle_bob).order_by(Pet.name): print pet.name
Fido Kitty
# Here are all the people, ordered youngest to oldest. for person in Person.select().order_by(Person.birthday.desc()): print person.name
Bob Herb Grandma L.
We can use python operators to create complex queries. Peewee supports multiple types of operations.
# Let’s get all the people whose birthday was either: # * before 1940 (grandma) # * after 1959 (bob) d1940 = date(1940, 1, 1) d1960 = date(1960, 1, 1) for person in Person.select().where((Person.birthday < d1940) | (Person.birthday > d1960)): print person.name
Bob Grandma L.
# Now let’s do the opposite. People whose birthday is between 1940 and 1960. for person in Person.select().where((Person.birthday > d1940) & (Person.birthday < d1960)): print person.name
Herb
# This will use a SQL function to find all people whose names start with either an upper or lower-case “G”: for person in Person.select().where(fn.Lower(fn.Substr(Person.name, 1, 1)) == 'g'): print person.name
Grandma L.
This is just the basics! Hopefully peewee is starting to make a little sense.
For further reading check out: | http://nbviewer.jupyter.org/gist/coleifer/d3faf30bbff67ce5f70c | CC-MAIN-2018-30 | refinedweb | 752 | 62.54 |
Usually frosted (bug symbols in left column of script editor), should be able to detect if an uninitialized variable is used somewhere in the script. However, currently this type of error is not detected. The cause for this is, that frosted can only detect this types of errors if no statement like from XYZ import * is within the script (since then, no clear knowledge about exernally defined variables... is available for frosted. However, the line
from itom import *
is always prepended to each script before calling the frosted syntax check, since all classes and methods from itom are (per default) globally imported to the global workspace and we then want to avoid that frosted says for instance that dataObject is not defined. However, due to this line, no variable name checks can be done for the script.
Task: replace from itom import * by something like from itom import dataObject, dataIO, actuator, filter, pluginHelp... (However the list of items should somehow be generated automatically).
Location: PythonEngine::pythonSyntaxCheck in pythonEngine.cpp
frosted syntax check can now also detect the usage of an unreference variable. fixes issue
#46.
→ <<cset a153d799fed1>> | https://bitbucket.org/itom/itom/issues/46/syntax-check-frosted-can-not-detect-all | CC-MAIN-2020-34 | refinedweb | 187 | 54.42 |
You is opened determines whether locks on a file are treated as mandatory or advisory.
Of the two basic locking calls, fcntl(2) is more portable, more powerful, and less easy to use than lockf(3C). fcntl(2) is specified in POSIX 1003.1 standard. lockf(3C) is provided to be compatible with older applications.
For mandatory locks, the file must be a regular file with the set-group-ID bit on and the group execute permission off. If either condition fails, all record locks are advisory.
Set a mandatory lock as follows.
#include <sys/types.h> #include <sys/stat.h> int mode; struct stat buf; ... if (stat(filename, &buf) < 0) { perror("program"); exit (2); } /* get currently set mode */ mode = buf.st_mode; /* remove group execute permission from mode */ mode &= ~(S_IEXEC>>3); /* set 'set group id bit' in mode */ mode |= S_ISGID; if (chmod(filename, mode) < 0) { perror("program"); exit(2); } ...
The operating system ignores record locks when the system is executing a file. Any files with record locks should not have execute permissions set.
The chmod(1) command can also be used to set a file to permit mandatory locking.
This command sets the O20n0 permission bit in the file mode, which indicates mandatory locking on the file. If n is even, the bit is interpreted as enabling mandatory locking. If n is odd, the bit is interpreted as “set group ID on execution.”
The ls(1) command shows this setting when you ask for the long listing format with the -l option:
This command displays the following information:
The letter “l” in the permissions indicates that the set-group-ID bit is on. Since the set-group-ID bit is on, mandatory locking is enabled. Normal semantics of set group ID are also enabled.
Keep in mind the following aspects of locking:
Mandatory locking works only for local files. Mandatory locking is not supported when accessing files through NFS.
Mandatory locking protects only the segments of a file that are locked. The remainder of the file can be accessed according to normal file permissions.
If multiple reads or writes are needed for an atomic transaction, the process should explicitly lock all such segments before any I/O begins. Advisory locks are sufficient for all programs that perform in this way.
Arbitrary programs should not have unrestricted access permission to files on which record locks are used.
Advisory locking is more efficient because a record lock check does not have to be performed for every I/O request. trying to lock the file.
#include <fcntl.h> ... struct flock lck; ... lck.l_type = F_WRLCK; /* setting a write lock */ lck.l_whence = 0; /* offset l_start from beginning of file */ lck.l_start = (off_t)0; lck.l_len = (off_t)0; /* until the end of the file */ if (fcntl(fd, F_SETLK, &lck) <0) { if (errno == EAGAIN || errno == EACCES) { (void) fprintf(stderr, "File busy try again later!\n"); return; } perror("fcntl"); exit (2); } ...
Using fcntl(2), you can set the type and start of the lock request by setting structure variables.
You cannot lock mapped files with flock(3UCB). However, you can use the multithread-oriented synchronization mechanisms with mapped files. These synchronization mechanisms can be used in POSIX styles as well as in Solaris styles.
When locking a record, do not set the starting point and length of the lock segment to zero. The locking procedure is otherwise identical to file locking.
Contention for data is why you use record locking. Therefore, you should have a failure response for when you cannot obtain all the required locks:
Wait a certain amount of time, then try again
Abort the procedure, warn the user
Let the process sleep until signaled that the lock has been freed
Do some combination of the previous
This example shows a record being locked by using fcntl(2).
{ struct flock lck; ... lck.l_type = F_WRLCK; /* setting a write lock */ lck.l_whence = 0; /* offset l_start from beginning of file */ lck.l_start = here; lck.l_len = sizeof(struct record); /* lock "this" with write lock */ lck.l_start = this; if (fcntl(fd, F_SETLKW, &lck) < 0) { /* "this" lock failed. */ return (-1); ... }
The next example shows the lockf(3C) interface.
#include <unistd.h> { ... /* lock "this" */ (void) lseek(fd, this, SEEK_SET); if (lockf(fd, F_LOCK, sizeof(struct record)) < 0) { /* Lock on "this" failed. Clear lock on "here". */ (void) lseek(fd, here, 0); (void) lockf(fd, F_ULOCK, sizeof(struct record)); return (-1); }
You remove locks in the same way the locks were set. Only the lock type is different (F_ULOCK). An unlock cannot be blocked by another process and affects only locks placed by the calling process. The unlock affects only the segment of the file specified in the preceding locking call..
; } }
When a process forks, the child receives a copy of the file descriptors that the parent opened. Locks are not inherited by the child because the locks are owned by a specific process. The parent and child share a common file pointer for each file. Both processes can try to set locks on the same location in the same file. This problem occurs with both lockf(3C) and fcntl(2). If a program holding a record lock forks, the child process should close the file. After closing the file, the child process should reopen the file to set a new, separate file pointer.. | http://docs.oracle.com/cd/E19253-01/817-4415/fileio-9/index.html | CC-MAIN-2014-15 | refinedweb | 879 | 66.74 |
updated copyright year
\ Etags support for GNU Forth. \ Copyright (C) 1995,1998,2001,2003,2007,2008 does not work like etags; instead, the TAGS file is updated \ during the normal Forth interpretation/compilation process. \ The present version has several shortcomings: It always overwrites \ the TAGS file instead of just the parts corresponding to the loaded \ files, but you can have several tag tables in emacs. Every load \ creates a new etags file and the user has to confirm that she wants \ to use it. \ Communication of interactive programs like emacs and Forth over \ files is clumsy. There should be better cooperation between them \ (e.g. via shared memory) \ This is ANS Forth with the following serious environmental \ dependences: the : tags-file-name ( -- c-addr u ) \ for now I use just TAGS; this may become more flexible in the \ future s" TAGS" ; variable tags-file 0 tags-file ! create tags-line 128 chars allot : skip-tags ( file-id -- ) \ reads in file until it finds the end or the loadfilename drop ; : tags-file-id ( -- file-id ) tags-file @ 0= if tags-file-name w/o create-file throw \ 2dup file-status \ if \ the file does not exist \ drop w/o create-file throw \ else \ drop r/w open-file throw \ dup skip-tags \ endif tags-file ! endif tags-file @ ; 2variable last-loadfilename 0 0 last-loadfilename 2! : put-load-file-name ( file-id -- ) >r sourcefilename last-loadfilename 2@ d<> if #ff r@ emit-file throw #lf r@ emit-file throw sourcefilename 2dup r@ write-file throw last-loadfilename 2! s" ,0" r@ write-line throw endif rdrop ; : put-tags-string ( c-addr u -- ) 2>r source-id dup 0<> swap -1 <> and \ input from a file current @ locals-list <> and \ not a local name if tags-file-id >r r@ put-load-file-name source drop >in @ r@ write-file throw 127 r@ emit-file throw r> 2r> rot dup >r write | http://www.complang.tuwien.ac.at/cvsweb/cgi-bin/cvsweb/gforth/etags.fs?rev=1.21 | CC-MAIN-2018-13 | refinedweb | 320 | 55.58 |
Version: unspecified (using KDE 4.6.2)
OS: Linux
Compare the following two screenshots:
Good:
Bad:
There is a visual glitch just below the separator between the menu and tab bars in the bad screenshot, causing a sharp-edged patch of a slightly lighter gradient.
This glitch was introduced by commit bcd081da2f7679c4199019f0ba0e0bcb5d1741fd "Apply inner shadow hack on GtkViewport", determined by git bisect.
Reproducible: Always
Steps to Reproduce:
Open an affected application (BOINC Manager in my testing). Observe separator.
Actual Results:
Narrow line of lighter gradient visible below separator
Expected Results:
No gradient difference visible
oxygen-gtk from git on Kubuntu 11.04 beta, KDE 4.6.2
mmm. Cannot reproduce here. Ruslan ? Can you ?
I should add that 11.04 has GTK 2.24.4.
The glitch also doesn't appear to manifest if BOINC manager loads when the system starts (i.e., I left it open when shutting down the computer). Close and reopen it and it appears, and continues to do so reliably from that point on.
Can't reproduce this on GTK 2.24.3.
Sam Lade,
Does this gradient appear if you apply this patch (it will make oxygen-gtk not draw window background, but is needed to somewhat localize the problem):
diff --git a/src/oxygenstyle.cpp b/src/oxygenstyle.cpp
index dbdf92e..8e5d81c 100644
--- a/src/oxygenstyle.cpp
+++ b/src/oxygenstyle.cpp
@@ -228,6 +228,7 @@ namespace Oxygen
GdkRectangle* clipRect, gint x, gint y, gint w, gint h,
const StyleOptions& options, TileSet::Tiles tiles )
{
+ return;
// define colors
ColorUtils::Rgba base( color( Palette::Window, options ) );
? Possibly let me see the screenshot with this patch applied.
The glitch isn't visible with this patch applied. Here are screenshots with and without the patch:
OK. Could you test (on clean master) if the glitch appears with ENABLE_INNER_SHADOWS_HACK set to 0 in CMakeLists.txt?
If it doesn't, could you give output with this patch (having ENABLE_INNER_SHADOWS_HACK reverted to 1):
diff --git a/src/animations/oxygeninnershadowdata.cpp b/src/animations/oxygeninnershadowdata.cpp
index 6014657..8845051 100644
--- a/src/animations/oxygeninnershadowdata.cpp
+++ b/src/animations/oxygeninnershadowdata.cpp
@@ -19,6 +19,8 @@
* MA 02110-1301, USA.
*/
+#define OXYGEN_DEBUG 1
+
#include <gtk/gtk.h>
#include "oxygeninnershadowdata.h"
#include "../oxygengtkutils.h"
Glitch doesn't appear with INNER_SHADOWS_HACK disabled. Here's the output with the debug patch:
Git commit 9e29948a7e00c2bcc29d8e4f0d1066a18f2a55c6 by Ruslan Kabatsayev.
Committed on 10/06/2011 at 20:13.
Pushed by kabatsayev into branch 'master'.
Disable inner shadow hack for GtkPizza
CCBUG: 270541
M +8 -4 src/animations/oxygeninnershadowdata.cpp
Please confirm that the above commit fixes this and close if yes.
Yup, that's fixed. Thanks! | https://bugs.kde.org/show_bug.cgi?id=270541 | CC-MAIN-2022-33 | refinedweb | 436 | 52.05 |
Email addresses are pretty complex and do not have a standard being followed all over the world which makes it difficult to identify an email in a regex. The RFC 5322 specifies the format of an email address. We'll use this format to extract email addresses from the text.
For example, for a given input string −
Hi my name is John and email address is john.doe@somecompany.co.uk and my friend's email is jane_doe124@gmail.com
We should get the output −
john.doe@somecompany.co.uk jane_doe124@gmail.com
We can use the following regex for exatraction −
[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+
We can extract the email addresses using the find all method from re module. For example,
import re my_str = "Hi my name is John and email address is john.doe@somecompany.co.uk and my friend's email is jane_doe124@gmail.com" emails = re.findall("([a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+)", my_str) for mail in an email: print(mail)
This will give the output −
john.doe@somecompany.co.uk jane_doe124@gmail.com | https://www.tutorialspoint.com/Extracting-email-addresses-using-regular-expressions-in-Python | CC-MAIN-2022-05 | refinedweb | 191 | 59.7 |
$79.20.
Premium members get this course for $349.00.
Premium members get this course for $99.99.
Premium members get this course for $62.50.
Premium members get this course for $63.20.
provide your own implementation. The ideal would be to subclass String and
override the trim() method by an home made one. However, String is a final class
and can not be subclassed (final classes are more easy to optimize, this is why the
String class is final). You will have to implement a trim() method as part of a utility
class, or directly as a private utility method part of the class that needs access to
the functionality, like in the following example:
public class Test {
public Test() {
}
public void doIt() {
String strings[] = {"aaa", " bbb ", "ccc", " ddd eee "};
for(int i=0; i< strings.length; i++) {
System.out.println("*" + trim(strings[i]) + "*");
}
return;
}
// utility method to trim a String.
// The following code is deeply inspired from the source code of SUN's JDK
// String.trim() method. It is hence functionaly equivalent.
private String trim(String toTrim) {
int count = toTrim.length();
int len = count;
int st = 0;
int off = 0;
char[] val = new char[len];
toTrim.getChars(0, len, val, 0);
while ((st < len) && (val[off + st] <= ' ')) {
st++;
}
while ((st < len) && (val[off + len - 1] <= ' ')) {
len--;
}
return ((st > 0) || (len < count)) ? toTrim.substring(st, len) : toTrim;
}
public static void main(String args[]) {
Test test = new Test();
test.doIt();
return;
}
}
let me test this on monday, then I'll give feedback.
THX for help.
Best regards
-Stavi-
Not trim() is the problem, it's String (byte[]) instead !
Now, where trim() is "replaced", I get an error again, so I found out that it's String(byte[]) which causes all my problems...
I think I have to use something like String(StringBuffer) to make my applet available for almost all browsers ?!
If you could support me on how to read byte by byte with "StringBuffer" I'll increase points to 75.
Please tell me if this is not ok for you...(then I'll try to post a new Q !) in any case you'll get current credits coz your suggestion worked for me.
Best regards
-Stavi-
With monday.com’s project management tool, you can see what everyone on your team is working in a single glance. Its intuitive dashboards are customizable, so you can create systems that work for you.
byte bytes[] = ...
if (bytes == null) {
System.out.println("bytes == null");
} else {
System.out.println("bytes <> null");
}
String myString = new String(bytes); etc.
and have a look at the Java console.
Also, what is exactly the error you have, a NullPointerException?
definitely not NULL.
here's the error msg from the console:
# Applet exception: java.lang.String: method <init> ([BII)V not found
java.lang.NoSuchMethodErro
The chars B and V seem to be from "BVLAB12.fh-reutlingen.de"
line 42 in code is:
sPadding += new String(b, 0, nread);
where b is:
byte b[] = new byte[cc.MAXBUFLEN];
and nread from type "int"
THX a lot for help
-Stavi-
1.1 constructor). Try out the following:
Before:
sPadding += new String(b, 0, nread);
After:
sPadding += new String(b, 0, 0, nread); // JDK 1.0.2 way...
never thought that this could work...but it works =:-))
Best regards and THX again
-Stavi-
P.S.:
increased pts. to 75...hope this is ok. | https://www.experts-exchange.com/questions/10100463/trim-won't-work-for-MSIE4-x.html | CC-MAIN-2018-09 | refinedweb | 564 | 84.98 |
September 20, 2017 Single Round Match 719 Editorials
Some of the SRM 719 Editorials are now published. Check out the editorials of the interesting SRM 719 problems below. Thanks to Shizhouxing,nitish_and square1001 for contributing to the editorials. If you wish to discuss the problems or editorials you may do it in the discussion forum here.
SRM 719 Round 1 – Division II, Level One – LongLiveZhangzj by Shizhouxing
We need to count the number of words that are exciting in speech.
For each word s[i] in speech, we just check whether there is a word in words which is exactly the same as s[i]. If so, word s[i] is considered to be exciting.
The answer to the problem is the number of exciting words in speech.
Code:
#include <bits/stdc++.h> using namespace std; class LongLiveZhangzj { public: int donate(vector <string> speech, vector <string> words) { int ans = 0; for (auto x:speech) { int exciting = 0; for (auto y:words) if (x == y) exciting = 1; ans += exciting; } return ans; } };
SRM 719 Round 1 – Division II, Level Two – LongMansionDiv2 – by nitish_
In total, it will be optimal to move only (N + M – 1) steps where N – the number of rows, M – the number of columns.This problem is a problem of a shortest path in a 2-D grid. Weights for crossing each box are given in an int[].The best solution for this problem is by greedy approach.
Reason for this is that it is optimal to choose a row with minimum weight and move horizontally across that row only because it will add minimum weight to the solution. Thus, the solution will be equal:
ans = M*(minumum_weight_among_all_rows) + cost_of_single_step_on_every_other_row.
Code:
#include <bits/stdc++.h> using namespace std; class LongMansionDiv2 { public: long long minimalTime(int M, vector <int> t) { long long ans = 0; long long sum = 0; for(int i =0; i < t.size(); ++i) sum += t[i]; long long minm = *min_element(t.begin(), t.end()); ans = minm*M + sum - minm; return ans; } };
Note: use long long to avoid overflow.
Complexity: O(N), since we iterate over the input array.
SRM 719 Round 1 – Division II, Level Three – TwoDogsOnATree by nitish_
Firstly, root the tree at vertex 0. In a tree, between any two nodes, there is exactly only one path. Hence, in order to solve this problem, we should be able to find the XOR of all the weights on the path as quickly as possible. This can be done in O(N) preprocessing and O(1) for query.
Find the XOR of edges of all the vertex from the root vertex and store it in XOR[].
Thus, XOR[x] will store the XOR of all the edges in the path between node x and the root. Now to compute this between any two vertex (x , y), simply xor the XOR[x]^XOR[y] in O(1). This statement is true, because if vertex x and y lie different side of root, then the path must go through the root, and one path is kind of extension of another. Otherwise, if they lie on the same side of root, then the repeated edges are disabled with xor operation, because x^x = 0; and 0^x = x. That’s why the above statement is correct.
Now, suppose you choose a pair of nodes (a,b) for DOG 1 and another pair of nodes (c,d) for DOG 2. If there is no common edge between the two paths, then the result of A XOR B i.e. A^B = (XOR[a] ^ XOR[B])^(XOR[C]^XOR[d]), where A and B were results for first and second paths respectively.
Now, consider the other case, when there is overlapping of edges, then in that case, we can choose another permutation formed with same set of nodes which does not overlap i.e : either {(a, c) ,(b,d)} or {(a,d), (b,c)}. Result for any of these combination would result same as above. A^B = (XOR[a] ^ XOR[B])^(XOR[C]^XOR[d]).
Thus, the problem reduces to choosing 4 vertex a, b, c, d for which the XOR[a]^XOR[b]^XOR[C]^XOR[d] is maximum.
To solve this, There are many methods:
Firstly, make a set of distinct values of all the pairs from the available nodes. This will give you maximum of N*N distinct values.
Now, among all these pairs, Take the XOR of all pairs and return the maximum from it.
Code:
#include <vector> #include <set> #include <algorithm> #include <cmath> using namespace std; class TwoDogsOnATree { public: int XOR[1020]; int maximalXorSum(vector<int> parent, vector<int> w) { int n = parent.size() + 1; int ans = 0; set<int> st; for (int i = 1; i < n; ++i) { XOR[i] = XOR[parent[i - 1]] ^ w[i - 1]; } for (int i = 0; i < n; ++i) { for (int j = 0; j < i; ++j) st.insert(XOR[i] ^ XOR[j]); } set<int>::iterator it1; set<int>::iterator it2; for (it1 = st.begin(); it1 != st.end(); ++it1) { for (it2 = st.begin(); it2 != st.end(); ++it2) ans = max(ans, *it1 ^ *it2); } return ans; } };
Complexity: O(N ^ 4), since there will be N^2 elements in st set.
SRM 719 Round 1 – Division I, Level One – LongMansionDiv1 by square1001
Make problem more simple
You are given a grid with H (H ≤ 50) rows by W (W ≤ 109) columns. Cell in i-th row and j-th column denotes (i, j). Each cell in a grid has written a positive integer. Also, each cell in the same row has written the same value ai. You are given the position of starting cell (sx, sy) and finishing cell (gx, gy). You can move to 4-directions (up, down, right, left). Calculate the minimum sum of numbers written in passed cells.
The solution
The optimal solution is, amazingly, can always construct by following 3 steps. Pay attention that is assuming sy ≤ gy (because if sy > gy you can swap start and goal).
a. Move some cells upwards or downwards.
b. Move right gy-sy times.
c. Move some cells upwards or downwards and reach goal.
You can choose row which uses in step b (row of finishing step a). In the constraint H ≤ 50, you can brute-force and get minimum of it. Also, you can calculate the cost of the path in O(H), so the total time complexity is O(H2).
Why this is optimal?
1. Moving extra left and right direction is not good
Moving left and right more times than shortest, is a waste of cost. Why? You can see from the picture.
You can erase the left arrow (assuming sy ≤ gy) and corresponding right arrow. Also, you can move the disconnected part one cell right. As all numbers in same row is same, the reduced cost is always the cost in left arrow row and plus cost in right arrow row, so it is always higher than zero.
2. Moving right in different row is not good
First, see the example in the picture.
In this example, the left one costs 3A+3B+C, the middle one costs 5A+B+C, and the right one costs A+5B+C. You can see that for any real number A, B, C, 3A+3B+C≤max(5A+B+C,A+5B+C). You can prove it by solving in case of A>B, A=B, A<B, and using that the number in the same row is the same. And, in any pattern, you can reduce zero or more cost with “two row that uses right arrow to one row”, like left to middle or right one in the example.
If you do operation in 1. and 2. completely, you can get the path that can get from 3 steps that I first mentioned. So it means the optimal solution is in one of the way which can get from “3 steps”.
Code:
#include <cmath> #include <vector> #include <algorithm> using namespace std; class LongMansionDiv1 { public: long long minimalTime(vector<int> v, int sx, int sy, int ex, int ey) { int n = v.size(); long long ret = 1LL << 62; for (int i = 0; i < n; i++) { long long res = 1LL * v[i] * (abs(sy - ey) - 1); for (int j = min(sx, i); j <= max(sx, i); j++) res += v[j]; for (int j = min(ex, i); j <= max(ex, i); j++) res += v[j]; ret = min(ret, res); } return ret; } };
Bonus: Also, if you use prefix sum technique, you can get the answer in time complexity O(H). Let’s think about the solution!
Harshit Mehta
Sr. Community Evangelist | https://www.topcoder.com/blog/single-round-match-719-editorials/ | CC-MAIN-2022-40 | refinedweb | 1,434 | 71.65 |
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preview
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Unformatted text preview: A text file called accidents.bin contains accident numbers on the main highways of Ontario for a typical year. Write a complete program (main only) that will read data from the file (we don't know how many highways in the file but there is only one year) and calculate the total number of accidents in the year. Print out the year and the total number of accidents. You must use the user-defined structure type accdata in your program to store the data. Ex: if the file contains 2004 401 400 402 70 403 80 your report will print 550 accidents in 2004 . #include <stdio.h> typedef struct { int highwayno; /* highway number */ int nacc; /* number of accidents */ } accdata; int main (void) { FILE *in; int totacc=0, year; accdata data; in = fopen ("accidents.bin", "r"); fscanf (in, "%d", &year); while (fscanf (in, "%d%d", &data.highwayno, &data.nacc)! =EOF) { totacc = totacc + data.nacc; } printf (%d accidents in %d\n", totacc, year); fclose (in); return (0); }...
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- Winter '11
- Panzer
- Addition, 2D array, int nRows, int ar1, possible array size, int sumcorners
Click to edit the document details | https://www.coursehero.com/file/6427098/practice-final-w05s/ | CC-MAIN-2018-26 | refinedweb | 201 | 63.9 |
Answered by:
SQLExpress security
hello,
i have a question. ive bundled my DB with normal windows authentication mode in a setup file and would be installing it at my clients place. is it safe or is there anything that i need to do so that the client does not tamper with the DB.
Secondly, do i need to to install MSSQL at client system for my project to work??
rgds
HV
Question
Answers
2. Public connetionString As String = "Data Source=.\SQLEXPRESS;Initial Catalog=t_sang_d;Integrated Security=True" (but i would like to change this connection string to make it secure so that the user does not tamper with this)
All replies
Hello,
Interesting but huge question.But to help you , we need more informations.
1) Please, could you tell you what is the version of SQL Server Express that you are using ( 2005,2008,2008 R2,2012 )
2) Please, could you provide the connection string used to connect to the database ( just in case of user instance ) ?
3) Please, could you tell us what is the type of application ( WinForms,ASP.Net,...) you are installing ? ( also the language used to develop your application )
4) Please, are your application and your database used alone or collaborating with other databases installed with your application ?
Your 2nd question seems easy to answer : i would say yes if the database is used in user instance. If the database can be accessed remotely : no ( in the case of a database which is not private to a given computer and which can be accessed remotely ).
We are waiting for your feedback to try to help you more efficiently
Have a nice day
Mark Post as helpful if it provides any help.Otherwise,leave it as it is.
Thanks Mark
below are the answers to your ?s
1. SQLEXPRESS version is 2005
2. Public connetionString As String = "Data Source=.\SQLEXPRESS;Initial Catalog=t_sang_d;Integrated Security=True" (but i would like to change this connection string to make it secure so that the user does not tamper with this)
3. type of application is winforms developed in VB.net
4. standalone
Also about your answer to my second question, im still not clear, if i have to install SQL in client system, then how do i do that as i would be giving a setup file to my client
rgds
HV
Hello,
I will try to answer your both questions in an understandable way.
1) SQL Server Express is an old version of which the life is finishing. I would suggest you to test your application version versus a SQL Server 2008 R2 or (better) SQL Server Denali (2012) as soon as this last one will be released ( it is only a question of weeks ). A little remark about SQL Server 2005 Express : the SQL Server Management Studio Edpress Edition ( SSMSEE for 2005 ) is a plea : it forbids any upgrade towards a more recent version of SQL Server ( there is a thread about from Mike Wachal explaining the origin of the problem ). It is an excellent reason to jump quickly to the a newer version.
2) Your connection string is good but i don't know how it has been built and where it has been created. It depends whether you have used the Visual Studio features to create it or not ( have you used the Data source menu of Visual Studio ? If yes, your connection string should be stored in the app.config file , so visible to everyone and modifiable by everybody . It can be crypted but it is a problem which should be treated in another forum ). For myself, i prefer to use the SqlConnectionStringBuilder class from the namespace System.Data.SqlClient to build the connection string, more code to write but you hide your connection string ). As you are using Window authentification to connect to the SQL Server Express, there is ( in theory ) no security problems. If i asked you this question, it is only because i was fearing the use of user instances.
3) To embed the install of SQL Server Express in your application, i would suggest this old link : . I think that i have seen other articles about this common subject , but i need some more time to do some research.
Don't hesitate to post again for more help or explanations.
Have a nice day
PS : A little remark , you wrote Hello Mark , but i am known on the forums as Papy Normand and my 1st name is Patrick. You have the choice, no problem for me ( i am not doing any reproach, it is only a little information )
Mark Post as helpful if it provides any help.Otherwise,leave it as it is.
sorry patrick,
i read "mark post as helpful......" and i was thinking about a solution to all this :-) really very sorry about it
coming back to my doubt, where can i find SQL Server 2008 R2 and is it free..... also how do i replace my sql 2005(sqlexpress with SQL Server 2008 R2) kindly help me with this please.....
rgds
hari vaag
HV
Hi hari,
You can only install SQL Server express shared features and other features, there is no need to install instances. And then detach the database from the old server and attach it on your client.
Please see: Detaching and attaching database
Best Regards,
Iric
Please remember to mark the replies as answers if they help and unmark them if they provide no help.
2. Public connetionString As String = "Data Source=.\SQLEXPRESS;Initial Catalog=t_sang_d;Integrated Security=True" (but i would like to change this connection string to make it secure so that the user does not tamper with this) | http://social.msdn.microsoft.com/Forums/sqlserver/en-US/ba6c31dc-3059-4f29-802f-d4d99aae1143/sqlexpress-security?forum=sqlexpress | CC-MAIN-2014-41 | refinedweb | 947 | 69.41 |
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instruct loadI2L_immI(iRegL dst, memory mem, immI mask, iRegI tmp) %{
match(Set dst (ConvI2L (AndI (LoadI mem) mask)));
From inspection, it appears that this rule (on all platforms) only works if the result of the AndI
doesn't need to be sign-extended (>= 0). My first attempt at a test program didn't work. For
some reason when using an array, C2 only takes a fast path if the value is positive:
static long foo(int[] x) {
return x[0] & 0xfffffffe;
}
However, using a field instead doesn't have that problem.
% cat a.java
public class a {
static int x;
static long foo() {
return x & 0xfffffffe;
}
public static void main(String[] args) {
x = -1;
long l = 0;
for (int i = 0; i < 100000; ++i) {
l = foo();
}
System.out.println(l);
}
}
% ./bin/java -Xint a
-2
% ./bin/java -XX:-TieredCompilation -server a
4294967294
7u60-critical-justification: A related issue to JDK-8032207 that the OpsCenter team is having. Fixing both issues is needed for a proper fix.
I'll push it today, I was waiting to check the nightlies in 9 first.
URL:
User: amurillo
Date: 2014-01-23 23:09:27 +0000
URL:
User: iveresov
Date: 2014-01-23 19:55:26 +0000
Release team: Approved for fixing
ILW=HHH=P1
Impact: Incorrect result (which is way worse than a crash), the test case is very simple.
Likelihood: This reproduces all the time.
Workaround: None
Justification: This affects any code that does a bitwise AND with a integer loaded from memory and constant mask value with conversion to a long.
The optimization transforms (ConvI2L (AndI (LoadI mem) mask)) to (AndI (LoadUI2L (mem) mask). If the mask constant has the highest bit set and the value is also negative the optimization behaves incorrectly and produces wrong result because the value is not sign-extended.
The fix is low risk since it conservatively doesn't introduce any new code generation but rather restricts when the existing optimizations are being applied.
Uh-oh, that's extremely bad! This should be a P1.
Suggest fix:
The bug exists on all platforms. x86, x64, sparc, arm
The optimization is incorrect, it would work only with mask <= 0x7fffffff. Predicating it off based on that should do the trick. | http://bugs.java.com/view_bug.do?bug_id=8031743 | CC-MAIN-2015-32 | refinedweb | 384 | 61.26 |
Slides is an awesome Elm presentation framework, inspired by reveal.js.
import Slides exposing (..) main = Slides.app slidesDefaultOptions [ md """ # A markdown slide _stuff follows..._ """ , mdFragments [ "Another slide with three fragments" , "This appears later" , "And this even later" ] ]
Slides is customizable and, since it follows the Elm Architecture, can be used like any other Elm component.
By default, a Slides app will respond to these controls:
Click on window bottom or right: Next slide
Click on window top or left: Previous slide
D, L, Arrow Right, Enter and Spacebar: Next slide/fragment
A, H, Arrow Left: Previous slide/fragment
Home: First slide
End: Last slide
P: pause animation (useful for debugging custom animations)
This is the DOM structure for your custom CSS:
body .slides section /* one per slide */ .slide-content /* useful for padding */ .fragment-content
Add more built-in slide and fragment animations.
Add more ready-to-use CSS themes.
Add support for touch/gestures. | https://package.frelm.org/repo/954/5.0.0 | CC-MAIN-2019-18 | refinedweb | 155 | 56.86 |
troubleshooting br-ex
Hi all,
Just did a juno build and have instances getting private IPs all ok.
I have 3 networks: admin, private, public. Public is 192.168.1.0/24 which is my home router network. Build is on VMware Fusion on OSX.
So, I created external network as per the guide:
neutron net-create ext-net --router:external True --provider:physical_network external --provider:network_type flat neutron subnet-create ext-net --name ext-subnet --allocation-pool start=192.168.1.200,end=192.168.1.210 --disable-dhcp --gateway 192.168.1.1 192.168.1.0/24 neutron router-gateway-set demo-router ext-net
This has assigned 192.168.1.200 to network:router_gateway as i expected. It does list it as "DOWN" but that seems to happen a lot :-)
However, from my mac, which is on 192.168.1.5 i can't ping 192.168.1.200 or any assigned floats behind it.
If i look in the router's namespace I see:
ip netns exec qrouter-d024a2ac-4563-4f0a-9e54-562d83dc0586 ifconfig <snip> qg-46dadc95-a8: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.1.200 netmask 255.255.255.0 broadcast 192.168.1.255 inet6 fe80::f816:3eff:fe90:b83b prefixlen 64 scopeid 0x20<link> <snip>
i can even ssh to the float of an instance in there:
ip netns exec qrouter-d024a2ac-4563-4f0a-9e54-562d83dc0586 ssh cirros@192.168.1.201
and it works.
tcpdumping in the namespace doesn't show any packets coming in from my pings/ssh.
I used the "autodetect" interface assignment in fusion if that means anything. I believe it's just to get an IP from the outside network and not fusion's internal DHCP one. The latter failed as well.
So, I'm hoping a networking/ops/etc guru can give me more tips to troubleshoot to reveal the problem.
August
PS.
# ovs-vsctl show 4c7b8e80-7420-4fb5-9c01-9bd961bc68dc Bridge br-tun Port patch-int Interface patch-int type: patch options: {peer=patch-tun} Port "vxlan-ac10470d" Interface "vxlan-ac10470d" type: vxlan options: {df_default="true", in_key=flow, local_ip="172.16.71.12", out_key=flow, remote_ip="172.16.71.13"} Port br-tun Interface br-tun type: internal Bridge br-ex Port "eno50332184" Interface "eno50332184" Port phy-br-ex Interface phy-br-ex type: patch options: {peer=int-br-ex} Port br-ex Interface br-ex type: internal Bridge br-int fail_mode: secure Port "tapf7b8b245-11" tag: 1 Interface "tapf7b8b245-11" type: internal Port int-br-ex Interface int-br-ex type: patch options: {peer=phy-br-ex} Port "qg-46dadc95-a8" tag: 4095 Interface "qg-46dadc95-a8" type: internal Port patch-tun Interface patch-tun type: patch options: {peer=patch-int} Port br-int Interface br-int type: internal Port "qr-d497c7e1-fb" tag: 1 Interface "qr-d497c7e1-fb" type: internal ovs_version: "2.1.3"
tag 4095 is not good. Try reconfiguring the network. I've hit this many times and reconfiguring usually resolves (may need to redo more than once).
does the ovs-agent know how to map ext-net to br-ex? have you
bridge_mappings = ext-net:br-ex
i'll get 4095 out and see. also .. plugin.ini:network_vlan_ranges =physnet-external plugins/openvswitch/ovs_neutron_plugin.ini:bridge_mappings=physnet-external:br-ex plugins/ml2/ml2_conf.ini:network_vlan_ranges =physnet-external which i think is right? i'll test some changes | https://ask.openstack.org/en/question/60145/troubleshooting-br-ex/ | CC-MAIN-2019-09 | refinedweb | 571 | 59.3 |
This is your resource to discuss support topics with your peers, and learn from each other.
01-22-2014 02:46 PM
I want to be able to do a Google search in a webview, by setting the URL to "" + "search".
The problem is that if the search query contains a + sign, it get interpreted as a space (this actually happens in some popular apps including Evolution browser).
I read that encodeURIComponent should fix this problem so I changed the code to "" + encodeURIComponent("+"), but the resulting search is actually for %2B. Strangely, when I type the resulting URL into my computer I get the corrrect result (a search for +).
import bb.cascades 1.2 Page { property string search: "" + encodeURIComponent("+") Container { TextField { text: web.url } WebView { id: web url: search } } }
Solved! Go to Solution.
01-23-2014 02:16 PM
Hi,
This is an effect of two things:
So - you're seeing the code getting double escaped.
I worked around this like this:
import bb.cascades 1.0 Page { property string search: "" + encodeURIComponent("+") Container { WebView { id: web onCreationCompleted: { app.setURL(web, search); } } } }
Functions for the manipulation:
Q_INVOKABLE QUrl urlMagic(QString source) { QByteArray data(source.toAscii()); QUrl toReturn; toReturn.setEncodedUrl(data); return toReturn; } Q_SLOT void setURL(bb::cascades::WebView * webView, QString url) { if (webView!=NULL) { QUrl toSet(urlMagic(url)); webView->setUrl(toSet); } }
Found I also needed to register WebView (i'm working with older SDK ATM)
qmlRegisterType<bb::cascades::WebView>("bb.cascade
s",1,0,"WebView");s",1,0,"WebView");
Hope this helps...
Thanks!
01-23-2014 04:11 PM
Hello,
Thank you for your reply.
I am new to coding and don't really understand where to put the functions.
Could you show me the full files?
Thank you
02-07-2014 12:33 PM
Hi,
Have you made any progress?
The first block goes in your QML, the second goes in your c++ header file (in the public: section). The third goes in main.cpp before cascades calls.
You'll also need :
* Correct includes to find these classes
* Insertion of the c++ class into the QML context.
Thanks.
02-07-2014 01:03 PM
robbieDubya wrote:
You'll also need :
* Correct includes to find these classes
* Insertion of the c++ class into the QML context.
I don't know how to do this.
robbieDubya wrote:
the second goes in your c++ header file (in the public: section).
I keep getting the error "return type 'struct QUrl' is incomplete" and "'bb::cascades::WebView' has not been declared".
Thank you
02-07-2014 01:54 PM
Here's the minimal project I used to test my code.
02-07-2014 02:40 PM | https://supportforums.blackberry.com/t5/Native-Development/Encode-part-of-URL-search/m-p/2748591/highlight/true | CC-MAIN-2016-36 | refinedweb | 441 | 67.15 |
Hi, On Mon, 3 Nov 2003, Karthik Kumar wrote: > -- Convert a string to an integer. > -- This works perfectly fine. > atoi :: [Char] -> Int > atoi (h : []) = if isDigit h then digitToInt h else 0 > atoi (h : t) = if isDigit h then digitToInt h * ( 10 ^ length t) + > atoi t else 0 you can use "read" for this. > -- validateBoardSize > -- To validate the board size > validateBoardSize :: Int -> Bool > validateBoardSize d = (d == 9 || d == 13 || d == 19 ) this looks fine > getBoardSize :: IO Bool > -- TODO : What could be the type of getBoardSize > getBoardSize = do c <- getLine > validateBoardSize ( atoi c ) > > ERROR "test1.hs":21 - Type error in final generator > *** Term : validateBoardSize (atoi c) > *** Type : Bool > *** Does not match : IO a this is telling you something important. it's saying that the final generator, "validateBoardSize (atoi c)" has type Bool, but it's expecting it to have type IO something. You need to "lift" the pure Bool value into IO by saying return: > getBoardSize = do > c <- getLine > return (validateBoardSize (read c)) -- Hal Daume III | hdaume at isi.edu "Arrest this man, he talks in maths." | | http://www.haskell.org/pipermail/haskell-cafe/2003-November/005420.html | CC-MAIN-2013-48 | refinedweb | 176 | 58.21 |
This is the third part of the How to Make Doodle Jump with Felgo tutorial. In this part we will cover two major features that no game should miss.
Having multiple scenes is essential for every decent game. To add this feature, we are going to perform some changes in our project.
Create a new file
SceneBase.qml in your
scenes folder.
SceneBase.qml
import Felgo 3.0 import QtQuick 2.0 Scene { id: sceneBase width: 320 height: 480 // by default, set the opacity to 0. We handle this property from Main.qml via PropertyChanges. opacity: 0 // the scene is only visible if the opacity is > 0. This improves performance. visible: opacity > 0 // only enable scene if it is visible. enabled: visible }
SceneBase.qml is going to be the base class for all our other scenes.
In this class we set the default
width and
height values for all other scenes. Also we define some basic scene transition properties. We will need those later, to navigate between
scenes.
Now change the GameScene's root element from Scene to SceneBase.
import Felgo 3.0 import QtQuick 2.0 import QtSensors 5.0 import "../" SceneBase { // ... }
Of course, we want to be able to navigate from the
GameScene to the
MenuScene. So let's prepare a new signal
menuScenePressed to your
GameScene.qml.
SceneBase { // ... signal menuScenePressed // ... }
Signals in QML are a great way to realize communication between components. Whenever you face a situation, where one component should react to an event that occurs in another component, signals are your best friend. To learn more about signals, see the official documentation here.
After that, we add this Image element just before the last closing } of your
GameScene.qml.
Image { id: menuButton source: "../../assets/optionsButton.png" x: gameScene.width - 96 y: -40 scale: 0.5 MouseArea { id: menuButtonMouseArea anchors.fill: parent onClicked: { menuScenePressed() // trigger the menuScenePressed signal // reset the gameScene frog.die() gameScene.state = "start" } } }
With this, we have a clickable button, that triggers our signal when it is pressed. We will handle the
menuScenePressed signal in our
Main.qml later.
Create
MenuScene.qml in the
scenes folder and paste the following code.
MenuScene.qml
import Felgo 3.0 import QtQuick 2.0 import "../" SceneBase { id:menuScene // signal indicating that the gameScene should be displayed signal gameScenePressed // background image Image { anchors.fill: menuScene.gameWindowAnchorItem source: "../../assets/background.png" } Column { anchors.centerIn: parent spacing: 20 Rectangle { width: 150 height: 50 color: "orange" Image { id: gameSceneButton source: "../../assets/playButton.png" anchors.centerIn: parent } MouseArea { id: gameSceneMouseArea anchors.fill: parent onClicked: gameScenePressed() } } Rectangle { width: 150 height: 50 color: "orange" Image { id: scoreSceneButton source: "../../assets/scoreButton.png" anchors.centerIn: parent } MouseArea { id: scoreSceneMouseArea anchors.fill: parent onClicked: frogNetworkView.visible = true } } } }
So we begin with creating a signal to trigger the GameScene transition. Then we set a background image.
The Column element helps us defining the layout of our menu. All elements defined in a Column are
placed below each other. We add two Rectangle elements - these are our menu buttons. The first one leads to the
GameScene, the second one to our
GameNetworkView.
If you are wondering why the two Rectangles are used to create the buttons, here's why: The Column component aligns the buttons based on the fixed height of the Rectangles. The Image inside is actually bigger. So by using the Rectangle for alignment, the Images overlap a bit in the middle.
That's all we need for our new scene. So let's add the MenuScene to our Main.qml and move the GameNetworkView from the game scene to the menu scene.
Main.qml
GameWindow { // ... GameScene { id: gameScene } // the menu scene of the game MenuScene { id: menuScene GameNetworkView { id: frogNetworkView visible: false anchors.fill: parent.gameWindowAnchorItem onShowCalled: { frogNetworkView.visible = true } onBackClicked: { frogNetworkView.visible = false } } } // ... }
As the last step, because we now access the game network from the menu, you can remove the makeshift SimpleButton in your
GameScene.qml.
So now that our scenes are all set up, we can handle the scene transitions.
In your
Main.qml update your
GameScene and
MenuScene,
Main.qml
GameWindow { GameScene { id: gameScene onMenuScenePressed: gameWindow.state = "menu" } MenuScene { id: menuScene onGameScenePressed: gameWindow.state = "game" GameNetworkView { // ... } } }
and finally add this piece of code, to add states and handle state transitions.
GameWindow { // ... // starting state is menu state: "menu" // state machine, takes care of reversing the PropertyChanges when changing the state. e.g. it changes the opacity back to 0 states: [ State { name: "menu" PropertyChanges {target: menuScene; opacity: 1} PropertyChanges {target: gameWindow; activeScene: menuScene} }, State { name: "game" PropertyChanges {target: gameScene; opacity: 1} PropertyChanges {target: gameWindow; activeScene: gameScene} } ] }
So what's happening here? In the
GameScene and
MenuScene we handle our navigation signals and change the game's
state to either
menu or
game. Our state machine
then activates and shows the respective scene.
Great, now that we have multiple scenes functionality, it's very easy to add even more scenes. For a more detailed description of how to create games with multiple scenes or levels, check out this tutorial.
Felgo offers many different plugins. They help you to display ads, connect to social media or even add in-app purchases to your game. For a list of all available plugins see here.
To add plugins, like Google Analytics, to your game, you will need the following things:
For a guide how to add Google Analytics plugin to your project, please visit the plugin integration page. After you successfully added the plugin, you can proceed with the next step of the tutorial.
If you have any troubles with the various installation steps, please ask for help in the forums: Felgo Plugin Support.
Go to the admin tab of your Google Analytics account and create a new property.
Select Mobile App, enter an App Name and press Get Tracking ID.
You are going to receive a property ID. This ID will look like this: UA-12341234-1. We will need this property ID to add the Google Analytics Plugin to our game.
Next you will need a Felgo license key, that allows you to use the Google Analytics plugin. You can create a license key here. Just select the plugin
and enter the correct app-identifier and version-code of your project. If you are not sure about these values, you can look them up in your
Other Files/qml/config.json file. In case you already have a
licenseKey set in your GameWindow, replace your previous
licenseKey with this new one.
Now open your
Main.qml and import Google Analytics.
import Felgo 3.0
Afterwards add the GoogleAnalytics element, right after the EntityManager.
GoogleAnalytics { id: ga licenseKey: "yourLicenseKey" // property tracking ID from Google Analytics dashboard propertyId: "UA-12341234-1" }
Enter both your Felgo
licenseKey for Google Analytics and the Google Analytics
propertyId. If you already use the
licenseKey in the GameWindow, you
may skip adding the licenseKey for the plugin. The GameWindow
licenseKey will be used automatically.
Now we have everything ready to start tracking the game. There are two functions you can use to track the game.
logScreen(string screenName)let's you keep track of screens.
logEvent(string eventCategory, string eventAction, string eventLabel, int value)helps you track events.
Events are a useful way to collect data about a user's behavior. For example you can track button presses or the use of a particular item in the game. Every event has to have at least an
eventCategory and an
eventAction.
Now let's add tracking to our game. In your
Main.qml add the
logEvent function to the
MenuScene and the
GameScene components.
GameWindow { // ... GameScene { id: gameScene onMenuScenePressed: { gameWindow.state = "menu" ga.logEvent("Click", "MenuScene") } } MenuScene { id: menuScene onGameScenePressed: { gameWindow.state = "game" ga.logEvent("Click", "GameScene") } GameNetworkView { // ... } } }
You see it's very simple. We log an event every time the user presses one of the buttons to switch scenes.
To see your collected data go to the Google Analytics page. Open the Reporting tab, click on Behavior in the sidebar, then open the Events subsection.
At first everything might look a bit confusing, but I'm sure you'll get the hang of it once you log more events and browse through the data and statistics.
Now you can track your user's behavior and use the collected data to further improve your games. In the next part of this tutorial I will explain how you can monetize your game to earn some money with two more Felgo plugins: AdMob and Chartboost.
Voted #1 for: | https://felgo.com/doc/howto-doodle-jump-game-analytics-tutorial/ | CC-MAIN-2019-47 | refinedweb | 1,414 | 68.77 |
Dmitri Pal wrote:
Jason Gerard DeRose wrote:Okay, finally here is the revised webui patch. Since the last version, I: * Ported to various API changed between wehjit 0.0.1 and 0.1.0 * Removed the session.py stuff, which will be in a separate patch * Added the plugin browser to help developers inspect the plugins The webui is still in a similar "dumb" state till I extend various meta-data in ipalib, which I will work on this week and will quickly get the UI into a more impressive state. I just can't let this patch get any larger... stop the madness! ;) There currently isn't a top-level webui-page at /ipa/ui, but pages exist for each command plugin, i.e., /ipa/ui/user_add This patch is big, but tries to be non-intrusive: the new webui stuff only runs from the new lite-server.py script, not for the installed version running under Apache. As far as I know, no existing functionality is disrupted by this patch. After making the meta-data changes, I will enable the new functionality under Apache also. I hope everyone will find the plugin-browser quite helpful. To run it, launch lite-server.py like this: ./lite-server.py And then point your browser to: All plugins in all namespaces are available in the browser, but details are currently only available for the Command and Object namespaces. I will also soon add an easy way to render the plugin browser to static pages to put on freeipa.org. This patch requires python-wehjit and python-assets, which are in Fedora12 and rawhide. Or you can install from tarballs here: A couple of weekends ago I also packaged assets and wehjit for Debian/Ubuntu. Karmic packages are available in my PPA: Sorry the patch is so large, subsequent ones wont be.Jason, The patch removes 4300 lines and adds 1000. Is this correct or we are missing something?
The majority of that 4300 is a single file, mootools-core.js. I'm guessing he is planning to use a different javascript toolkit.The majority of that 4300 is a single file, mootools-core.js. I'm guessing he is planning to use a different javascript toolkit.
rob
Attachment:
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dale3Courses Plus Student 3,566 Points
def suggest(product_idea): return product_idea + "inator" product_idea = input("Do you understand? ") if product_id
is this the correct code def suggest(product_idea): return product_idea + "inator" product_idea = input("Do you unde
def suggest(product_idea): return product_idea + "inator" product_idea = input("Do you understand? ") if product_idea < 3: raise ValueError("Are you sure you don't get it?")
1 Answer
Chris FreemanTreehouse Moderator 67,736 Points
Hey richarddale3, you have the parts, but they're out of order:
def suggest(product_idea): # in this challenge # the new code goes here return product_idea + "inator"
In this challenge check of the
product_idea size has to do with it's character length and not its value. Conveniently, the builtin function
len() will gives us the length of a string:
len(product_idea)
if product_idea < 3: # <--- change to use len() raise ValueError("Are you sure you don't get it?")
Corrected the length checking code and insert it the before the
return statement to pass the challenge.
There is no need for the
input() statement in this challenge. The challenge checker will exercise the code with various values for the product_idea.
Post back if you need more help. Good luck!! | https://teamtreehouse.com/community/def-suggestproductidea-return-productidea-inator-productidea-inputdo-you-understand-if-productid | CC-MAIN-2021-49 | refinedweb | 195 | 51.28 |
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RoboguyMember
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So, std::vector is...??
Roboguy replied to MarkS's topic in For Beginners's ForumQuote:Original post by boogyman19946 [...]but I doubt someone would spend that much time to create a new language just as a joke.[...] There are languages created as a joke, such as HQ9+ (See the joke language list on the esoteric programming language wiki). Unless you meant as much time as they put into making the C++ standard.
Python bug???
Roboguy replied to macktruck6666's topic in Engines and Middlewareappend adds a new element to the list, which, in this case, is []. So the list looks like this after the append: [[]]. That's a list containing one element; the one element being []. Also, you can use the [code] and tags in the forums to preserve indentation. Look here: GDNet Forums FAQ
Has anyone programmed anything with the Canvas tag in HTML 5?
Roboguy replied to Alpha_ProgDes's topic in GDNet LoungeQuote:Original post by LockePick I'm more than happy to have less people competing with me in the flash market, anyways. I would rather be in the (web) application development market than the Flash market. Why tie yourself to one platform? What if a platform does come around eventually that is superior in some sense?
RFC: Epoch Programming Language, Release 8
Roboguy replied to ApochPiQ's topic in General and Gameplay ProgrammingI've been thinking about this project since I read your first thread about the idea. I'm looking forward to trying it, but are there any plans for Mac OS X support in the near future (I do most of my coding on a Mac and have for some years now)? Also, did you ever post anything on Lambda the Ultimate about this project? They might give some good feedback.
Common Lisp: Confused about #' and functions
Roboguy replied to tufflax's topic in For Beginners's ForumInternally, Common Lisp uses two namespaces: one for function bindings and one for non-function bindings. This allows you to, for instance, have both an integer and a function bound to the symbol x at the same time. Scheme, which is a Lisp dialect, however, has one namespace. There is a more detailed discussion of this topic on this Wiki page.
compilers
Roboguy replied to jammerocker's topic in For Beginners's ForumQuote:Original post by XTAL256 Quote:Original post by jammerocker im using Learn C++ in 24 hours, anyone used this book? No, but i'd have to say i should think it would take a bit more that 24 hours to learn C++ [grin] Indeed. These titles always remind my of this article by Peter Norvig.
Guitar Hero - but with Real Instruments
Roboguy replied to prodigenius's topic in Your AnnouncementsLooks interesting. Are there any plans to support multiple notes playing simultaneously (like chords)? That would probably be hard to track, though.
A Slight Variant of Modern Exception Handling
Roboguy replied to ouraqt's topic in General and Gameplay ProgrammingYou might also want to look into how the Icon programming language works: Wikipedia Brief introduction Overview Main site I always thought that was an interesting way to handle control flow. Basically, the whole language is designed around generators.
Challeng website
Roboguy replied to Psilobe's topic in General and Gameplay ProgrammingSounds like Project Euler.
- Quote:Original post by Durakken It's not just like the real world. And haven't you ever heard of Role play? Sure, but typically people role play fantasies, i.e. stuff they can't do in the real world. Limiting resources like that might make it a bit too realistic. Realism isn't always good.
- I think there is a bigger issue than if this is feasable: would there be a point? What incentive would someone have to pay a monthly fee (I assume) to use a virtual world that is just like the real world, except not as detailed?
C++ or C?
Roboguy replied to Sheepz's topic in General and Gameplay ProgrammingQuote:Original post by CadetUmfer Quote:Original post by Telastyn Quote: But, the point is, I learned a lot about the details of how memory is stored, accessed, and what pointers are by starting with the harder way first. Which is useless knowledge. Taking some time to learn some algorithms, or how to architect programs... y'know, actually program? What? The Von Neumann architecture is here to stay, and our algorithms are based around that model. Better understanding that isn't "useless knowledge." The Von Neumann architecture is also going to become more and more abstracted until such knowledge will serve no purpose. There is already hardly any reason to be concerned with those details. Quote: Understanding the stack and function calls, and virtual function dispatch--that stuff helped me become a better programmer. It might have made you better at using C++. Frankly, I doubt it made you a better programmer. Quote: I'd take a doctor who knows how medicines work over one who can read journals and match up symptoms. And I would rather see a doctor than a biochemist.
Is search in Windows Explorer broken? (Thread Cleared)
Roboguy replied to shuma-gorath's topic in GDNet LoungeMaybe I'm misunderstanding you, but wildcards in searches are usually position dependent, meaning that, for example, ".txt*" will match any file with a file name starting with ".txt" and "*.txt" will match any file with a file name ending with ".txt". This is how it works in every search system I can think of. If wildcards were not position dependent it would be less powerful.
Paper Idea
Roboguy replied to Gametaku's topic in GDNet LoungeWell, you could compare it to other programming paradigms (e.g. procedural programming or plain OOP)..
Turing completeness
Roboguy replied to EmrldDrgn's topic in General and Gameplay ProgrammingI could, if I tried, speak code in any (textual) programming language in English. So yes, even though it does not make much sense to talk about natural languages in that context. Unless you mean something else.
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IRC log of i18n on 2012-06-20
Timestamps are in UTC.
14:50:04 [RRSAgent]
RRSAgent has joined #i18n
14:50:04 [RRSAgent]
logging to
14:50:08 [aphillip]
trackbot, prepare teleconference
14:50:10 [trackbot]
RRSAgent, make logs world
14:50:12 [trackbot]
Zakim, this will be 4186
14:50:12 [Zakim]
ok, trackbot; I see I18N_CoreWG()11:00AM scheduled to start in 10 minutes
14:50:13 [trackbot]
Meeting: Internationalization Core Working Group Teleconference
14:50:13 [trackbot]
Date: 20 June 2012
14:50:44 [aphillip]
Agenda:
14:50:44 [aphillip]
Chair: Addison Phillips
14:50:46 [aphillip]
Scribe: Addison Phillips
14:50:59 [aphillip]
ScribeNick: aphillip
14:50:59 [aphillip]
rrsagent, draft minutes
14:50:59 [RRSAgent]
I have made the request to generate
aphillip
14:51:27 [aphillip]
rrsagent, set logs world
14:57:48 [Gwyneth]
Gwyneth has joined #i18n
14:59:15 [Zakim]
I18N_CoreWG()11:00AM has now started
14:59:23 [Zakim]
+[Microsoft]
15:00:10 [Zakim]
+Addison_Phillips
15:01:19 [r12a]
r12a has joined #i18n
15:01:36 [Zakim]
+??P21
15:01:43 [r12a]
zakim, dial richard please
15:01:52 [Zakim]
ok, r12a; the call is being made
15:01:54 [Zakim]
+Richard
15:02:14 [Norbert]
Norbert has joined #i18n
15:03:07 [Zakim]
+ +1.415.885.aaaa
15:05:07 [aphillip]
Topic: Agenda and Minutes
15:05:30 [aphillip]
Topic: Action Items
15:06:48 [aphillip]
(AND ALL GROUP MEMBERS) study additional bidi controls proposal and express support or lack of support for it at Unicode
15:06:57 [r12a]
15:07:52 [aphillip]
close ACTION-128
15:07:52 [trackbot]
ACTION-128 Add member@ and bidi/cjk lists to tracker tracked lists closed
15:08:09 [aphillip]
close ACTION-131
15:08:09 [trackbot]
ACTION-131 Update the Activity about page etc to describe the adjusted use of the mailing lists and add information about tracker closed
15:08:21 [aphillip]
Topic: Info Share
15:08:46 [aphillip]
richard: has some info
15:09:02 [aphillip]
... was at ML-Web LT workshop
15:09:09 [aphillip]
... talked about linked ml data
15:09:16 [aphillip]
... talked about additions to ITS v2
15:09:28 [r12a]
Labra Gayo, José Emilio - Best Practices for Multilingual Linked Open Data - PDF
15:09:30 [aphillip]
... and those will be pursued by that wg
15:09:42 [aphillip]
... the above talk
15:09:50 [r12a]
temporary link:
15:09:51 [aphillip]
... (temporary link to follow)
15:10:22 [aphillip]
... basically an attempt to describe best practices for working with multilingual open data
15:10:42 [aphillip]
... proposed to make into best practices document on our site
15:10:53 [aphillip]
... some unanswered questions
15:11:34 [aphillip]
... to publish as WG Note techniques document
15:11:47 [RRSAgent]
I have made the request to generate
aphillip
15:12:15 [aphillip]
matial: draw attention to PRI issue 341
15:12:28 [aphillip]
... matching parentheses addendum to UBA
15:12:34 [aphillip]
... seeking advice
15:12:56 [aphillip]
... I have some comments
15:13:01 [Norbert]
15:13:34 [aphillip]
s/issue 341/issue 231/
15:13:55 [RRSAgent]
I have made the request to generate
aphillip
15:14:47 [r12a]
15:14:49 [aphillip]
richard:
15:15:02 [aphillip]
richard: report on luxembourg workshop above
15:15:15 [aphillip]
... good to watch the videos, since you get more info from them
15:15:34 [aphillip]
... only 15 min. each.... working on links... avail soon
15:15:43 [aphillip]
Topic: Charter review
15:15:56 [aphillip]
15:16:26 [aphillip]
richard: PLM wants to take to W3M next wednesday
15:16:34 [aphillip]
... so last chance to comment
15:17:11 [aphillip]
... main difference is that we'll be supporting REC-track (with encoding document as our only such deliverable)
15:17:45 [r12a]
s/PLM/PLH/
15:26:19 [aphillip]
Norbert: list Webapps
15:29:30 [RRSAgent]
I have made the request to generate
aphillip
15:30:20 [aphillip]
addison: charmod on rec track or no?
15:35:13 [aphillip]
gwyeth: when would it go into effect?
15:35:53 [aphillip]
richard: (reviews process---W3M, AC reps, etc.)
15:36:02 [aphillip]
... about two months??
15:36:49 [aphillip]
Topic: Web Notifications
15:36:52 [aphillip]
15:37:04 [aphillip].
15:37:33 [aphillip]
last call published end of last week
15:38:22 [aphillip]
s/last week/next week/
15:39:19 [aphillip]
ACTION: addison: (AND ALL GROUP MEMBERS) review Web Notifications for revew at 27 June WG teleconference
15:39:19 [trackbot]
Created ACTION-132 - (AND ALL GROUP MEMBERS) review Web Notifications for revew at 27 June WG teleconference [on Addison Phillips - due 2012-06-27].
15:39:54 [aphillip]
ACTION-132:
15:39:55 [trackbot]
ACTION-132 (AND ALL GROUP MEMBERS) review Web Notifications for revew at 27 June WG teleconference notes added
15:40:27 [aphillip]
Topic: XLIFF 2.0?
15:41:17 [aphillip]
(defer topic for later)
15:41:17 [aphillip]
Topic: IRI and IRI bidi documents
15:41:52 [aphillip]
15:42:53 [aphillip]
Norbert: discussed more in general layout of IRIs with bidi
15:43:08 [aphillip]
... it says "embed any IRIs in a LTR context"
15:45:11 [aphillip]
addison: doesn't solve problems with dot and slash, though... only provides a directional base
15:45:35 [aphillip]
gwyneth: hasn't had a chance to follow up with shawn steele until just now
15:46:47 [aphillip]
... wants a different presentation that UBA
15:47:04 [aphillip]
addison: problem is need for bidi controls to do that under UBA, so have leakage problem
15:53:03 [aphillip]
norbert: to make progress, need some "interesting IRIs"
15:53:08 [aphillip]
... and list of algorithms for rendering
15:54:17 [koji]
koji has joined #i18n
15:56:15 [aphillip]
ACTION: addison: ping Adil about status of bidi IRI examples/tests and any documentation or efforts in that direction
15:56:15 [trackbot]
Created ACTION-133 - Ping Adil about status of bidi IRI examples/tests and any documentation or efforts in that direction [on Addison Phillips - due 2012-06-27].
15:56:56 [aphillip]
Topic: AOB?
15:57:01 [aphillip]
addison: for next week
15:57:08 [aphillip]
richard: review Ruby document
15:57:17 [aphillip]
... move to FPWD next week
15:58:12 [aphillip]
Norbert: moving CSS Box Layout to last call... add to review radar
15:58:53 [aphillip]
Topic: XLIFF v2
15:59:36 [aphillip]
richard: XLIFF allowed namespaces
15:59:47 [aphillip]
... and folks implemented core features of XLIFF using their own namespaces
15:59:53 [aphillip]
... which is ugly/painful
15:59:57 [aphillip]
... two proposals
16:00:02 [aphillip]
... 1. drop namespaces
16:00:21 [aphillip]
... 2. special elements like <meta> to express extensibility
16:00:32 [aphillip]
richard: another proposal was keep both
16:00:46 [Zakim]
-Gwyneth
16:00:54 [aphillip]
... but tighten wording around namespaces to prevent recreating core features
16:01:12 [aphillip]
... having a second vote on this
16:01:28 [aphillip]
richard: think ITS and XLIFF should work closely together
16:01:44 [aphillip]
... so get ITS concepts into XLIFF
16:01:50 [aphillip]
... they hadn't thought about it
16:02:01 [aphillip]
... proposed using namespaces to do this
16:03:32 [aphillip]
... felix would be the best reporter
16:04:31 [fsasaki]
for the record: I'm lurking on IRC, happy to take an action item to follow up on this - e.g. 1st a mail draft to our member list, then sending that mail etc. to XLIFF folks
16:04:44 [fsasaki]
so feel free to give me AIs :)
16:04:53 [aphillip]
not ready for that, felix... waiting outcome of vote
16:05:02 [aphillip]
... but I can make up AIs if you need me to
16:05:27 [fsasaki]
OK
16:06:15 [Zakim]
-aphillip
16:06:19 [Zakim]
-matial
16:06:20 [Zakim]
-Norbert
16:07:08 [aphillip]
rrsagent, make minutes
16:07:08 [RRSAgent]
I have made the request to generate
aphillip
16:07:42 [aphillip]
zakim, bye
16:07:42 [Zakim]
leaving. As of this point the attendees were Gwyneth, aphillip, Richard, matial, +1.415.885.aaaa, Norbert
16:07:42 [Zakim]
Zakim has left #i18n
16:08:32 [aphillip]
Present: Addison, Richard, Norbert, Gwyneth, Mati, Felix (via IRC)
16:08:40 [aphillip]
Regrets: David
16:08:47 [aphillip]
rrsagent, make minutes
16:08:47 [RRSAgent]
I have made the request to generate
aphillip
16:08:51 [aphillip]
rrsagent, bye
16:08:51 [RRSAgent]
I see 2 open action items saved in
:
16:08:51 [RRSAgent]
ACTION: addison: (AND ALL GROUP MEMBERS) review Web Notifications for revew at 27 June WG teleconference [1]
16:08:51 [RRSAgent]
recorded in
16:08:51 [RRSAgent]
ACTION: addison: ping Adil about status of bidi IRI examples/tests and any documentation or efforts in that direction [2]
16:08:51 [RRSAgent]
recorded in | http://www.w3.org/2012/06/20-i18n-irc | CC-MAIN-2016-50 | refinedweb | 1,490 | 66.98 |
Hey all. I'm having a problem with a DLL being loaded. In codeblocks, if I don't export Main + ALL the functions in my DLL, they cannot be used by an external program! Yet in visual studio, I exported nothing and external programs are able to load the DLL.
Example:
Main.cpp:
#include <windows.h> #include "GLHook.hpp" BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) { switch (fdwReason) { case DLL_PROCESS_ATTACH: { MessageBox(NULL, "", "", 0); DisableThreadLibraryCalls(hinstDLL); return Initialize(); } break; case DLL_PROCESS_DETACH: { return DeInitialize(); } break; } return TRUE; }
GLHook.hpp:
typedef void (WINAPI *ptr_glAccum) (GLenum op, GLfloat value);
GLHook.cpp:
void GLHook_glAccum(GLenum op, GLfloat value) { (*optr_glAccum) (op, value); } bool Initialize(void) { if (!OriginalGL) { char Root[MAX_PATH]; GetSystemDirectoryA(Root, MAX_PATH); strcat(Root, "\\opengl32.dll"); OriginalGL = LoadLibraryA(Root); if (!OriginalGL) return false; if ((optr_glAccum = (ptr_glAccum) GetProcAddress(OriginalGL, "glAccum")) == NULL) { return false; } }
.DEF File:
LIBRARY OpenGL32 ;DESCRIPTION "GLHook Definition File" EXPORTS glAccum = GLHook_glAccum;
Now the above will compile and work flawlessly in VisualStudio but in codeblocks it'll say "Cannot Export Symbols Undefined"..
When I do export it in codeblocks, it shows 700 symbols in the DLLExport Viewer whereas the Visual Studio one shows 350. The game Loads the Visual studio one but crashes immediately on the Codeblocks one. Visual studio is 80kb in size whereas codeblocks is 744kb.
Why does it do this in codeblocks? I want to use Codeblocks so I can use C++11 ={ Anyway to fix it?
In other words, DLLExport view is showing:
glAccum; //Original functions and..
GLHook_glAccum @8; //The detoured functions.
for codeblocks whereas visual studio one just shows:
glAccum;
Edited by triumphost | https://www.daniweb.com/programming/software-development/threads/430410/dll-codeblocks-vs-vs2010 | CC-MAIN-2017-09 | refinedweb | 266 | 50.53 |
Hello ROOT community,
I am having trouble generating a root dictionary to access my class from within ROOT. I should say that I have successfully added my classes to ROOT in the past (thanks to the useful online tutorials). But this particular custom class refers to problematic typdef statements. It appears that rootcint does not know about a particular data type, called signed. The g++ compiler, however, does understand signed.
Here is a test case class that exhibits the problem:
//----Scope.hh-------
#ifndef SCOPE_HH
#define SCOPE_HH
#include “TString.h” // include any root file for ClassDef()
//#include “AlazarApi.h” // --> this is the problematic line
class Scope {
public:
Scope();
void Print();
ClassDef(Scope,1)
};
#endif
// – end of file
// ----- Scope.cc -----
#include “Scope.hh”
#include
ClassImp(Scope)
using std::cout;
using std::endl;
Scope::Scope() { cout << “Scope constructor” << endl; }
void Scope::Print() { cout << “Scope.Print()” << endl; }
// – end of file
The class, as listed above compiles and I can successfully generate a dictionary using rootcint and I can access the Scope class from within ROOT. However, if I uncomment the
#include "AlazarApi.h"
line, then I get the following error in rootcint (although the code does compile in g++ just fine):
$ make
Compiling… for linux
g++ -O -Wall -fPIC -pthread -I/usr/local/cern/root/include -c Scope.cc
Generating dictionary …
/usr/local/cern/root/bin/rootcint -f ScopeCint.cc -c Scope.hh
Error: class,struct,union or type signed not defined /usr/include/asm/types.h:11:
Error: class,struct,union or type signed not defined /usr/include/asm/types.h:14:
Error: class,struct,union or type signed not defined /usr/include/asm/types.h:17:
Error: class,struct,union or type signed not defined /usr/include/asm/types.h:21:
Error: class,struct,union or type __s8 not defined /usr/include\linux/types.h:78:
Error: class,struct,union or type __s16 not defined /usr/include/linux/types.h:80:
Error: class,struct,union or type __s64 not defined /usr/include/linux/types.h:93:
Error: class,struct,union or type __s8 not defined AlazarApi.h:39:
Error: class,struct,union or type __s16 not defined AlazarApi.h:41:
Error: class,struct,union or type __s64 not defined AlazarApi.h:45:
Warning: Error occurred during reading source files
Warning: Error occurred during dictionary source generation
!!!Removing ScopeCint.cc ScopeCint.h !!!
Error: /usr/local/cern/root/bin/rootcint: error loading headers…
make: *** [ScopeCint.cc] Error 1
The relevant line in AlazarApi.h is:
#include <linux/types.h>
The header file linux/types.h in turn includes asm/types.h, which uses signed, a symbol that rootcint does not know about, but g++ does know about.
I’ve spent a good deal of time on google to find out how g++ knows what signed is, in the hopes that I could pass that information to rootcint, but have had no success thus far.
I recognize that this issue may be more of a Linux question than a rootcint question, but hopefully someone in the ROOT community may have experienced a similar issue, or may have some suggestions. Any help would be greatly appreciated.
Thank you very much in advance,
James | https://root-forum.cern.ch/t/--signed---type-in-rootcint/7150 | CC-MAIN-2022-27 | refinedweb | 527 | 59.9 |
Using xUnit, MSTest or NUnit to test .NET Core libraries
Jürgen Gutsch - 31 March, 2017
MSTest was just announced to be open sourced, but was already moved to .NET Core some months ago. It seems it makes sense to write another blog post about unit testing .NET Core applications and .NET Standard libraries using .NET Core tools.
In this post I'm going to use the dotnet CLI and Visual Studio Code completely. Feel free to use Visual Studio 2017 instead, if you want to and if you don't like to use the console. Visual Studio 2017 is using the same dotnet CLI and almost the same commands in the background.
Setup the system under test
Our SUT is a pretty complex class, that helps us a lot to do some basic math operation. This class will be a part of a super awesome library:
namespace SuperAwesomeLibrary { public class MathTools { public decimal Add(decimal a, decimal b) => a + b; public decimal Substr(decimal a, decimal b) => a - b; public decimal Multiply(decimal a, decimal b) => a * b; public decimal Divide(decimal a, decimal b) => a / b; } }
I'm going to add this class to the "SuperAwesomeLibrary" and a solution I recently added like this:
mkdir unit-tests & cd unit-tests dotnet new sln -n SuperAwesomeLibrary mkdir SuperAwesomeLibrary & cd SuperAwesomeLibrary dotnet new classlib cd .. dotnet sln add SuperAwesomeLibrary\SuperAwesomeLibrary.csproj
The cool thing about the dotnet CLI is, that you are really able to create Visual Studio solutions (line 2). This wasn't possible with the previous versions. The result is a Visual Studio and MSBuild compatible solution and you can use and build it like any other solution in your continuous integration environment. Line 5 creates a new library, which will be added to the solution in line 7.
After this is done, the following commands will complete the setup, by restoring the NuGet packages and building the solution:
dotnet restore dotnet build
Adding xUnit tests
The dotnet CLI directly supports to add XUnit tests:
mkdir SuperAwesomeLibrary.Xunit & cd SuperAwesomeLibrary.Xunit dotnet new xunit dotnet add reference ..\SuperAwesomeLibrary\SuperAwesomeLibrary.csproj cd .. dotnet sln add SuperAwesomeLibrary.Xunit\SuperAwesomeLibrary.Xunit.csproj
This commands are creating the new xUnit test project, adding a reference to the SuperAwesomeLibrary and adding the test project to the solution.
If this was done, I created the xUnit tests for our MathHelper using VSCode:
public class MathToolsTests { [Fact] public void AddTest() { var sut = new MathTools(); var result = sut.Add(1M, 2M); Assert.True(3M == result); } [Fact] public void SubstrTest() { var sut = new MathTools(); var result = sut.Substr(2M, 1M); Assert.True(1M == result); } [Fact] public void MultiplyTest() { var sut = new MathTools(); var result = sut.Multiply(2M, 1M); Assert.True(2M == result); } [Fact] public void DivideTest() { var sut = new MathTools(); var result = sut.Divide(2M, 2M); Assert.True(1M == result); } }
This should work and you need to call your very best dotnet CLI friends again:
dotnet restore dotnet build
The cool thing about this commands is, it works in your solution directory and restores the packages of all your solution and it builds all your projects in your solution. You don't need to go threw all of your projects separately.
But if you want to run your tests, you need to call the library or the project directly, if you are not in the project folder:
dotnet test SuperAwesomeLibrary.Xunit\SuperAwesomeLibrary.Xunit.csproj
If you are in the test project folder just call
dotnet test without the project file.
This command will run all your unit tests in your project.
Adding MSTest tests
Adding a test library for MSTest works the same way:
mkdir SuperAwesomeLibrary.MsTest & cd SuperAwesomeLibrary.MsTest dotnet new mstest dotnet add reference ..\SuperAwesomeLibrary\SuperAwesomeLibrary.csproj cd .. dotnet sln add SuperAwesomeLibrary.MsTest\SuperAwesomeLibrary.MsTest.csproj
Event the test class looks almost the same:
[TestClass] public class MathToolsTests { [TestMethod] public void AddTest() { var sut = new MathTools(); var result = sut.Add(1M, 2M); Assert.IsTrue(3M == result); } [TestMethod] public void SubstrTest() { var sut = new MathTools(); var result = sut.Substr(2M, 1M); Assert.IsTrue(1M == result); } [TestMethod] public void MultiplyTest() { var sut = new MathTools(); var result = sut.Multiply(2M, 1M); Assert.IsTrue(2M == result); } [TestMethod] public void DivideTest() { var sut = new MathTools(); var result = sut.Divide(2M, 2M); Assert.IsTrue(1M == result); } }
And again our favorite commands:
dotnet restore dotnet build
The command
dotnet restorewill fail in offline mode, because MSTest is not delivered with the runtime and the default NuGet packages, but xUnit is. This means, it needs to fetch the latest packages from NuGet.org. Kinda weird, isn't it?
The last task to do, is to run the unit tests:
dotnet test SuperAwesomeLibrary.MsTest\SuperAwesomeLibrary.MsTest.csproj
This doesn't really look hard.
What about Nunit?
Unfortunately there is no default template for a Nunit test projects. I really like Nunit and I used it for years. It is anyway possible to use NUnit with .NET Core, but you need to do some things manually. The first steps seem to be pretty similar to the other examples, except we create a console application and add the NUnit dependencies manually:
mkdir SuperAwesomeLibrary.Nunit & cd SuperAwesomeLibrary.Nunit dotnet new console dotnet add package Nunit dotnet add package NUnitLite dotnet add reference ..\SuperAwesomeLibrary\SuperAwesomeLibrary.csproj cd ..
The reason why we need to create a console application is, that there is not yet a runner for visual studio available for NUnit. This also means
dotnet test will not work. The NUnit Devs are working on it, but this seems to need some more time. Anyway, there is an option to use NUnitLite to create a self executing test library.
We need to use NUnitLight and to change the
static void Main to a
static int Main:
static int Main(string[] args) { var typeInfo = typeof(Program).GetTypeInfo(); return new AutoRun(typeInfo.Assembly).Execute(args); }
This lines automatically executes all TestClasses in the current assembly. It also passes the NUnit arguments to NUnitLite, to e. g. setup the output log file, etc.
Let's add a NUnit test class:
[TestClass] public class MathToolsTests { [Test] public void AddTest() { var sut = new MathTools(); var result = sut.Add(1M, 2M); Assert.That(result, Is.EqualTo(3M)); } [Test] public void SubstrTest() { var sut = new MathTools(); var result = sut.Substr(2M, 1M); Assert.That(result, Is.EqualTo(1M)); } [Test] public void MultiplyTest() { var sut = new MathTools(); var result = sut.Multiply(2M, 1M); Assert.That(result, Is.EqualTo(2M)); } [Test] public void DivideTest() { var sut = new MathTools(); var result = sut.Divide(2M, 2M); Assert.That(result, Is.EqualTo(1M)); } }
Finally we need to run the tests. But this time we cannot use dotnet test.
dotnet restore dotnet build dotnet run -p SuperAwesomeLibrary.Nunit\SuperAwesomeLibrary.Nunit.csproj
Because it is a console application, we need to use
dotnet run to execute the app and the NUnitLite test runner.
What about mocking?
Currently creating mocking frameworks is a little bit difficult using .NET Standard, because there is a lot of reflection needed, which is not completely implemented in .NET Core or even .NET Standard.
My Favorite tool Moq is anyway available for .NET Standard 1.3, which means it should work here. Let's see how it works.
Lets assume we have a PersonService in the SuperAwesomeLibrary that uses a IPersonRepository to fetch Persons from a data storage:
using System; using System.Collections.Generic; public class PersonService { private readonly IPersonRepository _personRepository; public PersonService(IPersonRepository personRepository) { _personRepository = personRepository; } public IEnumerable<Person> GetAllPersons() { return _personRepository.FetchAllPersons(); } } public interface IPersonRepository { IEnumerable<Person> FetchAllPersons(); } public class Person { public string Firstname { get; set; } public string Lastname { get; set; } public DateTime DateOfBirth { get; set; } }
After building the library, I move to the NUnit test project to add Moq and GenFu.
cd SuperAwesomeLibrary.Nunit dotnet add package moq dotnet add package genfu dotnet restore
GenFu is a really great library to create the test data for unit tests or demos. I really like this library and use it a lot.
Now we need to write the actual test using this tools. This test doesn't really makes sense, but it shows how Moq works:
using System; using System.Linq; using NUnit.Framework; using SuperAwesomeLibrary; using GenFu; using Moq; namespace SuperAwesomeLibrary.Xunit { [TestFixture] public class PersonServiceTest { [Test] public void GetAllPersons() { var persons = A.ListOf<Person>(10); // generating test data using GenFu var repo = new Mock<IPersonRepository>(); repo.Setup(x => x.GetAllPersons()).Returns(persons); var sut = new PersonService(repo.Object); var actual = sut.GetAllPersons(); Assert.That(actual.Count(), Is.EqualTo(10)); } } }
As you can see the, Moq works the same was in .NET Core as in the full .NET Framework.
Now let's start the NUnit tests again:
dotnet build dotnet run
Et voilà:
Conclusion
Running unit tests within .NET Core isn't really a big deal and it is really a good thing that it is working with different unit testing frameworks. You have the choice to use your favorite tools. It would be nice to have the same choice even with the mocking frameworks.
In one of the next post I'll write about unit testing a ASP.NET Core application. Which includes testing MiddleWares, Controllers, Filters and View Components.
You can play around with the code samples on GitHub: | https://asp.net-hacker.rocks/2017/03/31/unit-testing-with-dotnetcore.html | CC-MAIN-2021-49 | refinedweb | 1,534 | 50.43 |
Next article: Friday Q&A 2018-06-29: Debugging with C-Reduce
Previous article: Friday Q&A 2017-12-08: Type Erasure in Swift
Tags: fridayqna
Markov chains make for a simple way to generate realistic looking but nonsensical text. Today, I'm going to use that technique to build a text generator based on this blog's contents, an idea suggested/inspired by reader Jordan Pittman.
Markov Chains
At a theoretical level, a Markov chain is a state machine where each transition has a probability associated with it. You can walk through the chain by choosing a start state and then transitioning to subsequent states randomly, weighted by the transition probabilities, until you reach a terminal state.
Markov chains have numerious applications, but the most amusing is for text generation. There, each state is some unit of text, typically a word. The states and transitions are generated from some input corpus, and then text is generated by walking through the chain and outputting the word for each state. The result rarely makes sense, as the chain doesn't contain enough information to retain any of the underlying meaning of the input corpus, or even much of the grammatical structure, but that lack of sense can be hilarious.
Representation
The nodes in the chain will be represented as instances of a
Word class. This class will store a
String for the word it represents, and a set of links to other words.
How do we represent that set of links? The most obvious approach would be some sort of counted set, which would store other
Word instances along with a count of the number of times that transition was seen in the input corpus. Randomly choosing a link from such a set can be tricky, though. A simple way is to generate a random number betewen 0 and the total count of the entire set, then iterate through the set until you encounter that many links, and choose the link you landed on. This is easy but slow. Another approach would be to precompute an array that stores the cumulative total for each link in the array, then do a binary search on a random number between 0 and the total. This is harder but faster. If you want to get really fancy, you can do even more preprocessing and end up with a compact structure you can query in constant time.
Ultimately, I decided to be lazy and use a structure that's extremely wasteful in space, but efficient in time and easy to implement. Each
Word contains an array of subsequent
Words. If a link occurs multiple times, the duplicates remain in the array. Choosing a random element with the appropriate weight consists of choosing a random index in the array.
Here's what the
Word class looks like:
class Word { let str: String? var links: [Word] = [] init(str: String?) { self.str = str } func randomNext() -> Word { let index = arc4random_uniform(UInt32(links.count)) return links[Int(index)] } }
Note that the
links array will likely result in lots of circular references. To avoid leaking memory, we'll need to have something manually clean those up.
That something will be the
Chain class, which will manage all of the
Words in a chain:
class Chain { var words: [String?: Word] = [:]
In
deinit, it clears all of the
links arrays to eliminate any cycles:
deinit { for word in words.values { word.links = [] } }
Without this step, a lot of the
Word instances would leak.
Let's look at how words are added to the chain. The
add method will take an array of
Strings, each one of which holds a word (or any other unit that the caller wants to work with):
func add(_ words: [String]) {
If there aren't actually any words, bail out early:
if words.isEmpty { return }
We want to iterate over pairs of words, where the second element in the pair is the word that follows the first element. For example, in the sentence "Help, I'm being oppressed," we want to iterate over
("Help", "I'm"),
("I'm", "being"),
("being", "oppressed").
Actually, we want a bit more as well, since we want to encode the beginning and end of the sentence. We represent those as
nil, so the actual sequence we want to iterate over is
(nil, "Help"),
("Help", "I'm"),
("I'm", "being"),
("being", "oppressed"),
("oppressed", nil).
To allow for
nil, we need an array whose contents are
String? rather than plain
String:
let words = words as [String?]
Next, we'll construct two arrays, one by prepending
nil and one by appending
nil. Zipping them together produces the sequence we want:
let wordPairs = zip([nil] + words, words + [nil]) for (first, second) in wordPairs {
For each word in the pair, we'll fetch the corresponding
Word object using a handy helper function:
let firstWord = word(first) let secondWord = word(second)
Then all we have to do is add
secondWord into the links of
firstWord:
firstWord.links.append(secondWord) } }
The
word helper fetches the instance from the
words dictionary if it exists, otherwise it creates a new instance and puts it into the dictionary. This frees other code from worrying about whether there's already a
Word for any given string:
func word(_ str: String?) -> Word { if let word = words[str] { return word } else { let word = Word(str: str) words[str] = word return word } }
Finally, we want to generate new sequences of words:
func generate() -> [String] {
We'll generate the words one by one, accumulating them here:
var result: [String] = []
Loop "forever." The exit condition doesn't map cleanly to a loop condition, so we'll handle that inside the loop:
while true {
Fetch the
Word instance for the last string in
result. This neatly handles the initial case where
result is empty, since
last produces
nil which indicates the first word:
let currentWord = word(result.last)
Randomly get a linked word:
let nextWord = currentWord.randomNext()
If the linked word isn't the end, append it to
result. If it is the end, terminate the loop:
if let str = nextWord.str { result.append(str) } else { break } }
Return the accumulated result:
return result } }
One last thing: we're using
String? as the key type for
words, but
Optional doesn't conform to
Hashable. Here's a quick extension that adds it when its wrapped type conforms:
extension Optional: Hashable where Wrapped: Hashable { public var hashValue: Int { switch self { case let wrapped?: return wrapped.hashValue case .none: return 42 } } }
Generating Input
That's the Markov chain itself, but it's pretty boring without some real text to put into it.
I decided to pull text from an RSS feed. What better feed to choose than my own blog's full text feed?
let feedURL = URL(string: "")!
RSS is an XML format, so use
XMLDocument to parse it:
let xmlDocument = try! XMLDocument(contentsOf: feedURL, options: [])
The article bodies are in XML
description nodes which are nested inside
item nodes. An XPath query retrieves those:
let descriptionNodes = try! xmlDocument.nodes(forXPath: "//item/description")
We want the strings in the XML nodes, so extract those and throw away any that are
nil:
let descriptionHTMLs = descriptionNodes.compactMap({ $0.stringValue })
We don't care about the markup at all.
NSAttributedString can parse
HTML and produce a string with attributes, which we can then throw away:
let descriptionStrings = descriptionHTMLs.map({ NSAttributedString(html: $0.data(using: .utf8)!, options: [:], documentAttributes: nil)!.string })
Let's take a quick detour to a function that breaks up a string into parts. We ultimately want to consume arrays of
String, where each array represents a sentence. A string will contain zero or more sentences, so this
wordSequences function returns an array of arrays of
String:
func wordSequences(in str: String) -> [[String]] {
Results get accumulated into a local variable:
var result: [[String]] = []
Breaking a
String into sentences isn't always easy. You could search for the appropriate punctuation, but consider a sentence like "Mr. Jock, TV quiz Ph.D., bags few lynx." That's one sentence, despite having four periods.
NSString provides some methods for intelligently examining parts of a string, and
String gets those when you
import Foundation. We'll ask
str to enumerate its sentences, and let
Foundation figure out how:
str.enumerateSubstrings(in: str.startIndex..., options: .bySentences, { substring, substringRange, enclosingRange, stop in
We face a similar problem splitting each sentence into words.
NSString does provide a method for enumerating over words, but this presents some problems, like losing punctuation. I ultimately decided to take a dumb approach for word splitting and just split on spaces. This means that you end up with words that contain punctuation as part of their string. This constrains the Markov chain more than if the punctuation was removed, but on the other hand it means that the output naturally contains something like reasonable punctuation. It seemed like a good tradeoff.
Some newlines make their way into the data set, so we'll cut those off at this point:
let words = substring!.split(separator: " ").map({ $0.trimmingCharacters(in: CharacterSet.newlines) })
The sliced-up sentence gets added to
result:
result.append(words) })
After enumeration is complete,
result is filled out with the sentences from the input, and we return it to the caller:
return result }
Back to the main code. Now that we have a way to convert a string into a list of sentences, we can build our Markov chain. We'll start with an empty
Chain object:
let chain = Chain()
Then we go through all the strings, extract the sentences, and add them to the chain:
for str in descriptionStrings { for sentence in wordSequences(in: str) { chain.add(sentence) } }
All that's left is to generate some new sentences! We'll call
generate() and then join the result with spaces. The output is hit-or-miss (which is no surprise given the random nature of the technique) so we'll generate a lot:
for _ in 0 ..< 200 { print("\"" + chain.generate().joined(separator: " ") + "\"") }
Example Output
For your entertainment, here are some examples of the output of this program:
- "We're ready to be small, weak references in New York City."
- "It thus makes no values?"
- "Simple JSON tasks, it's wasteful if you can be."
- "Another problem, but it would make things more programming-related mystery goo."
- "The escalating delays after excessive focus on Friday, September 29th."
- "You may not set."
- "Declare conformance to use = Self.init() to detect the requested values."
- "The tagged pointer is inlined at this nature; even hundreds of software and writing out at 64 bits wide."
- "We're ready to express that it works by reader ideas, so the decoding methods for great while, it's inaccessible to 0xa4, which takes care of increasing addresses as the timing."
- "APIs which is mostly a one-sided use it yourself?"
- "There's no surprise."
- "I wasn't sure why I've been called 'zero-cost' in control both take serious effort to miss instead of ARC and games."
- "For now, we can look at the filesystem."
- "The intent is intended as reader-writer locks."
- "For example, we can use of the code?"
- "Swift's generics can all fields of Swift programming, with them is no parameters are static subscript, these instantiate self = cluster.reduce(0, +) / Double(cluster.count)"
- "However, the common case, you to the left-hand side tables."
There's a lot of nonsense as well, so you have to dig through to find good ones, but Markov chains can produce some pretty funny output.
Conclusion
Markov chains have many practical uses, but they can also be hilariously useless when used to generate text. Aside from being entertaining, this code also demonstrates how to deal with circular references in a situation where there's no clear directionality, how to use
NSString's intelligent enumeration methods to extract features from text, and a brief demonstration of the power of conditional conformances.
That wraps it up for today. Stop by next time for more fun, games, and maybe even a little education. Until then, Friday Q&A is driven by reader ideas, so if you have a topic you'd like to see covered here, please send it in!
Add your thoughts, post a comment:
Spam and off-topic posts will be deleted without notice. Culprits may be publicly humiliated at my sole discretion.
For example, if you had a large body of writing from User_123 and used it to populate the probabilities of a Markov chain, you would expect that another large body of writing from the same user would generate similar probabilities. So given a body of writing from an unknown user, you could compare the probabilities and determine whether or not User_123 wrote both. Although I imagine this approach would have quite large error bars - and would be more error prone as you dealt with smaller and smaller bodies of writing.
I'm also guessing the accuracy of the above approach would be affected by the topic covered by the body of writing - for instance I'm guessing the Markov chain generated from your blog would be very different from one generated from your text messages to family members - probably fewer references to ARC and APIs.
In any case - very interesting write up! | https://www.mikeash.com/pyblog/friday-qa-2018-04-27-generating-text-with-markov-chains-in-swift.html | CC-MAIN-2018-30 | refinedweb | 2,203 | 62.07 |
Farid Zaripov wrote:
[...]
> The basic_stringbuf<>::str (const char_type *, _RWSTD_SIZE_T)
> have the assertions at begin and at end (sstream.cc line 72 and 167),
> and
> both assertions passes.
Ah, yes, thanks for the pointer! I was looking at the other
two overloads in the header that just call the one in the
.cc file and didn't realize that that one was the workhorse.
>
>.
#include <cassert>
#include <cstdio>
#include <sstream>
int main ()
{
struct Buf: std::stringbuf {
Buf (std::string s, std::ios::openmode m)
: std::stringbuf (s, m) { }
void setget (int beg, int cur, int end) {
setg (eback () + beg, eback () + cur, eback () + end);
}
void setput (int beg, int cur, int end) {
setp (pbase () + beg, pbase () + end);
pbump (cur);
}
};
{
Buf buf ("abcde", std::ios::in);
buf.setget (1, 2, 4);
std::printf ("%s\n", buf.str ().c_str ());
assert ("bcd" == buf.str ());
}
{
Buf buf ("abcde", std::ios::out);
buf.setput (1, 2, 4);
std::printf ("%s\n", buf.str ().c_str ());
assert ("bcd" == buf.str ());
}
}
Martin | http://mail-archives.apache.org/mod_mbox/incubator-stdcxx-dev/200705.mbox/%3C465779AD.4020201@roguewave.com%3E | CC-MAIN-2015-27 | refinedweb | 162 | 76.52 |
03 October 2012 09:38 [Source: ICIS news]
SINGAPORE (ICIS)--?xml:namespace>
The nameplate capacity of the LDPE facility is 40,000 tonnes/year, the source said.
“We are still accessing the situation, so we have no idea when it will be restarted,” he said.
The outage at this LDPE unit lifted buying sentiment slightly, although buying activity has slowed down this week as restocking activities have mostly been completed.
A producer based in the Gulf Cooperation Council (GCC) region has raised its offer by $20/tonne (€15/tonne) to $1,400/tonne CFR (cost & freight) Mumbai as a result, local players said, adding that Iranian cargoes were being offered at $1,360/tonne CFR Mumbai.
The equivalent import parity price, following RIL’s list price reduction on 1 October of Indian rupees (Rs) 2.00/kg (4 cents/kg) to Rs95.00-95.50/kg DEL (delivered) Mumbai, was at $1,440/tonne CFR Mumbai, based on an exchange rate of Rs53.50 against $1, the company source said.
“Offers for imports are higher now. We will have to see how long this outage will last because the fundamental demand is still weak,” a trader based in Mumbai said.
($1 = €0.77)
($1 = Rs52 | http://www.icis.com/Articles/2012/10/03/9600542/indias-ril-shuts-vadodara-ldpe-plant-on-technical-woes.html | CC-MAIN-2015-06 | refinedweb | 205 | 64.51 |
Yesterday, I gave a basic overview of descriptors and what they can do, including a simple example to demonstrate one in action. That’s all well and good, but today I’ll explain how this can be genuinely useful in your apps, particularly when used in models.
Yesterday’s example generated a new value each time it was accessed, which is really only useful in a few situations. More often, you’ll need to still store a value somewhere, and just do something special when its modified or retrieved. There are a few ways to approach this, but I’ll just cover one.
The simplest way to store a value for a desciptor takes advantage of a subtle distinction of how Python accesses values on an instance object. Every Python object has a namespace that’s separate from the namespace of its class, so that each object can have different values attached to it. Normally, the object’s attributes are a direct pass-through to this namespace, but descriptors short-circuit that process. Thankfully, Python allows another way to access the object’s namespace directly: the
__dict__ attribute of the object.
Every object has a
__dict__ attribute, which is a standard Python dictionary containing mappings for the various values attached to it. Even though descriptors get in the way of how this is normally accessed, your code can use
__dict__ to get at it directly, and it’s a great place to store a single value. Yesterday, I mentioned that descriptors can be used to cache values to speed up subsequent accesses, and this is a good way to go about that.
from myapp.utils import retrieve class CachedValue(object): def __init__(self, name): self.name = name def __get__(self, instance, owner): if self.name not in instance.__dict__: instance.__dict__[self.name] = retrieve() return instance.__dict__[self.name]
Of course, you’ll notice something interesting here. We have to assign the value to the dictionary using a name, and the only way we know what name to use is to supply it explicitly. For this example, the constructor takes a required
name argument, which will be used for the dictionary’s key, but Django provides a much better way to solve this problem. More on that later.
So far, the examples have only involved retrieval. This technique is easily extended to allow the value to be modified as well, by adding a
__set__ method. The following example should look fairly straightforward, now that you know the
__dict__ technique:
class SimpleDescriptor(object): def __init__(self, name): self.name = name def __get__(self, instance, owner): if self.name not in instance.__dict__: raise AttributeError, self.name return instance.__dict__[self.name] def __set__(self, instance, value): instance.__dict__[self.name] = value
This also illustrates another interesting point with
__get__: if the value being retrieved isn’t set, the expected behavior is to raise an
AttributeError. That’s what Python does internally, and that’s what most code will be expecting when this occurs.
Field
One of the most important uses for descriptors in Django is when creating new
Field types for use with models. There’s a lot that can be done when creating new field types, but that’s a topic for its own series of posts, perhaps some other time. For today’s purposes, I’ll just cover how descriptors can help the process along. Descriptors are especially useful for model fields, because they allow you to integrate specialized Python types with the standard Django database API.
Of course, his is all fairly educational. This particular process is done much more easily by Django now, if you’re tracking trunk. This information is still good to know, though, because the official support in Django uses descriptors behind the scenes, and not all situations are covered, so you might need to implement this yourself if you find the need.
The base class,
Field, makes use of a special hook in Django, by defining a method called
contribute_to_class, and many subclasses override this to provide their own functionality. Again, I won’t get into everything that’s possible with this, but it provides a very simple solution to our naming problem. Essentially, this method gets called for any object that defines it, instead of being simply attached to the class as normal. The method uses the following definition:
def contribute_to_class(self, cls, name)
self- the object being assigned to the model
cls- the model class the object is being assigned to
name- the name that was used in the assignment.
That’s right,
contribute_to_class gets the name that was given to the object when it was assigned, so we don’t have to expect anyone to provide it explicitly!
This isn’t a complete tutorial for subclassing
Field, just like the last one wasn’t a complete discussion of descriptors. There’s plently more that can be done, but the best place I can point to is the source for GeoDjango, where Robert Coup so brilliantly implemented descriptors for a very specialized use case. Beyond that, be sure to read the source to Malcolm’s recent addition to Django’s source, to make this all a lot easier. | https://www.martyalchin.com/2007/nov/24/python-descriptors-part-2-of-2/ | CC-MAIN-2017-13 | refinedweb | 867 | 61.67 |
Recursive React tree component implementation made easy
Explore our services and get in touch.
The challenges that I’ve faced and how I solved them
When I was building tortilla.acedemy’s diff page, I was looking to have a tree view that could represent a hierarchy of files, just like Windows’ classic navigation tree. Since it was all about showing a git-diff, I also wanted to have small annotations next to each file, which will tell us whether it was added, removed, or deleted. There are definitely existing for that out there in the echo system, like Storybook’s tree beard, but I’ve decided to implement something that will work just the way I want right out of the box, because who knows, maybe someone else will need it one day.
This is how I wanted my tree’s API to look like:
import React from 'react'; import FSRoot from 'react-fs-tree'; const FSTree = () => ( <FSRoot childNodes={[ { name: 'file' }, { name: 'added file', mode: 'a' }, { name: 'deleted file', mode: 'd' }, { name: 'modified file', mode: 'm' }, { name: 'folder', opened: true, childNodes: [ { name: 'foo' }, { name: 'bar', selected: true }, { name: 'baz' }, ], }, ]} /> ); export default FSTree;
During my implementation of that tree I’ve faced some pretty interesting challenges, and I have thought to write an article about it and share some of my insights; so let’s cut to the chase.
Architecture
My tree is made out of 3 internal components:
- FSRoot (see FSRoot.js) - This is where the tree starts to grow from. It’s a container that encapsulates internal props which are redundant to the user (like props.rootNode, props.parentNode, etc) and exposes only the relevant parts (like props.childNodes, props.onSelect, etc). It also contains a tag which rules that are relevant nested components.
- FSBranch (see FSBranch.js) - A branch contains the list that will iterate through the nodes. The branch is what will give the tree the staircase effect and will get further away from the edge as we go deeper. Any time we reveal the contents of a node with child nodes, a new nested branch should be created.
- FSNode (see FSNode.js) - The node itself. It will present the given node’s metadata: its name, its mode (added, deleted or modified), and its children. This node is also used as a controller to directly control the node’s metadata and update the view right after. More information about that further this article.
The recursion pattern in the diagram above is very clear to see. Programmatically speaking, this causes a problematic situation where each module is dependent on one another. So before FSNode.js was even loaded, we import it in FSBranch.js which will result in an undefined module.
/* FSBranch.js - will be loaded first */ import React from 'react'; import FSNode from './FSNode'; // implementation... export default FSBranch; /* FSNode.js - will be loaded second */ import React from 'react'; // The following will be undefined since it's the caller module and was yet to be loaded import FSBranch from './FSBranch'; // implementation... export default FSNode;
There are two ways to solve this problem:
- Switching to CommonJS and move the require() to the bottom of the first dependent module — which I’m not gonna get into. It doesn’t look elegant and it doesn’t work with some versions of Webpack; during the bundling process all the require() declarations might automatically move to the top of the module which will force-cause the issue again.
- Having a third module which will export the dependent modules and will be used at the next event loop — some might find this an anti pattern but I like it because we don’t have to switch to CommonJS and it’s highly compatible with Webpack’s strategy.
The following code snippet demonstrates the second preferred way of solving recursive dependency conflict:
/* module.js */ export const exports = {}; export default { exports }; /* FSBranch.js */ import React from 'react'; import { exports } from './module'; class FSBranch extends React.Component { render() { return <exports.FSNode />; } } exports.FSBranch = FSBranch; /* FSNode.js */ import React from 'react'; import { exports } from './module'; class FSNode extends React.Component { render() { return <exports.FSBranch />; } } exports.FSNode = FSNode;
Style
There are two methods to implement the staircase effect:
- Using a floating tree — where each branch has a constant left-margin and completely floats.
- Using a padded tree — where each branch doesn’t move further away but has an incremental padding.
A floating tree makes complete sense. It nicely vertically aligns the nodes within it based on the deepness level we’re currently at. The deeper we go the further away we’ll get from the left edge, which will result in this nice staircase effect.
However, as you can see in the illustrated tree, when selecting a node it will not be fully stretched to the left, as it completely floats with the branch. The solutions for that would be a padded tree.
Unlike the floating tree, each branch in the padded tree would fully stretch to the left, and the deeper we go the more we gonna increase the pad between the current branch and the left edge. This way the nodes will still be vertically aligned like a staircase, but now when we select them, the highlight would appear all across the container. It’s less intuitive and slightly harder to implement, but it does the job.
Programmatically speaking, this would require us to pass a counter that will indicate how deep the current branch is (n), and multiply it by a constant value for each of its nodes (x) (See implementation).
Event Handling
One of the things that I was looking to have in my tree was an easy way to update it, for example, if one node was selected, deselected the previous one, so selection can be unique. There are many ways that this could be achieved, the most naive one would be updating one of the node’s data and then resetting the state of the tree from its root.
There’s nothing necessarily bad with that solution and it’s actually a great pattern, however, if not implemented or used correctly, this can cause the entire DOM tree to be re-rendered, which is completely unnecessary. Instead, why not just use the node’s component as a controller?
You heard me right. Directly grabbing the reference from the React.Component’s callback and use the methods on its prototype. Sounds tricky, but it works fast and efficiently (see implementation).
function onSelect(node) { // A React.Component is used directly as a controller assert(node instanceof React.Component); assert(node instanceof FSNode); if (this.state.selectedNode) { this.state.selectedNode.deselect(); } this.setState({ selectedNode: node, }); } function onDeselect() { this.setState({ selectedNode: null, }); }
One thing to note is that since the controllers are hard-wired to the view, hypothetically speaking we wouldn’t be able to have any controllers for child nodes of a node that is not revealed (
node.opened === false). I’ve managed to bypass this issue by using the React.Component’s constructor directly. This is perfectly legal and no error is thrown, unless used irresponsibly to render something, which completely doesn’t make sense (
new FSNode(props); see implementation).
Final Words
A program can be written in many ways. I know that my way of implementing a tree view can be very distinct, but since all trees should be based around recursion, you can take a lot from what I’ve learnt.
Below is the final result of the tree that I’ve created. Feel free to visit its Github page or grab a copy using NPM.
| https://the-guild.dev/blog/recursive-react-tree-component-implementation-made-easy | CC-MAIN-2021-31 | refinedweb | 1,264 | 62.98 |
With my Hostmonster account, I host this website with my domain, but I also have many other machines that are referred to with subdomains. For example, dev.jasonernst.com is my home machine and lab.jasonernst.com is my office machine at school.
However, as you can imagine with the home machine in particular the IP is prone to change occasionally since it is given from the ISP using DHCP. So I searched around for some script to be able to change the zone file in Hostmonster since this controls the IP addresses of all my subdomains.
** Of course the obvious and easy way to do this is with some kind of dyndns account, but I’m picky and like to have everything working under my own domain 😛
I was looking for some type of SSH script way to do it, but it looks like there is no easy way to do this, but I found a ruby script here: which allows me to do what I want. Unfortunately the script was written a little while ago and some of it needs to be changed a bit to work.
The first part is the required libraries that must be installed. This has changed because the ruby-mechanize library does not seem to be found in the Ubuntu 12.04 repos. This should do the trick though:
sudo apt-get install libwww-mechanize-ruby ruby-json ruby
The other problem is in the ruby script itself. It seems verify_mode does not exist anymore, so just comment that line out. Another problem is the user-agent which does not seem to be found in the version I was using with Ubuntu. So you can change that to “Windows IE 7” and it should fix it. Here is the code with the 7'
m = Mechanize.new do |a|
#a.verify_mode = OpenSSL::SSL::VERIFY_NONE
a.user_agent_alias = USER_AGENT
end
def get_ip
r = Net::HTTP.get('jasonernst.com', '/ip.php') last thing that should be done is a server page somewhere for this code to find out it’s own IP address. All the page should return is the IP address itself, not any HTML. You can leave the default in the script which will use my IP script, or you can make your own. It’s as simple as this:
echo $_SERVER['REMOTE_ADDR']; ?>
And one more thing, if you are so inclined is to add the script as a chronjob. I have mine set to run every hour, but you can do it more or less often according to your preferences.
crontab -e
I named put my script in a /scripts/ folder I made and named it “hostmonster-auto-ip.sh”
So the crontab entry is:
@hourly /scripts/hostmonster-auto-ip.sh | https://www.jasonernst.com/tag/subdomain/ | CC-MAIN-2019-22 | refinedweb | 457 | 80.31 |
package UV::TTY; our $VERSION = '2.000'; use strict; use warnings; use Carp (); use parent 'UV::Stream'; sub _new_args { my ($class, $args) = @_; my $fd = delete $args->{fd} // delete $args->{single_arg}; return ($class->SUPER::_new_args($args), $fd); } 1; __END__ =encoding utf8 =head1 NAME UV::TTY - TTY stream handles in libuv =head1 SYNOPSIS #!/usr/bin/env perl use strict; use warnings; # A new stream handle will be initialised against the default loop my $tty = UV::TTY->new(fd => 0); # set up the data read callback $tty->on(read => sub { my ($self, $err, $buf) = @_; say "More data: $buf"; }); $tty->read_start(); =head1 DESCRIPTION This module provides an interface to L<libuv's TTY|> stream handle. TTY handles represent a stream for the console. =head1 EVENTS L<UV::TTY> inherits all events from L<UV::Stream> and L<UV::Handle>. =head1 METHODS L<UV::TTY> inherits all methods from L<UV::Stream> and L<UV::Handle> and also makes the following extra methods available. =head2 set_mode $tty->set_mode($mode); The L<set_mode|> method sets the mode of the TTY handle, to one of the C<UV_TTY_MODE_*> constants. =head2 get_winsize my ($width, $height) = $tty->get_winsize(); The L<get_winsize|> method returns the size of the window. =head1 AUTHOR Paul Evans <leonerd@leonerd.org.uk> =head1 LICENSE This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =cut | https://web-stage.metacpan.org/dist/UV/source/lib/UV/TTY.pm | CC-MAIN-2021-39 | refinedweb | 232 | 60.55 |
Hi there,
I am using SSRS 2008 for reports, In my report I am showing text that is coming from Word document along with some formatting like bold italic etc, but along with the Text one extra
line is also coming.
<?xml:namespace prefix = o
Is there any way that i can avoid this line in my report. this line should not come with contents of report.
Hi Shaikh,
I would suggest you copying the text from Word to Notepad before pastering in a report.
Or, if you have reports that has the extra line, please follow these steps to remove them:
1. In Business Intelligence Development Studio(BIDS), right-click each report from "Solution Explore" panel.
2. Then click "View code"
3. Now, press "CTRL" + "H"(combinated key), replace the extra line with null.
If you have more questions regarding SQL Server Reporting Services, please feel free to ask.
Thanks,
Jin Chen
Hi Jin Chen,
Thanks for ur reply, but I am First Copying the word document data(Rich text) in Rich Text box on page and saving it.then i am retrieving the data from DB on my Report. hence its not possible to copy it to Notepad.
Let me know, if there is any possible solution other than making the last line NUll, since I can not predict whether user will enter data in RTB using word or he/she will type in.
Thanks
Sadaf
Hi Shaikh
I added a replace to the sql request:
replace(<fieldname>,'<?xml:namespace prefix = o','') as <fieldname>
Microsoft is conducting an online survey to understand your opinion of the Msdn Web site. If you choose to participate, the online survey will be presented to you when you leave the Msdn Web site.
Would you like to participate? | https://social.msdn.microsoft.com/Forums/sqlserver/en-US/fe2a7d9f-a358-4771-90a8-c99479f54ebf/how-to-remove-xmlnamespace-prefix-o-ns-urnschemasmicrosoftcomofficeoffice-on-report?forum=sqlreportingservices | CC-MAIN-2016-22 | refinedweb | 296 | 71.34 |
ZipFile extracting spanned files
It looks like ZipFile (lib_zipfile.h) can create spanning zip files using SetSpanning(). But can you extract spanned zip files using either the Legacy API or the new Maxon API?
file.zip.001
file.zip.002
file.zip.003
Can these be extracted using any of the SDK methods?
Thanks,
Kent
Hi,
I do not know what MAXON's lib can do and cannot, but Python's
zipfilecan also handle split and spanned archives.
import zipfile import os def some_filter(name): """A filter function to sort out file objects based on their name and extension. """ return True def unpack(input_path, output_path): """Unpacks a (split or spanned) zip file. Args: input_path (str): The input path. output_path (str): The output path. Raises: ValueError: When the input path does not exist. """ if not os.path.exists(input_path): raise ValueError("Something meaningful.") with zipfile.ZipFile(input_path, "r") as zip_object: # Extract only parts of the volume that match a specific filter. for name in [n for n in zip_object.namelist() if some_filter(n)]: zip_object.extract(name, output_path) # Or just extract everything, but since our filter just passes # through everything, this would be redundant. # zip_object.extractall(output_path) def main(): """ """ # Note that 'zipfile' actually looks for the file extension '.zip' in # passed path arguments. If you have split or spanned zip archives that # do not fully conform to the ISO norm, i.e. do not have a dedicated # header file with the '.zip' extension, your file names have to follow # the form '*.zip.enumerator'. '*.enumerator' will NOT be recognized. # I once learned this the hard way. # Also note that there is a difference between split, spanned, and # volume zip archives, but 'zipfile' will handle most of it for you. # Unpack the split archive starting with "test.zip.001" into the same # directory. unpack("test.zip.001", "") if __name__ == "__main__": main()
Cheers,
zipit
- m_magalhaes last edited by
Hi,
sorry for the late reply.
the spanning function isn't working as we could expect. It doesn't cut the file.
If you have 10 Mb file and ask for 1Mb archive size, it will create two archives, one with the 10 Mb file (and that archive will be 1Gb) and one empty.
If you have 10 * 1 Mb files, it will create 10 archives with each file on each archives.
Every Archive are independent zip files. There name will not be (as you pointed)
file.zip.001
but
file.zip
file_1.zip
file_2.zip
You can just unzip all archive as independent files.
In every archive there is a dummy txt file that have to be added for osx.
You have to create your own solution. Using the Maxon API you need to read the file that you want to compress and write the buffer.
Cheers,
Manuel
Thanks Manuel. Sounds like the MAXON implementation is indeed completely different to regular splitting of zip files. No worries, I will just create my own implementation to do what I need. Always try to see if the MAXON api can do it first though.
Cheers,
Kent
Hi,
I still do not know what Maxon's library does, but I just wanted to stress again (like in my code above) that splitting and spanning are not the the same thing and are also not part of the zip ISO norm AFAIK [1]. Spanning zip files are usually meant to occupy multiple exchangeable resources and therefor are of a fixed size (matching the size of the media type). Split archives are meant to be placed in a single directory and are of user chosen size. Both have a dedicated *.zip file as their first file which contains structural information as well as the first volume.
What you did show here (no dedicated *.zip file is present) is something some tools can do and I think it places the meta information in each file and allows you by that to loose parts of the archive while still being able to uncompress the rest. At least 7zip simply calls this Volumes.
Cheers,
zipit
[1] Due to not being normed, only a dodgy third party link here, but they have a nice table and also list compatibilities. They did forget Python's
zipfilethough, which tries to be a jack of all trades ;)
- m_magalhaes last edited by
thanks @zipit
so if i understand, what why the function is called SetSpanning because it doesn't split the files.
I understood kent wanted to split his files.
But he showed the volume result as you mentioned :p
in any case, our api just do the Spanning.
Hi,
I actually just wanted to point out the differences, as the terms have here been used as if they were interchangeable. With you I was referring to @kbar. If anything, my post was a mild indicator for that Maxon's use of the term spanning is actually correct, as the function seems to output volumes of fixed size.
But as already stated twice: I have no clue what is going in Maxon's library ;)
Cheers,
zipit
I may have had my terminology wrong so sorry if that caused any confusion. But my example of the output files was correct in what I wanted to unzip/extract.
I was wanting to extract "Split" files, not "Spanned".
In my case I have 1 very large file that I is split into multiple volumes. Each volume being the same number of bytes. This can be done in 7zip by choosing "split to volumes, bytes:" when using "Add to Archive".
So if myfile is 22MB file and I split by 10MB then you get the following files all in the same directory.
myfile.zip.001 - 10MB
myfile.zip.002 - 10MB
myfile.zip.003 - 2MB
These are "Split".
The reason I thought this might be the same as Spanning is because I thought that it actually was the same, expect that spanning is used when the files are on different archive devices. IE split is in the same folder, spanned is across multiple DVDs.
In any case it looks like the C++ SDKs can't handle extracting these, which is what I was wanting to find out. So I will just do this myself.
Note that I haven't used the C++ SDK to create a spanned file either. Since I have no need to. I want to extract them, not create them. So I have no idea what setting the "SetSpanning" flag actually does. But if it did indeed split them into different volumes of a fixed byte size, and put then into the same output folder, then I assumed there would be a feature also in the SDK to read these back and extract them. Otherwise what is the point of C4D being able to create them in the first place?
.
Cheers.
Kent
@kbar said in ZipFile extracting spanned files:
.
Hi,
first of all, as already stated, neither splitting nor spanning are standardized by the ISO norm for document containers[1]. The norm actually makes a point of it to stress that these forms are not supported.
So every tool does what it wants in the first place. Because of that I probably should have written in most cases. But as stated above and also in my code, there is a third form, 7zip calls these Volumes.
We haven't dealt with this form in university, so I cannot say much about it, but I suspect that it has a better error correction as explained above. If you loose a file in the classic split scheme we were taught, you are basically screwed. The volume form also comes without the dedicated zip files. There are probably also other tools that can write this form, but they might using a different naming scheme. I at least once encountered such volume form that didn't use 7zips naming scheme and it tripped Pythons zipfile.
Probably all this is more on the irrelevant side of things, but I felt that with my forum alias I had to chime in ;)
Cheers,
zipit
[1]
@zipit Really great insights.Totally appreciate all your comments. I have worked with zlib for many years and integrated it into many different platforms, apps and plugins. This is just the first time I have ever looked into splitting or spanning features.
Off topic: Would be great to work on compression algorithms again. I keep eyeing up all the image compression formats being used and developed these days. Fun stuff. | https://plugincafe.maxon.net/topic/12775/zipfile-extracting-spanned-files | CC-MAIN-2021-17 | refinedweb | 1,407 | 73.78 |
Hi
Whenever I create figures with at least 3x3 subplots, the x-tick
labels overlap with each other and they also overlap with the title of
the adjacent subplot, rendering the entire figure illegible. I know
that I can fine-tune the plot to look exactly the way I want with
"wspace" and "hspace" for instance, but I don't understand why this is
the default behavior. I wonder if I have a system font issue, such
that matplotlib thinks the fonts are smaller than they really are.
My questions:
1) Is this the intended behavior of matplotlib, or is there something
wrong with my installation?
2) Assuming I don't have an installation issue, is there a very
general parameter I can change so that the overlap doesn't occur,
rather than manually adjusting every figure?
Minimal code to reproduce the problem:
import numpy as np
import matplotlib.pyplot as plt
plt.figure()
plt.subplot(331)
plt.subplot(334)
plt.plot(np.arange(10000))
plt.title('Title')
plt.show()
I'm attaching the output figure, although I'm not sure if the list
accepts attachments. The x-tick labels on subplot 334 overlap each
other, and the title of subplot 334 overlaps with the x-tick labels in
subplot 331.
System:
Ubuntu 10.04 x64
All packages are the stable versions from Synaptic, including ipython,
python, numpy, matplotlib 0.99.1.1
I've also tried the Enthought distribution with matplotlib 1.0.1 and
the results are the same
I've tried both "Wx" and "Tk" backends and the results are the same
I've tried `matplotlib.rcParams['xtick.labelsize'] = 'x-small'`, and
this does make the labels smaller, but for sufficiently large numbers
the overlap still occurs.
Thanks for any help!
Chris | https://discourse.matplotlib.org/t/subplot-x-tick-labels-overlap-with-each-other-and-with-titles/15422 | CC-MAIN-2022-21 | refinedweb | 295 | 62.38 |
project
project detail - Java Beginners
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I’ve been trying to learn how things work on Windows based on whether you write code in C# or C++, target a 32- or 64-bit platform, and produce files with either native code or one of the CLR options. One of my focuses is the interaction between exes and dlls. I think I’ve got things mostly straightened out, so this is what I’ve learned.
First, the basics: a 32-bit platform can run 32-bit apps, but not 64-bit apps. A 64-bit platform can run either, but 32-bit apps run in an emulation environment called WOW64 (Windows on Windows 64). When Windows starts your app, it decides whether WOW64 is necessary. You can tell whether your app is running in WOW64 using this C++ code:
#include "stdafx.h" #include <windows.h> typedef BOOL (WINAPI *LPFN_ISWOW64PROCESS) (HANDLE, PBOOL); LPFN_ISWOW64PROCESS fnIsWow64Process; BOOL isWow64() { BOOL ret = FALSE; fnIsWow64Process = (LPFN_ISWOW64PROCESS)GetProcAddress( GetModuleHandle(TEXT("kernel32")), "IsWow64Process"); if (NULL != fnIsWow64Process) { if (!fnIsWow64Process(GetCurrentProcess(), &ret)) { printf("Got some error\n"); } } return ret; } int _tmain(int argc, _TCHAR* argv[]) { if (isWow64()) { printf("Running under WOW64.\n"); } else { printf("NOT running under WOW64.\n"); } scanf("press return"); return 0; }
It’s easy enough to call
isWow64 from C#, like so:
[DllImport]("IsWow64Dll.dll")] static extern bool isWow64(); static void Main(String[] args) { Console.WriteLine(isWow64().ToString()); Console.ReadLine(); }
Visual Studio lets you build files for either 32- or 64-bit platforms. I’ve already written how to build for 32 or 64 bits in C++. C# actually provides three options: 32-bits, 64-bits, or “Any CPU.” We can use a tool called corflags to see what results we get depending on which option we choose. Corflags comes with Visual Studio and can be run by choosing the special DOS prompt command under Visual Studio in the Start menu. This is a little different from the regular DOS prompt: it has a specially-tailored environment for running Visual Studio’s command-line utilities. From there, you can ask corflags to report information about any exe or dll, like this:
C:\> corflags myapp.exe Microsoft (R) .NET Framework CorFlags Conversion Tool. Version 3.5.21022.8 Copyright (c) Microsoft Corporation. All rights reserved. Version : v2.0.50727 CLR Header: 2.5 PE : PE32 CorFlags : 3 ILONLY : 1 32BIT : 1 Signed : 0
We’re mostly interested in three values: PE, 32BIT, and ILONLY. There is also a line labelled “Signed,” which I’m not interested in right now. Finally, the “CorFlags” line appears to be a combination of the four other values.
PE specifies whether or not the file can run on 32-bit platforms. It is either PE32 or PE32+. A PE32+ file cannot run on a 32-bit machine.
Next there is the 32BIT flag. This is a little different from PE. If PE indicates whether your app can run as 32 bits, then 32BIT indicates whether it must run as 32 bits. If this flag is 0, your app can run on a 64-bit machine without WOW64. But if the flag is 1, then your app has to run under WOW64. Here is a table showing how the bits are set depending on your compiler’s /platform setting:
From this table, you can see that the corflags example above is inspecting a C# app built for the x86 platform. Note that you could never have a file that is PE32+ with the 32BIT flag set, because then one flag would require 32 bits and the other 64.
To put all this together, a 32-bit machine can run anything with a PE set to PE32, but nothing with a PE of PE32+. A 64-bit machine can run your file in 64-bit mode as long as 32BIT is 0, but if 32BIT is 1 then it must use WOW64.
The ILONLY flag indicates that your file contains only MSIL opcodes (recently renamed to CIL), with no native assembly instructions. A C# app will always have this flag set (unless you use something like ngen to compile down to machine language—an approach with some distribution problems), but a C++ app’s setting depends on your compiler options (described below).
When it comes to loading dlls, these flags control whether your app loads the dll successfully or gets a BadImageFormatException. Basically, a 32-bit app can only load 32-bit dlls, and a 64-bit app can only load 64-bit dlls. But what about apps compiled as “Any CPU”? In that case, you can only load dlls matching whatever bitness you’re currently running as. Of course, if you’re running on a 32-bit machine, there is no complication, because everything is 32-bit already.
But on a 64-bit machine, you may have problems. Windows will not use WOW64 for your app, because it claims to support 64-bit operation. But if your app has a dependency on a 32-bit dll, then you’ll get a BadImageFormatException, because the 32-bit dll only works in WOW64. The choice to use WOW64 happens only when starting your app. You can’t run an app natively and load just the dlls in WOW64. So you get the exception.
The solution is to tell Windows that your app must start in WOW64 from the beginning. You should probably do this by building your app for x86, not Any CPU, but if that is somehow a problem (e.g. you don’t have the code), then you can use corflags to set the 32BIT flag. You just type something like this:
corflags /32BIT+ myapp.exe
For C++ applications, you can do something similar with the linker’s /clrimagetype flag.
Another choice, at least when writing in C++, is how to support the CLR. You can choose among four options: native (the default), /clr, /clr:pure, and /clr:safe. The first one is simple enough: you get a file with machine language instructions. The other three give you a file that is partially or entirely composed of MSIL. Using /clr will produce a CLR header and mostly MSIL code, but with some native code mixed in. Specifically, you get native data types but MSIL functions, unless the function uses something unsupported like function pointers. (Everyday pointers to data are supported.) You can also use
#pragma unmanaged to force native code. Because these files have some native code, they must be built for a specific platform, either x86 or x64.
The /clr:pure option does what it sounds like: it gives you a file of entirely MSIL. Nonetheless, it must be built for either x86 or x64. This option is said to be equivalent to a C# project with unsafe code.
Microsoft’s documentation on the /clr and /clr:pure flags says that they can only produce x86 files, but my tests prove this to be false. If I build the C++ version of the WOW64-tester, using x64 and /clr compilation options, then it reports that it is not running in WOW64. So apparently you can in fact produce x64 applications with these options.
The last one, /clr:safe, enforces code that is verifiably type-safe—but I’m not sure what all that means. I’ve read that if you use this option, your file can run on any platform, like building as Any CPU in C#. This option requires that you use Microsoft’s C++/CLI language, formerly known as Managed C++. I know nothing about this, but people say it’s virtually a new language. I tried to build a Hello World app with
printf and got innumerable compile errors, so I wasn’t able to run any tests on what this option produces.
There is also a /clr:oldSyntax option, which is like /clr:safe but with the old Managed C++ syntax rather than C++/CLI. Since Managed C++ is deprecated, I’m not sure why you’d use this for new code.
I don’t know what the /clr* options mean for P/Invoke. If I build a dll with /clr or /clr:pure, does that mean I can call its exported functions from C# without a
DllImport statement? I haven’t tried. Using
DllImport on these dlls doesn’t cause problems, though.
You can use a tool called dumpbin to see which /clr options were used to produce a given file. Dumpbin comes with Visual Studio and runs from the command-line:
dumpbin /CLRHEADER myapp.exe
This will print (among other things) a
Flags value, which is 0 if the file was build with /clr, 1 with /clr:safe, and 3 with /clr:pure.
I’m also curious about the interaction between WOW64 and the CLR. If I run a 32-bit C# app on x64, then which comes first: WOW64 or the CLR? Is there a 64-bit CLR that can JIT-compile to either 32- or 64-bit code? Or do I have two CLRs, one for 32 bits and one for 64, and the former runs under WOW64? I suspect the answer is the latter, but I’m not sure how to tell. Either way my code is running in WOW64, so the check I described above won’t tell me anything.
I created a table to keep track of the data from all my tests. Here it is:1
There may be some option like the linker’s /CLRHEADER for C# apps.2
Can’t run on x86, and won’t be in WOW64 on x64. But see note 1.
There are still some gaps in this table. I’m not that concerned about the interactions between C++ exes and C++ dlls, so I’ve left those cells blank. I’ve also left some cell blanks regarding when C++ files are managed/unmanaged and when they contain an assembly. If I figure any of this out, I’ll update the table.
One final notable tool is ildasm (IL-disassembler), which also comes with Visual Studio. This lets you inspect the IL of an exe or dll. Most of it is over my head, but it’s intetesting to see what your code becomes.blog comments powered by Disqus Prev: C# XmlTextReader Tutorial Next: Decline in Inverse and Leveraged ETFs | http://illuminatedcomputing.com/posts/2010/02/sorting-out-the-confusion-32-vs-64-bit-clr-vs-native-cs-vs-cpp/ | CC-MAIN-2014-52 | refinedweb | 1,708 | 73.07 |
As many developers have noticed, the reflection APIs changed in the .NET API set for Windows Store apps. Much of .NET’s ability to offer a consistent programming model to so many platforms over the last ten years has been the result of great architectural thinking. The changes to reflection are here to prepare for the challenges over the next decade, again with a focus on great architecture. Richard Lander and Mircea Trofin, program managers respectively from the Common Language Runtime and .NET Core Framework teams, wrote this post. — Brandon
In this post, we will look at changes to the reflection API for the .NET Framework 4.5 and .NET APIs for Windows Store apps (available in Windows 8). These changes adopt current API patterns, provide a basis for future innovation, and retain compatibility for existing .NET Framework profiles.
Reflecting on a popular .NET Framework API
The .NET Framework is one of the most extensive and productive development platforms available. As .NET developers, you create a broad variety of apps, including Windows Store apps, ASP.NET websites, and desktop apps. A big part of what enables you to be so productive across Microsoft app platforms is the consistency of the developer experience. For many developers, the language – be it C# or Visual Basic – is this common thread. For others, it is the Base Class Libraries (BCL). When you look more closely, you’ll see that reflection is the basis for many language, BCL, and Visual Studio features.
Many .NET Framework tools and APIs rely on CLR metadata, accessed via reflection, to operate. Examples include static analysis tools, application containers, extensibility frameworks (like MEF), and serialization engines. The ability to query, invoke, and even mutate types and objects is a focal point for .NET developers in many scenarios.
In the .NET Framework 4, we support a rich but narrow set of views and operations over both static metadata and live objects. As we looked at expanding reflection scenarios, we realized that we first needed to evolve the reflection API to enable further innovation.
We saw the design effort to create .NET APIs for Windows Store apps as the avenue to establish the changes that we needed in reflection. We defined a set of updates to reflection that would enable more flexibility for future innovation. We were able to apply that design to .NET APIs for Windows Store apps and also to the Portable Class Library. At the same time, we were able to compatibly enable that design in the .NET Framework 4.5. As a result, we were able to evolve the reflection API consistently and compatibly across .NET Framework API subsets.
We took an in-depth look at the .NET APIs for Windows Store apps in an earlier .NET Team blog post. In this post, we saw that this new API subset is considerably smaller than the .NET Framework 4.5. We have documented the differences on MSDN. One difference that applies is Reflection.Emit, which is not available to Windows Store apps.
Reflection scenarios
Reflection can be described in terms of three big scenarios:
- Runtime reflection
- Primary scenario: You can request metadata information about loaded assemblies, types, and objects, instantiate types, and invoke methods
- Status: Supported
- Reflection-only loading for static analysis
- Extensibility of reflection
- Primary scenario: You can augment metadata in either of the two scenarios above
- Status: Supported, but complicated
Today, we have reasonable support for runtime reflection, but not for the other two scenarios. Given that reflection is such a key API, richer support across all three scenarios would likely enable new classes of tools, component frameworks, and other technologies. Full support is inhibited by some limitations in the reflection API in the .NET Framework 4. Primarily, reflection innovation is constrained by a lack of separation of concepts within the API, particularly as it relates to types. The System.Type class is oriented (per its original design) around the runtime reflection scenario. This is problematic because System.Type is used to represent types across all scenarios. Instead, we would benefit from a broader representation of types, designed to support all three scenarios.
Splitting System.Type into two concepts
System.Type is the primary abstraction and entry point into the reflection model. It is used to describe two related but different concepts, reference and definition, and enables operations across both. This lack of separation of concepts is the primary motivation for changing the reflection API. For example, the following scenarios are either difficult or unsupported with the existing model:
- Reading CLR metadata without execution side-effects
- Augmenting type representation (for example, changing shape, adding attributes)
In other parts of the product, we have first-class concepts of reference and definition. At a high level, a reference is a shallow representation of something, whereas a definition provides a rich representation. One needs to look no farther than assemblies, a higher level part of reflection, to see this..
In order to achieve a similar split for the System.Type concept and class, we created a new System.Reflection.TypeInfo class and shrunk the meaning of the System.Type class.. Given a TypeInfo object, you can perform all the rich behavior that you expect with a type definition, such as getting lists of members, implemented interfaces, or the base type.
The value of Type and TypeInfo
The API changes in the .NET Framework 4.5 were made such that we could evolve the reflection API to deliver new scenarios and value. While we changed the shape of the API, we haven’t yet added the additional features that would deliver the value. This section provides a preview of what that value would look like in practice.
Suppose that we are using a static analysis tool that is implemented with the new reflection model. We are looking for all types in an app that derive from the UIControl class. We want to be able to run this tool on workstations on which the UIControl assembly (which contains the UIControl class) does not exist. In this example, let’s assume that we open an assembly that contains a class that derives from the UIControl class:
class MyClass : UIControl
In the .NET Framework 4 reflection model, the Type object (incorporating both reference and definition) that represents MyClass would create a Type object for the base class, which is UIControl. On machines that don’t have the UIControl assembly, the request to construct the UIControl Type object would fail, and so too would the request to create a Type object for MyClass, as a result.
Here you see what the reference/definition split achieves. In the new model, MyClass is a TypeInfo (definition); however, BaseType is a Type (reference), and will contain only the information about UIControl that the (MyClass) assembly contains, without requiring finding its actual definition.
Type baseType = myClassTypeInfo.BaseType;
In other scenarios, you may need to obtain the definition of UIControl. In that case, you can use the extension method on the Type clas, GetTypeInfo, to get a TypeInfo for UIControl:
TypeInfo baseType = myClassTypeInfo.BaseType.GetTypeInfo();
Of course, in this case, the UIControl assembly would need to be available. In this new model, your code (not the reflection API) controls the assembly loading policy.
Once again, in the .NET Framework 4.5, the reflection API still eagerly loads the type definition for the base class. The reflection API implementation is largely oriented around the runtime reflection scenario, which has a bias towards loading base type definitions eagerly. At the point that we build support for the static analysis scenario described earlier, we will be able to deliver on full value of the reference/definition split, made possible by Type and TypeInfo.
Applying the System.Type split to the Base Class Libraries
Changing the meaning of Type and adding TypeInfo made it necessary to ensure consistency in the .NET Framework BCL. The .NET Framework has many APIs that return the Type class. For each API, we needed to decide whether a Type (reference) or a TypeInfo (definition) was appropriate. In practice, these choices were easy, since the API inherently either returned a reference or a definition. You either have access to rich data or you don’t. We’ll look at a few examples that demonstrate the trend.
- The Assembly.DefinedTypes property returns TypeInfo.
- This API gets the types defined in that assembly.
- The Type.BaseType property returns a Type.
- This API returns a statement of what the base type is, not its shape.
- The base type could be defined in another assembly, which would require an assembly load.
- The Object.GetType method returns a Type.
- This API returns a Type, since you only need a representation of a type, not its shape.
- The type could be defined in another assembly, which would require an assembly load.
- By returning a Type and not a TypeInfo, we also removed a dependency on the reflection subsystem from the core of the .NET Framework.
- Language keywords, like C# typeof, return a Type.
- Same rationale and behavior as Object.GetType.
Deeper dive into the reflection model update
So far, we’ve been looking at better abstraction in the reflection API, which is the reference/definition split that we made with Type and TypeInfo. We also made other changes, some of which contributed to the reference/definition split and others that satisfied other goals. Let’s dive a little deeper into those changes.
Replacing runtime reflection-oriented APIs
In the .NET Framework 4.5 (and earlier releases), you can call Type.GetMethods() to get a list of methods that are exposed on a given type. Such a list of methods will include inherited methods. Our implementation of the GetMethods method has a particular policy for how it traverses the inheritance chain to get the complete list of methods, including loading assemblies for base types that are located in other assemblies. This approach can sometimes be problematic, since loading assemblies can have side-effects that change the execution of your program. The GetMethods method is an example of the heavy bias that the reflection API has to satisfying runtime reflection scenarios, and therefore, is not appropriate for reflection-only loading scenarios.
For the new model, we introduced the DeclaredMethods property that reports the members that are declared (as opposed to members that are available via inheritance) on a given type. There are several other properties, such as DeclaredMembers and DeclaredEvents that follow the same pattern.
The following example illustrates the difference in the behavior between Type/TypeInfo.GetMethods and TypeInfo.DeclaredMethods, using the .NET Framework 4.5.
class MyClass
{
public void SomeMethod() { }
} class Program { static void Main(string[] args) { var t = typeof(MyClass).GetTypeInfo(); Console.WriteLine("---all methods---"); foreach (MethodInfo m in t.GetMethods()) Console.WriteLine(m.Name); Console.WriteLine("======================="); Console.WriteLine("---declared methods only---"); foreach (MethodInfo m in t.DeclaredMethods) Console.WriteLine(m.Name); Console.ReadKey(); } }
The output is:
---all methods--- SomeMethod ToString Equals GetHashCode GetType ======================= —declared methods only--- SomeMethod
You will notice that the GetMethods method retrieves all the public methods accessible on MyClass – including the ones defined on System.Object, like ToString, Equals, GetType and GetHashCode. DeclaredMethods returns all the declared methods (in this case, one method) on a given type, regardless of visibility, and including static methods.
Adopting current API patterns — IEnumerable<T>
In the era of the async programming model, the reflection APIs stand out since many of them, such as MemberInfo[], return arrays. As you likely know, arrays need to be fully populated before they are returned from an API. This characteristic is bad for both working-set and responsiveness. In the .NET APIs for Windows Store apps, we have replaced all the array return types with IEnumerable<T> collections. Most of you will appreciate working with this friendlier API pattern, which will likely blend in better with the rest of your code.
We have not yet fully taken advantage of this model yet. In our internal implementation of these APIs, we are still using the arrays that were formerly part of the public API contract. In a later version of the product, we can change the implementation to lazy evaluation without needing an associated change to the public API.
Compatibility across .NET target frameworks
We designed the reflection API updates with a goal of compatibility with existing code. In particular, we wanted developers to be able to share code between the .NET Framework 4.5 and .NET APIs for Windows Store apps.
In .NET APIs for Windows Store apps, TypeInfo inherits from MemberInfo, while Type inherits from Object. Type definitions must inherit from MemberInfo to allow for nested types – types that are members of other types – in the same way that methods, properties, events, fields, or constructors are members of a type. You can see that this inheritance approach makes sense, particularly now that Type is very light-weight.
In the .NET Framework 4.5, TypeInfo inherits from Type, while Type is still a MemberInfo. In order to maintain compatibility with the .NET Framework 4, we could not change the base type of Type. We expect that future .NET Framework releases will maintain this same factoring (that is, Type will continue to be a MemberInfo) for backward compatibility.
However, if you are writing code that targets the .NET Framework 4.5, and you want to use the new reflection model, we encourage you to write that code as a Portable Class Library. Portable Class Library projects that target the .NET Framework 4.5 and .NET APIs for Windows Store apps follow the new model, as described above.
See the figure below for a visual illustration of the reflection type hierarchy in the .NET Framework 4.5 and .NET APIs for Windows Store apps.
Figure: Reflection type hierarchy in the .NET Framework 4.5 and .NET APIs for Windows Store apps
Updating your code to use the new reflection model
Now that you have a fundamental understanding of the new model, let’s look at the mechanics of the APIs. Basically, you need to know three things:
- The Type class exposes basic data about a type.
- The TypeInfo class exposes all the functionality for a type. It is also a proper superset of Type.
- The GetTypeInfo extension method enables you to get a TypeInfo object from a Type object.
The following sample code demonstrates the basic mechanics of Type and TypeInfo. It also provides examples of the data that you can get from Type and TypeInfo.
class Class1 { public void Type_TypeInfo_Demo() { //Get a Type Type type = typeof(Class1); //Gets the name of the type String typeName = type.FullName; //Gets the assembly-qualified type name String aqtn = type.AssemblyQualifiedName; //Get TypeInfo via the type //Note that .GetTypeInfo is an extension method TypeInfo typeInfo = type.GetTypeInfo(); //Get the list of members IEnumerable<MemberInfo> members = typeInfo.DeclaredMembers; //You can do many other things with a TypeInfo } }
We have received feedback that this change inserts another step – calling the GetTypeInfo extension method – and that it represents a migration hurdle for developers. This change is opt-in for the .NET Framework 4.5, for compatibility reasons. You do not have to use the GetTypeInfo method or the TypeInfo class if you are targeting the .NET Framework 4.5.. The same is true for Portable Class Library code that targets both .NET APIs for Windows Store apps and the .NET Framework 4.5.
Writing code for the new reflection API – Windows Store and Portable Class Library
As we discussed above, you’ll need to adopt the new reflection model if your code targets .NET APIs for Windows Store apps or you’re creating a Portable Class Library project that targets both .NET APIs for Windows Store apps and the .NET Framework 4.5.
For example, you will notice that the Get* methods (for example, GetMethod) described earlier are not available, but are replaced by the Declared* properties (for example, DeclaredMethod). If the Get* methods are not present, the reflection binding constraints (BindingFlags options) are not available either. If you’re writing new code, you’ll need to follow the new model, and if you’re porting code from another project, you’ll need to update your code to the same model. We understand that these changes may result in non-trivial migration efforts in some cases; however, we hope that you can see the value that can be achieved with the type/typeinfo split.
While the APIs have changed, you may still need to access inherited APIs and filter results. There are a couple of patterns that you can use to accommodate those changes. We’ll look at those now.
We recommend that you write the code that provides the reflection objects that you need. You’ll actually get a clearer view of what the reflection sub-system does by seeing the code in your source file. Your implementation may also be more efficient than our implementation in the .NET Framework, since we accommodate several uncommon cases.
You’ll need some code that is a proxy for GetMethods, but that is implemented in terms of the new reflection API. You might need a replacement for another Get* method, such as GetInterfaces; however, you should find that the GetMethods example equally applies. The most straightforward implementation for GetMethods follows. It walks the inheritance chain of a type, and requests the set of declared methods on each class in that chain.
public static IEnumerable<MethodInfo> GetMethods(this Type someType) { var t = someType; while (t != null) { var ti = t.GetTypeInfo(); foreach (var m in ti.DeclaredMethods) yield return m; t = ti.BaseType; } }
Since binding flags are not provided in the new reflection API, you do not immediately have an obvious way to filter results, to public, private, static members, or to choose any of the other options offered by the BindingFlags enum. To accommodate this change, you can write pretty simple LINQ queries to filter on the results of the Declared* APIs, as you see in the following example:
IEnumerable<MethodInfo> methods = typeInfo.DeclaredMethods.Where(m => m.IsPublic);
We do offer another pattern as an option for porting code more efficiently. We created the GetRuntimeMethods extension method as a convenience API that provides the same semantics as the existing GetMethods API. Related extension methods have been created as an option for the other Get* methods, such as GetRuntimeProperties, as well. As the API names suggests, they are runtime reflection APIs, which will load all base types, even if they are located in other assemblies. These new extension methods do not support the BindingFlags enum, so the filtering approach suggested with LINQ above also applies.
Both of these suggested patterns are good choices for adopting the new reflection model. Note that if reflection support expands in the future to include reflection-only scenarios for static analysis, GetRuntime* methods would no longer be appropriate, should you want to take advantage of those new scenarios.
Writing code for the new reflection API – .NET Framework 4.5
If your code targets the .NET Framework 4.5, you can opt to use the new model, but you do not have to. The .NET Framework 4.5 API is a superset of old and new reflection models, so all the APIs that you’ve used before are available, plus the new ones.
Portable Class Library projects that target the .NET Framework 4, Silverlight, or Windows Phone 7.5 expose only the old model. In these cases, the new reflection APIs are not available.
Conclusion
In this post, we’ve discussed the improvements that we made to reflection APIs in .NET APIs for Windows Store apps, the .NET Framework 4.5, and Portable Class Library projects. These changes are intended to provide a solid basis for future innovation in reflection, while enabling compatibility for existing code.
For more information, porting guides, and utility extension methods, please see .NET for Windows Store apps overview in the Windows Dev Center.
–Rich and Mircea
Follow or talk to us on twitter —.
Join the conversationAdd Comment
Making a breaking change like this across a variant of .NET seems like a really bad idea. You should either take the breaking change, or not take it. This whole concept of "well in this flavor of .NET, you do things this way…" defeats one of the major purposes of .NET – that code is portable.
Also, I really don't agree with the idea that you expect developers to write their own extension methods if they want to get the functionality of methods that you removed. As you admit in this blog post, those methods you removed can be useful. Do they really harm anything leaving them in there?
There seems to be a variable name missing here:
IEnumerable<members> = typeInfo.DeclaredMembers;
Other than that I agree with MgSm88.
Also please keep that CxO Bullshit about "delivering value" out of blog posts intended for developers.
@qqq — code sample fixed. Thanks.
Richard Lander [MSFT]
@MgSm88: we saw the .NET APIs for Windows Store subset as an important opportunity for evolving framework APIs. We knew that there was a tradeoff – and that not everyone would be happy
– but felt that we were on the right side of it.
Portable code is a very important goal to us, and we agree with your comment on “variants of .NET”. You’ll find that the new APIs play a significant role in this story. Some details are in this channel 9 video (channel9.msdn.com/…/NET-45-David-Kean-and-Marcea-Trofin-Portable-Libraries). The core of it is that the shape of APIs you see in .NET for Windows Store constitute the basis we intend to build portability from grounds up in the .NET ecosystem, moving forward.
WRT removing methods, for those that were deemed quite useful, we actually provided the extension methods ourselves. For example, in the GetMethods case, we provided a GetRuntimeMethods extension method. These ship in the box, so you just need to use them, if you need the functionality. To your question about the impact of “leaving them in”, the simple answer is that whatever we pulled out contradicted one or more of our principles we presented in an earlier post (blogs.msdn.com/…/net-for-metro-style-apps.aspx)
Mircea ("Mitch") Trofin [MSFT]
I totally follow the rationale of the change, especially since I have worked with the native metadata APIs, but I still find it very sad that there has to be so many versions of .NET each with small and not-so-small API differences. It's even more painful as documentation for this new .NET profile is really lacking (as is general WinRT, if that's what it's still called, documentation). For example, I haven't found any way to get documentation for the System.Type type from this .NET profile other than through Intellisense.
What little documentation there is is also very hard to search for, again not only for this .NET profile but also for WinRT in general. This is especially a pain point since Microsoft sources themselves can't agree on whether it's "Metro", "Windows 8 Apps", "Windows Store Apps" or "Modern UI". As a result, we now have to try various permutations of ".NET for Modern UI Windows 8 Store Apps" to get any pertinent search results.
Basically, I like the general direction of the changes from a design perspective, but the impact on the .NET ecosystem is really unpleasant and the documentation needs to be vastly improved.
@TrillianX — The documentation issue is both known and noted. We want to get this fixed in one of our next doc refreshes. The search engine issue is annoying, but should sort itself out relatively quickly as the old permutations fall away in the search rankings.
I think it is a very good change, the only issue is that you can not change it across all versions, but it is understandable.
The breaking changes here is just another item to add to the very long list of reasons why .NET 4.5 should not have been an in-place upgrade.
@Vaccano — There are no changes discussed in this post that break compatibility w/rt .NET 4 apps. The post clearly states in the first section that "we were able to compatibly enable that design in the .NET Framework 4.5".
If you re-read the post, you'll find this text:
. "
As the post states, we took the opportunity to create a fully consistent API with .NET APIs for Windows Store apps. You can consider that a "source break" with .NET 4 if you'd like, but not a binary break as your comment would suggest.
Does that help?
thanks — rich
Because .net 4.5 does not support Windows XP and Windows Server 2003, So my team can not update to .net 4.5. Any improvements you done have no meanings to us.
Instead if IE<T>, which is the least rich interface possible, you could have returned a custom IList<T> derived type that still does lazy loading internally.
What types of app do you have in mind for "Reflection-only loading for static analysis"? I can't come up with one that would depend on System.Reflection and have a problem with unavailable dependencies.
I think the lazy loading changes largely could have been implemented transparently inside of System.Type. With the exception of array-based properties.
But why would anyone only need a part of that array? Caller always either check the length (!= 0) or they iterate all members to find all matching stuff. Why would anyone stop (significantly!) earlier? When searching for the first match on average half of the collection would have been saved. And that is the most favorable example I can come up with.
The hierarchy split across the project types/targets is awful. The different .NET targets are a mess even today. Portable libraries are really only portable by disallowing half of the framework! This is awful for developers. Never know where a member is available, in what versions and targets. Now we even change the type hierarchy of a core API.
Is there someone centrally planning this stuff? Seems like there isn't.
@tobi: We picked IEnumerable<T> exactly because it is the least rich interface. Consider the DeclaredMethods property on TypeInfo. IList<T> would have suggested you could add to that list (you can't), and the index would have suggested you could rely on order (we deliberately do not want you to rely on that order).
For your static analysis apps question, we want to enable building apps like Reflector, where you can load one assembly at a time and then the user may ask for the dependencies of an API. Suppose that our dll was compiled against .NET 4.5, but you don't have 4.5 yet and don't want to upgrade just yet. Ideally, you could see the list of APIs required by this dll without having to resolve them to implementation and without requiring the presence of 4.5 dlls (installed or otherwise).
On transparently implementing lazy loading in Type; the main idea is control over when and where dependencies are loaded from. We opted for a design where the control is explicit rather than transparent. This is mostly based on feedback from compiler or other metadata tools (like the architecture explorer in VS).
On the array question, suppose all I care about is finding types marked with some attribute. Arrays have eager semantics in .NET. This means that for every API I look for that attribute, I'd have to first get them all. That'd be quite inefficient, hence the preference for IEnumerable<T>
For your last point, please refer to my earlier reply on this post.
Makes sense. Thanks.
I think it's a great change and I applaud that you are still willing to make major changes to core APIs. The new model is a lot more consistent and cleaner. Even though I wish to have .NET 4.5 and the Windows Store API to behave the same I understand that MS was unwilling to break compatibility and since it's an in-place upgrade it obviously can't break any existing code.
I only have 2 wishes. First of all you should consider marking methods from the old model as obsolete in the next Framework version so that people are encouraged to change to the new model and second please avoid extensive use of extension methods. In this case it should have been easier to create a TypeInfo by passing a Type in the constructor or creating a factory method. Extension methods should be the exception, not the rule.
Thanks!
Good. In my experience though even runtime reflection does not work in some common scenarios. Like how do you get all the events defined on a C# or VB class and raise one of them. E.g. I want to create a method which, once given a string containing the name of the event and another the name of the class, use reflection on the class to find the event and raise it passing the correct eventargs to it. It is thoroughly compilcated to achieve this simple goal it seems. C# and VB compilers do not store events the right way it seems. I am not sure. But the reflection methods do not work on events both for .NET 4 and for Silverlight. I presume for all .NET versions. I think the reason is that C# and VB compilers do not store events in the right way but use a private field. I am not sure. Please clarify.
I cant get this to work when creating a portable class library for .NET 4.5 and Windows Store Apps the GetTypeInfo() method is not available for types. What am I missing?
I have the same problem as Harry. This post is very old so it is probably the wrong place to ask, but there is very little around the web about this. I have a PCL class library and I am trying to get all properties of a class. System.Type offers neither a list of properties nor a way to get a TypeInfo instance. I am lost here.
@Harry
> I cant get this to work when creating a portable class library for .NET 4.5 and Windows Store Apps the GetTypeInfo() method is not available for types. What am I missing?
I'm only two and half years late, but hey — better late than never, right?
You need to import the namespace System.Reflection. GetTypeInfo() is actually an extension method and lives on System.Reflection.IntrospectionExtensions.
msdn.microsoft.com/…/system.reflection.introspectionextensions.gettypeinfo(v=vs.110).aspx
Looking back, it was clearly a mistake. We should have put this type in the System namespace to help with discovery. Sorry about that!
@Rushtik
> I have a PCL class library and I am trying to get all properties of a class. System.Type offers neither a list of properties nor a way to get a TypeInfo instance.
See above, hope this helps!
> I am lost here.
From talking to other customers it's clear you're not the only one. Apologies: we clearly haven't done a great job explaining this concept to folks. In case you want to learn more, here is a Channel 9 video on how we changed the reflection APIs and why:
channel9.msdn.com/…/NET-45-David-Kean-and-Marcea-Trofin-Portable-Libraries
By the way, I've also talked to our documentation team and they will create a topic dedicated for how to convert the code to accommodate the changes we've done in reflection.
Hope this helps! | https://blogs.msdn.microsoft.com/dotnet/2012/08/28/evolving-the-reflection-api/ | CC-MAIN-2016-22 | refinedweb | 5,274 | 66.13 |
Introduction
Neural networks are a different breed of models compared to the supervised machine learning algorithms. Why do I say so? There are multiple reasons for that, but the most prominent is the cost of running algorithms on the hardware.
In today’s world, RAM on a machine is cheap and is available in plenty. You need hundreds of GBs of RAM to run a super complex supervised machine learning problem – it can be yours for a little investment / rent. On the other hand, access to GPUs is not that cheap. You need access to hundred GB VRAM on GPUs – it won’t be straight forward and would involve significant costs.
Now, that may change in future. But for now, it means that we have to be smarter about the way we use our resources in solving Deep Learning problems. Especially so, when we try to solve complex real life problems on areas like image and voice recognition. Once you have a few hidden layers in your model, adding another layer of hidden layer would need immense resources.
Thankfully, there is something called “Transfer Learning” which enables us to use pre-trained models from other people by making small changes. In this article, I am going to tell how we can use pre-trained models to accelerate our solutions.
You can check out our list of the top pretrained models for computer vision and NLP here:
- Top 10 Pretrained Models to get you Started with Deep Learning (Part 1 – Computer Vision)
- 8 Excellent Pretrained Models to get you Started with Natural Language Processing (NLP)
Note – This article assumes basic familiarity with Neural networks and deep learning. If you are new to deep learning, I would strongly recommend that you read the following articles first:
What is deep learning and why is it getting so much attention?
Deep Learning vs. Machine Learning – the essential differences you need to know!
25 Must Know Terms & concepts for Beginners in Deep Learning
Why are GPUs necessary for training Deep Learning models?
Table of Contents
- What is transfer learning?
- What is a Pre-trained Model?
- Why would we use pre-trained models? – A real life example
- How can I use pre-trained models?
- Extract Features
- Fine tune the model
- Ways to fine tune your model
- Use the pre-trained model for identifying digits
- Retraining the output dense layers only
- Freeze the weights of first few layers
What is transfer learning?
Let us start with developing an intuition for transfer learning. Let us understand from a simple teacher – student analogy.
A teacher has years of experience in the particular topic he/she teaches. With all this accumulated information, the lectures that students get is a concise and brief overview of the topic. So it can be seen as a “transfer” of information from the learned to a novice.
Keeping in mind this analogy, we compare this to neural network. A neural network is trained on a data. This network gains knowledge from this data, which is compiled as “weights” of the network. These weights can be extracted and then transferred to any other neural network. Instead of training the other neural network from scratch, we “transfer” the learned features.
Now, let us reflect on the importance of transfer learning by relating to our evolution. And what better way than to use transfer learning for this! So I am picking on a concept touched on by Tim Urban from one of his recent articles on waitbutwhy.com
Tim explains that before language was invented, every generation of humans had to re-invent the knowledge for themselves and this is how knowledge growth was happening from one generation to other:
Then, we invented language! A way to transfer learning from one generation to another and this is what happened over same time frame:
Isn’t it phenomenal and super empowering? So, transfer learning by passing on weights is equivalent of language used to disseminate knowledge over generations in human evolution.. You can spend years to build a decent image recognition algorithm from scratch or you can take inception model (a pre-trained model) from Google which was built on ImageNet data to identify images in those pictures.
A pre-trained model may not be 100% accurate in your application, but it saves huge efforts required to re-invent the wheel. Let me show this to you with a recent example.
Why would we use Pre-trained Models?
I spent my last week working on a problem at CrowdAnalytix platform – Identifying themes from mobile case images. This was an image classification problem where we were given 4591 images in the training dataset and 1200 images in the test dataset. The objective was to classify the images into one of the 16 categories. After the basic pre-processing steps, I started off with a simple MLP model with the following architecture-
To simplify the above architecture after flattening the input image [224 X 224 X 3] into [150528], I used three hidden layers with 500, 500 and 500 neurons respectively. The output layer had 16 neurons which correspond to the number of categories in which we need to classify the input image.
I barely managed a training accuracy of 6.8 % which turned out to be very bad. Even experimenting with hidden layers, number of neurons in hidden layers and drop out rates. I could not manage to substantially increase my training accuracy. Increasing the hidden layers and the number of neurons, caused 20 seconds to run a single epoch on my Titan X GPU with 12 GB VRAM.
Below is an output of the training using the MLP model with the above architecture.
Epoch 10/10
50/50 [==============================] – 21s – loss: 15.0100 – acc: 0.0688
As, you can see MLP was not going to give me any better results without exponentially increasing my training time. So I switched to Convolutional Neural Network to see how they perform on this dataset and whether I would be able to increase my training accuracy.
The CNN had the below architecture –
I used 3 convolutional blocks with each block following the below architecture-
- 32 filters of size 5 X 5
- Activation function – relu
- Max pooling layer of size 4 X 4
The result obtained after the final convolutional block was flattened into a size [256] and passed into a single hidden layer of with 64 neurons. The output of the hidden layer was passed onto the output layer after a drop out rate of 0.5.
The result obtained with the above architecture is summarized below-
Epoch 10/10
50/50 [==============================] – 21s – loss: 13.5733 – acc: 0.1575
Though my accuracy increased in comparison to the MLP output, it also increased the time taken to run a single epoch – 21 seconds.
But the major point to note was that the majority class in the dataset was around 17.6%. So, even if we had predicted the class of every image in the train dataset to be the majority class, we would have performed better than MLP and CNN respectively. Addition of more convolutional blocks substantially increased my training time. This led me to switch onto using pre-trained models where I would not have to train my entire architecture but only a few layers.
So, I used VGG16 model which is pre-trained on the ImageNet dataset and provided in the keras library for use. Below is the architecture of the VGG16 model which I used.
The only change that I made to the VGG16 existing architecture is changing the softmax layer with 1000 outputs to 16 categories suitable for our problem and re-training the dense layer.
This architecture gave me an accuracy of 70% much better than MLP and CNN. Also, the biggest benefit of using the VGG16 pre-trained model was almost negligible time to train the dense layer with greater accuracy.
So, I moved forward with this approach of using a pre-trained model and the next step was to fine tune my VGG16 model to suit this problem.
How can I use Pre-trained Models?
What is our objective when we train a neural network? We wish to identify the correct weights for the network by multiple forward and backward iterations. By using pre-trained models which have been previously trained on large datasets, we can directly use the weights and architecture obtained and apply the learning on our problem statement. This is known as transfer learning. We “transfer the learning” of the pre-trained model to our specific problem statement.
You should be very careful while choosing what pre-trained model you should use in your case. If the problem statement we have at hand is very different from the one on which the pre-trained model was trained – the prediction we would get would be very inaccurate. For example, a model previously trained for speech recognition would work horribly if we try to use it to identify objects using it.
We are lucky that many pre-trained architectures are directly available for us in the Keras library. Imagenet data set has been widely used to build various architectures since it is large enough (1.2M images) to create a generalized model. The problem statement is to train a model that can correctly classify the images into 1,000 separate object categories. These 1,000 image categories represent object classes that we come across in our day-to-day lives, such as species of dogs, cats, various household objects, vehicle types etc.
These pre-trained networks demonstrate a strong ability to generalize to images outside the ImageNet dataset via transfer learning. We make modifications in the pre-existing model by fine-tuning the model. Since we assume that the pre-trained network has been trained quite well, we would not want to modify the weights too soon and too much. While modifying we generally use a learning rate smaller than the one used for initially training the model.
Ways to Fine tune the model
- Feature extraction – We can use a pre-trained model as a feature extraction mechanism. What we can do is that we can remove the output layer( the one which gives the probabilities for being in each of the 1000 classes) and then use the entire network as a fixed feature extractor for the new data set.
- Use the Architecture of the pre-trained model – What we can do is that we use architecture of the model while we initialize all the weights randomly and train the model according to our dataset again.
- Train some layers while freeze others – Another way to use a pre-trained model is to train is partially. What we can do is we keep the weights of initial layers of the model frozen while we retrain only the higher layers. We can try and test as to how many layers to be frozen and how many to be trained.
The below diagram should help you decide on how to proceed on using the pre trained model in your case –
Scenario 1 – Size of the Data set is small while the Data similarity is very high – In this case, since the data similarity is very high, we do not need to retrain the model. All we need to do is to customize and modify the output layers according to our problem statement. We use the pretrained model as a feature extractor. Suppose we decide to use models trained on Imagenet to identify if the new set of images have cats or dogs..
Scenario 2 – Size of the data is small as well as data similarity is very low – In this case we can freeze the initial (let’s say k) layers of the pretrained model and train just the remaining(n-k) layers again. The top layers would then be customized to the new data set. Since the new data set has low similarity it is significant to retrain and customize the higher layers according to the new dataset. The small size of the data set is compensated by the fact that the initial layers are kept pretrained(which have been trained on a large dataset previously) and the weights for those layers are frozen.
Scenario 3 – Size of the data set is large however the Data similarity is very low – In this case, since we have a large dataset, our neural network training would be effective. However, since the data we have is very different as compared to the data used for training our pretrained models. The predictions made using pretrained models would not be effective. Hence, its best to train the neural network from scratch according to your data.
Scenario 4 – Size of the data is large as well as there is high data similarity – This is the ideal situation. In this case the pretrained model should be most effective. The best way to use the model is to retain the architecture of the model and the initial weights of the model. Then we can retrain this model using the weights as initialized in the pre-trained model.
Use the pre-trained models to identify handwritten digits
Let’s now try to use a pretrained model for a simple problem. There are various architectures that have been trained on the imageNet data set. You can go through various architectures here. I have used vgg16 as pretrained model architecture and have tried to identify handwritten digits using it. Let’s see in which of the above scenarios would this problem fall into. We have around 60,000 training images of handwritten digits. This data set is definitely small. So the situation would either fall into scenario 1 or scenario 2. We shall try to solve the problem using both these scenarios. The data set can be downloaded from here.
- Retrain the output dense layers only – Here we use vgg16 as a feature extractor. We then use these features and send them to dense layers which are trained according to our data set. The output layer is also replaced with our new softmax layer relevant to our problem. The output layer in a vgg16 is a softmax activation with 1000 categories. We remove this layer and replace it with a softmax layer of 10 categories. We just train the weights of these layers and try to identify the digits.
# importing required libraries
train=pd.read_csv("R/Data/Train/train.csv")
test=pd.read_csv("R/Data/test.csv")
train_path="R/Data/Train/Images/train/"
test_path="R/Data/Train/Images/test/"
from scipy.misc import imresize
# preparing the train dataset
train_img=[]
for i in range(len(train)):
temp_img=image.load_img(train_path+train['filename'][i],target_size=(224,224))
temp_img=image.img_to_array(temp_img)
train_img.append(temp_img)
#converting train images to array and applying mean subtraction processing
train_img=np.array(train_img)
train_img=preprocess_input(train_img)
# applying the same procedure with the test dataset
test_img=[]
for i in range(len(test)):
temp_img=image.load_img(test_path+test['filename'][i],target_size=(224,224))
temp_img=image.img_to_array(temp_img)
test_img.append(temp_img)
test_img=np.array(test_img)
test_img=preprocess_input(test_img)
model = VGG16(weights='imagenet', include_top=False)
# Extracting features from the train dataset using the VGG16 pre-trained model
features_train=model.predict(train_img)
# Extracting features from the train dataset using the VGG16 pre-trained model
features_test=model.predict(test_img)
# flattening the layers to conform to MLP input
train_x=features_train.reshape(49000,25088)
# converting target variable to array
train_y=np.asarray(train['label'])
# performing one-hot encoding for the target variable
train_y=pd.get_dummies(train_y)
train_y=np.array(train_y)
# creating training and validation set
from sklearn.model_selection import train_test_split
X_train, X_valid, Y_train, Y_valid=train_test_split(train_x,train_y,test_size=0.3, random_state=42)
# creating a mlp model
from keras.layers import Dense, Activation
model=Sequential()
model.add(Dense(1000, input_dim=25088, activation='relu',kernel_initializer='uniform'))
keras.layers.core.Dropout(0.3, noise_shape=None, seed=None)
model.add(Dense(500,input_dim=1000,activation='sigmoid'))
keras.layers.core.Dropout(0.4, noise_shape=None, seed=None)
model.add(Dense(150,input_dim=500,activation='sigmoid'))
keras.layers.core.Dropout(0.2, noise_shape=None, seed=None)
model.add(Dense(units=10))
model.add(Activation('softmax'))
model.compile(loss='categorical_crossentropy', optimizer="adam", metrics=['accuracy'])
# fitting the model
model.fit(X_train, Y_train, epochs=20, batch_size=128,validation_data=(X_valid,Y_valid))
2. Freeze the weights of first few layers – Here what we do is we freeze the weights of the first 8 layers of the vgg16 network, while we retrain the subsequent layers. This is because the first few layers capture universal features like curves and edges that are also relevant to our new problem. We want to keep those weights intact and we will get the network to focus on learning dataset-specific features in the subsequent layers.
Code for freezing the weights of first few layers.
from keras.utils.np_utils import to_categorical
from sklearn.preprocessing import LabelEncoder
from keras.models import Sequential
from keras.optimizers import SGD
from keras.layers import Input, Dense, Convolution2D, MaxPooling2D, AveragePooling2D, ZeroPadding2D, Dropout, Flatten, merge, Reshape, Activation
from sklearn.metrics import log_loss
train=pd.read_csv("R/Data/Train/train.csv")
test=pd.read_csv("R/Data/test.csv")
train_path="R/Data/Train/Images/train/"
test_path="R/Data/Train/Images/test/"
from scipy.misc import imresize
train_img=[]
for i in range(len(train)):
temp_img=image.load_img(train_path+train['filename'][i],target_size=(224,224))
temp_img=image.img_to_array(temp_img)
train_img.append(temp_img)
train_img=np.array(train_img)
train_img=preprocess_input(train_img)
test_img=[]
for i in range(len(test)):
temp_img=image.load_img(test_path+test['filename'][i],target_size=(224,224))
temp_img=image.img_to_array(temp_img)
test_img.append(temp_img)
test_img=np.array(test_img)
test_img=preprocess_input(test_img)
from keras.models import Model
def vgg16_model(img_rows, img_cols, channel=1, num_classes=None):
model = VGG16(weights='imagenet', include_top=True)
model.layers.pop()
model.outputs = [model.layers[-1].output]
model.layers[-1].outbound_nodes = []
x=Dense(num_classes, activation='softmax')(model.output)
model=Model(model.input,x)
#To set the first 8 layers to non-trainable (weights will not be updated)
for layer in model.layers[:8]:
layer.trainable = False
# Learning rate is changed to 0.001
sgd = SGD(lr=1e-3, decay=1e-6, momentum=0.9, nesterov=True)
model.compile(optimizer=sgd, loss='categorical_crossentropy', metrics=['accuracy'])
return model
train_y=np.asarray(train['label'])
le = LabelEncoder()
train_y = le.fit_transform(train_y)
train_y=to_categorical(train_y)
train_y=np.array(train_y)
from sklearn.model_selection import train_test_split
X_train, X_valid, Y_train, Y_valid=train_test_split(train_img,train_y,test_size=0.2, random_state=42)
# Example to fine-tune on 3000 samples from Cifar10
img_rows, img_cols = 224, 224 # Resolution of inputs
channel = 3
num_classes = 10
batch_size = 16
nb_epoch = 10
# Load our model
model = vgg16_model(img_rows, img_cols, channel, num_classes)
model.summary()
# Start Fine-tuning
model.fit(X_train, Y_train,batch_size=batch_size,epochs=nb_epoch,shuffle=True,verbose=1,validation_data=(X_valid, Y_valid))
# Make predictions
predictions_valid = model.predict(X_valid, batch_size=batch_size, verbose=1)
# Cross-entropy loss score
score = log_loss(Y_valid, predictions_valid)
Projects
Now, its time to take the plunge and actually play with some other real datasets. So are you ready to take on the challenge? Accelerate your deep learning journey with the following Practice Problems:
End Notes.You can also read this article on Analytics Vidhya's Android APP
26 Comments
Hey! You havent given folder structure and format in which training data is stored. People wishing to try out this example may not be having idea where to download training data from and where to place it. It would elucidate them if you update the same.
I have added the link for the download of MNIST data.
perfect
Same here, what does the CSV files contain? please explain why the train and test data was loaded twice esp. why it is required to load while freezing the weights?
appreciate your response..
So I have added the link of MNIST data. The csv file for train consists the name of images and the corresponding digits for them.
The test and train files have been loaded just because I wanted to keep the two codes exclusive.
Hi,
Your presentation is very nice. But my case is that I just begin to deal with image classification with CNN. I Know how to convert mnist data to csv file since it’s a 1-D image.
I really need help to know how to convert a 3-Dimensional images into csv file.
Thanks,
@b.diaby248 : Basically each colored image consist of 3 channels( red, green and blue). In case of grayscale image it consist of only one channel. We put values of all pixels per channel basis in single row of csv. For ex: if i have 28X28X3 image where 28 are height and width and 3 represents channels(rgb) then we would put (28X28) red, (28X28)green and (28X28) blue channel values along a single row of csv file for single image. Hope it helps.
Thanks for your sharing.
Quick question:
1. Can we substract the data from the mean of our data for each channel instead of from the mean of vgg16 data? What is the difference for this two preprocess?
2. What if I want to train by grayscale image?
Hi!
Should we apply the same preprocess function from the network we transfer on our data?
i.e. substract training data from the mean of our data or the mean of transfer network’s data?
Hi Kai,
So the preprocess function is subtracting the mean of your own dataset rather than the data of the pretrained.
It doesn’t mean much to actually subtract the mean of the network’s data since it might be very different than your own.
Dear Dishashree.
When trying to apply this to my own dataset, the program throws the error ValueError: cannot reshape array of size 5143040 into shape (49000,25088).
I guess this is because of the size difference in the datasets.
Can you explain what the numbers 49000 and 25088 mean?
Best regards
Hi Rico,
the numbers 49000 and 25088 are the dimensions of your data set. So you would have 49000 records with each record having 25088 features. You should check your reshaping function. Since the error lies there !
Hi, I would like to know what should I enter in (“R/Data/Train/train.csv”), [‘filename’] and [‘label’]?
And my image size is 850*600. Where should I mention the size and what other specifications should I consider to accord with my image size?
train=pd.read_csv(“R/Data/Train/train.csv”)
test=pd.read_csv(“R/Data/test.csv”)
train_path=”R/Data/Train/Images/train/”
test_path=”R/Data/Train/Images/test/”
temp_img=image.load_img(train_path+train[‘filename’][i],target_size=(224,224))
train_y=np.asarray(train[‘label’])
Hello,
Thank you for posting this. I have though some problems in implementing your algorithm:
1) what is train[‘filename’][i] ? where is defined in the code? I just downloaded the csv files from your ink. Did I missed something?
2) why target_size=(224,224) when the images are 28×28?
Could you help me with this?
Thank you!
awesome explanation
This is a very informative article. I also agree with your post title and your really well explain your point of view. I am very happy to see this post. Thanks for share with us. Keep it up and share the more most related post.
quiz online Programming test
Ma’am can you help me to solve the Identifying themes from mobile case images problem.
This problem has been assigned to me as project.
my [email protected]
Thank you for this amazing blog,
In the link of the MNSIT data. I did not find train.csv.
Could you provide us with some explanation for this?
Good stuff! Thanks.
Could you provide some paper references which speak about the relation between data size and data similarity?
I rarely leave any comment, but this post is fantastic! Exactly what I was looking for at least. Appreciated it!
Thanks for your sharing and it is very valuable
But
Please, Could you provide Matlab code ?
Or
abbreviate explanation for each step
Hey Dishashree,
Great analogy to explain transfer learning. Very well written article.
Thanks,
Tavish
Great article! Very well detailed.
If I may add something, I like to replace the last layers with a different classifier, like support vector machines for instance. I find it somehow more easy to implement and in my experience, it leads to better results. If you’re interested, I’ve written a post here on how to perform transfer learning using support vector classifiers to replace the last layers.
Thanks for sharing Pierre
Do you have code in GitHub?
Hi,
The code is added in the article itself. | https://www.analyticsvidhya.com/blog/2017/06/transfer-learning-the-art-of-fine-tuning-a-pre-trained-model/?utm_source=blog&utm_medium=innoplexus-sentiment-analysis-hackathon-top-3-out-of-the-box-winning-approaches | CC-MAIN-2019-39 | refinedweb | 4,086 | 56.76 |
I have setup a DFS system as follows.
Office 1 (10MB Leased Line) SBS 2003 Server - Runs the network Windows 2008 Standard Server - Member Server + DFS Services (Namespace server)
Office 2 (4 x Bonded Broadband Lines) Windows 2008 Standard Server - BDC + DFS Services (Namespace server)
If i log on to any server and browse the DFS shared folder I can create a file and watch it replicate almost immediately across to the other office DFS share. Accessing the shares is pretty instant even across the broadband links.
On the network PC's at office 1, they are connected to the LAN at 100mb and have created shortcuts to the shared area on their desktop. When they try and browse the shares their response is incredibly slow, 2 mins for a folder list of shares etc.
They can browse \servername quickly and view shares quickly but when accessing the shared namespace url and the shared folders it is very slow for some reason. Any ideas why this is?
The clients can still access the SBS2003 server shares instantly without an issue. The load (cpu/disk/network counters in resource manager) seems fine on both DFS servers too.
Also if anyone knows any tools for DFS to see live what is being replicated/queued up that would be great to use to see if the broadband links are causing a large bottleneck.
Thanks | https://serverfault.com/questions/48494/distributed-file-system-2008-speed-issue | CC-MAIN-2022-27 | refinedweb | 231 | 65.35 |
With our latest Unity Core Assets release , we’re excited to unveil full support for the Unity 5.4 beta, which features native support for the HTC Vive. This is the fourth release since the previous installment in this series , when we shared some background on the ground-up re-architecting of our hand data pipeline. Today we’re going to look under the surface and into the future.
As our Orion beta tracking evolves, we’ve continued behind the scenes to hammer on every aspect of our client-side data handling for performance and efficiency. We’re also actively refining developer-side workflows and expanding the features of our toolset for building hand-enabled VR experiences. And in some cases, we’re adding features to the Core Assets to support upcoming Unity Modules.
For this release, we focused on our HandPool class. This Unity MonoBehavior component not only manages the collection of hand models for the rest of the system, it defines much of the workflow for the way you add hands to your scene. This release brings some refinements but also a significant new feature – the ability to have multiple pairs of hand models and to easily enable or disable those pairs at runtime.
While working on demonstration projects here at Leap Motion, we’ve found ourselves wanting to use different sets of hands for a variety of reasons. For complex graphical representations, it might be helpful to have hand models that only provide shadows, or only provide glows in addition to the main hands. A superhero game could benefit from the flexibility of completely different iHandModel implementations for fire hands versus ice hands. And some experiences might benefit from different hands for different UI situations.
The HandPool component, located on the same GameObject as the LeapHandController and LeapServiceProvider components, now has an exposed Size value for our ModelPool’s list of ModelGroups. Setting this value allows you to define how many pairs of hands you’d like in your scene. If you change this number from 2 to 3, slots for another pair of models will appear. You can assign a name for your new model pair so you can refer to it at runtime.
As in previous versions of Core Assets, you can drag iHandModel prefabs from the Project window to be children of the LeapHandController GameObject in the Hierarchy window. When you do this, the iHandModel component in the model prefab receives a default Leap hand pose. Since all Leap hand models inherit from the iHandModel, class this means that each pair of hands will align with the others.
You can test this by adding two DebugHand prefabs to your LeapHandController. In the Inspector for each DebugHand, you can set the Handedness to Left and Right. Then drag these children into their new slots. For the iHandModels to align, just be sure that the local translations and rotations of your iHandModel’s transform are zeroed out.
We’ve also improved the DebugHand script to show the rotation basis for each Leap Bone. These are immediately visible in the Scene window, but there’s a trick that allows you to view them in the game window as well. If the Gizmos button at the top right of the Game window is enabled and you select the LeapHandController in the Hierarchy window, you can view collider-based physics hands as well as the new Debug hands.
Using the Debug hands in this way can be help for – wait for it – debugging your other hands to verify they’re lining up with Leap Motion data! We hope this will be a helpful workflow when you’re building your own iHandModel implementations.
The new multiple hands feature becomes even more powerful with the added ability to enable and disable pairs at runtime.In the Inspector, you can set the IsEnabled boolean value for each model pair. This will control whether those models are used when you Start your scene. But more importantly, you can enable and disable these pairs at runtime with HandPool’s EnableGroup() and DisableGroup() methods.
Here’s a simple script you can attach to the LeapHandController. It will allow you to use the keyboard to enable and disable groups:
using UnityEngine; using System.Collections; using Leap.Unity; public class ToggleModelGroups : MonoBehaviour { private HandPool handPool; void Start() { handPool = GetComponent<HandPool>(); } void Update () { if (Input.GetKeyDown(KeyCode.U)) { handPool.DisableGroup("Graphics_Hands"); } if (Input.GetKeyDown(KeyCode.I)) { handPool.EnableGroup("Graphics_Hands"); } } }
Refactoring the HandPool class to support these new features while maintaining and improving encapsulation required some scrutiny and iteration. This work also allowed us to simplify the developer-facing UI we exposed in the Inspector. Where previous versions had the notion of a ModelCollection which populated our ModelPool at runtime, the new workflow is to add iHandModels directly to the HandPool simplifying the code and UI simultaneously.
To watch the ModelPool system at work and get a solid understanding of the system (like we did in theprevious blog post), you can comment out the [ HideInInspector ] tag above the modeList variable on line 39 of HandPool.cs. Each pair of iHandModels is part of a ModelGroup class. Its modeList gets populated at runtime. When a new Leap Hand starts tracking, an iHandModel is removed from the modelList and returned to the modelList – and therefore the ModelPool – when that Leap Hand stops tracking.
Each model pair has a CanDuplicate boolean value that works in tandem with iHandModel’s public Handedness enum. When CanDuplicate is set to True, this provides some flexibility to the Leap Motion tracking by allowing more than one copy of a Right or Left iHandModel. This can allow hands to initialize slightly faster in some cases, but also lets you create scenes where you’d like other users to put their hands in as well. Setting this to False allows you to ensure that only one Right and Left hand will be used at any time, which is useful if you’re going to drive the hands of a character or avatar.
Finally, our further refactoring has allowed us to relax the requirement that HandPool receive only instances from the scene Hierarchy. Prefabs can once again be dragged directly from the Project window directly into HandPool’s iHandModel slots. While this removes our ability to visualize the hand in the Scene view during edit time, we’re striving to allow the most flexibility for all sorts of workflows.
These new features are already allowing us to experiment with and demonstrate new use cases. But more importantly, they’re immediately providing the basis for new Unity Modules currently under construction. These will unlock new features and workflows like hand models, the ability to create your own hand models, user interface assets to streamline the creation of wearable menus in VR, and more.
Barrett Fox / An interaction engineer at Leap Motion, Barrett has been working at the intersection of game design, information visualization and animation craft for 20 years as a producer, game designer, and animator.
评论 抢沙发 | http://www.shellsec.com/news/17384.html | CC-MAIN-2017-04 | refinedweb | 1,168 | 51.48 |
Created on 2019-01-10 17:11 by remi.lapeyre, last changed 2019-01-17 13:37 by theophile.
When creating a class, I sometimes wish to get this behavior:
def MyClass:
def __init__(self, param):
self._param = param
def __repr__(self):
return f"MyClass(param={self._param})"
Unless I'm making a mistaking, this behavior is not currently possible with dataclasses.
I propose to change:
field(*, default=MISSING, default_factory=MISSING, repr=True, hash=None, init=True, compare=True, metadata=None)
to:
field(*, default=MISSING, default_factory=MISSING, repr=True, hash=None, init=True, compare=True, metadata=None, target=None)
with target being used as the init parameter name for this field and in the repr.
If this is accepted, I can post the patch to make this change.
"target" seems too general for the OP's use case. "private=False" would be more focused. General renaming occasionally has uses but is mostly an anti-pattern.
Some thought also needs to be given to downstream effects of renaming (what shows up in help(), impact of renaming on type annotations, introspection challenges, what asdict() should do, whether the overall implementation would be made more complex, is the attribute now out of reach for __post_init__(), is this even within the scope of what dataclasses set out to do, etc). | https://bugs.python.org/issue35710 | CC-MAIN-2019-26 | refinedweb | 216 | 54.63 |
Details
- Type:
New Feature
- Status: Resolved
- Priority:
Major
- Resolution: Duplicate
- Affects Version/s: None
- Fix Version/s: None
- Component/s: None
- Labels:None
Description
Issue Links
- is blocked by
HADOOP-6149 FileStatus can support a fileid per path
- Resolved
- is duplicated by
-
- is related to
-
Activity
as far as i know, nobody is working on this one
Is fileid in the foreseeable future?
Hi Dhruba, this will take some time as up to now my interaction with hdfs was based on javadoc only. I will check what can I do.
Hi Tigran, thanks for doing this. As you rightly pointed out, hdfs will need to support a persistent fileid for a file. If you are interested in implementing this, you could follow the steps outlined in. For a big feature like this, a good way to start is with a requirements and design document.
I have implemented nfsv4.1/pNFS server and interfaced it with hdfs. The missing path to get it production ready is a unique
file id and a way to access a file with it as nfs IO operations done with filehandles. Currently I maintain a path to it mapping,
but this is not en elegant solution and does not survives restarts. A native hadoop way of doing that is required.
Hi folks, now that
HDFS-385 has been committed I would like to resurrect the discussion about fileids for HDFS files.
The negative feedback earlier was from Raghu who mentioned that it may be premature to introduce the concept of a fileid. In some sense, this is true but is more of a chicken-and-egg problem. The existence of a fileid simplifies many-a-applications. Can we have some discussion on what the possible dis-advantages of introducing a fileid might be?
Thanks Dhruba. It looks like the specifics of why a fileid is required (or if it even helps) depend on future features. I think it is better to wait.
I think should really have strong requirements before adding such important features or contracts in HDFS. Once it is provided it will stay for a long time.. even if there is limited use.
The API for pluggable block placement (
HDFS-385) provides the pathname of the file to the block placement policy. The block placement policy can use the filename to determine what kind of placement algorithm to use for blocks in that file. This works well in the current NN design. However, if in future, we separate out the Block Manager from the NN, the Block Manager might not know the pathname for which the block belongs to. In that case, the Block manager will not be able to provide the filename when invoking the pluggable-block-placement-policy API. So, in some sense, using a fileid (instead of a filename) is future-proofing the API.
Again to emphasize,
HDFS-385 does not really need fileids, although it is good to have. The API designed in HDFS-385 shoudl be marked as "experimental", and we can change it if/when the Block Manager is separated out from the NN. Which option do you prefer?
Dhruba, can you describe how fileid helps with pluggable block placement. Many use cases are mentioned here but I can't find description of how.
'distcp -update' is not expected to be fool-proof (just like rsync). Even with fileid, should distcp store fileids in previous update (or source and destination files are expected to have same fileid?)?
> So truncating a file would change the fileid?
Truncating a file does not change the fileid. There isn't an operation that can change the fileid of an existing file. The filid is associated with a file at file creation time. If you delete a file and then recreate a file with the same pathname, the new file will get a new fileid. The reason I mention truncate is to exemplify the fact that the heuristic used in "distcp -update" option might not work very well when hdfs supports truncates. "distcp -update" could use the fileid to reduce the probability of not detecting modified files.
> I am still not clear about block placement use case.. may be it can use id of the first block (it comes for free).
A blockid of a block is a concatenation of a 64 bit blockid and a 64 bit generation stamp. An error while writing to a block causes the generation stamp of that block to be modified. So, the blockid of the first block of a file does not remain fixed for the lifetime of that file. That means, it cannot be used as an unique identifier for a file.
> (3) separation of block management.
UUIDs probably make it somewhat futureproof, but we can also upgrade the unique-within-filesystem-fileid to a globally-unique-fileid when the use case arises. Such an upgrade will be easy to do. (The tradeoff is using more memory in the NN)
UUID is not a requirement based on the usage cases everybody presented here. But it would probably make the system a bit more future proof. The few cases I can think of (not necessarily independent) are (1) cross co-lo synchronization; (2) federated hdfs systems; (3) separation of block management.
So truncating a file would change the fileid?
btw, 'distcp -update' is expected guarantee just that 'copy-if-modified' and nothing else.. just like any rsync or other sync that rely modification files and file lengths (by default). If user wants to handle other cases, then they should ask distcp to check file checksums.
I am still not clear about block placement use case.. may be it can use id of the first block (it comes for free).
Even for hardlinks I don't see how fileids help...
I am of the opinion that it would be sufficient to go with a 64 bit fileid that is unique to the namespace.
Another use case: "distcp -update" looks at modification time and length of a file to determine whether it should be copied or not. This is not ideal, especially if somebody deletes and recreates a file with different contents within the time-precision of the clock used by HDFS. Also, it will not work when HDFS supports "truncates". (The modtime of a file can be set by an application). Having a unique fileid makes distcp work accurately.
Are you proposing a UID so that fileIds can be global across NN volumes?
Isn't an ID unique to the NN volume sufficient for our needs?
It would be useful to articulate the various use cases for the file id plus the mapping data structures that would be needed.
Dhruba has given one use case.
Another one is that if we propagate the fileId to the DNs than one can reconstruct files from blocks (though without their file names.)
Hard links is another use case though I am not a fan of hard links.
Others?
Would fileIds simplify things inside the NN?
Mappings:
Currently, inside a NN we have mappings from filename->inode,, inode->blocks.
To make the file id useful we would have to add a mapping from fileId->inode. This mapping would use up memory which is scarce inside a NN, but perhaps it could replace
other data structures.
Wouldn't one need the fileId to inode->blocks for puggable block placement policies?
> Given that there is mapping [...]
should be 'there is NO mapping [...]'
> ... path is needed ...
Oops, should be "path is not needed".
Given that there is mapping from id to the file, I am not sure if it really works like an id. Can you explain the use case bit more? (I haven't read the patch for pluggable block placement)
When I first read the title of the jira, thought this might be about file handles...
> ... What are the parameters for calculating a UUID?
I mean what parameters should we choose. Obviously, path is needed. Anything else?
> ... This has some impact on the amount of memory needed by the NN. ...
Ideally, if we can compute the UUID in runtime, no additional memory is needed.
Using a globally unique UUID means that it has to be at least 128 bits whereas a id that is unique within a cluster needs 64 bits. This has some impact on the amount of memory needed by the NN. What do other people think about sing 64 bit ids vs 128 bit ids?
> can be calculated independently by any process.
This may not be trivial. What are the parameters for calculating a UUID?
This patch implements a 64 bit fileid per file. It uses the already existing generation stamp counter to populate this field.
One major question that is unanswered by this patch: what to do with files that were created by older versions of hadoop. I think a good answer will be assign them unique fileids.
A few preliminary requirements as I see it:
1. The fileid should be unique per path for the lifetime of a filesystem.
2. FileStatus should contain the fileid, typical aplications like "hadoop dfs -ls" and "fsck" should be able to display the fileid
3. There is no need for an API to map a fileid to a pathname.
4. Regular files as well as directories have valid fileids.
This requirement has been addressed by
HDFS-4489. | https://issues.apache.org/jira/browse/HDFS-487?focusedCommentId=12731670&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel | CC-MAIN-2015-18 | refinedweb | 1,556 | 73.88 |
Hello, I met a problem that I could not solve, he reported this error, I did not touch the bottom things, and I changed the code back to the successfully compiled before, and clean build will still have this error
In file included from lib/lvgl/src/lv_core/lv_obj.h:1216:0, from lib/lvgl/lvgl.h:33, from src/lv_cubic_gui.h:12, from src/lv_cubic_gui.c:4: lib/lvgl/src/lv_core/lv_obj_style_dec.h: In function 'lv_obj_get_style_size': lib/lvgl/src/lv_core/lv_obj_style_dec.h:64:71: error: 'LV_STYLE_4' undeclared (first use in this function) return (value_type) _lv_obj_get_style##style_type (obj, part, LV_STYLE_##prop_name); \ | https://forum.lvgl.io/t/error-lv-style-4-undeclared-first-use-in-this-function/7179 | CC-MAIN-2021-49 | refinedweb | 101 | 51.14 |
Write a program that generates a diamond pattern of stars. The user is prompted for the number of stars for the largest row in the pattern and the program must call a recursive function to generate it.
I can get half of to produce but not in the shape of a diamond. Any pointers on how to make it appear as a diamond would be great.
Here is my code thus far:
#include <iostream> #include <string> using namespace std; void printStars(int count, int num); int main() { cout << "Enter the number for the largest line to print: "; int x; cin >> x; int ind = 1; printStars(ind, x); system("PAUSE"); return 0; } void printStars(int count, int num) { for (int i = 0; i < count; i++) cout << "*"; cout << endl; if (count < num) printStars(count + 1, num); for (int i = 0; i < count; i++) cout << "*"; cout << endl; } //Output should look similiar depending on the number for the largest row // * // * * // * * * // * * * * // * * * // * * // * | http://www.dreamincode.net/forums/topic/57573-print-a-diamond-pattern-using-recursion/ | CC-MAIN-2017-09 | refinedweb | 156 | 66.2 |
Because of JAX-RPC's limited support for certain XML schema constructs, it's not unusual for a JAX-RPC-based WSDL-to-Java generation tool to leave you with a set of Java beans that don't really behave like you were expecting. This is most commonly evidenced by getting a javax.xml.soap.SOAPElement when you expected to have a constructed Java type representing your schema type. Creating and populating these SOAPElements directly instead of populating normal Java beans can become a little unwieldy and can quickly clutter an application.
Alternately, you may already be using a particular XML binding technology in your application, which you now want to expose as a Web service. In this case, you probably don't want to rewrite the application to handle the overlap between your existing beans and the new ones JAX-RPC may require.
Using examples, we'll show you how WebSphere's new Custom Data Binding feature works, and how it can help address these scenarios by allowing you to use your own mapping technology for your Web services data. This feature was first introduced in WebSphere Application Server Base and Network Deployment Version 6.
Serialization and deserialization in WebSphere
Before we dive down into the specifics of Custom Data Binding, an understanding of the current serialization and deserialization environment in WebSphere will help you understand how it can be extended for custom serialization.
Type mapping vs. element mapping
The current Web services runtime (introduced in WebSphere V5.0.2) supports the JAX-RPC programming model, which is based on the notion of a type-mapping registry. That is, each type that exists in the WSDL or XSD file will have a special serializer or deserializer created for it that knows how to handle those types. This notion of type-mapping is a key point to remember when developing your Custom Data Binding application. This is different from an element-centric mapping, in which the Java types are generated based on a particular root element definition within the WSDL. In a type-centric mapping, the user view of the data is based on the types that exist within the XSD associated with the particular WSDL.
Let's look at an example. Listing 1 shows an XSD snippet pulled from a associated WSDL file, with two elements that correspond to the input and output of an operation. The request takes an input object of type OpType, while the response returns a simple String. JAX-RPC would map the complex type OpType to a Java object called OpType that contains two attributes, c1 and c2, each of type String..
Listing 1. Sample XSD from WSDL
An example of this class is shown seen in Listing 2. If these elements were more complex types, further nesting would be created
Listing 2. Java bean mapping for sample XSD.
Another common example uses the notion of a wrapped operation, which has become widely accepted within the industry despite the fact that there is no formal definition for the pattern. This pattern defines an element/complexType mapping whose element name is the same as the operation name. The child elements in the complex type represent the parameters of the operation.
Looking at a snippet of the sample WSDL file in Listing 3, you'll see that there are two elements defined, followed by two parts pointing to those elements. The first element is an operation wrapper, which takes two arguments (one of type xsd:int and one of type xsd:string). The second is a response element, which holds one element (of type xsd:string).
These elements are defined as the input and output parts of the WSDL message (operation1Request and operation1Response).
Listing 3. Sample wrapped WSDL snippet
In JAX-RPC, these parameters are deserialized into normal Java objects and primitive data types. Using the WSDL2Java tool provided by WebSphere, the generated JAX-RPC service interface for this WSDL would look like the one shown below in Listing 4. Note that, in this example, the runtime has unwrapped the operational wrapper to give it a more RPC-like flavor.
Listing 4. Sample JAX-RPC Service Endpoint Interface
Using the -noWrappedOperations flag on the WSDL2Java tool, the WSDL would not be treated as having a wrapped operation, and the contents of the element will not be unwrapped before returning them to the bean. In this scenario, beans would have been generated for all of the complex types, and instead of accepting the two individual params (int and String), the interface will have to accept the entire operation wrapper element. When the Service Endpoint Interface (SEI) is generated from the portType, it will look like the one in Listing 5. This example becomes key when dealing with trying to map full XML documents, which we'll get to later).
Listing 5. Sample JAX-RPC Service Endpoint Interface
Making Your Service Generic
Now that you have a high-level understanding of how types are mapped and serialized within WebSphere, let's take a look at what you need to do to your Web service to make use of Custom Data Binding. This section discusses how the data model (your custom Java beans) for a particular Web service can be separated from the invocation model (the interfaces that you're invoking against).
To be able to achieve our goal of plugging in alternate mapping technologies, we first need the ability to work with the data model separate from the invocation model. We need the parameter(s) to the Web service to be in a more generic form, so that we can easily go to and from the generic representation to the custom objects. To do this, we'll use the -noDataBinding option on WebSphere's WSDL2Java tool.
When the -noDataBinding flag is specified, WSDL2Java refrains from binding any of the schema artifacts to their normal Java bean representation. Instead, everything is mapped to an SAAJ SOAPElement. The SOAPElement API is used in JAX-RPC as a generic form to encapsulate the schema types and nuances that it does not have a mapping for (for example xsd:choice).
If you take a look at Listing 6, you'll see the generated JAX-RPC interface for this scenario. This interface is based on the sample WSDL in Listing 3. As mentioned, all of the input and output types are mapped to SOAPElement trees containing the XML text.
Listing 6. Sample JAX-RPC interface with no data binding
It's important to remember that this is a WebSphere-specific feature, and as such, there is not a specification or standard that defines what the WSDL-to-Java mapping would be for this No Data Binding format. However, the pattern used by the tool is that the signature for methods generated in the JAX-RPC interface contains a SOAPElement for each part within the WSDL. In other words, the number of input parameters on the method corresponds to the number of <wsdl:part/>s within <wsdl:message>. Looking back at our WSDL defined in Listing 3, you'll see that there is a single part parameters for the message operation1Request that represents the request. Thus, we see only one SOAPElement representing the entire request payload.
If you're using the Rational® Application Developer tool to develop your Web services applications, the option for disabling data binding on the generated interfaces can be a little tricky to find. To find it, select Preferences => Web Services => Code Generation => IBM WebSphere Runtime, then select Disable data binding and use SOAPElement.
Figure 1. Disable data binding in Rational Application Developer
While it's possible to implement a Web service that uses the No Data Binding pattern with only the offical SAAJ 1.2 SOAPElement APIs, IBM has introduced some additional methods on their SOAPElement implementation in order to support these extensions. These are defined in a public, IBM-specific SOAPElement interface in com.ibm.websphere.webservices.soap.IBMSOAPElement.
Specifically, there are two methods on this interface that are useful when writing a no data binding application: toXMLString(boolean) and toInputSource(boolean).
- toXMLString(boolean) allows you to get the contents of the SOAPElement as an XML string. The string returned is be the exact contents of the current SOAPElement and its descendants. This string can then be parsed in whatever manner you choose and deserialized into your chosen object form. In some cases, the contents of the SOAP Body may rely on namespace declarations that occur at a higher level in the SOAP Envelope. In these cases, if the boolean parameter is set to true, the returned string will include the SOAPElement data along with all namespace declarations from ancestor elements.
- toInputSource(boolean) allows you to get the contents of the SOAPElement as an InputSource. This InputSource can be fed into other runtimes or parsers in order to deserialize the data into other object types. As with the toXMLString, the boolean parameter determines whether all namespace declarations from the ancestors are included.
Listing 7. The IBMSOAPElement interface
The API described in Listing 7 is useful only when you have an existing SOAPElement and need to get the data out in an easy manner. That means that you would only use the APIs when a SOAPElement comes into your system (an inbound request to a server or an inbound response to a client). However, there are also APIs that have been created to assist with creating new SOAPElements. You can use these in an outbound scenario in which you have an object containing some form of XML data and would like to create a SOAPElement out of it. IBM has provided an optimized solution for this scenario through the com.ibm.websphere.webservices.soap.IBMSOAPElementFactory. This interface allows for the creation of SOAPElements from both an InputSource and an XML String.
Listing 8. The IBMSOAPElementFactory interface
Invariably, the question comes up: why did IBM create these APIs and why should I use them? These APIs are provided as tools to make working with SOAPElements easier, but are by no means required to implement what is needed for this scenario. Using them does simplify the code a bit for the cases where you'll need to handle the SOAPElements themselves instead of working with your data objects.
How custom data binding works
Now that you've been introduced to the enhanced SOAPElement support and understand the concept of No Data Binding, you have all the tools needed to leverage the new Custom Serialization feature within WebSphere.
What is custom data binding?
Looking at JAX-RPC, you'lll see that the WSDL/XML Schema to Java mappings are somewhat limited. For some of the more complicated schema concepts, JAX-RPC choses to map these (for example, xsd:anyAttribute, xsd:choice, and so on) to a SOAPElement. If we look forward to JAX-WS 2.0, the next evolution of the J2EE Web services programming model, you'll note that instead of defining its own mappings, it chooses to use the JAX-B 2.0 specification for its data binding. JAX-B is a more complete mapping of XML schema than JAX-RPC provides, but they are distinct. Unfortunately, it was not possible for JAX-RPC to use JAX-B 2.0 as it's data binding mechanism since the specification was not yet complete. In many cases though, you'll want to map your Web services data using JAX-B or another binding technology that makes more sense to your and your application. Or, perhaps you've already got a set of Java beans that you're using and you'd like to maintain that mapping over a different one chosen by JAX-RPC.
Using some of the concepts and features introduced above, it's possible to handle this by working with the raw SOAPElements as the input and output parameters and doing the conversions yourself. However, this means that the SOAPElement will now appear in your Service Endpoint Interface (or as properties inside of an object) and anyone that you provide that to will have to understand how to deal with SOAPElement as well. Custom Data Binding allows you to hide this logic below the interface level and present a more application-centric API.
Specifically, WebSphere allows this by introducing a Custom Binder interface, which allows a mapping from an XML schema type to a Java type (and vice versa). A Custom Binder has methods that are capable of handling specific XML schema types, turning them into designated Java objects. Conversely, the Custom Binder also handles serializing your custom Java object into its correct XML representation.
Let's say, for example, that you've generated your SEI from the WSDL in Listing 9 that contains an xsd:choice in one of the complex types. For the purposes of this example, we'll call the interface InventorySearch. Without the use of a Custom Binder, the generated interface would look like the one in Listing 10, with a SOAPElement as the return type. However, if we have a Custom Binder in place for the schema type in question, the generated interface would look more like what you expect (as shown in Listing 11), and would expose the appropriate data types as the input and response type.
Listing 9. A sample WSDL with an unmappable complex type
Listings 10 and 11 shows a Service Endpoit Interface without and with custom data binding.
Listing 10. A Service Endpoint Interface without custom data binding
Listing 11. A Service Endpoint Interface with custom data binding
Where to use custom binders
The WebSphere runtime and tooling uses of the custom binders at development time as well as runtime. At development time, it searches for available custom binders, and queries each of them to find the schema type and Java type they support. This information is used to update the type mapping registries, and when it is time to produce interfaces or stubs, will generate code that uses the correctly mapped types instead of a SOAPElement or some other type.
Similarly, the runtime locates the custom binders and uses whatever binders it needs to perform its function. It tries to find all instances of /META-INF/services/CustomBindingProvider.xml and uses that information to set up its type mapping registries and to get each of the custom binders ready to serialize and deserialize.
In the WebSphere runtime, it searches the classpath for the available custom binders. You can define your custom binders at varying levels of the classpath depending on the level of granularity you want. For instance, if you bundle your custom binder within your EJB jar or web application war file, the custom binder will be available only to that particular module. Or, you can make it more widely available by creating a shared library so that any module using that shared library can see it. Also, you can make it visible to all of WebSphere by placing it in the lib directory of your WebSphere installation.
Creating a custom binder and custom binding artifacts
A custom binder consists of two artifacts that you'll need to create. The first is an XML file, CustomBindingProvider.xml, that declares all the necessary information for the tooling and runtime to locate the binder. The second is an implementation of the binder class that is specified in the CustomBindingProvider.xml. This class handles the serialization and deserialization of objects by implementing a specific interface. We'll discuss the custom binder class at greater length later in this article.
Below you'll find a list of the different elements that are required in an instance of the CustomBindingProvider.xml. Each of these is required to be populated in your file, and must have a value in order for the custom binder to work correctly.
xmlQName: The XML named type that you are mapping from
javaName:The Java class name that you are mapping to
qnameScope: The scope of the type
binder: The Java class name of the custom binder to be used when this type is encountered
Once created, the CustomBindingProvider.xml is normally packaged along with the binder class(es) in the same jar file, and must be saved under the path /META-INF/services/CustomBindingProvider.xml. Listing 12 is an example instance of a CustomBindingProvider.xml based on the InventorySearch example we started above.
Listing 12. A sample CustomBindingProvider.xml file
In the example above, you can see that we've specified a custom binder that maps the mycorp:IventoryItem complex type that was defined in the schema and maps that on to the com.mycorp.InventoryItem Java type.
The custom binder class specified in the <binder/> element is a Java class that implements the interface com.ibm.wsspi.webservices.binding.CustomBinder required for custom binding. These methods provide information to the runtime as to what QNames and/or what Java types they map to, along w/the serialization and deserialization methods. The two methods are: serialize(Object, SOAPElement, CustomBindingContext) and deserialize(SOAPElement, CustomBindingContext). Once the custom binder is recognized by the runtime, it communicates with the runtime via the SOAPElement in the following ways:
- For serialization, the binder's serialize method is invoked by the runtime and it receives a Java object and a SOAPElement. The Java object is the data to be serialized, and SOAPElement is the context element for the serialization. This SOAPElement represents the place in the SOAP Envelope where your data will go so that all you have to do is populate it.
- Unlike the conventional serializer which writes out the raw data, the custom binder produces an intermediate form of SOAP message as a SOAPElement. The runtime takes care of writing the SOAPElement to the raw data. Obviously, it's easier to create the SOAPElement rather than the raw text because SAAJ APIs are available to help. Once the SOAPElement has been populated with the necessary data, it must be returned to the caller.
- Similarly during deserialization, the runtime builds an appropriate javax.xml.soap.SOAPElement instance and passes it to the binder, which then deserializes it to a Java object. It's the responsibility of the custom binder to build and populate the correct Java object instance based on the SOAPElement that was passed in.
Listing 13 shows the CustomBinder interface.
Listing 13. The CustomBinder interface
Listing 14 contains a skeleton of what a custom binder class would look like for our InventorySearch example.
Listing 14. A sample CustomBinder skeleton implementation
As of now, there are no tools for creating the CustomBindingProvider.xml or the custom binder class automatically, so you'll need to create these by hand. Using the examples above, you should be able to put together both of these artifacts using Rational Application Developer or a text editor.
Once you've created these two items, the next step is to package them up in a custom binder jar file so that you can use it to develop and deploy your Web services application. The best thing to do is to create a new jar file (either manually or using Rational Application Developer) and include in it the binder class, along with the CustomBindingProvider.xml. Remember, the XML file must be saved under the path /META-INF/services/CustomBindingProvider.xml.
With the custom binder now assembled, you're ready to develop the rest of your application. If you're using the WebSphere Web services command line tools (Java2WSDL and WSDL2Java) to develop your application, run the following command:
As you can see, the only change you need to make to your normal WSDL2Java usage is to include the path to the binder jar you created. By doing this, the WSDL2Java tool searches the classpath for all available instances of the CustomBindingProvider.xml and configures itself appropriately. The classes and deployment descriptors that are generated should reflect this and should now contain your specific data type in place of the SOAPElements that they had before.
If you're using Rational Application Developer, all you need to do is ensure that the custom binder jar is added as an external jar file. Rational Application Developer addds all of these jar files to the classpath prior to invoking the WSDL2Java and Java2WSDL tools.
Figure 2. Include a Custom Binding jar in Rational Application Developer
Using the information outlined above, you should now be able to create WebSphere-based Web service applications that can map some of the more complex schema types not covered by JAX-RPC. The interfaces created now should look more like what is expected by someone trying to use your application and no longer require users to have an in-depth understanding of SAAJ and the expected SOAPElement structure.
As mentioned earlier, the purpose of this article was mostly to provide an overview of Custom Data Binding and how it can benefit your application. The next article in this series will provide an in-depth look at a Custom Binder class that we'll use to serialize and deserialize data types based on a user-defined type mapping (in other words, not using a specific data binding technology). We'll also discuss a few useful tips to keep in mind when developing your specific Custom Binders.
In future parts of this series, we'll discuss specific examples of how to integrate different data binding technologies, including JAX-B 2.0, EMF/SDO and XML Beans.
Information about download methods
Learn
- Which style of WSDL should I use? (developerWorks, 2005) outlines the four patterns a WSDL file can conform to and the benefits of each.
- Use the XML Schema Primer to get more familiar with some of the aspects of XML schema.
- Here's another article that describes how to use the SAAJ API.
- Read the Java API for XML-Based RPC (JAX-RPC) specification for more information about the limitations of the type mappings.
- Find out more about the SAAJ specification and SOAPElement.
- Visit the developerWorks Web Services zone to expand your Web Services and SOA skills.
- Visit the developerWorks WebSphere Web services zone to learn more about WebSphere and Web services.
- Discover many other useful and interesting articles and tutorials in WebSphere's Technical Library.
Get products and technologies
- Build your next development project with IBM trial software, available for download from developerWorks.
Discuss
- Participate in developerWorks blogs and get involved in the developerWorks community.
Nick Gallardo works as a software engineer on the IBM WebSphere platform, focusing on various aspects of the Web services support. His previous work in IBM includes other assignments within the WebSphere and Tivoli platforms. Nick came to IBM in 2001 after working in development in two different technology start-ups in Austin, Texas.
Greg Truty is an IBM WebSphere Application Server Web services architect. He has been doing distributed computing for over 10 years, and has been involved in Web services for over 5 years. He has participated in implementing the Web services for J2EE (JSR 109) and JAX-RPC (JSR 101) specifications for WebSphere. He was involved in pushing JAX-RPC 1.0 out to Apache Axis. You can contact Greg at gtruty@us.ibm.com. | http://www.ibm.com/developerworks/websphere/library/techarticles/0601_gallardo/0601_gallardo.html | crawl-003 | refinedweb | 3,845 | 50.97 |
Previous Articles:
You may be wondering why we even need to add longer sound files to the game. As I mentioned in article 8, most games include fully featured soundtracks in addition to the regular game sounds. These sound tracks are often produced specifically for the game much like a movie soundtrack is produced for a movie. A well made sound track can add additional drama to the game and provide a memorable experience. Sometimes these game tracks are also available as separate music CDs or downloads to bring more players to the game. There is really no way that anyone is going to be able to produce a nice sounding soundtrack as a WAV file. Most music uses the MP3 codec or can be converted to this codec.
Using the DirectSound namespace we were only able to play WAV files. Longer music is normally encoded in more efficient formats such as MP3 or WMA. To play these files we have to access the API in the AudioVideoPlayback namespace. This namespace is the smallest of the namespaces and contains a single class called Audio for playing audio files. (It also contains a Video class which I will not cover)
Using the Audio class to play an audio file is very easy.
1. Create a new Audio class and pass the path to the Audio file to the constructor.
Audio audio = new Audio("AudioFileName"););
if ( _isRepeat )
Stop ( );
Play ( );
NextSong ( );
public void NextSong ( )
_songCounter++;
if ( _songCounter == _songList.Length )
_songCounter = 0;
if ( _audio.Playing == true )
_audio.Stop ( );
_audio.Open ( _songList[ _songCounter ].ToString ( ) );
_audio.Play ( );
The only remaining method we now need is to stop the player
public void Stop ( )
if ( _audio != null )
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COMMENTARY
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ARCHIVES
The government has further liberalised the
import policy for gold and silver.
This has been done to provide a fillip to the export of gold and
jewellery, bring into legal channels the possible illegal financing
of gold and silver, and a step to move towards capital account
convertibility.
Under the new scheme, the import of gold and silver will be done
through three channelising agencies -- STC, MMTC and HHEC -- and the
eight banks already authorised by the Reserve Bank of India. These banks are the State Bank of India, Bank
of India, Canara Bank, Indian Overseas Bank, Allahabad Bank, Bank of
Nova Scotia, Standard Chartered Bank and ABN-Amro Bank.
Up to now, imports by these eleven agencies are only for exports. With the
liberalisation, these agencies will now supply gold and silver for
general sales in the domestic market as well.
The RBI may nominate other agencies to undertake such imports.
The rate of import duty under the new scheme will be Rs 220 per
10 gm for gold and Rs 500 per kg for silver. The duty will be
payable in terms of rupees. There will not be any value addition
norms for exports of gold and silver jewellery that is linked to
imports of gold and silver through the new scheme.
However, value
addition norms will continue to apply where exporters access gold
and silver through the existing zero-duty facilities.
Payment of duty under the special import licences is
presently required to be made from the exchange earners' foreign
currency accounts. This requirement is being abolished and
payments will now be accepted in rupees.
It may be recalled that the three windows were already available
for the legal imports of gold and silver. These are imports by non-resident Indians,
imports against special import licences, imports by nominated agencies and banks
authorised by RBI only for zero-duty sales to jewellery exporters,
NRIs and the special import licence holders.
UNI | http://inhome.rediff.com/money/oct/16gold.htm | crawl-003 | refinedweb | 329 | 57.91 |
Project Euler #98: Anagramic squares
Project Euler #98: Anagramic squares
nomail_forme + 1 comment
Hint : The problem boils down to writing an acceptable hash method for anagramic strings. The last test case will fail with naive hash methods. Despite the same O(n) complexity for both methods, it makes a huge difference 2+s vs 0.64s.
drubanov + 0 comments
Yes, I got about 50% drop in time from a better hash function. But before I went that way, tighter memory use gave me a 10% increase in speed. Still wasn't enough to get #10 though. Had to be very careful with memory and get the perfect (not near, but perfect) hash function here. The data range here actually allows for a PERFECT hash function.
nonanon + 2 comments
I also find the question not-well defined. I suspect the association between words and numbers is misleading (since a list of English words would be required if each number really had to correspond to a word) and instead is introduced as an analogy for the anagram of an arbitrary number (reordering of the decimal digits). Perhaps it is an intentional distraction to obfuscate the question.
I could give a precise mathematical description of what I think is required, but (a) that probably wouldn't be in the spirit of the competition, (b) my code doesn't work, so my interpretation is likely to be wrong :-).
nonanon + 1 comment
It would also help the problem description to explain the reason why 9216 is the solution for N=4. If I understand it correctly, it is because there are three anagrams of 1296 that are squares: 1296, 2916, and 9216. There are no other "square anagram word sets" (a term that probably should be defined in the problem description) for numbers of length 4 that have as many elements as this set. 9216 is the largest element of this set, so it is the solution.
Where there are multiple "square anagram word sets" that have the same maximal size for a different value of N. I presume you would take the largest square in the union of these sets.
ActonLB + 1 comment
Remember that zeroes are not permitted so your solution is not valid or at least thats the only reason I can think of why its not valid
nonanon + 1 comment
(I worked out the meaning and my code is succcessful now)
Leading zeros are not permitted, but other zeros are permitted. The reason 9801 is not the solution is that its "square anagram word set" only has two elements, whereas 9216's has three.
If 0189 were also a square then 9801 would still not be the solution, since anagrams with leading zeros are not counted in the "square anagram word set".
However, if instead 1089 were also a square, then 9801 would be the solution, as its "square anagram word set" would have three elements, tying with 9216's.
nonanon + 1 comment
Whoops! You are right; 9801 and 1089 are the two squares. I meant if 1098 (or some other anagram not starting with 0) were another square, then there would be three solutions.
kdimou + 1 comment
Why the 1089 ~ 9801 pair is not the right solution for N=4?
4
32^2 = 1024 ~ 49^2 = 2401
33^2 = 1089 ~ 99^2 = 9801 <<<< largest square number
36^2 = 1296 ~ 54^2 = 2916
36^2 = 1296 ~ 96^2 = 9216
37^2 = 1369 ~ 44^2 = 1936
42^2 = 1764 ~ 69^2 = 4761
54^2 = 2916 ~ 96^2 = 9216
64^2 = 4096 ~ 98^2 = 9604
9801
zquanghoangz + 1 comment
The biggest number in the largest set. Set of 9216 have 3 numbers in set
ActonLBAsked to answer + 1 comment
Ok so for what I read the deal goes like this: given an integer N your goal is to find an integer of N digits where neither one of them is either zero or repeated, check if this digit is a perfect square and then rearrange these digits until you find the largest perfect square with those same digits. As for the words "CARE & RACE" in the description it seems they only wanted to use them as an example of what an anagram is. This is my humble conclusion of the problem, I could be wrong in something.
nonanon + 0 comments
It is confusing, but I finally worked it out:
Zeros are permitted (as are repeated digits), but anagrams with a leading zero are not included in each "square anagram word set". We are looking for the biggest (greatest number of elements) square anagram word sets and then within those the greatest element.
bhavikgevariya + 1 comment
961 , 9216 , 96100 , 501264 , 9610000 , . , . , . , . , . , .
gaurya95 + 0 comments
Hi! I am getting only one correct test case. Can anyone help me where I might be going wrong? I have used the correct logic according to myself. If you want I can provide code too. I have used Hashtable in java in this code.
import java.io.; import java.util.; import java.text.; import java.math.; import java.util.regex.*;
public class Solution { public static boolean isAna(int a,int b){
int []hash=new int[10]; int c=0; while(a>0) {hash[a%10]++;a=a/10;} if(hash[0]>0) return false; while(b>0) { hash[b%10]--;b=b/10;} for(int i=0;i<10;i++) if(hash[i]!=0) return false; return true; } public static int max(int ... m){ int max=0; for(int i=0;i<m.length;i++){ if(max<m[i]) max=m[i]; } return max; } public static void main(String[] args) { Scanner sc=new Scanner(System.in); int N=sc.nextInt(); int a=(int)Math.floor(Math.sqrt(Math.pow(10,N-1))); int b=(int)Math.floor(Math.sqrt(Math.pow(10,N))); int temp=0; Integer m=0; Hashtable<Integer,Integer> maximum=new Hashtable<Integer,Integer>(); for(int i=a;i<b-1;i++){ for(int j=i+1;j<b;j++){ if(isAna(i*i,j*j)){ if(!maximum.containsKey(i*i) || !maximum.containsKey(j*j)) maximum.put(Math.max(i*i,j*j),2); else {if(maximum.containsKey(i*i)){ temp=maximum.get(i*i);maximum.remove(i*i);} if(maximum.containsKey(j*j)){ temp=Math.max(temp,maximum.get(j*j));maximum.remove(j*j);} maximum.put(Math.max(i*i,j*j),temp+1); } } } } Set set=maximum.entrySet(); Iterator i=set.iterator(); Map.Entry p=null; while(i.hasNext()){ Map.Entry me=(Map.Entry)i.next(); if((Integer)me.getValue()>m) {m=(Integer)me.getValue();p=me;} } System.out.println(p.getKey()); }
}
ms_shiva90 + 0 commentsTime OUT ERROR : testcase 4 and above.
.Code worked for testcase 0 ,1,2,3. Stuck!! :(
I calculated all permutaions of the number which had perfect square root and added the permutation which had perfect sqroot and found the largest list and printed out its largest number.
import java.io.; import java.util.; import java.text.; import java.math.; import java.util.regex.*;
public class AnagramicSquares {
public static void main(String[] args) { /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */ List<List<String>> ans_set = new ArrayList<List<String>>(); Scanner sc = new Scanner(System.in); int n = sc.nextInt(); double init = Math.pow(10.0 ,n) - 1; double min = Math.pow(10.0,n-1); for(double i = init;i > min-1;i--) { double sqrt = Math.sqrt(i); //shud be a integer if(sqrt % 1 == 0) { //chk for perfect sqrt in its anagram except leading zeroes List<String> li = check(String.valueOf((int)i)); if(li != null) { ans_set.add(li); } } } int max_index = 0; int maxSize = 0; for(int i=0;i < ans_set.size(); i++){ List<String> li = ans_set.get(i); int size = li.size(); if(size > maxSize){ maxSize = size; max_index = i; } } System.out.println(ans_set.get(max_index).get(0)); } public static List<String> check(String val) { int n = val.length(); List<String> li = new ArrayList<String>(); for(int i = 0; i < n; i++) { String initialLetter = String.valueOf(val.charAt(i)); if(!initialLetter.equals("0")){ permute(initialLetter, val.substring(0,i)+val.substring(i+1,n),li); } } if(li.size() == 1) return null; else { return li; } } public static void permute(String part, String rem,List<String> li) { //add only those permutations which math squares i.e it has a square root integer if(rem.equals("")){ int ans = Integer.valueOf(part); //check for decimal values if(Math.sqrt(ans) % 1 == 0) { //check if the number is already present in the list for we dont want repetitions i.e 7744 , 7744 if(checkNoRepeatExists(part,li)) li.add(part); } } int n = rem.length(); for(int i=0;i<n;i++){ permute(part+String.valueOf(rem.charAt(i)), rem.substring(0,i)+rem.substring(i+1,n),li); } } private static boolean checkNoRepeatExists(String part, List<String> li) { // TODO Auto-generated method stub for(String str : li){ if(str.equals(part)) return false; } return true; }
}
ms_shiva90 + 0 comments
My code gets timed out for testcases 5 and above.
I have no clue how to do this quicker???. I computed all permutations of a N digit number if the number had a perfect square root and all the permutations which were square roots as well were added to a list.
In the end I took the largest list and printed out the largest number in the list. Complexity was O(N)+O(mk!)
where N is input. m is number of perfect squares and k! to generate all permutations of the given number in m.
zack_kenyon + 1 comment
this is perhaps the most poorly worded question I have ever read without being wrong. who does quality control on these?
shashank21jHackerRank AdminChallenge Author + 1 comment
Can you tell which part needs better wording?
zack_kenyon + 1 comment
yeah sure, Here it is.
"By replacing each of the letters in the word CARE with 1,2,9, and 6 respectively, we form a square number: 1296=36^2. What is remarkable is that, by using the same digital substitutions, the anagram, RACE, also forms a square number: 9216=96^2. We shall call CARE (and RACE) a square anagram word pair and specify further that leading zeroes are not permitted, neither may a different letter have the same digital value as another letter.
What is the largest square number formed by the largest set of anagrams of the given length?"
instead try:
"some square numbers are numerical anagrams of other square numbers. For instance, 1296=36^2 and 9216=96^2. The set of square anagrams of 1296 is [1296, 9216]. For each value of N, we wish to know the largest set of square anagrams for a number with N digits. . Print out the largest number of this set. If the largest set is not unique, pick whichever one has the largest maximum element."
shashank21jHackerRank AdminChallenge Author + 0 comments
updated. Didn't realize as I use same statement from PE. And here we are not using the words hence doesn't make sense.
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Please Login in order to post a comment | https://www.hackerrank.com/contests/projecteuler/challenges/euler098/forum | CC-MAIN-2019-35 | refinedweb | 1,845 | 65.52 |
Hope someone will help me with the problem I face.
Now I'm working on Modbus RTU tests and faced that sometimes time.sleep_us provides a wrong sleep period.
Please look at code and diagram from my Logic.
The idea of the test example is to send via UART 255 symbols and rise up an additional pin during the transmission.
If you look at the diagram you will see that time to time my UPes pin going Down with the delay (marked red).
I do not understand what is the reason.
I'm testing it on esp32-20190529-v1.11.bin
Will be glad for any ideas.
Thank you.
Code: Select all
import machine import time tx = 17 rx = 2 ctrl = 23 baudrate = 300 ctrlPin = machine.Pin(ctrl, mode=machine.Pin.OUT) symbol_us = (10 * 1000000) / baudrate # time we need to send 1 symbol bin_arr = bytearray(b'') # Payload for test for i in range(1,256): bin_arr.append(i) ctl_up_us = int( symbol_us * len(bin_arr) ) # Time of expected TX print ('Length of payload: {}'.format(len(bin_arr))) print ('Ctl Pin UP, us: {}'.format(ctl_up_us)) # timeout_char=10 uart = machine.UART( 0x02, baudrate=baudrate, bits=8, parity=None, stop=1, tx=tx, rx=rx) while True: ctrlPin(1) uart.write(bin_arr) time.sleep_us( ctl_up_us ) # !!! Problematic place ctrlPin(0) time.sleep_us(300000) | https://forum.micropython.org/viewtopic.php?f=18&t=6654&p=37936 | CC-MAIN-2019-51 | refinedweb | 216 | 76.93 |
Answered by:
KB2707511 causes NTVDM crash when a DOS program attempts to open a pipe
We have a large number of customers using some legacy 16-bit DOS code. This code communicates with our Windows application using named pipes.
Since KB2707511 started rolling out, the legacy DOS code crashes when it attempts to open a pipe. The crash is in NTVDMD.DLL (0xC00000005: Access violation).
I have reduced the code to a bare minimum to reproduce the crash:#include <dos.h>
#include <fcntl.h>
#include <share.h>
#include <stdio.h>
unsigned fdout;
int err;
int main() {
printf("Opening pipe %s\n");
err = _dos_open("\\\\.\\PIPE\\SGO0001.TMP", O_WRONLY, &fdout);
if(err) {
printf("Open failed:%d\n", err);
_exit(1);
}
printf("Done\n");
return 0;
}
This code is compiled with DOS C (V5), and crashes every time.
What do I do now?
Question
Answers
-
All replies
That's going to really impress all our customers.
Many of them are not technically proficient (so would struggle to uninstall the update without help).
The situation is clearly a bug in the update - I would expect Microsoft to investigate the bug report, fix the update, and reissue it.
Any luck finding a solution that doesn't require uninstalling the update? This is really a pain for our customers who's IT demand updates be applied.
In my case the code looks like this creating something like a named pipe as well:
DOSHANDLE xOpen( LPTSTR name, UCHAR flags )
{
WORD savPSP;
WORD handle;
WORD savDS;
handle = INVALID_DOS_HANDLE;
savPSP = xSwitchPSP(); // Program Segment Prefix
savDS = _DS;
_DS = FP_SEG(name);
_DX = FP_OFF(name);
_AL = flags;
_AH = 0x3d;
asm {
int 21h
jc x1
}
handle = _AX;
x1:
_DS = savDS;
xSetPSP(savPSP);
return handle;
}
static WORD xSwitchPSP(VOID)
{
WORD savPSP;
savPSP = xGetPSP();
xSetPSP(_psp);
return savPSP;
}
static VOID xSetPSP( WORD psp )
{
_BX = psp;
_AH = 0x50;
asm {
int 21h
}
}
As an MSDN subscriber, I solicited an accident vs. Microsoft technical support. The reply was to uninstall the KB. They don't seem to realize that they suddendly broke Dos sessions. Contrary to the specifications, Windows XP don't support DOS sessions any more. Microsoft should really fix it !!!
- I have opened a support incident too. I have spoken on the phone to a Senior Support Engineer in the Windows Server Setup & Core Cluster Team, and he passed the incident on to the Development team on 3 July 2012. I have heard nothing since, but live in hope!
I will report back if we ever hear anything. Holding your breath is NOT recommended!
I am investigating a workround. I have had some success with the following:
Windows program runs a 32-bit console app instead of running the DOS program directly.
This app opens the pipes, and assigns the pipe handles to stdin and stderr when it starts the DOS process. DOS process uses stdin and stderr instead of the pipe handles. Of course, this only works if the DOS process is not using stdin or stderr for something else!
This works on my machine, but it doesn't seem to work on some of my colleagues machines. I am awaiting a copy of a VM on which it is alleged not to work, to see if it is finger trouble, something I have done, or something in Windows.
- If your running DOS under XP one of those commands is setting the enviroment for the application.
So your windows application that calls your DOS application must use either command.com or cmd.exe to start the DOS window.
- How do I tell?
The code which starts the process is:
STARTUPINFO sti;
PROCESS_INFORMATION pi;
sti.cb = sizeof(sti);
GetStartupInfo(&sti);
sti.lpReserved = 0;
sti.lpDesktop = 0;
sti.lpTitle = "Window title";
sti.dwFlags = STARTF_USESHOWWINDOW;
sti.wShowWindow = SW_HIDE;
sti.cbReserved2 = 0;
sti.lpReserved2 = 0;
CreateProcess(0,
"dosprogram dos parameters",
0,
0,
0,
CREATE_NEW_CONSOLE|CREATE_SEPARATE_WOW_VDM,
0,
0,
&sti,
pi);
One easy way to tell is to run process explorer and see what starts when you run your code. If it is cmd.exe it will show that, if it is command.com it will show ntvdm.exe. I am not a developer but I think your code would use ntvdm.exe with the create_new_console call. Not sure though.
Honestly I think I may be sidetracking you on this, I expect either way the behaviour might be the same regarding your problem but I was interested in seeing if there was some workaround or fix that could be applied while leaving the patch in place.
I can tell you are not a developer! And you are indeed side tracking.
The following is to the best of my knowledge...
Neither command.com nor cmd.exe are involved. All 16-bit programs are run within NTVDM (including command.com, and my 16-bit program). Command.com is the 16-bit command interpreter (what you see as a "Dos Box"). Cmd.exe is the 32-bit command interpreter (which looks much the same at first glance). If you run a 16-bit program from command.com, it will run in the same 16-bit NTVDM session as the command.com is currently running in.
If you run a 16-bit program from cmd.exe, it will have to start a new NTVDM 16-bit session in which to run the program.
The only workround I have found so far is the one I detailed above (involving opening the pipes in a 32-bit console program and redirecting the 16-bit programs stdin/stderr to those pipes). This is still in the process of being tested. I will report back if the workround actually works.
I have the same problem with a dos program that initializes a proprietary serial card that communicates with a silicon wafer measuring device. With KB2707511 dos program crashes and exits. Without KB2707511 all is fine. Please release updates that are backward compatible – this is a mission critical device, and there are no upgrades or replacements for the device. Most DOS programs call named pipes, why on earth would Microsoft release an update that break these critical pipes?
- | https://social.technet.microsoft.com/Forums/windows/en-US/295b18be-4b08-4d52-8bca-c269f4999784/kb2707511-causes-ntvdm-crash-when-a-dos-program-attempts-to-open-a-pipe?forum=itproxpsp | CC-MAIN-2015-22 | refinedweb | 1,008 | 76.11 |
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On Mon, Jul 24, 2006 at 03:31:40PM +1000, David Creelman wrote:
>?
I haven't tried any of this, but I *have* compiled ECL "natively" for
Win32 using msvc. I posted a zip of C:\Program Files\ECL here[1] if
you want it. (Note: this includes a patch I posted to this list last
night (7/23/06) that allows sub-second SLEEPing on W32 platforms.
Other than that, it's CVS from 7/15/06.)
-- Larry
[1]
Hello,?
Regards
David
diff -uwr ecls-cvs-2006.07.15.09.48.31/src/c/time.d ecls-cvs-2006.07.15.09.48.31-w32/src/c/time.d
--- ecls-cvs-2006.07.15.09.48.31/src/c/time.d 2006-05-29 04:51:21.000000000 -0400
+++ ecls-cvs-2006.07.15.09.48.31-w32/src/c/time.d 2006-07-23 20:26:26.770953600 -0400
@@ -29,9 +29,7 @@
#include <ecl/internal.h>
#if defined(mingw32) || defined(_MSC_VER)
-/* The function sleep() in MinGW is bogus: it counts millisecons! */
#include <windows.h>
-#define sleep(x) Sleep(x*1000)
#endif
#ifndef HZ /* usually from <sys/param.h> */
@@ -79,6 +77,10 @@
tm.tv_nsec = (long)((r - floor(r)) * 1e9);
nanosleep(&tm, NULL);
#else
+# if defined(mingw32) || defined(_MSC_VER)
+ r = object_to_double(z) * 1000;
+ Sleep( (long) r );
+# else
z = round1(z);
if (FIXNUMP(z))
sleep(fix(z));
@@ -86,6 +88,7 @@
for(;;)
sleep(1000);
#endif
+#endif
@(return Cnil)
} | http://sourceforge.net/p/ecls/mailman/ecls-list/?viewmonth=200607&viewday=24 | CC-MAIN-2014-35 | refinedweb | 278 | 69.68 |
24 Essential C++ Interview Questions *
Looking for Freelance C++ Developer jobs? Design your lifestyle as a C++ developer with Toptal.Submit an Interview Question will the line of code below print out and why?
#include <iostream> int main(int argc, char **argv) { std::cout << 25u - 50; return 0; }.
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and enjoy reliable, steady, remote Freelance C++ Developer Jobs..
Assuming
buf is a valid pointer, the two code snippets below for printing a vector. Is there any advantage of one vs. the other? Explain.
Option 1:
vector vec; /* ... .. ... */ for (auto itr = vec.begin(); itr != vec.end(); itr++) { itr->print(); }
Option 2:
vector vec; /* ... .. ... */ for (auto itr = vec.begin(); itr != vec.end(); ++itr) { itr->print(); } may not generate inline code since the compiler cannot determine the depth of recursion at compile time. A compiler with a good optimizer can inline recursive calls till some depth fixed at compile-time (say three or five recursive calls), and insert non-recursive calls at compile time for cases when the actual depth gets exceeded at run.)
Implement a void function F that takes pointers to two arrays of integers (
A and
B) and a size
N as parameters. It then populates
B where
B[i] is the product of all
A[j] where
j != i.
For example: If
A = {2, 1, 5, 9}, then
B would be
{45, 90, 18, 10}.) { // Set prod to the neutral multiplication element int prod = 1; for (int i = 0; i < N; ++i) { // For element "i" set B[i] to A[0] * ... * A[i - 1] B[i] = prod; // Multiply with A[i] to set prod to A[0] * ... * A[i] prod *= A[i]; } // Reset prod and use it for the right elements prod = 1; for (int i = N - 1; i >= 0; --i) { // For element "i" multiply B[i] with A[i + 1] * ... * A[N - 1] B[i] *= prod; // Multiply with A[i] to set prod to A[i] * ... * A[N - 1] prod *= A[i]; } } <iostream>.
How can you make sure a C++ function can be called as e.g.
void foo(int, int) but not as any other type like
void foo(long, long)?
Implement
foo(int, int)…
void foo(int a, int b) { // whatever }
…and delete all others through a template:
template <typename T1, typename T2> void foo(T1 a, T2 b) = delete;
Or without the
delete keyword:
template <class T, class U> void f(T arg1, U arg2); template <> void f(int arg1, int arg2) { //... }
What is the problem with the following code?
class A { public: A() {} ~A(){} }; class B: public A { public: B():A(){} ~B(){} }; int main(void) { A* a = new B(); delete a; }
The behavior is undefined because
A’s destructor is not virtual. From the spec:
( C++11 §5.3.5.
What is a storage class?
A class that specifies the life and scope of its variables and functions is called a storage class.
In C++ following the storage classes are supported:
auto,
static,
extern, and
mutable.
Note, however, that the keyword
register was deprecated in C++11. In C++17, it was removed and reserved for future use.
How can a C function be called in a C++ program?
Using an
extern "C" declaration:
//C code void func(int i) { //code } void print(int i) { //code }
//C++ code extern "C"{ void func(int i); void print(int i); } void myfunc(int i) { func(i); print(i); }
What will be the output of the following program?
#include <iostream> struct A { int data[2]; A(int x, int y) : data{x, y} {} virtual void f() {} }; int main(int argc, char **argv) { A a(22, 33); int *arr = (int *) &a; std::cout << arr[2] << std::endl; return 0; }
In the main function the instance of
struct A is treated as an array of integer values. On 32-bit architectures the output will be 33, and on 64-bit architectures it will be 22. This is because there is virtual method
f() in the struct which makes compiler insert a vptr pointer that points to vtable (a table of pointers to virtual functions of class or struct). On 32-bit architectures the vptr takes 4 bytes of the struct instance and the rest is the data array, so
arr[2] represents access to second element of the data array, which holds value 33. On 64-bit architectures the vptr takes 8 bytes so
arr[2] represents access to the first element of the data array, which holds 22.
This question is testing knowledge of virtual functions internals, and knowledge of C++11-specific syntax as well, because the constructor of
A uses the extended initializer list of the C++11 standard.
Compiled with:
g++ question_vptr.cpp -m32 -std=c++11 g++ question_vptr.cpp -std=c++11
Are you allowed to have a
static const member function? Explain your answer.
A
const member function is one which isn’t allowed to modify the members of the object for which it is called. A
static member function is one which can’t be called for a specific object.
Thus, the
const modifier for a
static member function is meaningless, because there is no object associated with the call.
A more detailed explanation of this reason comes from the C programming language. In C, there were no classes and member functions, so all functions were global. A member function call is translated to a global function call. Consider a member function like this:
void foo(int i);
A call like this:
obj.foo(10);
…is translated to this:
foo(&obj, 10);
This means that the member function
foo has a hidden first argument of type
T*:
void foo(T* const this, int i);
If a member function is const,
this is of type
const T* const this:
void foo(const T* const this, int i);
Static member functions don’t have such a hidden argument, so there is no
this pointer to be
const or not.
Explain the
volatile and
mutable keywords.
The
volatile keyword informs the compiler that a variable may change without the compiler knowing it. Variables that are declared as
volatile will not be cached by the compiler, and will thus always be read from memory.
The
mutable keyword can be used for class member variables. Mutable variables are allowed to change from within const member functions of the class.
C++ supports multiple inheritance. What is the “diamond problem” that can occur with multiple inheritance? Give an example.
It means that we cannot create hybrid inheritance using multiple and hierarchical inheritance. the role of a Teaching Assistant (TA)? Typically, a TA is both a grad student and a faculty member. This yields the classic diamond problem of multiple inheritance and the resulting ambiguity regarding the TA’s
getRole() method:
(Note the diamond shape of the above inheritance diagram, hence the name.)..
Abhimanyu Veer Aditya
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lpc bootloader
Table of Contents
Once you have created a prototype of your product, you may want to be able to use the developed code on a target MCU (NXP LPC) in situ in your end-application board.
This page documents the development of a LPC bootloader program which makes the following process possible:
- The binary file to flash the target MCU with is placed on the mbed's local filesystem.
- The bootloader program is loaded onto the mbed's local filesystem and run, loading an encoded version of the binary file onto the LPC chip.
Chris Styles already experimented with bootloading NXP chips in Prototype to Hardware. This carries out the desired process, but makes use of the Flash Magic flash utility. This requires the user to convert the binary file into hex and then put it through the flash utility. Hence, the process could be streamlined by allowing binary files to be directly loaded, which is now possible using this bootloader program.
Bootloader Program¶
In order to use the program, compile the program you want to bootload onto another chip and drop it into the mbed's filesystem flash with the suffix .LPC (in place of the standard pin names (PinName7, LED1 etc.), you can access any of the LPCs pins in the format shown in the compiler image above of P(Bank number)_(Pin number), for example P1_18).
Then drop the program below onto the mbed, and reset the mbed to flash it to the chip. Simple! (With some chips, you will need to alter the baud rate first, as 230400 is not supported by some LPC chips.)
main.cpp
#include "mbed.h" #include "LPC.h" SerialBuffered lpc(1024, p9, p10); int main() { //RESET CHIP TO LOAD TO BEFORE RUNNING PROGRAM!!! lpc.InitUART(230400); //Specified limit of 230400 baud lpc.ProgramFile(); }
Table of the LPC chips confirmed it works with (please add to):
The Task Ahead¶
I started off by leafing through the UM10360 datasheet, which contains the information on the current evolution of the mbed (LPC1768). As always, you should start by reading from the very beginning (of page 615). This chapter looks at the flash memory interface and documents the In-System Programming (ISP) which is the serial communication path used for this bootloader. From reading through it, you gauge what is required:
Hardware (for the LPC1768):¶
- In order to start the chip up in ISP bootloader mode, you need to breakout P2.10 and pull it low when resetting the board, for at least three milliseconds (possibly with a push button).
- Connect P9 of the mbed to P0.2 of the LPC chip
- Connect P10 of the mbed to P0.3 of the LPC chip
I used a Keil MCB1760 evaluation board as a 'breakout board' for my chip to bootload to (LPC1768 as well). This allowed easy access to the pins I required access to without any pixie soldering and conveniently gives me LEDs to flash to let me know when my work has been done. Well, that was easy. The MCB1760 had the ISP entry pin, P2.10, already pulled high, so I was lazy and just put in place a pushbutton connected to ground in order to pull the pin low when ISP bootloader mode entry was required. Now onto the software...
Software:¶
- Get the mbed to access the desired file on the local filesystem.
- Synchronise the mbed with the chip, by doing the handshaking (in ASCII strings).
- Prepare and erase the entire flash memory.
- Override the 8th DWORD with the two's complement of sum of the first 7 DWORDs. This is the chip's first checksum (it sums the first 8 DWORDs continues if the result is zero).
- Convert the file line-by-line into the UU-encoded format (discussed later) ending with a line feed and/or carriage return character).
- Send the checksum of the sum of the raw bytes sent in the last block (sent after a 20 line block).
- Write a 1KB block of the binary file to the RAM in the above process.
- Prepare the flash memory for writing to and copy the RAM block to the suitable location in the flash.
I developed the code on the mbed's online compiler and debugged the serial communications using a USBee SX with its accompanying USBee Suite software and drivers.
(If trying to replicate the debugging setup, ensure you set up an asynchronous (8-N-1) connection decoding into ASCII unless you're fluent in binary.)
Code Development¶
Setting up Communication¶
I started off the code writing by looking at the section entitled 'Communicating with the LPC1768' in the Prototype to Hardware page. The communication with the LPC occurs via ASCII strings. I began by ensuring I could replicate the communication, so I opened up TeraTerm and began typing away.
I sent it a question mark.
It replied 'Synchronized(+CR)'.
I then said '4000(+CR)', stating that I was running at 4000kHz/4MHz.
It replied 'OK(+CR)'.
Now all the necessary handshaking had been done. I could send it various letters as detailed in UM10360 to get such information as ID code and part number etc. but I was now happy that the hardware was set up correctly and I could confidently start putting pen to paper or finger to keyboard.
The code I used to set up the communication was very simple:
#include "mbed.h" Serial pc (USBTX,USBRX); Serial target (p9,p10); int main() { pc.baud(9600); target.baud(9600); while (1) { if (pc.readable()) { target.putc(pc.getc()); } if (target.readable()) { pc.putc(target.getc()); } } }
UU-Encoding¶
Next I turned my attention to the UU-encoding formula, documented very well on it's own Wikipedia page. It essentially consists of breaking down a file into ASCII lines of maximum length 45 raw bytes, performing a relatively simple operation on them turning them into 60 UU-encoded bytes, and then sticking a checksum (number of raw bytes sent + 0x20) at the beginning of the line and a carriage return(CR) and/or line return(LR) at the end.
I now turn to Wikipedia to explain the basic encoding operation involved in full:
The mechanism of UU-encoding repeats the following for every 3 bytes:
- Start with 3 bytes from the source.
- Convert to 24 bits.
- Convert into 4 6-bit groupings, bits (00-05),(06-11),(12-17),(18-23).
- Evaluate the decimal equivalent of each of the (4) 6-bit groupings. 6 bits allows a range of 0 to 63.
- Add 32 to each of the 4. With the addition of 32 this means that possible results can be between 32 (" " space) and 95 ("_" underline). 96 ("`" grave accent) as the "special character" is a logical extension of this range.
- Output the ASCII equivalent of these numbers.
Note that if the source is not divisible by 3 the last 4-byte section will contain padding bytes to make it cleanly divisible. These bytes are subtracted from the line's <length character> so that the decoder does not append unwanted null characters to the file.
The encoding process is demonstrated by this table, which shows the derivation of the above encoding for "Cat".
So armed with my UU-encoding knowledge, I wrote a small program to carry out the conversion and explicitly show the process going on. Note the if statements at the bottom replacing any 0x00s with 0x60s. This is something I didn't discover on the first day and so I kept on getting slight discrepancies between my conversion and that provided by the online UU-Encoder I was using to check my output.
Type in 'Cat' and see for yourself that it agrees with the gods of Wikipedia.
Encoder.cpp
#include "mbed.h" Serial pc(USBTX, USBRX); int ch1, ch2, ch3; int n1,n2,n3,n4; int main() { while(1) { pc.baud(230400); n1 = 0; n2 = 0; n3 = 0; n4 = 0; ch1 = pc.getc(); pc.printf("Raw bytes: %c", ch1); ch2 = pc.getc(); pc.printf("%c", ch2); ch3 = pc.getc(); pc.printf("%c\n\r", ch3); if ((ch1-128)>=0) {ch1-=128; n1+=32;} if ((ch1-64)>=0) {ch1-=64; n1+=16;} if ((ch1-32)>=0) {ch1-=32; n1+=8;} if ((ch1-16)>=0) {ch1-=16; n1+=4;} if ((ch1-8)>=0) {ch1-=8; n1+=2;} if ((ch1-4)>=0) {ch1-=4; n1+=1;} if ((ch1-2)>=0) {ch1-=2; n2+=32;} if ((ch1-1)>=0) {ch1-=1; n2+=16;} if ((ch2-128)>=0) {ch2-=128; n2+=8;} if ((ch2-64)>=0) {ch2-=64; n2+=4;} if ((ch2-32)>=0) {ch2-=32; n2+=2;} if ((ch2-16)>=0) {ch2-=16; n2+=1;} if ((ch2-8)>=0) {ch2-=8; n3+=32;} if ((ch2-4)>=0) {ch2-=4; n3+=16;} if ((ch2-2)>=0) {ch2-=2; n3+=8;} if ((ch2-1)>=0) {ch2-=1; n3+=4;} if ((ch3-128)>=0) {ch3-=128; n3+=2;} if ((ch3-64)>=0) {ch3-=64; n3+=1;} if ((ch3-32)>=0) {ch3-=32; n4+=32;} if ((ch3-16)>=0) {ch3-=16; n4+=16;} if ((ch3-8)>=0) {ch3-=8; n4+=8;} if ((ch3-4)>=0) {ch3-=4; n4+=4;} if ((ch3-2)>=0) {ch3-=2; n4+=2;} if ((ch3-1)>=0) {ch3-=1; n4+=1;} if (n1 == 0x00) n1=0x60; else n1+=0x20; if (n2 == 0x00) n2=0x60; else n2+=0x20; if (n3 == 0x00) n3=0x60; else n3+=0x20; if (n4 == 0x00) n4=0x60; else n4+=0x20; pc.printf("U-Encoded bytes: %c",n1); pc.printf("%c",n2); pc.printf("%c",n3); pc.printf("%c\n\n\r",n4); } }
Maximising the Baud Rate¶
Initially, I could only communicate successfully with the mbed by sending commands to it at a 9600 baud rate. It turned out that this was as a result of the echo which the chip automatically has switched on when reset. To tackle this, I introduced a previously developed SerialBuffered class into my program to extend the FIFOs present on the mbed and switched off the echo as soon as handshaking had been achieved (sending the command 'A 0(+CR)'). After carrying out these adjustments, I could take it all the way up to 230400 baud, which is the limit described in the LPC1768 handbook. I tried higher, but apparently and annoyingly, they're right :(
The First Encoded Block¶
There is a small peculiarity in the process with which you carry out the encoding of the first block of data to be sent to the chip. This first block requires the 8th DWORD (a DWORD is a chunk of data consisting of 32 bits/4 bytes), to be the two's complement of the sum of the first 7 DWORDs. This is carried out by inverting all the bits in the 8th DWORD and adding 1 to it.
The code below is a slightly adapted version of the respective function in the final program at the end of this page. It carries out the summing, the two's complement creation (taking into account both little-endian and big-endian) and writes the altered first chunk of data to a temporary file called 'delete.bin'. Then this file can be opened, encoded and sent to the chip before reopening the original file and continuing from where it stopped before.
FirstEncode()
int SerialBuffered::FirstEncode() { long int precheck = 0; int a; for (a=0; a<9; a++) { ch1 = fgetc(f); ch2 = fgetc(f); ch3 = fgetc(f); sum[a*3]=ch1; sum[(a*3)+1]=ch2; sum[(a*3)+2]=ch3; } ch1 = fgetc(f); fgetc(f); fgetc(f); fgetc(f); fgetc(f); //Ignores the 4 bytes which are to be overwritten sum[27] = ch1; for (a=0; a<7; a++) { sum1[a*4] = sum[a*4+3]; sum1[a*4+1] = sum[a*4+2]; sum1[a*4+2] = sum[a*4+1]; sum1[a*4+3] = sum[a*4]; precheck += (sum1[a*4]*0x1000000) + (sum1[a*4+1]*0x10000) + (sum1[a*4+2]*0x100) + sum1[a*4+3]; } precheck = ~precheck+1; //Takes the two's complement of the checksum sum[28] = precheck & 0xFF; sum[29] = (precheck >> 8) & 0xFF; sum[30] = (precheck >>16) & 0xFF; sum[31] = (precheck >>24) & 0xFF; sum[32] = fgetc(f); for (int a=33; a<46; a++) sum[a] = fgetc(f); f=fopen("/fs/delete.bin", "w"); //Opens a temporary file for writing to fwrite (sum, 1, sizeof(sum), f); //Writes the checksum-added and encoded bytes fclose(f); return 0; }
Initial Programming Concept¶
The overview of the communication protocol as given in the user manual is as follows:
__ISP data format:__
The data stream is in UU-encoded format. The UU-encode algorithm converts 3 bytes of
binary data in to 4 bytes of printable ASCII character set. It is more efficient than Hex
format which converts 1 byte of binary data in to 2 bytes of ASCII hex. The sender should
send the check-sum after transmitting 20 UU-encoded lines. The length of any
UU-encoded line should not exceed 61 characters (bytes) i.e. it can hold 45 data bytes.
The receiver should compare it with the check-sum of the received bytes. If the
check-sum matches then the receiver should respond with "OK<CR><LF>" to continue
further transmission. If the check-sum does not match the receiver should respond with
"RESEND<CR><LF>". In response the sender should retransmit the bytes.
__Write to RAM <start address> <number of bytes>:__
The host should send the data only after receiving the CMD_SUCCESS return code. The
host should send the check-sum after transmitting 20 UU-encoded lines. The checksum is
generated by adding raw data (before UU-encoding) bytes and is reset after transmitting
20 UU-encoded lines. The length of any UU-encoded line should not exceed
61 characters (bytes) i.e. it can hold 45 data bytes. When the data fits in less than
20 UU-encoded lines then the check-sum should be of the actual number of bytes sent.
These two paragraphs are vital to understanding the communication protocol and are fairly self-explanatory apart from the last bit. When the data fits in less than 20 UU-encoded lines, then the check-sum should be the sum of the raw bytes sent since the previous checksum was sent. The description given is too ambiguous and it would be nice to see a graphical explanation.
So for the bulk of the program from information gleaned from the user manual, the pseudo-code description (with example ASCII string commands+CR) is:
- Handshake (discussed previously)
- Prepare and erase all the flash sectors ('P 0 29' and 'E 0 29')
- Send 1KB of data to the RAM ('W 268435968 1024' and '1KB of encoded data')
- Prepare flash and copy from RAM to flash ('P 0 29' and 'C 0 268435968 1024')
Each block of 1KB of encoded data consists of one normal block of 20 UU-encoded lines (45x20=900 bytes long) plus a smaller block of 124 bytes to make it up to the correct size. So I needed to include a case for when this smaller block needed to be sent. All I do differently is send the checksum earlier and pad any unrequired bytes in the last 3 to be UUencoded with 0x00s. The chip will read the 124 bytes, bringing the overall total it has received up to 1024 and then expect a checksum to be sent, so little has to be altered.
Then all that needs to be thought about is how to deal with reaching the end of the file. I had a counter that knew when the end was coming up and adjusted the copy to flash and write to RAM commands to specify that less data will be sent and then send the last few bytes.
Revised Programming Concept¶
Including the adjustment to the copy to flash and write to RAM commands brought up a few problems, and made the code a bit more complex, so in the end I decided upon sending only in 1KB blocks, but simply padding the rest of the 1KB which wasn't needed with 0x00s. The sacrifice I made to the speed of the program is a maximum of 1s, so I think I'll be able to sleep at night.
Success!¶
What Now?¶
If anyone takes a keen interest in this project and uses it with different chip types, please add the confirmed successful chip types at the top of this page, where I've started off a table. In that way it can develop as a resource and the utility can be developed further, making it even more useful. I'm now heading back to university, but managed to get very close to hooking up a LPC1343 and a LPC1114 chip to the utility; just trying to iron out an odd bug, which lookw hardware-based, where all the command codes have been successful, but partway through sending the first 1KB block, the chips start sending back the code I sent to them...
The following .zip file contains some useful reference projects and links. LPC Bootloader
If anything needs explaining, then feel free to comment below and I'll try to get round to answering any queries that crop up. | https://os.mbed.com/cookbook/lpc-bootloader | CC-MAIN-2021-39 | refinedweb | 2,868 | 67.28 |
It may seem rather unnecessary to start a book on MySQL for Python with a chapter on setting it up. There are, in fact, chapter
sudoto.
Tip.
Noteâboth
One of the best known
egg utilitiesâEasy Install, is available from the PEAK Developers' Center at. How you install it depends on your operating system and whether you have package management software available. In the following section, we look at several ways to install
Easy Install on the most common systems. <name of egg file>
For Windows, you will use a command similar to this one:
C:\Python25\Scripts\easy_install.exe <name of egg file> full path command-line calls.
If your system has MySQL, Python, and
setuptools, but you still don't have administrative access, it is advisable to unpack the
egg file manually and call it as a local module. To do this, use an archiving program to unzip the file.
The content listing for the Windows egg will look like this:
Egg-info
MySQLdb
_mysql_exceptions.py
_mysql_exceptions.pyc
_mysql.py
_mysql.pyc
_mysql.pyd
And the Linux egg unpacks to the following files:
Egg-info
MySQLdb
_mysql_exceptions.py
_mysql_exceptions.pyc
_mysql.py
_mysql.pyc
_mysql.so
With the exception of the
egg-info directory, the contents are the basic ingredients of a Python module and can be imported locally if one's program resides in the same directory as the files are located.
Due to the need for certain programming libraries, this method of installation applies only to users of Unix-derived operating systems. This method involves installing from the source files and so requires the necessary C libraries to compile a binary version. Windows users should therefore use one of the other methods discussed previously.
If you cannot use
egg files or if you use an earlier version of Python, you should use the
tar.gz file, a
tar and
gzip archive. The
tar.gz archive follows the Linux
egg files in the file listing. The current version of MySQL for Python is 1.2.3c1, so the file we want is as following:
MySQL-python-1.2.3c1.tar.gz
This method is by far more complicated than the others. If at all possible, use your operating system's installation method or an
egg file.
This version of MySQL for Python is compatible up to Python 2.6. It is worth noting that MySQL for Python has not yet been released for Python 3.0 or later versions. In your deployment of the library, therefore, ensure that you are running Python 2.6 or earlier. As noted, Python 2.5 and 2.6 have version-specific releases. Prior to Python 2.4, you will need to use either a
tar.gz version of the latest release or use an older version of MySQL for Python. The latter option is not recommended.
Most Unix-derived operating systems (Linux, Mac) come with the
tar and
gzip utilities pre-installed. For users of these systems, unpacking the archive is as simple as the following command:
shell> tar xvzf MySQL-python-1.2.3c1.tar.gz
The archive will then unpack into a directory called
MySQL-python-1.2.3c1.
Windows users can use any of the following archive programs to unpack the
tarball:
PowerArchiver 6.1
7-Zip
WinZip
Once the file is unpacked, you need to ensure that you have the program
mysql_config in your path. For Mac users, this usually comes with the MySQL installation itself. For Linux, if you are using bash or another shell with command-line completion, you can check this by typing the following in a terminal:
shell> mysql_conf
Then press the tab key. If the command is completed to
mysql_config, there are no issues, otherwise your operating system does not know of any such command, and you need to either find it or install it.
An alternative way of checking is to use the
whereis command. Type the following from the command-line:
shell> whereis mysql_config
If it is installed, the system will return its location. Then echo your current
PATH value by typing:
shell> echo $PATH
and compare the results. If the location of
mysql_config is one of the values in your path, there are no issues otherwise, we need to either find it or install it.
The
mysql_config program comes with the MySQL client development libraries. If you have these installed, check the directory that holds the MySQL client binary (use
whereis mysql if necessary). If you are unsure, you can check with a package manager using the following commands:
shell> aptitude search mysql | grep client | grep dev
This will work for Debian-based systems. Users of RPM-based systems should substitute either
yum search or
urpmq for
aptitude search. This query will return results for the development files and for the MySQL client, and you can then see if the appropriate package is installed. If it is not, you can install it with the
install argument (for either
aptitude or
yum) or by using
urpmi.
If the
mysql_config program is installed, but is outside your path, you need to indicate its location to the MySQL for Python setup configuration. Navigate to the
MySQL-python-1.2.3c1 directory and open the file
site.cfg in your favorite text editor. The file is not large, and the following section is easily seen as the second part of the file:
#The path to mysql_config #Only use this if mysql_config is not on your PATH,or you have some weird setup that requires it #mysql_config = /usr/local/bin/mysql_config
If
mysql_config is outside of your path, uncomment the last line of the part cited here and enter the correct path. So, if
mysql_config is installed to:
/usr/local/bin/mysql/bin/mysql_config
The last line should read:
mysql_config = /usr/local/bin/mysql/bin/mysql_config
Then save the file and close it.
Next, we should build the package using the instructions that came with it in
setup.py. Use the following command to attempt a build without installing it:
shell> python setup.py build
If the process goes through without error, which it usually does, the build is successful. If there is an error, it usually involves the lack of a module or software package. In which case, confirm that you have all the prerequisites needed for the task by checking the list in the
readme file that comes with the archive.
Note
Be sure to read the
readme file that comes with the source code. It contains a lot of help on the installation process.
Once the build is successful, installation can be done with the following command:
shell> python setup.py install
The.
As with other modules, Python is able to provide online help about MySQL for Python. In the following sections, we look at the
MySQLdb and
_mysql modules in greater depth using Python's built-in
help() function.âDB.
In making a phone call, one picks up the handset, dials a number, talks and listens, and then hangs up. Making a database connection through MySQL for Python is nearly as simple. The four stages of database communication in Python are as follows:
Creating a
connectionobject
Creating a
cursorobject
Interacting with the database
Closing the connection
As mentioned previously, we use
connect() to create an object for the program's connection to the database. This process automates logging into the database and selecting a database to be used.
The syntax for calling the
connect() function and assigning the results to a variable is as follows:
[variable] = MySQLdb.connect([hostname], [username], [password],[database name])
Naming these variables as you assign the values is not required, but it is good practice until you get used to the format of the function call. So for the first few chapters of this book, we will use the following format to call the
connect() function:
[variable] = MySQLdb.connect(host="[hostname]", user="[username]", passwd="[password]", db="[database name]")
Let's say we have a database-driven application that creates the menu for a seafood restaurant. We need to query all of the fish from the menu database in order to input them into a new menu. The database is named menu.
Note
If you do not have a database called
menu, you will obviously not be able to connect to it with these examples. To create the database that we are using in this example, put the following code into a text file with the name
menu.sql:
CREATE DATABASE `menu`; USE menu; DROP TABLE IF EXISTS `fish`; SET @saved_cs_client = @@character_set_client; SET character_set_client = utf8; CREATE TABLE `fish` ( `ID` int(11) NOT NULL auto_increment, `NAME` varchar(30) NOT NULL default ââ, `PRICE` decimal(5,2) NOT NULL default â0.00â, PRIMARY KEY (`ID`) ) ENGINE=MyISAM AUTO_INCREMENT=27 DEFAULT CHARSET=latin1; SET character_set_client = @saved_cs_client; LOCK TABLES `fish` WRITE; INSERT INTO `fish` VALUES (1,âcatfishâ,â8.50â),(2,âcatfishâ,â8.50â),(3,âtunaâ,â8.00â),(4,âcatfishâ,â5.00â),(5,âbassâ,â6.75â),(6,âhaddockâ,â6.50â),(7,âsalmonâ,â9.50â),(8,âtroutâ,â6.00â),(9,âtunaâ,â7.50â),(10,âyellowfin tunaâ,â12.00â),(11,âyellowfin tunaâ,â13.00â),(12,âtunaâ,â7.50â); UNLOCK TABLES;
Then log into your MySQL session from the directory in which the file
menu.sql is located and type the following:
source menu.sql
This will cause MySQL to create and populate our example database.
For this example, the database and program reside on the same host, so we can use localhost. The user for the database is skipper with password mysecret. After importing the MySQL for Python module, we would call the
connect() function as follows:
mydb = MySQLdb.connect(host="localhost", user="skipper", passwd="mysecret", db="menu")
The
connect() function acts as a foil for the
connection class in
connections.py and returns an object to the calling process. So in this example, assigning the value of
MySQLdb.connect() to
mydb renders
mydb as a
connection object. To illustrate this, you can create the necessary database in MySQL, connect to it as shown previously, then type
help(mydb) at the Python shell prompt. You will then be presented with large amounts of information pertinent to
MySQLdb.connections objects.
After the
connection object is created, you cannot interact with the database until you create a cursor object. The name cursor belies the purpose of this object. Cursors exist in any productivity application and have been a part of computing since the beginning. The point of a cursor is to mark your place and to allow you to issue commands to the computer. A cursor in MySQL for Python serves as a Python-based proxy for the cursor in a MySQL shell session, where MySQL would create the real cursor for us if we logged into a MySQL database. We must here create the proxy ourselves.
To create the cursor, we use the
cursor() method of the
MySQLdb.connections object we created for the connection. The syntax is as follows:
[cursor name] = [connection object name].cursor()
Using our example of the menu database above, we can use a generic name
cursor for the
database cursor and create it in this way:
cursor = mydb.cursor()
Now, we are ready to issue commands.
Many SQL commands can be issued using a single function as:
cursor.execute()
There are other ways to issue commands to MySQL depending on the results one wants back, but this is one of the most common. Its use will be addressed in greater detail in future chapters.
In MySQL, you are expected to close the databases and end the session by issuing either
quit or
exit.
To do this in Python, we use the
close() method of the database object. Whether you close a database outright depends on what actions you have performed and whether MySQL's auto-commit feature is turned on. By default, MySQL has autocommit switched on. Your database administrator will be able to confirm whether auto-commit is switched on. If it is not, you will need to commit any changes you have made. We do this by calling the
commit method of the database object. For
mydb, it would look like this:
mydb.commit()
After all changes have been committed, we can then close the database:
mydb.close()
In MySQL for Python, all database objects are discrete. All you need do is to connect with each under a different name. Consider the following:
mydb1 = MySQLdb.connect(host="localhost", user="skipper", passwd="mysecret", db="fish") mydb2 = MySQLdb.connect(host="localhost", user="skipper", passwd="mysecret", db="fruit") cursor1 = mydb1.cursor() cursor2 = mydb2.cursor()
The objects then function like any other variable or object. By calling their methods and attributes separately, you can interact with either or even copy from one to the other.
In this chapter we have looked at where to find MySQL for Python, as it is not part of Python by default. We have also seen how to install it on both Windows and non-Windows systemsâUNIX-like and Linux distributions. The authors of MySQL for Python have taken the pain out of this by providing a very easy way to install through an egg utility like
EasyInstall.
Like most modules, MySQL for Python must be imported before you can use it in Python. So we then looked at how to import it. Unlike most modules, we saw that MySQL for Python needs to be imported by its earlier moniker,
MySQLdb.
After that, we took a peek at what is waiting for us under the MySQL for Python covers using
help(). We saw that MySQL for Python is not an interface to MySQL itself but to a MySQL Database API that is built into Python. It has a large number of classes for handling errors, but only one for processing data (There are different kinds of cursors). Further, it does not even use classes to access MySQL, but uses functions to process and pass information to
_mysql, which then passes it to the C MySQL database interface.
Following this trail, we also saw that
_mysql does not have a robust facility for handling errors, but only passes them to the calling process. That is why MySQL for Python has such a robust error handling facility.
Next, we saw how to connect to a MySQL database. As with most parts of Python, this is easy for beginners. But the function used is also sufficiently robust to handle the more complex needs of advanced solutions.
After connecting, we created a
MySQLdb cursor and prepared to interact with the database. This showed that, while there are many things that
MySQLdb will take care of for us (like connection closure), there are some things we need to do manually. In this instance, it is creating the
cursor object that represents the MySQL cursor.
Finally, we saw that one can connect to multiple databases by simply using different object names for each connection. This has the consequence of necessitating different namespaces as we refer to the methods and attributes of each object. But it also allows one to bridge between databases across multiple hosts seamlessly and to present a unified interface for a user.
In the next chapter, we will see how to form a MySQL query and pass it from Python using variables from the system, MySQL, and the user. | https://www.packtpub.com/product/mysql-for-python/9781849510189 | CC-MAIN-2020-40 | refinedweb | 2,548 | 63.8 |
Version 1.23.0
For an overview of this library, along with tutorials and examples, see CodeQL for JavaScript
.
A scope induced by a for statement.
for
import javascript
Gets the for statement that induces this scope.
Gets a textual representation of this element.
Gets a variable declared in this scope.
Gets a scope nested in this one, if any.
Gets the location of the program element this scope is associated with, if any.
Gets the scope in which this scope is nested, if any.
Gets the program element this scope is associated with, if any.
Gets the variable with the given name declared in this scope. | https://help.semmle.com/qldoc/javascript/semmle/javascript/Variables.qll/type.Variables$ForScope.html | CC-MAIN-2020-05 | refinedweb | 107 | 77.74 |
I had been using SQL long before discovering Perl and became quite fond of the SQL *IN* operator. Not having found the equivalent in Perl, I usually construct a hash with my values as the keys. Unless something similar has already been done (and I have not discovered it yet), would this be something worth petitioning the Perl gods for?
# What I want to do
if ($value == 1 or $value == 5 or $value == 21 or $value == 99){...
# How I often do it:
my %list = (1 => 1, 5 => 1, 21 => 1, 99 => 1);
if ($list{$value}){...
# Wouldn't something like this be better?
if ($value IN (1, 5, 21, 99)){...
[download]
UPDATE: Thanks everyone. It looks like Quantum::Superpositions does what I had in mind (didn't find it initially searching CPAN). Since I'm still trying to fill the holes in my *swiss cheese* knowledge of Perl 5, I haven't looked into Perl 6 much.
Sounds like you need Quantum::Superpositions :-)
Also, see Perl 6's smart match operator.
See the Copyright notice on my home node.
"The first rule of Perl club is you do not talk about
Perl club." -- Chip Salzenberg
If there was a poll for the least sensibly named CPAN module Quantum::Superpositions is sure to get my vote. The name belongs to the Acme:: namespace.
Jenda
grep $_ == $value, 1,5,21,99;
[download]
Liz
Update: yes, I mean even the XS version
if $value == 1 | 5 | 21 | 99 { ...
[download]
if $value == any( 1, 5, 21, 99) { ...
[download]
In Perl 6 you will be able to...
And before that comes out (*ducks*), you'll be able use smart matching in perl 5.10:
use 5.9.5;
my $var = shift;
my @f = (1,2,3,5,8,13,21);
print "fibo!" if $var ~~ @f;
[download]
• another intruder with the mooring in the heart of the Perl
Cheers - L~R
That can be a hard thing to find in CPAN ... so look behind the readmore for one | http://www.perlmonks.org/?node_id=607459 | CC-MAIN-2015-35 | refinedweb | 332 | 83.25 |
Page Objects
Introduction
A Page Object in EPiServer CMS is basically a normal .NET object instance that is associated with a CMS page. The Page Object functionality can be utilized in a mulitude of ways, the scenario described in this document is just one way how Page Object can be used.
Table of Contents
- Associating a Page with a Page Object
- Working with Page Objects
» Saving
» Deleting
- Examples
» Page OwnerOption
» PageLanguageBranch OwnerOption
» PageVersion OwnerOption
Associating a Page with a Page Object
A Page Object can be associated to a page in 3 different ways. This is known as the Page Object’s Owner Option. These options are:
- Page – the Page Object is owned by the CMS Page (defined by its Guid). That is all versions of a page work against the same Page Object instance.
- PageLanguageBranch – the Page Object is owned by the CMS Page’s Language Branch. That is all versions of a page with the same language branch work against the same Page Object instance.
- PageVersion – the Page Object is owned by the CMS Page Version. That is all versions of a page regardless of language branch work against their own version of the Page Object.
Each Page Object is given a name which must be unique per page.
Working with Page Objects
In order to work with Page Objects you instantiate an instance of the EPiServer.Core.PageObjectManager class.
Construction
The public constructors available take parameters which tell the PageObjectManager which EPiServer CMS page version you want it to manage Page Objects for:
public PageObjectManager(PageData pageData)
public PageObjectManager(PageData pageData, IPageObjectRepository repository)
public PageObjectManager(Guid pageGuid, string pageLanguageBranch, int workPageId)
public PageObjectManager(Guid pageGuid, string pageLanguageBranch, int workPageId, IPageObjectRepository repository)
The PageObjectManager requires an IPageObjectRepository to work with. If one is not provided via the constructor then the EPiServer ClassFactory mechanism is queried to see if one has been registered with it. If one has not been registered with the ClassFactory then an instance of the default EPiServer.DataAccess. DdsPageObjectRepository is instantiated and used.
There are several methods for loading Page Objects
public virtual Object Load(string name)
public virtual TObject Load<TObject>(string name)
public virtual PageObject LoadMetaObject(string name)
public virtual IDictionary<string, Object> LoadAll()
public virtual IEnumerable<PageObject> LoadAllMetaObjects()
The PageObject instances returned by the LoadMetaObject and LoadAllMetaObjects methods are objects that are managed by the PageObjectManager and as their name suggests contain meta-data for the Page Object. These may be useful in debugging scenarios or if you are just curious.
The EPiServer.Core namespace also has a class which defines a generic extension method called ItemAs<> for the IDictionary<string, Object> type. This allows you to access your objects in a strongly typed way:
PageObjectManager pom = new PageObjectManager(……);
IDictionary<string, object> objects = pom.LoadAll();
MyClass myObject = objects.ItemAs<MyClass>("MyObject");
Saving
There are two public save methods:
public virtual void Save(string name, Object value, PageObject.OwnerOption ownerOption)
public virtual void Save(string name, Object value)
The first overload takes the Page Object name, the object to save and the OwnerOption. If you save an existing Page Object with a different OwnerOption to the one it already has then the existing one will be overwritten. It is very important to understand the consequence of this especially if Page Objects are used with Dynamic Content and the web editor it given the ability to set the OwnerOption via the Dynamic Content User Interface.
Consider the following scenario:
A Page Object which holds the rating (i.e. a score from 1 to 5) for a CMS page has been wrapped in a Dynamic Content object and is therefore optionally insertable on a page by the web editor. The developer of the Rating Dynamic Content has quite reasonably decided that the web editor should decide what the rating applies to:
- The page regardless of language / version
- The page language: the page is rating separately for each language
- The page version: each version of the page is rated separately
These options you will notice map quite nicely to the OwnerOption that is set when saving the Page Object.
The problem potentially comes when the page exists in more than one language. This means that the Rating Dynamic Content needs to be added to each language branch of the page and there lies an opportunity for the editor to chose one owner type for one language and a different owner type for another. The system does not allow the same named Page Object to coexist on the same page with different owner types which means that they will constantly overwrite each other when saved.
The second overload of Save does not require an OwnerOption. When this is called for a new Page Object then the default OwnerOption of PageLanguageBranch will be assigned to it. When this is called for an existing Page Object then the OwnerOption remains unchanged. This allows for code that saves a Page Object without having to know what OwnerOption to specify.
Deleting
There a two public delete methods:
public virtual void Delete(params string[] pageObjectsNames)
public virtual void DeleteAll()
Delete removes all the Page Objects for the names passed. This works in conjunction with the OwnerOption which means that only the Page Objects the CMS page the PageObjectManager is associated with will be deleted.
DeleteAll deletes all Page Objects for the CMS page associated with the PageObjectManager.
Examples
Page OwnerOption
An EPiServer CMS Page Template is created to show news items. The template also has a text box and a submit button to allow logged in users to comment on the page’s content and renders the last 5 comments posted. The Page Template has code to load and retrieve the comments using a Page Object named “Comments”.
An EPiServer CMS page called “News” is created for the default language branch (English) using the Page Template above.
The first time the PageObjectManager.Load method is called for the “Comments” Page Object it will return null as one has not yet been saved. The code will create a new instance of the class developed for the comments and call the PageObjectManager.Save method with the name “Comments”, the object instance value and an OwnerOption of Page. The next time the Page Template is executed for the “News” page the PageObjectManager.Load method will return the “Comments” Page Object previously saved (note that it will not be the same physical object instance due to how the Dynamic Data Store caches objects. See for more details).
Next a version of the “News” page is created in another language branch, say Swedish. When the Page Template executes for the Swedish version of the page it will get the same “Comments” Page Object returned as the English version as the Page Object was saved with Page OwnerOption. Only one instance of the Page Object will exist.
Later on the Swedish language branch is deleted for the “News” page. The “Comments” Page Object instance will remain as it is shared between all language branches / versions of the page.
PageLanguageBranch OwnerOption
If the “Comments” Page Object is saved with PageLanguageBranch OwnerOption then the PageObjectManager.Load method will return null when the Page Template is executed for the Swedish version of the “News” page. The Page Template will then save a new instance of the Page Object for that language branch. An instance of the Page Object will exist per language branch.
If the Swedish language branch for the page is deleted then the “Comments” Page Object owned by that language branch will be deleted but not those owned by other language branches.
PageVersion OwnerOption
If the “Comments” Page Object is saved with PageVersion OwnerOption then the PageObjectManager.Load method will return null when the Page Template is executed for every new version of the CMS Page regardless of language branch. The Page Template will then save a new instance of the Page Object for every page version. An instance of the Page Object will exist per CMS page version.
If a version of the page is deleted then the “Comments” Page Object owned by that version will be deleted but not those owned by other versions of the page. | http://world.episerver.com/Documentation/Items/Tech-Notes/EPiServer-CMS-6/EPiServer-CMS-60/Page-Objects/ | CC-MAIN-2017-09 | refinedweb | 1,360 | 50.77 |
While the bulk of the changes in Java 1.1 are additions to
the core Java API, there has also been a major addition to
the language itself. The language has been
extended to allow class definitions to be nested within
other classes, and even to be defined locally, within blocks
of code. Altogether, there are four new types of classes
that can be defined in Java 1.1; these four new types
are sometimes loosely referred to as "inner classes."
Chapter 5, Inner Classes and Other New Language Features
explains in detail how to define and use each of the four
new types of classes. As we'll see, inner classes are
useful primarily for defining simple "helper" or "adaptor"
classes that serve a very specific function at a particular
place in a program, and are not intended to be
general-purpose "top-level" classes. By using inner classes
nested within other classes, you can place the definition of
these special-purpose helper classes closer to where they
are actually used in your programs. This makes your code
clearer, and also prevents you from cluttering up the
package namespace with small special purpose classes that
are not of interest to programmers using your package.
We'll also see that inner classes are particularly useful
in conjunction with the new AWT event model in Java 1.1.
One important feature of inner classes is that no changes to
the Java Virtual Machine are required to support them.
When a Java 1.1 compiler encounters an inner class, it
transforms the Java 1.1 source code in a way that converts
the nested class to a regular top-level class. Once that
transformation has been performed, the code can be compiled
just as it would have been in Java 1.0. | https://docstore.mik.ua/orelly/java/javanut/ch04_02.htm | CC-MAIN-2019-26 | refinedweb | 300 | 60.45 |
I am an amateur programmer currently taking a c++ class in college. I am working on Visual Studios 2019 and my code for a project keeps saying there are build errors but doesn’t tell me what they are and refuses to debug.
#include <iostream> using namespace std; // Initialize the array int linearSearch(int[], int, int); int main() { const int SIZE = 10; int lotterySelections[SIZE] = { 13579, 26791, 26792, 33445, 55555, 62483, 77777, 85647, 93121 }; int results, number; // Ask user to input latest lottery numbers cout << "Please input this weeks lottery numbers."; cin >> number; // Search the array for a match results = linearSearch(lotterySelections, SIZE, number); // If linearSearch returned -1, then a match was not found if (results == -1) cout << "You didn't win this week. :("; else { // Otherwise program shows you win cout << "You won!!! :D"; } return 0; }
Is there something wrong with my code?
Source: Windows Questions C++ | https://windowsquestions.com/2021/09/28/visual-studios-returning-system-cannot-find-the-file-specified-closed/ | CC-MAIN-2021-43 | refinedweb | 147 | 67.79 |
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Re: Can I get some help please "warning: multi-character character constant" and more
From:
"kanze" <kanze@gabi-soft.fr>
Newsgroups:
comp.lang.c++.moderated
Date:
6 May 2006 10:12:05 -0400
Message-ID:
<1146817373.411558.326940@j33g2000cwa.googlegroups.com>
Allan W wrote:
[Just a couple of nits. Your explination is actually quite
good.]
Here's a more detailed explanation:
There are several different types of "literals" in C++.
3 -- is an "integer-literal" with the value 3. You
can use it in expressions such as
age = 3;
3.0 -- is a "floating-literal" with the value 3. You
can use it in expressions such as
result = 3.0;
"Three" -- is a "string-literal" with five characters plus
the terminating null character. You can use it
in expressions such as
std::cout << "Three" << std::endl;
(or, sinc you've use "using namespace std;" you
can just write)
cout << "Three" << endl;
'X' -- is a "character-literal" which is the letter X.
In some contexts you can use it as if it was an
integer with the same value as the character
code for an X (this is 88 in ASCII, other values
on non-ASCII systems).
The type is also a key difference. The literals 3.0 and 3 have
the same "value" (for the usual, everyday meaning of value), but
have different types.
It's important to realize that different types use different
interpretations of the underlying bits to represent the value.
Arguably, 3, 3.0 and '3' represent the same value; their size
and bit patterns are, however, different. In the case of C++,
the issue is further clouded by the fact that C++ has no real
character type: '3' is still an integral type, but not the
same integral type as 3, and also not the same value -- as you
say, it's value is the value of the character code (which is
still a number, and not a character).
Of course, how different bit patterns are interpreted is a
question of convention. Sometimes, the convention is practially
imposed: the C++ standard requires integral values to be
represented in a base 2 notation. Othertimes, hardware offers
direct suppport -- most modern platforms have hardware floating
point support, for example. In the case of characters, the
issue is a bit more complex: the conventions are established by
the software in the windowing drivers or in the printer
hardware; on at least some systems, the conventions can vary
according to the user environment, and it isn't rare for the
system to tell the program that one convention is in effect, but
to use a different one for display in the windowing driver, and
yet a third in the printer. (For the original poster: don't
worry about this yet! You can get a lot of work done,
especially in an English speaking environment, without it ever
being a problem. On the other hand, in a multilingual,
networked environment, it can drive you nuts, because you have
no control over so many of the factors.)
On some computers, the data type that holds single characters is
actually able to hold more than one character at the same time,
but this is not portable. On those systems, you could write
'AB'
and your character-literal would contain both the letters A and B
(in that order). But this is still different than a string.
It's worse than that. Historically, C promoted everything in an
expression to an int. And character literals had type int,
which typically could hold more than one character. C++ broke
with C here, because you really do want character literals to
overload differently than int's: "cout << ' '" should output
" ", and not "32". But it only did a minimal break:
multi-character literals were still supported, with exactly the
same semantics as in C (which is to say: implementation defined
semantics). Thus, '3' has a type char, and an integral value of
51 (0x33), but '32' has a type int, and an integral value of
13106 (0x3332) on my machines -- more importantly, overload
resolution prefers char for '3', but int for '32', so that "cout
<< '3'" outputs "3", but "cout << '32'" outputs 13106. For the
orginal poster: this brings us back to the conventions
concerning the representation, above. The convention for <<
char is to treat the set of bits (the integral value) as a
character code, and output the corresponding character; the
convention for << int is to treat the set of bits as a signed
integer, and output the value of that integer. (This convention
is defined by the C++ standard in the case of a << operator
where the left hand operand is an ostream.)
Of course, if the execution character set includes multibyte
characters, the issue becomes even more clouded. Supposing
UTF-8 as the execution (and source) character set, something
like '?' is a multibyte character constant: type int, and << '?'
would output something like "50089". (I say would, because none
of my compilers support UTF-8 as a character set.) On the other
hand, if the source character set is UTF-8, and the execution
character set is ISO 8859-1, then '\xC3\xA9' is a single byte
character constant, and << '\xC3\xA9' should output "?".
--. | https://preciseinfo.org/Convert/Articles_CPP/PPP_Experts/C++-VC-ATL-STL-PPP-Experts-060506171205.html | CC-MAIN-2022-05 | refinedweb | 884 | 61.36 |
Today I was playing a little bit with encoding variables in c style to get easy communication to a necessary c-program.
I read
I know that \x starts 2 digit hex representation but for a few numbers I get:
from struct import *
datum=239179
buf = pack(">Q", datum)
buf
'\x00\x00\x00\x00\x00\x03\xa6K'
What ist \xa6K? \xa6 is the valid form.
Unpacking this variable works totally fine, so it seems a legit way of hex but why? For a similar problem a friend wrote a go-program, which gives him for the same number
00 00 00 00 00 03 a6 4b . Now if we check the hex value of K it is 4b.
tldr;
Why is \xa6K the same as \xa6\x4b ?
Thanks for your help :)
Thanks for this solution , i feel a little bit stupid :D
struct.pack returns a
str object (
bytes in python3). Strings choose to represent non-printing characters using hex codes (
'\xa6' for instance). However, the byte corresponding to
'\x4b' is a printable character, so the string uses that instead. | http://m.dlxedu.com/m/askdetail/3/f48cfa021bbc76d6bb6046c82e7ba984.html | CC-MAIN-2018-47 | refinedweb | 180 | 72.97 |
Andrew Gerrand
4 August 2010
Go has the usual mechanisms for control flow: if, for, switch, goto. It also has the go statement to run code in a separate goroutine. Here I'd like to discuss some of the less common ones: defer, panic, and recover.
A defer statement pushes a function call onto a list. The list of saved calls is executed after the surrounding function returns. Defer is commonly used to simplify functions that perform various clean-up actions.
For example, let's look at a function that opens two files and copies the contents of one file to the other:
func CopyFile(dstName, srcName string) (written int64, err error) {
src, err := os.Open(srcName)
if err != nil {
return
}
dst, err := os.Create(dstName)
if err != nil {
return
}
written, err = io.Copy(dst, src)
dst.Close()
src.Close()
return
}
This works, but there is a bug. If the call to os.Create fails, the function will return without closing the source file. This can be easily remedied by putting a call to src.Close before the second return statement, but if the function were more complex the problem might not be so easily noticed and resolved. By introducing defer statements we can ensure that the files are always closed:
func CopyFile(dstName, srcName string) (written int64, err error) {
src, err := os.Open(srcName)
if err != nil {
return
}
defer src.Close()
dst, err := os.Create(dstName)
if err != nil {
return
}
defer dst.Close()
return io.Copy(dst, src)
}
Defer statements allow us to think about closing each file right after opening it, guaranteeing that, regardless of the number of return statements in the function, the files will be closed.
The behavior of defer statements is straightforward and predictable. There are three simple rules:
1. A deferred function's arguments are evaluated when the defer statement is evaluated.
In this example, the expression "i" is evaluated when the Println call is deferred. The deferred call will print "0" after the function returns.
func a() {
i := 0
defer fmt.Println(i)
i++
return
}
2. Deferred function calls are executed in Last In First Out order after the surrounding function returns.
This function prints "3210":
func b() {
for i := 0; i < 4; i++ {
defer fmt.Print(i)
}
}
3. Deferred functions may read and assign to the returning function's named return values.
In this example, a deferred function increments the return value i after the surrounding function returns. Thus, this function returns 2:
func c() (i int) {
defer func() { i++ }()
return 1
}
This is convenient for modifying the error return value of a function; we will see an example of this shortly.
Panic is a built-in function that stops the ordinary flow of control and begins panicking. When the function F calls panic, execution of F stops, any deferred functions in F are executed normally, and then F returns to its caller. To the caller, F then behaves like a call to panic. The process continues up the stack until all functions in the current goroutine have returned, at which point the program crashes. Panics can be initiated by invoking panic directly. They can also be caused by runtime errors, such as out-of-bounds array accesses.
Recover is a built-in function that regains control of a panicking goroutine. Recover is only useful inside deferred functions. During normal execution, a call to recover will return nil and have no other effect. If the current goroutine is panicking, a call to recover will capture the value given to panic and resume normal execution.
Here's an example program that demonstrates the mechanics of panic and defer:
package main
import "fmt"
func main() {
f()
fmt.Println("Returned normally from f.")
}
func f() {
defer func() {
if r := recover(); r != nil {
fmt.Println("Recovered in f", r)
}
}()
fmt.Println("Calling g.")
g(0)
fmt.Println("Returned normally from g.")
}
func g(i int) {
if i > 3 {
fmt.Println("Panicking!")
panic(fmt.Sprintf("%v", i))
}
defer fmt.Println("Defer in g", i)
fmt.Println("Printing in g", i)
g(i + 1)
}
The function g takes the int i, and panics if i is greater than 3, or else it calls itself with the argument i+1. The function f defers a function that calls recover and prints the recovered value (if it is non-nil). Try to picture what the output of this program might be before reading on.
The program will output:
Calling g.
Printing in g 0
Printing in g 1
Printing in g 2
Printing in g 3
Panicking!
Defer in g 3
Defer in g 2
Defer in g 1
Defer in g 0
Recovered in f 4
Returned normally from f.
If we remove the deferred function from f the panic is not recovered and reaches the top of the goroutine's call stack, terminating the program. This modified program will output:
Calling g.
Printing in g 0
Printing in g 1
Printing in g 2
Printing in g 3
Panicking!
Defer in g 3
Defer in g 2
Defer in g 1
Defer in g 0
panic: 4
panic PC=0x2a9cd8
[stack trace omitted]
For a real-world example of panic and recover, see the json package from the Go standard library. It encodes an interface with a set of recursive functions. If an error occurs when traversing the value, panic is called to unwind the stack to the top-level function call, which recovers from the panic and returns an appropriate error value (see the 'error' and 'marshal' methods of the encodeState type in encode.go).
The convention in the Go libraries is that even when a package uses panic internally, its external API still presents explicit error return values.
Other uses of defer (beyond the file.Close example given earlier) include releasing a mutex:
mu.Lock()
defer mu.Unlock()
printing a footer:
printHeader()
defer printFooter()
and more.
In summary, the defer statement (with or without panic and recover) provides an unusual and powerful mechanism for control flow. It can be used to model a number of features implemented by special-purpose structures in other programming languages. Try it out. | https://blog.golang.org/defer-panic-and-recover?source=post_page--------------------------- | CC-MAIN-2019-35 | refinedweb | 1,022 | 58.48 |
July
Security.
Brief items
Why would we want to terrorize our own population by doing exactly what we
don't want anyone else to do? And a national emergency is precisely the
worst time to do it.
New vulnerabilities
From the MeeGo advisory:
The file /usr/libexec/abrt-hook-python is setuid as the abrt user.
As there is no explicit reason to be setuid as the abrt user, this
violates best known practices for security; specifically by not using
the principles of least privilege and unintentionally expanding the
attackable surface area of MeeGo.
From the Pardus advisory:
CVE-2010-2431:
The cupsFileOpen function in CUPS before 1.4.4 allows local users, with
lp group membership, to overwrite arbitrary files via a symlink attack
on the (1) /var/cache/cups/remote.cache or (2) /var/cache/cups/job.cache
file.
CVE-2010-24.
David Srbecky discovered that Ghostscript incorrectly handled debug
logging. If a user or automated system were tricked into opening a crafted
PDF file, an attacker could cause a denial of service or execute arbitrary
code with privileges of the user invoking the program. (CVE-2009-4270)
It was discovered that Ghostscript incorrectly handled certain malformed
files. If a user or automated system were tricked into opening a crafted
Postscript or PDF file, an attacker could cause a denial of service or
execute arbitrary code with privileges of the user invoking the program. (CVE-2009-4897)
Dan Rosenberg discovered that Ghostscript incorrectly handled certain
recursive Postscript files. If a user or automated system were tricked into
opening a crafted Postscript file, an attacker could cause a denial of
service or execute arbitrary code with privileges of the user invoking the
program. (CVE-2010-1628)
The /usr/bin/gnomine binary is setgid for the games group. There is
no explicit reason to be setgid and this violates best known practices
for security; specifically by not using the prinicples of least
privilege and unintentionally expanding the attackable surface area of
MeeGo.
a deficiency in the way gv handled temporary file creation,
when used for opening Portable Document Format (PDF) files.
A local attacker could use this flaw to conduct symlink attacks,
potentially leading to denial of service (un-athorized overwrite
of file content). (CVE-2010-2056)
From the Red Hat bugzilla:
A security flaw was found in the way gs handled its initialization:
1, certain files in current working directory were honored at startup,
2, explicit use of "-P-" command line option, did not prevent
ghostscript from execution of PostScript commands, contained
within "gs_init.ps" file.
A local attacker could use this flaw to execute arbitrary PostScript
commands, if the victim was tricked into opening a PostScript file
in the directory of attacker's intent. (CVE-2010-2055)
CVE-2010-1641:
The do_gfs2_set_flags function in fs/gfs2/file.c in the Linux kernel
before 2.6.34-git10 does not verify the ownership of a file, which
allows local users to bypass intended access restrictions via a SETFLAGS
ioctl request.
CVE-2010-2071:
The btrfs_xattr_set_acl function in fs/btrfs/acl.c in btrfs in the Linux
kernel 2.6.34 and earlier does not check file ownership before setting
an ACL, which allows local users to bypass file permissions by setting
arbitrary ACLs, as demonstrated using setfacl.
CVE-2010-2066:
If the donor file is an append-only file, we should not allow the
operation to proceed, lest we end up overwriting the contents of an
append-only file.
On a 32-bit machine, info.rule_cnt >= 0x40000000 leads to integer overflow and the buffer may be smaller than needed. Since ETHTOOL_GRXCLSRLALL is
unprivileged, this can presumably be used for at least denial of service. (CVE-2010-2478). (CVE-2010-2495)
Heap-based buffer overflow in IN_MOD.DLL (aka the Module Decoder
Plug-in) in Winamp before 5.57, and libmikmod 3.1.12, might allow
remote attackers to execute arbitrary code via an Ultratracker file.
From the Red Hat advisory:
An input validation flaw was discovered in libtiff. An attacker could use
this flaw to create a specially-crafted TIFF file that, when opened, would
cause an application linked against libtiff to crash. (CVE-2010-2598))
CVE-2010-0653: Opera permits
cross-origin loading of CSS style sheets even when the
style sheet download has an incorrect MIME type and the
style sheet document is malformed, which allows remote HTTP
servers to obtain sensitive information via a crafted
document.
CVE-2010-1993: Opera 9.52 does not properly handle an
IFRAME element with a mailto: URL in its SRC attribute,
which allows remote attackers to cause a denial of service
(resource consumption) via an HTML document with many
IFRAME elements.
From the Ubuntu advisory:
Denis Excoffier discovered that the PAM MOTD module in Ubuntu did
not correctly handle path permissions when creating user file stamps.
A local attacker could exploit this to gain root privilieges.
Matt Giuca discovered a buffer overflow in python-cjson, a fast JSON
encoder/decoder for Python.
This allows a remote attacker to cause a denial of service (application crash)
through a specially-crafted Python script.
From the Fedora advisory:
Fix potential single-quoting XSS vulnerability.
From the Red Hat bugzilla:
An off by one memory corruption issue exists in
WebSocketHandshake::readServerHandshake(). This issue is addressed by improved bounds checking. (CVE-2010-1766)
From the Red Hat bugzilla:
A use after free issue exists in WebKit's handling of geolocation events.
Visiting a maliciously crafted website may lead to an unexpected application
termination or arbitrary code execution. This issue is addressed through
improved handing of geolocation events. (CVE-2010-1772)
From the Red Hat bugzilla:
An off by one memory read out of bounds issue exists in WebKit's handling of HTML lists. Visiting a maliciously crafted website may lead to an unexpected application termination or the disclosure of the contents of memory. This issue is addressed through improved bounds checking. (CVE-2010-1773)
Multiple buffer overflow flaws were found in scsi-target-utils' tgtd
daemon. A remote attacker could trigger these flaws by sending a
carefully-crafted Internet Storage Name Service (iSNS) request, causing the
tgtd daemon to crash. (CVE-2010-2221).
It was discovered that znc, an IRC bouncer, is vulnerable to denial
of service attacks via a NULL pointer dereference when traffic
statistics are requested while there is an unauthenticated connection.
Page editor: Jake Edge
Kernel development
The current development kernel is 2.6.35-rc5, released on July 12. "And
I merged the ARM defconfig minimization thing, which isn't the final word
on the whole defconfig issue, but since it removes almost 200 _thousand_
lines of ARM defconfig noise, it's a pretty big deal." We looked at the ARM defconfig
issue a few weeks back, and Linus has pulled from Uwe Kleine-König's tree that provides a
starting point for the defconfig cleanup. The short-form changelog is
appended to the announcement, and all the details are available in the full changelog.
Five stable kernels were released on July 5: 2.6.27.48,
2.6.31.14, 2.6.32.16, 2.6.33.6, and 2.6.34.1.
Kernel development news
This article was contributed by Greg Kroah-Hartman.
In the tradition of summarizing the statistics of the Linux kernel
releases before the actual release of the kernel version itself, here is
a summary of what has happened in the Linux kernel tree over the past
few months.
This kernel release has seen 9460 changesets from about 1145 different
developers so far. This continues the trend over the past few kernel
releases for the size of both the changes as well as the development
community as can be seen in this table:
KernelPatchesDevs
2.6.29
11,600
1170
2.6.30
11,700
1130
2.6.31
10,600
1150
2.6.32
10,800
1230
2.6.33
10,500
1150
2.6.34
9,100
1110
2.6.35
9,460
1145
Perhaps our years of increasing developer activity — getting more
developers per release and more changes per release — has finally
reached a plateau. If so, that is not a bad thing, as a number of us
were wondering what the limits of our community were going to be. At
around 10 thousand changes per release, that limit is indeed quite high,
so there is no need to be concerned, as the Linux kernel is still, by
far, the most active software development project the world has ever
seen.
In looking at the individual developers, the quantity and size of
contributions is still quite large:
Most active 2.6.35 developers
By changesets
Mauro Carvalho Chehab2282.3%
Dan Carpenter1351.3%
Greg Kroah-Hartman1341.3%
Arnaldo Carvalho de Melo1211.2%
Johannes Berg1051.0%
Ben Dooks981.0%
Julia Lawall961.0%
Hans Verkuil920.9%
Alexander Graf840.8%
Eric Dumazet820.8%
Peter Zijlstra790.8%
Paul Mundt790.8%
Johan Hovold750.7%
Tejun Heo740.7%
Stephen Hemminger740.7%
Mark Brown710.7%
Sage Weil700.7%
Alex Deucher680.7%
Randy Dunlap670.7%
Frederic Weisbecker660.7%
By changed lines
Uwe Kleine-König19424918.5%
Ralph Campbell532505.1%
Greg Kroah-Hartman317143.0%
Stepan Moskovchenko300372.9%
Arnaud Patard287832.7%
Mauro Carvalho Chehab279022.7%
Eliot Blennerhassett184901.8%
Luis R. Rodriguez165551.6%
Daniel Mack161761.5%
Bob Beers117031.1%
Jason Wessel105021.0%
Viresh KUMAR104991.0%
Barry Song101161.0%
James Chapman96450.9%
Steve Wise95800.9%
Sjur Braendeland87750.8%
Alex Deucher77210.7%
Jassi Brar75540.7%
Sujith75440.7%
Giridhar Malavali68670.7%
Uwe Kleine-König, who works for Pengutronix, dominates the
"changed lines" list due to one patch that Linus just pulled for the 2.5.35-rc5 release that deleted almost all of the ARM
default config files. Linus responded when
Uwe posted his patch with:
> 177 files changed, 652 insertions(+), 194157 deletions(-)
Other than that major cleanup, the majority of the work was in drivers.
Ralph Campbell did a lot of Infiniband driver work, I did a lot of
cleanup on some staging drivers, and Stepan Moskovchenko and Arnaud
Patard contributed new drivers to the staging tree.
Mauro Carvalho Chehab contributed lots of Video for Linux driver work —
rounding out the top 6 contributors by lines of code changed.
Continuing the view that this kernel is much like previous ones, 177
different employers were found to have contributed to the 2.6.35 kernel
release:
Most active 2.6.35 employers
By changesets
(None)142914.2%
Red Hat118511.8%
(Unknown)9049.0%
Intel6376.3%
Novell5595.6%
IBM2952.9%
Nokia2532.5%
(Consultant)2152.1%
Atheros Communications1751.7%
AMD1731.7%
Oracle1691.7%
Samsung1631.6%
Texas Instruments1621.6%
(Academia)1401.4%
Fujitsu1381.4%
Google1221.2%
Renesas Technology1021.0%
Analog Devices981.0%
Simtec961.0%
NTT930.9%
By lines changed
Pengutronix19517518.6%
Red Hat823347.8%
(None)793137.6%
(Unknown)724266.9%
QLogic721316.9%
Novell496514.7%
Intel472604.5%
Code Aurora Forum400813.8%
Mandriva291052.8%
Atheros Communications290552.8%
Samsung258172.5%
ST Ericsson204632.0%
Analog Devices188891.8%
AudioScience Inc.185451.8%
caiaq161941.5%
Nokia148911.4%
Texas Instruments148641.4%
(Consultant)142091.4%
IBM122351.2%
ST Microelectronics117281.1%
But enough of the normal way of looking at the kernel as a whole body.
Let's try something different this time, and break the contributions
down by the different functional areas of the kernel.
The kernel is a bit strange in that it is a mature body of code that still
changes quite frequently and throughout the whole body of code. It is not
just drivers that are changing, but the "core" kernel as well. That is
pretty unusual for a mature code base.
The core kernel code — those files that all architectures and
users use no matter what their configuration is — comprises 5% of the
kernel (by lines of code), and you will find that 5% of the total kernel
changes happen
in that code. Here is the raw number of changes for the "core" kernel
files for the 2.6.35-rc5 release.
ActionLines% of all changes
Added
27,550
4.50%
Deleted
7,450
1.90%
Modified
6,847
4.93%
Note that the percent deleted are a bit off because of the huge defconfig
delete by Uwe
as described above.
So, if the changes are made in a uniform way across the kernel, does
that mean that the same companies contribute in a uniform way as well,
or do some contribute more to one area than another?
I've broken the kernel files down into six different categories:
Category% Lines
Core
4.37%
Drivers
57.06%
Filesystems
7.21%
Networking
5.03%
Arch-specific
21.92%
Miscellaneous
4.43%
Here are the top companies contributing to the different areas of the
kernel:
Most active 2.6.35 employers (core)
By changesets
Red Hat21816.5%
(None)14811.2%
IBM665.0%
Novell604.5%
Intel594.5%
(Unknown)574.3%
Fujitsu332.5%
Google302.3%
Wind River221.7%
Oracle221.7%
Nokia221.7%
(Consultant)221.7%
By lines changed
Wind River953525.4%
Red Hat627716.7%
Novell23856.4%
(None)20745.5%
IBM20645.5%
Intel14803.9%
Fujitsu14313.8%
Google14173.8%
VirtualLogix Inc.9922.6%
ST Ericsson9572.6%
caiaq7071.9%
(Unknown)6141.6%
The companies contributing to the core kernel files are not surprising.
These companies have all contributed to Linux for a long time, and it is
part of their core strategy. Wind River has a high number of lines
changed due to all of the KGDB work that Jason Wessel has been doing in
getting that codebase cleaned up and merged into the main kernel tree.
Most active 2.6.35 employers (drivers)
By changesets
(None)102218.1%
(Unknown)67812.0%
Red Hat5289.4%
Intel4998.9%
Novell3366.0%
Nokia1993.5%
Atheros Communications1652.9%
(Academia)941.7%
IBM861.5%
QLogic861.5%
By lines changed
QLogic7212212.2%
(None)6135610.4%
(Unknown)6080210.3%
Red Hat472048.0%
Intel398916.7%
Novell369516.2%
Code Aurora Forum348885.9%
Mandriva288674.9%
Atheros Communications288444.9%
AudioScience Inc.185353.1%
Because the drivers make up over 50% of the overall
size of the kernel, the contributions here track the overall company statistics
very closely. The company AudioScience Inc. sneaks onto the list of
changes due to all of the work that Eliot Blennerhassett has been doing
on the asihpi sound driver.
Most active 2.6.35 employers (filesystems)
By changesets
Red Hat13415.9%
Oracle779.1%
New Dream Network769.0%
Novell769.0%
(Unknown)738.7%
(None)586.9%
NetApp425.0%
Parallels394.6%
IBM232.7%
Univ. of Michigan CITI232.7%
By lines changed
Oracle719424.2%
Red Hat639221.5%
Novell398913.4%
(Unknown)308110.4%
(None)20246.8%
New Dream Network14234.8%
NetApp8973.0%
Google8572.9%
Parallels6872.3%
(Consultant)5461.8%
Filesystem contributions, like drivers, match up with the different
company strengths. New Dream Network might not be a familiar name to a
lot of people, but their development on the Ceph filesystem pushed it
into the list of top contributors. The University of Michigan did a lot
of NFS work, bringing that organization into the top ten.
Most active 2.6.35 employers (networking)
By changesets
SFR749.6%
(Consultant)739.5%
Red Hat729.3%
(None)678.7%
ProFUSION557.1%
Intel455.8%
Astaro354.5%
Vyatta344.4%
(Unknown)344.4%
Oracle202.6%
ST Ericsson202.6%
Univ. of Michigan CITI202.6%
By lines changed
Katalix Systems921324.2%
ST Ericsson800321.0%
(Consultant)36919.7%
Univ. of Michigan CITI23346.1%
Astaro19565.1%
Red Hat18824.9%
Intel16074.2%
SFR15554.1%
ProFUSION10652.8%
(None)10602.8%
(Unknown)10352.7%
Like the filesystem list, networking also shows the University of
Michigan's large contributions as well as many of the other common Linux
companies. But here a number of not-so-familiar companies start showing
up.
SFR is a French mobile phone company, and contributed lots of changes
all through the networking core. ProFUSION is an embedded development
company that did a lot of Bluetooth development for this kernel release.
Katalix Systems is another embedded development company and they
contributed a lot of l2tp changes. Astaro is a networking security
company that contributed a number of netfilter changes.
Most active 2.6.35 employers (architecture-specific)
By changesets
Red Hat1467.2%
(None)1437.0%
IBM1205.9%
Novell1095.4%
Samsung1004.9%
Texas Instruments944.6%
AMD904.4%
Simtec854.2%
(Unknown)753.7%
(Consultant)733.6%
By lines changed
Pengutronix19421160.5%
Samsung153414.8%
ST Microelectronics100383.1%
(None)83382.6%
Red Hat79812.5%
(Consultant)66952.1%
IBM60641.9%
Novell59731.9%
Code Aurora Forum51141.6%
Analog Devices43451.4%
With the architecture-specific files taking up the second largest chunk
of code in the kernel, the list of contributing companies is closer to
the list of overall contributors as well, with more hardware companies
showing that they contribute a lot of development to get Linux working
properly on their specific processors.
Most active 2.6.35 employers (miscellaneous)
By changesets
Red Hat20626.9%
(None)11014.4%
(Unknown)354.6%
Novell283.7%
Intel273.5%
IBM182.4%
Fujitsu162.1%
Google152.0%
Wind River91.2%
(Academia)91.2%
Vyatta91.2%
By lines changed
Red Hat1277234.0%
Broadcom608216.2%
(None)515613.7%
(Unknown)27577.3%
Intel22125.9%
(Academia)18504.9%
Samsung7692.1%
Wind River5931.6%
Fujitsu5921.6%
Nokia5321.4%
IBM4991.3%
The rest of the various kernel files that don't fall into any other
major category show that Red Hat has done a lot of work on the userspace
performance monitoring tools that are bundled with the Linux kernel.
As for overall trends in the different categories, Red Hat shows that
they completely dominate all areas of developing the Linux kernel when it
comes to the number of contributions. No other company shows up in the top
ten contributors for all categories like they do. But, by breaking out the
kernel contributions in different areas of the kernel, we see that a number
of different companies are large contributors in different, important
areas. Normally these contributions get drowned out by the larger
contributors, but the more specialized contributors are just as important
to advancing the Linux kernel.
This article was contributed by Valerie Aurora (formerly Henson)
Several weeks ago, I mentioned on my blog that I
planned to
move out of programming in the near future. A few days later I
received this email from a kernel hacker friend:
At first, I thought we were losing a great hacker... But
then I read on your blog: "Don't worry, I'm going to get union mounts
into mainline before I change careers," and I realized this means
you'll be with us for a few years yet! :)
How long has union mounts existed without going into the mainline
Linux kernel? Well, to put it in a human perspective, if you'd been
born the same year as the first Linux implementation of union mounts,
you'd be writing your college application essays right now. Werner
Almsberger began work on
the Inheriting
File System, one of the early ancestors of Linux union mounts, in
1993 - 17 years ago!
A union mount does the opposite of a normal mount: Instead of hiding
the namespace of the file system covered by the new mount, it shows a
combination of the namespaces of the unioned file systems. Some use
cases include a writable live CD/DVD-based system (without a
complicated mess of symbolic links, bind mounts, and writable
directories), and a shared base file system used by multiple clients.
For an extremely detailed review of unioning file systems in general,
see the LWN series:
This article will provide a high-level overview of various
implementations of union mounts from the original 1993 Inheriting File
System through the present day VFS-based union mount implementation
and plans for near-term development. We deliberately leave aside
unionfs, aufs, and other non-VFS implementations of unioning, in large
part because the probability of merging a non-VFS unioning file system
into mainline appears to be even lower than that of a VFS-based
solution.
One of the great tragedies of the UNIX file system interface is the
enshrinement
of readdir(), telldir(), seekdir(),
etc. family in the POSIX standard. An application may begin reading
directory entries and pause at any time, restarting later from the
"same" place in the directory. The kernel must give out 32-bit magic
values which allow it to restart the readdir() from the point
where it last stopped. Originally, this was implemented the same way
as positions in a file: the directory entries were stored sequentially
in a file and the number returned was the offset of the next directory
entry from the beginning of the directory. Newer file systems use more
complex schemes and the value returned is no longer a simple
offset. To support readdir(), a unioning file system must
merge the entries from lower file systems, remove duplicates and
whiteouts, and create some sort of stable mapping that allows it to
resume readdir() correctly. Support from userspace libraries
can make this easier by caching the results in user memory.
As mentioned earlier, one of the first implementations of a unioning
was the Inheriting
File System. In a pattern to be repeated by many future
developers, Werner quickly became disenchanted with the complexity of
the implementation of IFS and stopped working on it, suggesting that
future developers try a mixed user/kernel implementation instead:.
Many other kernel developers agreed with Werner. One of Linus
Torvalds' earliest
recorded NAKs of a kernel-based union file system came in 1996:
In 1998, Werner updated his IFS page to suggest working on
a unioning file system as a good academic research topic:
Sounds like a very nice master's thesis topic for some good Linux
hacker ;-) [...] So far nobody has taken the challenge. So, if you're
an aspiring kernel hacker, aren't afraid of complexity, have a lot of
time, and are looking for an interesting but useful project, you may
just have found it :-)
Around 2003 - 2004, Jan Blunck took up the gauntlet Werner threw down
and
began working
on union mounts for his thesis. The union mount implementation
Jan produced lay dormant until 2007, when discussion about
merging unionfs
into mainline
triggered renewed interest in a VFS-based version of unioning. At
that point, Bharata B. Rao took the lead and began working with Jan
Blunck on a new version of union mounts. Bharata and Jan posted
several versions in 2007.
The first
version posted in April 2007 used Jan's original strategy of keeping two
pointers in the dentry for each directory, one pointing to the
directory below this dentry's in the union stack, and one to the
dentry of the topmost directory. The drawback to this implementation
is that each file system can only be in one union stack at a time,
since dentries are shared between all mounts of the same underlying
file system.
The second
version posted in May 2007 implemented yet another minor variation on
in-kernel readdir(), this time using per file pointer cookies. From
the patch set's documentation:
When two processes issue readdir()/getdents() call
on the same unioned directory, both of them would be referring to the
same dentries via their file structures. So it becomes necessary to
maintain rdstate separately for these two instances. This is achieved
by using a cookie variable in the rdstate. Each of these rdstate
instances would get a different cookie thereby differentiating them.
In June 2007, Bharata and
Jan posted
a third version with an important and novel change to the way
union stacks are formed. They replaced the in-dentry links to the
topmost and lower directories with an external structure of pointers
to (vfsmount, dentry) pairs. For the first time, a file system could
be part of more than one union mount. From the patch set's
documentation:.
In July 2007, Jan
posted
a fourth version with some relatively minor changes to the way
whiteouts were implemented, among a few other things. Jan says,
"I'm able to compile the kernel with this patches applied on a 3
layer union mount with the [separate] layers bind mounted to different
locations. I haven't done any performance tests since I think there is
a more important topic ahead: better readdir() support."
In December 2007, Bharata B.
Rao posted
a fifth version that implemented another in-kernel version
of readdir():.
However, this approach had multiple problems, including excessive use
of kernel memory to cache directory entries and to keep the mapping of
indices to dentries.
readdir() continued to be a stumbling block, and union mounts
development slowed down for most of 2008. In April 2008, Nagabhushan
BS implemented
and posted
a version of union mounts with most of the readdir() logic
moved to glibc. "I went through Bharata's RFC post on glibc
based Union Mount readdir solution
()
and have come up with patches against glibc to implement the
same."
However, moving the complexity to user space wasn't the panacea everyone
had hoped for. The glibc maintainers had many objections, the kernel
interface was an obvious kludge (returning whiteouts for "." to signal
a unioned directory), and no one could figure out how to handle NFS
sanely.
In November 2008, Miklos
Szeredi posted
a simplified version of union mounts that implemented readdir() in the
kernel.
The directory entries are read starting from the top layer and they
are maintained in a cache. Subsequently when the entries from the
bottom layers of the union stack are read they are checked for
duplicates (in the cache) before being passed out to the user
space. There can be multiple calls to readdir/getdents routines for
reading the entries of a single directory. But union directory cache
is not maintained across these calls. Instead for every call, the
previously read entries are re-read into the cache and newly read
entries are compared against these for duplicates before being they
are returned to user space.
This implementation only worked for file systems that return a simple
increasing offset in the d_off field for readdir(). So ext2 worked,
but any file system with a modern directory hashing scheme did not.
In early 2009, I started to get interested in union mounts. I talked
to several groups inside Red Hat and asked them what they needed most
from file systems. I heard the same story over and over: "We
really really need a unioning file system, but for some reason no one
at Red Hat will support unionfs..." I did some research on the
available implementations and decided to go to work on Jan Blunck's
union mount patch set.
In May 2009, Jan Blunck and
I posted
a version of union mounts that implemented
in-kernel readdir() using a new concept: the fallthru
directory entry. The basic idea is that the first
time readdir() is called on a directory, the visible
directory entries from all the underlying directories are copied up to
the topmost directory as fallthru directory entries. This eliminated
all the problems I knew of in previous readdir()
implementations, but required the topmost file system to always be
read-write. This implementation also was limited to only two layers:
one read-only file system overlaid with one read-write file system
because we were concerned with lock ordering problems.
In October 2009,
I posted
a version of union mounts that implemented some of the more difficult
system calls, such as truncate(), pivot_root(),
and rename(). However, implementing chmod() and
other system calls that modified files without opening them turned out
to be fairly difficult with the current code base. We thought the
hard part was copying up file data
in open(), rename, and link(), but it
turned out they were somewhat easier to implement because they already
looked up the parent directory of the file to be altered. For union
mounts, we need the parent directory's
dentry and vfsmount in order to create a new version
of the file in the topmost level of the union file system if
necessary. open(), rename, and link() also
needed the parent directory in order to create new directory entries,
so we just reused the parent in the union mount in-kernel copyup code.
But system calls like chmod() that only alter existing files
did not bother to lookup the parent directory's path, only the
target. Regretfully, I decided to start on a major rewrite.
In March 2010,
I posted
a rewrite of the pathname lookup mechanism for union mounts, taking
into account Al Viro's recent VFS cleanups and removing a great deal
of unnecessary code duplication.
In May 2010,
I
posted the first version of union mounts that implemented nearly
all file related system calls correctly. The four exceptions
were fchmod(), fchown(), fsetxattr(),
and futimensat(), which will fail on read-only file
descriptors. (UNIX is full of surprises; none of the VFS experts I
talked to knew that these system calls would succeed on a read-only
fd.)
The central primitive in this version is a function
called user_path_nd(). It is a combination
of user_path(), which looks up a pathname and returns the
corresponding dentry and vfsmount, and user_path_parent(),
which looks up the parent directory of the file or directory given by
the pathname and returns the struct nameidata for the parent. (struct
nameidata is too complex to describe in full here, but suffice to say
it is usually needed to create an entry in a
directory.) user_path_nd() returns both the parent's
nameidata and the child's path. Once we have both these pieces of
information, we can do an in-kernel copyup of a file
in chmod() or any other system call that modifies a file.
Unfortunately, user_path_nd() is also the weakest point in
this version of union mounts: it's racy, inefficient, and copies up
files even if the system call fails.
The day after I posted that version, I flew to North Carolina for a
long-anticipated in-person code review with Al Viro. We spent three
days in his office painfully reviewing the entire union
mount implementation. Al immediately figured out how to delete a
third of the code I'd spent the last year carefully massaging, and
then outlined how to rewrite the other two-thirds of the code more
elegantly, including user_path_nd(). As a result of this
code review marathon, Linux has a feature-complete implementation of
union mounts that has undergone a full code review by the Linux VFS
maintainer for the first time. Of course, the resulting todo list is
long and complex, and some problems may turn out to be insoluble, but
it's an important step forward.
The biggest design change Al suggested was to move the head of the
union stack back into the dentry, while keeping the rest of the union
stack in a singly linked list of struct union_dir's allocated
external to the dentries for the read-only parts of the union stack.
This combines the speed and elegance of Jan Blunck's original
design using in-dentry pointers to the union
stack, with the flexibility of Bharata B. Rao's (vfsmount,
dentry) pairs, which allow file systems to be part of many
read-only layers. This change removed the entire union stack hash
table and the associated lookup logic and shrunk
the union_dir struct from 7 members to 2.
I posted
this hybrid linked list version on June 15, 2010.
Most recently, on June 25th, 2010,
I posted
a version that implemented submounts in the read-only layers, as well
as allowed more than two read-only layers again. Then I went on a two
week vacation - the longest vacation I've had since I started working
on union mounts - and tried to forget everything I knew about it.
The next step is to implement the remainder of Al Viro's review
rewriting user_path_nd() and the in-kernel file copyup
boilerplate. After that, it's back for another round of code review
from Al and the other VFS maintainers. The 2010 Linux Storage and
File Systems workshop is in early August. With luck we can hash out
any remaining architectural problems face-to-face at the workshop and
possibly merge union mounts into mainline before it's old enough to
vote. Or it might languish for another 17 years outside the kernel.
Such are the vicissitudes of Linux kernel development.
Acknowledgments: I want to extend special thanks to the following
people: Kevin Roderick, who provided moral support, Tim Bowen, who
gave me a free day at the
Spoke6 co-working space while I
worked on this article, and, of course, Jake Edge, whose editorial
suggestions were, as usual, right on..
Patches and updates
Kernel trees
Architecture-specific
Build system
Core kernel code
Development tools
Device drivers
Documentation
Filesystems and block I/O
Memory management
Networking
Security-related
Distributions
This article was contributed by Koen Vervloesem
Until not so long ago, your author's main computer was a PowerPC machine, but the number of Linux distributions that officially support this platform is diminishing year by year. So is it still viable to run Linux on a PowerPC computer these days? We'll explore the options, which are roughly subdivided into three categories: PowerPC ports of Linux distributions, PowerPC-specific Linux distributions, and PowerPC ports of non-Linux free operating systems (the BSDs).
When Apple still sold Macs based on the PowerPC processor, the
architecture was relatively well supported by mainstream Linux
distributions. In 2010, PowerPC seems to have fallen off the radar. The
number one reason is that there are currently not many PowerPC systems for
desktop users on the market. For a time, Terra Soft Solutions sold
PowerPC-based workstations, such as the YDL PowerStation, but the
product has been discontinued after Fixstars Solutions acquired the
company. Another popular PowerPC system for Linux users was the PlayStation
3, but Sony removed Linux
support in April of this year. So, at this point, there doesn't seem to
be a mainstream PowerPC desktop system you can buy. Luckily, owners of used
Macs and other PowerPC systems are not left out in the cold, as they can still
run free operating systems.
Ubuntu supported the PowerPC platform officially until version 6.10 ("Edgy Eft"). From 7.04 on, it has still been available, but as a community port. In February 2007, Matt Zimmerman explained the decision in the ubuntu-announce mailing list:
At the moment, Canonical has still one supported PowerPC release: the server edition of Ubuntu 6.06 LTS, which will be supported on PowerPC until June 2011. The Ubuntu community picked up PowerPC maintenance for the other releases, and interested users can still download ISO images for the 7.10 through 10.04 releases in the ports section of the main Ubuntu mirror. Ubuntu's wiki contains a FAQ and a list of known issues for PowerPC users, although the information is slightly outdated.
OpenSUSE dropped official support for PowerPC in its 11.2 release in November 2009. This was done rather quietly: openSUSE 11.2 was released on November 12 without repositories and ISO files for PowerPC, but without any official word that PowerPC support had been removed. After a bug report, Novell's Michael Loeffler gave the official response:
This essentially made the openSUSE PowerPC port a community effort. Stephan Kulow clarified what this required from the community:
More than half a year later, no one seems to have picked up development
and maintenance of the PowerPC port. OpenSUSE has still a POWER@SUSE wiki page with some
general information. This page states that Novell is still planning a
PowerPC port for SUSE Linux Enterprise Server. OpenSUSE users can discuss
PowerPC-related matters in the opensuse-ppc mailing
list, but, not surprisingly, discussions died out this year.
More recently, Fedora 13 dropped official PowerPC support. More specifically, PowerPC has been moved to Fedora's secondary architectures, which means that a build failure on the PowerPC platform doesn't hold back a Fedora release. Moreover, neither Fedora nor Red Hat provide hosting space or build servers for secondary architectures.
In a response to a user's outcry, Red Hat's Tom Callaway explained the reason of the move to the secondary architectures:
In short, it's up to the community to maintain the PowerPC port of Fedora if they want it to continue, but so far they don't seem to have the necessary infrastructure. More information can be found on the fedora-ppc mailing list.
So among the Linux distributions that dropped official PowerPC support, only Ubuntu has managed to keep it alive as a community effort. But there are still a handful of distributions with "official" PowerPC support. The most important among them is Debian. This is actually the Linux distribution that your author has been running on his PowerMac G5 for years after he ditched Mac OS X. As can be seen on the debian-powerpc mailing list, there's still a lot of activity going on in Debian PPC land.
The Debian PowerPC
port began in 1997 and was first officially released with Debian
GNU/Linux 2.2 ("Potato"). A completely 64-bit environment doesn't exist,
though. On 64-bit processors such as the G5, Debian PPC uses a 64-bit
kernel with 32-bit user space. This is because the 64-bit PowerPC
processors have no "32-bit mode" like the Intel 64/AMD64
architecture. Hence, 64-bit PowerPC programs that do not need 64-bit
mathematical functions will run somewhat slower than their 32-bit
counterparts because 64-bit pointers and long integers consume twice as
much memory, fill the CPU cache faster, and thus need more frequent memory
accesses. There is, however, a Debian PPC64 port in
development, offering a complete 64-bit user space for those that want it.
Gentoo Linux also has a PowerPC port, both for
32 and 64 bits. The most recent ISO
image is from October 2009, while the most recent stage3 file (the Gentoo base system tarball) is from May. As can be expected from Gentoo, the project has an extensive PPC handbook and FAQ. Users that get into trouble can find help on the gentoo-ppc-users mailing list.
While Arch Linux is focused on
the i686 and x86-64 architectures, there is a separate spin-off project for
PowerPC machines: Arch Linux
PPC. The port offers a 32-bit user space, but it has various kernels
for 64-bit machines. The most recent release for which an ISO file can be
downloaded is
2010.02.26 with a 2.6.33 kernel. In addition, Arch Linux PPC has a special install guide for PowerPC machines.
CRUX has the same approach: the
distribution is focused on the i686 architecture, but some users wanted a
PowerPC port and just made it happen: CRUX PPC. Note, however, that the team
is small and development is slow. The latest release is CRUX PPC
2.6 and it dates from January. There are both 32-bit and 64-bit ISO
images available. In the same style as Gentoo, CRUX PPC has an extensive handbook and
FAQ, as well as a cruxppc mailing list, but it is not very active.
Another general-purpose Linux distribution that supports PowerPC is T2 SDE. The project has a small but
dedicated community, and the PowerPC (32-bit and 64-bit) platform is well
supported. The main developer René Rebe is using it on some of his
machines. Users that want to install T2 SDE on their Mac can download the recently released minimal ISO images for T2 SDE 8.0 or build the ISO file themselves. T2 SDE is not an easy-to-use Linux distribution (it's comparable to Gentoo Linux), but your author has been testing it for some time on his PowerMac G5 and was interested by the clean source-based approach.
Yellow Dog Linux (YDL), a
Linux distribution specifically developed for the PowerPC architecture,
closes out the list. It is based on CentOS and uses Enlightenment as its default desktop environment, although GNOME and KDE can also be installed. Before Apple's transition to the Intel architecture, Terra Soft Solutions was the only company licensed by Apple to resell Apple computers with Linux pre-installed, so it has a history with PowerPC machines.
The latest version is 6.2, released in June 2009. Users can download a big DVD ISO image from one of the mirrors. There is a list of supported hardware, which also includes non-Apple PowerPC machines, a lot of documentation about the installation and configuration, and some HOWTOs about various topics. Meanwhile, Terra Soft Solutions has been acquired by Fixstars, which refocused its Linux distribution on high performance computing and GPU systems. So, while YDL 6.2 still supports PowerPC-based Apple machines, it's main target is now the Sony PlayStation 3 and IBM pSeries platforms.
For users that don't mind leaving the Linux ecosystem, there are some other options in the BSD world. FreeBSD, OpenBSD and NetBSD all have a PowerPC port, and most of the supported software is the same as on a Linux distribution, so for most practical purposes it doesn't matter if you're running Linux or BSD.
NetBSD (the operating system with the motto "Of course it runs NetBSD") has different ports for various Power PC systems: ofppc, macppc, evbppc, mvmeppc, bebox, sandpoint, and amigappc. The relevant port for Mac Users is of course macppc, which was introduced in NetBSD 1.4.
There is a complete list of supported hardware by the NetBSD/macppc port, and there is an extensive FAQ, which includes a list of supported peripherals. The installation procedure for NetBSD/macppc is documented well to help users get NetBSD on their Mac. As for mailing lists, issues specific to NetBSD on Apple's PowerPC machines are discussed on the port-macppc mailing list, while port-powerpc is about issues relevant to all PowerPC-based NetBSD ports.
The OpenBSD/powerpc port initially supported Motorola computers, but
later refocused on Apple hardware, based on code from the NetBSD/macppc
port. For OpenBSD 3.0 it was renamed to OpenBSD/macppc. Support for
the 64-bit G5 processor (with a 32-bit user space) was added in OpenBSD 3.9. The port's web page has an extensive list of supported hardware and peripherals, and it lists some caveats: sleep/suspend on laptops is not supported, Bluetooth and FireWire are not supported, and SATA doesn't work yet on PowerMac G5 and Xserve G5 systems. The latest OpenBSD/macppc 4.7 release has some installation instructions and users can discuss their problems on the ppc mailing list of OpenBSD.
Last but not least, FreeBSD officially supports the PowerPC port since version 7.0, although it's still a Tier 2 platform. This means that FreeBSD's security officer, release engineers, and toolchain maintainers don't fully support it yet. Nathan Whitehorn has published some installation instructions, and users can discuss matters in the freebsd-ppc mailing list.
Since FreeBSD 8.0, the PowerMac G5 and iMac G5 are supported, and the upcoming 8.1 release also supports the Xserve G5 and the late 2005 model of the PowerMac G5. Previous PowerPC Macs are already supported since version 7.0. There are some caveats, however: the current 32-bit PPC port only supports 2 GB of RAM, and 64-bit PPC support (with support for more RAM) will only be appearing in FreeBSD 9.
While at first sight PowerPC seems to be a dying platform, there's actually still a lot of choice for users that want to run a free operating system on their aged Mac. In the last 10 years, your author has prolonged the life of two PowerPC-based Macs by swapping Mac OS X for a Linux distribution: one time Gentoo Linux, the other time Debian. These are also the two distributions that seem to have the best PowerPC support while still being all-round enough and having a community that is big enough to be of any help. For more adventurous users, there are a lot of other options, with the source-based T2 SDE or NetBSD as notable examples.
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Development
Big projects
switching to a distributed version control system (DVCS) is pretty common
occurrence these days, but it is not always easy or straightforward. Guido
van Rossum
first announced that Python
would move to Mercurial (aka
Hg) in March
2009, but the project is still using Subversion (aka svn) more than a year later.
While the conversion is still in the works, the schedule for the switch is
still up in the air. Recent discussions have pushed it back until sometime
later this year, or possibly early next year.
There appear to be a number of different things that got in the way of
adopting Hg, but clearly the biggest has been problems with how it handled
end-of-line (EOL) conventions. As described
by Brett Cannon, the Python folks were under the impression that Hg had
ways to handle EOL conventions that would make it act like Subversion's
svn:eol setting. When that turned not to be the case, it set the
conversion back.
Efforts were made to design a Mercurial extension—which is written in
Python after all—that would "do the right thing" for line-endings on
Windows, Linux,
and Mac OS X, while not making a mess of binary files. That culminated in
an EOL
Extension that was released as part of Mercurial 1.5.4 in June of this
year. Some of the time it took to get from a design to a working, released
extension can be blamed on Mercurial hacker Martin Geisler's PhD work,
which is something of a recurring theme.
Cannon, who did much of the work in evaluating Git, Bazaar, and Mercurial
before Python chose a DVCS, was delayed shortly after the decision by work on
his PhD. That led
Dirkjan Ochtman to step in and write Python Enhancement Proposal
(PEP) 385, which describes the migration path from svn to Hg. Now
Ochtman is unavailable
to work on the transition until some time in August due to work on his
Master's thesis.
It is a tad amusing to note that projects might be best-served by contributors who either
already have advanced degrees or have decided not to pursue them, but that,
of course,
is a trivialization. There does seem to be a lack of people interested
in making the transition, at least in any hurried fashion, or perhaps there
is a lack of pressure to make the change from the development community side.
In some ways, it would seem that Mercurial has moved into the "nice to
have, but not required" bucket, at least for now.
The timing of making a change to a different VCS can be tricky. There are
lots of dependencies for ongoing release efforts and the like. The
unavailability of Cannon and Ochtman led Martin v. Löwis to put out a call for volunteers. "If nobody volunteers, I propose that we release 3.2
from Subversion, and reconsider Mercurial migration
next year." The first alpha of 3.2 is scheduled for early August,
while the final release is planned for January of next year. Waiting until
after 3.2 would likely mean that the Hg transition will have taken Python
around two years.
Some folks did volunteer, and there was talk of releasing the first 3.2 alpha from
svn, with later releases coming out of Hg, but no firm decision seems to
have been made. There is also some resistance to phasing out svn. Anatoly
Techtonik is concerned about moving away:
But Stephen J. Turnbull disagrees with that
assessment. The transition was planned because it would make developers'
lives easier:
Turnbull notes that a "new proponent and supporting
cast" are actively being sought for the transition.
In addition, he is optimistic about the timing:
At this point, it is in the hands of the Python team. Before the
completion of the EOL Extension, it was relatively easy to find other
things to work on while awaiting the extension. Now that the ball is
firmly back in their court, the importance of Mercurial to the Python
hackers will likely become
more clear. If the team is unable to find the time to make that switch, it
is by no means the end of the world, it is just an indicator that many are
fairly comfortable with their current workflow.
That may be a little
surprising to some, but each project has its own way of working and some
are more suited to a DVCS development style than others. Python has always
been fairly rigorous in its processes, with PEPs for all major—and
many minor—decisions, and a pretty conservative development style.
Moving unhurriedly to switch to Mercurial may fit in with that just fine.
A secondary reasoning for some open source licenses might be to
prevent others from running off with the good stuff and selling it for
profit. The GPL is big on that, but it's never motivated me with
Python (hence the tenuous relationship at best with the FSF and GPL
software).
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Linux is a registered trademark of Linus Torvalds | http://lwn.net/Articles/395455/bigpage | CC-MAIN-2013-48 | refinedweb | 8,226 | 55.03 |
sec_rgy_attr_get_effective-Reads effective attributes by ID
#include <dce/sec_rgy_attr.h> void sec_rgy_attr_get_effective( sec_rgy_handle_t context, sec_rgy_domain_t name_domain, sec_rgy_name_t name, unsigned32 num_attr_keys, sec_attr_t attr_keys[], sec_attr_vec_t *attr of the effective attributes that the caller is authorized to see are returned.
- attr_keys[]
An array of values of type sec_attr_t that specify the UUIDs of the attributes to be returned if they are effective..
Output
- attr_list
A pointer an attribute vector allocated by the server containing all of the effective attributes matching the search criteria (defined in num_attr_keys or attr_keys). The server allocates a buffer large enough to return all the requested attributes so that subsequent calls are not necessary.
- status
A pointer to the completion status. On successful completion, the routine returns error_status_ok. Otherwise, it returns an error.
The sec_rgy_attr_get_effective() routine returns the UUIDs of a specified object's effective attributes. Effective attributes are determined by setting of the schema entry sec_attr_sch_entry_use_defaults flag:
- If the flag is set off, only the attributes directly attached to the object are effective.
- If the flag is set on, the effective attributes are obtained by performing the following steps for each attribute identified by UUID in the attr_keys array:
- If the object named by name is a principal and if the a requested attribute exists on the principal, that attribute is effective and is returned. If it does not exist, the search continues.
- The next step in the search depends on the type of object:
For principals with accounts:
- The organization named in the principal's account is examined to see if an attribute of the requested type exists. If it does, it is effective and is returned; then the search for that attribute ends. If it does not exist, the search for that attribute continues to the policy object as described in b, below.
- The registry policy object is examined to see if an attribute of the requested type exits. If it does, it is returned. If it does not, a message indicating the no attribute of the type exists for the object is returned.
For principals without accounts, for groups, and for organizations:
The registry policy object is examined to see if an attribute of the requested type exits. If it does, it is returned. If it does not, a message indicating the no attribute of the type exists for the object is returned.
For multi-valued attributes, the call returns a sec_attr_t for each value as an individual attribute instance. For attribute sets, the call returns a sec_attr_t for each member of the set; it does not return the set instance. requested attribute type is associated with a query trigger, the value returned for the attribute will be the binding (as set in the schema entry) of the trigger server. The caller must bind to the trigger server and pass the original input query attribute to the sec_attr_trig_query() call in order to retrieve the attribute value.
- /usr/include/dce/sec_rgy_attr.idl
The idl file from which dce/sec_rgy_attr.h was derived.
- error_status_ok
The call was successful. | http://pubs.opengroup.org/onlinepubs/9696989899/sec_rgy_attr_get_effective.htm | CC-MAIN-2016-30 | refinedweb | 501 | 53.71 |
Exegesis 5Exegesis 5
Editor's note: this document is out of date and remains here for historic interest. See Synopsis 5 for the current design information.
$hunk
$hunk...'
Apocalypse 5 marks a significant departure in the ongoing design of Perl 6.
Previous Apocalypses took an evolutionary approach to changing Perl's general syntax, data structures, control mechanisms and operators. New features were added, old features removed, and existing features were enhanced, extended and simplified. But the changes described were remedial, not radical.
Larry could have taken the same approach with regular expressions. He could
have tweaked some of the syntax, added new
(?...) constructs, cleaned
up the rougher edges, and moved on.
Fortunately, however, he's taking a much broader view of Perl's future
than that. And he saw that the problem with regular expressions was not
that they lacked a
(?$var:...) extension to do named captures, or
that they needed a
\R metatoken to denote a recursive subpattern,
or that there was a
[:YourNamedCharClassHere:] mechanism missing.
He saw that those features, laudable as they were individually, would just compound the real problem, which was that Perl 5 regular expressions were already groaning under the accumulated weight of their own metasyntax. And that a decade of accretion had left the once-clean notation arcane, baroque, inconsistent and obscure.
It was time to throw away the prototype.
Even more importantly, as powerful as Perl 5 regexes are, they are not nearly powerful enough. Modern text manipulation is predominantly about processing structured, hierarchical text. And that's just plain painful with regular expressions. The advent of modules like Parse::Yapp and Parse::RecDescent reflects the community's widespread need for more sophisticated parsing mechanisms. Mechanisms that should be native to Perl.
As Piers Cawley has so eloquently misquoted: “It is a truth universally acknowledged that any language in possession of a rich syntax must be in want of a rewrite.” Perl regexes are such a language. And Apocalypse 5 is precisely that rewrite.
So let's take a look at some of those new features. To do that, we'll consider a series of examples structured around a common theme: recognizing and manipulating data in the Unix diff
A classic diff consists of zero-or-more text transformations, each of
which is known as a “hunk”. A hunk consists of a modification specifier,
followed by one or more lines of context. Each hunk is either an append,
a delete, or a change, and the type of hunk is specified by a single
letter (
'a',
'd', or
'c'). Each of these single-letter specifiers is
prefixed by the line numbers of the lines in the original document it
affects, and followed by the equivalent line numbers in the transformed
file. The context information consists of the lines of the original file
(each preceded by a
'<' character), then the lines of the
transformed file (each preceded by a
'>'). Deletes omit the
transformed context, appends omit the original context. If both contexts
appear, then they are separated by a line consisting of three hyphens.
Phew! You can see why natural language isn't the preferred way of specifying data formats.
The preferred way is, of course, to specify such formats as patterns. And, indeed, we could easily throw together a few Perl 6 patterns that collectively would match any data conforming to that format:
$file = rx/ ^ <$hunk>* $ /;
$hunk = rx :i { [ <$linenum> a :: <$linerange> \n <$appendline>+ | <$linerange> d :: <$linenum> \n <$deleteline>+ | <$linerange> c :: <$linerange> \n <$deleteline>+ --- \n <$appendline>+ ] | (\N*) ::: { fail "Invalid diff hunk: $1" } };
$linerange = rx/ <$linenum> , <$linenum> | <$linenum> /;
$linenum = rx/ \d+ /;
$deleteline = rx/^^ \< <sp> (\N* \n) /; $appendline = rx/^^ \> <sp> (\N* \n) /;
# and later...
my $text is from($*ARGS);
print "Valid diff" if $text =~ /<$file>/;
There's a lot of new syntax there, so let's step through it slowly, starting with:
$file = rx/ ^ <$hunk>* $ /;
This statement creates a pattern object. Or, as it's known in Perl 6, a
“rule”. People will probably still call them “regular expressions” or
“regexes” too (and the keyword
rx reflects that), but Perl patterns
long ago ceased being anything like “regular”, so we'll try and avoid
those terms.
In any case, the
rx constructor builds a new rule, which is then
stored in the
$file variable. The Perl 5 equivalent would be:
# Perl 5 my $file = qr/ ^ (??{$hunk})* $ /x;
This illustrates quite nicely why the entire syntax needed to change.
The name of the rule constructor has changed from
qr to
rx,
because in Perl 6 rule constructors aren't quotelike contexts.
In particular, variables don't interpolate into
rx constructors
in the way they do for a
qx. That's why we can embed the
$hunk variable before it's actually initialized.
In Perl 6, an embedded variable becomes part of the rule's implementation rather than part of its “source code”. As we'll see shortly, the pattern itself can determine how the variable is treated (i.e., whether to interpolate it literally, treat it as a subpattern or use it as a container).
by Damian Conway
Editor's note: this document is out of date and remains here for historic interest. See Synopsis 5 for the current design information.
In Perl 6, each rule implicitly has the equivalent of the Perl 5
/x modifier
turned on, so we could lay out (and annotate) that first pattern like this:
$file = rx/ ^ # Must be at start of string <$hunk> # Match what the rule in $hunk would match... * # ...zero-or-more times $ # Must be at end of string (no newline allowed) /;
Because
/x is the default, the whitespace in the pattern is ignored,
which allows us to lay out the rule more readably. Comments are also honored,
which enables us to document the rule sensibly. You can even use the closing
delimiter in a comment safely:
$caveat = rx/ Make \s+ sure \s+ to \s+ ask \s+ (mum|mom) # handle UK/US spelling \s+ (and|or) # handle and/or \s+ dad \s+ first /;
Of course, the examples in this Exegesis don't represent good comments in general, since they document what is happening, rather than why.
The meanings of the
^ and
* metacharacters are unchanged
from Perl 5. However, the meaning of the
$ metacharacter has
changed slightly: it no longer allows an optional newline before the end
of the string. If you want that behavior, then you need to specify it
explicitly. For example, to match a line ending in digits:
/ \d+ \n? $/
The compensation is that, in Perl 6, a
\n in a pattern matches a logical
newline (that is any of:
"\015\012" or
"\012" or
"\015"
or
"\x85" or
"\x2028"), rather than just a
physical ASCII newline (i.e. just
"\012"). And a
\n will always
try to match any kind of physical newline marker (not just the current system's
favorite), so it correctly matches against strings that have been
aggregated from multiple systems.
The really new bit in the
$file rule is the
<$hunk> element.
It's a directive to grab whatever's in the
$hunk variable (presumably
another pattern) and attempt to match it at that point in the rule. The
important point is that the contents of
$hunk are only grabbed when
the pattern matching mechanism actually needs to match against them,
not when the rule is being constructed. So it's like the mysterious
(??{...}) construct in Perl 5 regexes.
The angle brackets themselves are a much more general mechanism in Perl 6 rules.
They are the “metasyntactic markers” and replace the Perl 5
(?...) syntax.
They are used to specify numerous other features of Perl 6 rules, many of which
we will explore below.
Note that if we hadn't put the variable in angle-brackets, and had just written:
rx/ ^ $hunk* $ /;
then the contents of
$hunk would still not be interpolated when
the pattern was parsed. Once again, the pattern would grab the
contents of the variable when it reached that point in its match.
But, this time, without the angle brackets around
$hunk, the
pattern would try to match the contents of the variable as an
atomic literal string (rather than as a subpattern). “Atomic”
means that the
* repetition quantifier applies to everything
that's in
$hunk, not just to the last character
(as it does in Perl 5).
In other words, a raw variable in a Perl 6 pattern is matched
as if it was a Perl 5 regex in which the interpolation had been
quotemeta'd and then placed in a pair of noncapturing parentheses.
That's really handy in something like:
# Perl 6 my $target = <>; # Get literal string to search for $text =~ m/ $target* /; # Search for them as literals
which in Perl 5 we'd have to write as:
# Perl 5 my $target = <>; # Get literal string to search for chomp $target; # No autochomping in Perl 5 $text =~ m/ (?:\Q$target\E)* /x; # Search for it, quoting metas
Raw arrays and hashes interpolate as literals, too. For example, if we use an array in a Perl 6 pattern, then the matcher will attempt to match any of its elements (each as a literal). So:
# Perl 6 @cmd = ('get','put','try','find','copy','fold','spindle','mutilate');
$str =~ / @cmd \( .*? \) /; # Match a cmd, followed by stuff in parens
is the same as:
# Perl 5 @cmd = ('get','put','try','find','copy','fold','spindle','mutilate'); $cmd = join '|', map { quotemeta $_ } @cmd;
$str =~ / (?:$cmd) \( .*? \) /;
By the way, putting the array into angle brackets would cause the matcher to try and match each of the array elements as a pattern, rather than as a literal.
$hunk
The rule that
<$hunk> tries to match against is the next one defined
in the program. Here's the annotated version of it:
$hunk = rx :i { # Case-insensitively... [ # Start a non-capturing group <$linenum> # Match the subrule in $linenum a # Match a literal 'a' :: # Commit to this alternative <$linerange> # Match the subrule in $linerange \n # Match a newline <$appendline> # Match the subrule in $appendline... + # ...one-or-more times | # Or... <$linerange> d :: <$linenum> \n # Match $linerange, 'd', $linenum, newline <$deleteline>+ # Then match $deleteline once-or-more | # Or... <$linerange> c :: <$linerange> \n # Match $linerange, 'c', $linerange, newline <$deleteline>+ # Then match $deleteline once-or-more --- \n # Then match three '-' and a newline <$appendline>+ # Then match $appendline once-or-more ] # End of non-capturing group | # Or... ( # Start a capturing group \N* # Match zero-or-more non-newlines ) # End of capturing group ::: # Emphatically commit to this alternative { fail "Invalid diff hunk: $1" } # Then fail with an error msg };
The first thing to note is that, like a Perl 5
qr, a Perl 6
rx can take
(almost) any delimiters we choose. The
$hunk pattern uses
{...}, but
we could have used:
rx/pattern/ # Standard rx[pattern] # Alternative bracket-delimiter style rx<pattern> # Alternative bracket-delimiter style rx«forme» # Délimiteurs très chic rx>pattern< # Inverted bracketing is allowed too (!) rx»Muster« # Begrenzungen im korrekten Auftrag rx!pattern! # Excited rx=pattern= # Unusual rx?pattern? # No special meaning in Perl 6 rx#pattern# # Careful with these: they disable internal comments
In fact, the only characters not permitted as
rx delimiters are
':' and
'('. That's because
':' is the character used to
introduce pattern modifiers in Perl 6, and
'(' is the character used
to delimit any arguments that might be passed to those pattern modifiers.
In Perl 6, pattern modifiers are placed before the pattern, rather
than after it. That makes life easier for the parser, since it doesn't
have to go back and reinterpret the contents of a rule when it reaches
the end and discovers a
/s or
/m or
/i or
/x. And it makes life
easier for anyone reading the code -- for precisely the same reason.
The only modifier used in the
$hunk rule is the
:i (case-insensitivity)
modifier, which works exactly as it does in Perl 5.
The other rule modifiers available in Perl 6 are:
:eor
:each
This is the replacement for Perl 5's
/g modifier. It causes a
match (or substitution) to be attempted as many times as possible.
The name was changed because “each” is shorter and clearer in intent
than “globally”. And because the
:each modifier can be combined with
other modifiers (see below) in such a way that it's no longer “global”
in its effect.
:x($count)
This modifier is like
:e, in that it causes the match or substitution
to be attempted repeatedly. However, unlike
:e, it specifies exactly
how many times the match must succeed. For example:
"fee fi " =~ m:x(3)/ (f\w+) /; # fails "fee fi fo" =~ m:x(3)/ (f\w+) /; # succeeds (matches "fee","fi","fo") "fee fi fo fum" =~ m:x(3)/ (f\w+) /; # succeeds (matches "fee","fi","fo")
Note that the repetition count doesn't have to be a constant:
m:x($repetitions)/ pattern /
There is also a series of tidy abbreviations for all the constant cases:
m:1x/ pattern / # same as: m:x(1)/ pattern / m:2x/ pattern / # same as: m:x(2)/ pattern / m:3x/ pattern / # same as: m:x(3)/ pattern / # etc.
:nth($count)
This modifier causes a match or substitution to be attempted repeatedly,
but to ignore the first
$count-1 successful matches. For example:
my $foo = "fee fi fo fum";
$foo =~ m:nth(1)/ (f\w+) /; # succeeds (matches "fee") $foo =~ m:nth(2)/ (f\w+) /; # succeeds (matches "fi") $foo =~ m:nth(3)/ (f\w+) /; # succeeds (matches "fo") $foo =~ m:nth(4)/ (f\w+) /; # succeeds (matches "fum") $foo =~ m:nth(5)/ (f\w+) /; # fails $foo =~ m:nth($n)/ (f\w+) /; # depends on the numeric value of $n
$foo =~ s:nth(3)/ (f\w+) /bar/; # $foo now contains: "fee fi bar fum"
Again, there is also a series of abbreviations:
$foo =~ m:1st/ (f\w+) /; # succeeds (matches "fee") $foo =~ m:2nd/ (f\w+) /; # succeeds (matches "fi") $foo =~ m:3rd/ (f\w+) /; # succeeds (matches "fo") $foo =~ m:4th/ (f\w+) /; # succeeds (matches "fum") $foo =~ m:5th/ (f\w+) /; # fails
$foo =~ s:3rd/ (f\w+) /bar/; # $foo now contains: "fee fi bar fum"
By the way, Perl isn't going to be pedantic about these “ordinal” versions
of repetition specifiers. If you're not a native English speaker, and you
find
:1th,
:2th,
:3th,
:4th, etc., easier to remember, then that's
perfectly OK.
The various types of repetition modifiers can also be combined by separating them with additional colons:
my $foo = "fee fi fo feh far foo fum ";
$foo =~ m:2nd:2x/ (f\w+) /; # succeeds (matches "fi", "feh") $foo =~ m:each:2nd/ (f\w+) /; # succeeds (matches "fi", "feh", "foo") $foo =~ m:x(2):nth(3)/ (f\w+) /; # succeeds (matches "fo", "foo") $foo =~ m:each:3rd/ (f\w+) /; # succeeds (matches "fo", "foo") $foo =~ m:2x:4th/ (f\w+) /; # fails (not enough matches to satisfy :2x) $foo =~ m:4th:each/ (f\w+) /; # succeeds (matches "feh")
$foo =~ s:each:2nd/ (f\w+) /bar/; # $foo now "fee bar fo bar far bar fum ";
Note that the order in which the two modifiers are specified doesn't matter.
:p5or
:perl5
This modifier causes Perl 6 to interpret the contents of a rule as a regular expression in Perl 5 syntax. This is mainly provided as a transitional aid for porting Perl 5 code. And to mollify the curmudgeonly.
:wor
:word
This modifier causes whitespace appearing in the pattern to match optional whitespace in the string being matched. For example, instead of having to cope with optional whitespace explicitly:
$cmd =~ m/ \s* <keyword> \s* \( [\s* <arg> \s* ,?]* \s* \)/;
we can just write:
$cmd =~ m:w/ <keyword> \( [ <arg> ,?]* \)/;
The
:w modifier is also smart enough to detect those cases where
the whitespace should actually be mandatory. For example:
$str =~ m:w/a symmetric ally/
is the same as:
$str =~ m/a \s+ symmetric \s+ ally/
rather than:
$str =~ m/a \s* symmetric \s* ally/
So it won't accidentally match strings like
"asymmetric ally" or
"asymmetrically".
:any
This modifier causes the rule to match a given string in every possible way, simultaneously, and then return all the possible matches. For example:
my $str = "ahhh";
@matches = $str =~ m/ah*/; # returns "ahhh" @matches = $str =~ m:any/ah*/; # returns "ahhh", "ahh", "ah", "a"
:u0,
:u1,
:u2,
:u3
These modifiers specify how the rule matches the dot (
.)
metacharacter against Unicode data. If
:u0 is specified, then dot matches
a single byte; if
:u1 is specified, then dot matches a single codepoint
(i.e. one or more bytes representing a single Unicode “character”).
If
:u2 is specified, then dot matches a single grapheme (i.e. a base
codepoint followed by zero or more modifier codepoints, such as
accents). If
:u3 is specified, then dot matches an appropriate “something”
in a language-dependent manner.
It's OK to ignore this modifier if you're not using Unicode (and maybe even
if you are). As usual, Perl will try to do the right thing.
To that end, the default behavior of rules is
:u2, unless an
overriding pragma (e.g.
use bytes) is in effect.
Note that the
/s,
/m, and
/e modifiers are no longer available.
This is because they're no longer needed. The
/s isn't needed because
the
. (dot) metacharacter now matches newlines as well. When we want
to match “anything except a newline”, we now use the new
\N metatoken
(i.e. “opposite of
\n”).
The
/m modifier isn't required, because
^ and
$ always mean start and
end of string, respectively. To match the start and end of a line, we use
the new
^^ and
$$ metatokens instead.
The
/e modifier is no longer needed, because Perl 6 provides the
$(...) string interpolator (as described in Apocalypse 2). So a
substitution such as:
# Perl 5 s/(\w+)/ get_val_for($1) /e;
becomes just:
# Perl 6 s/(\w+)/$( get_val_for($1) )/;
by Damian Conway
Editor's note: this document is out of date and remains here for historic interest. See Synopsis 5 for the current design information.
The first character of the
$hunk rule is an opening square bracket.
In Perl 5, that denoted the start of a character class, but not in Perl 6.
In Perl 6, square brackets mark the boundaries of a noncapturing
group. That is, a pair of square brackets in Perl 6 are the same as a
(?:...) in Perl 5, but less line-noisy.
By the way, to get a character class in Perl 6, we need to put the square brackets inside a pair of metasyntactic angle brackets. So the Perl 5:
# Perl 5 / [A-Za-z] [0-9]+ /x # An A-Z or a-z, followed by digits
would become in Perl 6:
# Perl 6 / <[A-Za-z]> <[0-9]>+ / # An A-Z or a-z, followed by digits
The Perl 5 complemented character class:
# Perl 5 / [^A-Za-z]+ /x # One-or-more chars-that-aren't-A-Z-or-a-z
becomes in Perl 6:
# Perl 6 / <-[A-Za-z]>+ / # One-or-more chars-that-aren't-A-Z-or-a-z
The external minus sign is used (instead of an internal caret), because Perl 6 allows proper set operations on character classes, and the minus sign is the “difference” operator. So we could also create:
# Perl 6 / < <alpha> - [A-Za-z] >+ / # All alphabetics except A-Z or a-z # (i.e. the accented alphabetics)
Explicit character classes were deliberately made a little less
convenient in Perl 6, because they're generally a bad idea in a
Unicode world. For example, the
[A-Za-z] character class in the
above examples won't even match standard alphabetic Latin-1
characters like
'Ã',
'é',
'ø', let alone alphabetic characters from code-sets
such as Cyrillic, Hiragana, Ogham, Cherokee, or Klingon.
$hunk...
The noncapturing group of the
$hunk pattern groups together three
alternatives, separated by
| metacharacters (as in Perl 5).
The first alternative:
<$linenum> a :: <$linerange> \n <$appendline>+
grabs whatever is in the
$linenum variable, treats it as a
subpattern, and attempts to match against it. It then matches a
literal letter
'a' (or an
'A', because of the
:i modifier on the rule).
Then whatever the contents of the
$linerange variable match. Then a
newline. Then it tries to match whatever the pattern in
$appendline
would match, one or more times.
But what about that double-colon after the
a? Shouldn't the
pattern have tried to match two colons at that point?
Actually, no. The double-colon is a new Perl 6 pattern-control
structure. It has no effect (and is ignored) when the pattern is
successfully matching, but if the pattern match should fail, and consequently
back-track over the double-colon -- for example, to try and rematch an
earlier repetition one fewer times -- the double-colon causes the entire
surrounding group (i.e. the surrounding
[...] in this case) to fail as well.
That's a useful optimization in this case because, if we match a line
number followed by an
'a' but subsequently fail, then there's no
point even trying either of the other two alternatives in the same
group. Because we found an
'a', there's no chance we could match a
'd' or a
'c' instead.
So, in general, a double-colon means: “At this point I'm committed to this alternative within the current group -- don't bother with the others if this one fails after this point”.
There are other control directives like this, too. A single colon means: “Don't bother backtracking into the previous element”. That's useful in a pattern like:
rx:w/ $keyword [-full|-quick|-keep]+ : end /
Suppose we successfully match the keyword (as a literal, by the way) and
one or more of the three options, but then fail to match
'end'.
In that case, there's no point backtracking and trying to match one
fewer option, and still failing to find an
'end'. And then
backtracking another option, and failing again, etc. By using
the colon after the repetition, we tell the matcher to give up after
the first attempt.
However, the single colon isn't just a “Greed is Good” operator. It's much more like a “Resistance is Futile” operator. That is, if the preceding repetition had been non-greedy instead:
rx:w/ $keyword [-full|-quick|-keep]+? : end /
then backtracking over the colon would prevent the
+? from attempting
to match more options. Note that this means that
x+?: is just a
baroque way of matching exactly one repetition of
x, since the
non-greedy repetition initially tries to match the minimal number of
times (i.e. once) and the trailing colon then prevents it from
backtracking and trying longer matches. Likewise,
x*?:
and
x??: are arcane ways of matching exactly zero repetitions of
x.
Generally, though, a single colon tells the pattern matcher that there's no point trying any other match on the preceding repetition, because retrying (whether more or fewer repetitions) would just waste time and would still fail.
There's also a three-colon directive. Three colons means: “If we have
to backtrack past here, cause the entire rule to fail” (i.e. not just
this group). If the double-colon in
$hunk had been triple:
<$linenum> a ::: <$linerange> \n <$appendline>+
then matching a line number and an
'a' and subsequently failing would
cause the entire
$hunk rule to fail immediately (though the
$file
rule that invoked it might still match successfully in some other way).
So, in general, a triple-colon specifies: “At this point I'm committed to this way of matching the current rule -- give up on the rule completely if the matching process fails at this point”.
Four colons ... would just be silly. So, instead, there's a special named
directive:
<commit>. Backtracking through a
<commit>
causes the entire match to immediately fail. And if the current rule is
being matched as part of a larger rule, that larger rule will fail as
well. In other words, it's the “Blow up this Entire Planet and Possibly
One or Two Others We Noticed on our Way Out Here” operator.
If the double-colon in
$hunk had been a
<commit> instead:
<$linenum> a <commit> <$linerange> \n <$appendline>+
then matching a line number and an
'a' and subsequently
failing would cause the entire
$hunk rule to fail immediately, and
would also cause the
$file rule that invoked it to fail immediately.
So, in general, a
<commit> means: “At this point I'm
committed to this way of completing the current match -- give up
all attempts at matching anything if the matching process fails at
this point”.
The other two alternatives:
| <$linerange> d :: <$linenum> \n <$deleteline>+ | <$linerange> c :: <$linerange> \n <$deleteline>+ --- \n <$appendline>+
are just variants on the first.
If none of the three alternatives in the square brackets matches, then the alternative outside the brackets is tried:
| (\N*) ::: { fail "Invalid diff hunk: $1" }
This captures a sequence of non-newline characters (
\N means “not
\n”, in the same way
\S means “not
\s” or
\W means “not
\w”). Then it invokes a block of Perl code inside the pattern. The
call to
fail causes the match to fail at that point, and sets an
associated error message that would subsequently appear in the
$!
error variable (and which would also be accessible as part of
$0).
Note the use of the triple colon after the repetition. It's needed
because the
fail in the block will cause the pattern match to
backtrack, but there's no point backing up one character and trying
again, since the original failure was precisely what we wanted. The
presence of the triple-colon causes the entire rule to
fail as soon as the backtracking reaches that point the first time.
The overall effect of the
$hunk rule is therefore either to match one
hunk of the diff, or else fail with a relevant error message.
The third and fourth rules:
$linerange = rx/ <$linenum> , <$linenum> | <$linenum> /;
$linenum = rx/ \d+ /;
specify that a line number consists of a series of digits, and that a line
range consists of either two line numbers with a comma between them or a single
line number. The
$linerange rule could also have been written:
$linerange = rx/ <$linenum> [ , <$linenum> ]? /;
which might be marginally more efficient, since it doesn't have to
backtrack and rematch the first
$linenum in the second alternative.
It's likely, however, that the rule optimizer will detect such cases and
automatically hoist the common prefix out anyway, so it's probably not
worth the decrease in readability to do that manually.
The final two rules specify the structure of individual context lines in the diff (i.e. the lines that say what text is being added or removed by the hunk):
$deleteline = rx/^^ \< <sp> (\N* \n) / $appendline = rx/^^ \> <sp> (\N* \n) /
The
^^ markers ensure that each rule starts at the beginning
of an entire line.
The first character on that line must be either a
'<' or a
'>'. Note that we have to escape these characters since angle
brackets are metacharacters in Perl 6. An alternative would be to use
the “literal string” metasyntax:
$deleteline = rx/^^ <'<'> <sp> (\N* \n) / $appendline = rx/^^ <'>'> <sp> (\N* \n) /
That is, angle brackets with a single-quoted string inside them match the string's sequence of characters as literals (including whitespace and other metatokens).
Or we could have used the quotemeta metasyntax (
\Q[...]):
$deleteline = rx/^^ \Q[<] <sp> (\N* \n) / $appendline = rx/^^ \Q[>] <sp> (\N* \n) /
Note that Perl 5's
\Q...\E construct is replaced in Perl 6 by
just the
\Q marker, which now takes a group after it.
We could also have used a single-letter character class:
$deleteline = rx/^^ <[<]> <sp> (\N* \n) / $appendline = rx/^^ <[>]> <sp> (\N* \n) /
or even a named character (
\c[CHAR NAME HERE]):
$deleteline = rx/^^ \c[LEFT ANGLE BRACKET] <sp> (\N* \n) / $appendline = rx/^^ \c[RIGHT ANGLE BRACKET] <sp> (\N* \n) /
Whether any of those MTOWTDI is better than just escaping the angle bracket is, of course, a matter of personal taste.
After the leading angle, a single literal space is expected. Again, we
could have specified that by escapology (
\ ) or literalness
(
<' '>) or quotemetaphysics (
\Q[ ]) or character classification
(
<[ ]>), or deterministic nomimalism (
\c[SPACE]), but Perl 6
also gives us a simple name for the space character:
<sp>.
This is the preferred option, since it reduces line-noise and makes the
significant space much harder to miss.
Perl 6 provides predefined names for other useful subpatterns as well, including:
<dot>
which matches a literal dot (
'.') character (i.e. it's a more elegant
synonym for
\.);
<lt>and
<gt>
which match a literal
'<' and
'>' respectively. These
give us yet another way of writing:
$deleteline = rx/^^ <lt> <sp> (\N* \n) / $appendline = rx/^^ <gt> <sp> (\N* \n) /
<ws>
\s+). Optional whitespace is, therefore, specified as
<ws>?or
<ws>*(Perl 6 will accept either);
<alpha>
<[A-Za-z]>but it handles accented characters and alphabetic characters from non-Roman scripts as well);
<ident>
[ [<alpha>|_] \w* ](i.e. a standard identifier in many languages, including Perl)
Using named subpatterns like these makes rules clearer in intent, easier to read, and more self-documenting. And, as we'll see shortly, they're fully generalizable...we can create our own.
Finally, we're ready to actually read in and match a diff file. In Perl 5, we'd do that like so:
# Perl 5
local $/; # Disable input record separator (enable slurp mode) my $text = <>; # Slurp up input stream into $text
print "Valid diff" if $text =~ /$file/;
We could do the same thing in Perl 6 (though the syntax would differ slightly) and in this case that would be fine. But, in general, it's clunky to have to slurp up the entire input before we start matching. The input might be huge, and we might fail early. Or we might want to match input interactively (and issue an error message as soon as the input fails to match). Or we might be matching a series of different formats. Or we might want to be able to leave the input stream in its original state if the match fails.:
my $text is from($*ARGS); # Bind scalar to input stream
print "Valid diff" if $text =~ /<$file>/; # Match against input stream
The important point is that, after the match, only those characters that the pattern actually matched will have been removed from the input stream.
It may also be possible to skip the variable entirely and just write:
print "Valid diff" if $*ARGS =~ /<$file>/; # Match against input stream
or:
print "Valid diff" if <> =~ /<$file>/; # Match against input stream
but that's yet to be decided.
The previous example solves the problem of recognizing a valid diff file quite nicely (and with only six rules!), but it does so by cluttering up the program with a series of variables storing those precompiled patterns.
It's as if we were to write a collection of subroutines like this:
my $print_name = sub ($data) { print $data{name}, "\n"; }; my $print_age = sub ($data) { print $data{age}, "\n"; }; my $print_addr = sub ($data) { print $data{addr}, "\n"; };
my $print_info = sub ($data) { $print_name($data); $print_age($data); $print_addr($data); };
# and later...
$print_info($info);
You could do it that way, but it's not the right way to do it. The right way to do it is as a collection of named subroutines or methods, often collected together in the namespace of a class or module:
module Info {
sub print_name ($data) { print $data{name}, "\n"; } sub print_age ($data) { print $data{age}, "\n"; } sub print_addr ($data) { print $data{addr}, "\n"; }
sub print_info ($data) { print_name($data); print_age($data); print_addr($data); } }
Info::print_info($info);
So it is with Perl 6 patterns. You can write them as a series of pattern objects created at run-time, but they're much better specified as a collection of named patterns, collected together at compile-time in the namespace of a grammar.
Here's the previous diff-parsing example rewritten that way (and with a few extra bells-and-whistles added in):
grammar Diff { rule file { ^ <hunk>* $ }
rule hunk :i { [ <linenum> a :: <linerange> \n <appendline>+ | <linerange> d :: <linenum> \n <deleteline>+ | <linerange> c :: <linerange> \n <deleteline>+ --- \n <appendline>+ ] | <badline("Invalid diff hunk")> }
rule badline ($errmsg) { (\N*) ::: { fail "$errmsg: $1" }
rule linerange { <linenum> , <linenum> | <linenum> }
rule linenum { \d+ }
rule deleteline { ^^ <out_marker> (\N* \n) } rule appendline { ^^ <in_marker> (\N* \n) }
rule out_marker { \< <sp> } rule in_marker { \> <sp> } }
# and later...
my $text is from($*ARGS);
print "Valid diff" if $text =~ /<Diff.file>/;
The
grammar declaration creates a new namespace for rules
(in the same way a
class or
module declaration creates
a new namespace for methods or subroutines). If a block is
specified after the grammar's name:
grammar HTML {
rule file :iw { \Q[<HTML>] <head> <body> \Q[</HTML>] }
rule head :iw { \Q[<HEAD>] <head_tag>+ \Q[<HEAD>] }
# etc.
} # Explicit end of HTML grammar
then that new namespace is confined to that block. Otherwise the namespace continues until the end of the source section of the current file:
grammar HTML;
rule file :iw { \Q[<HTML>] <head> <body> \Q[</HTML>] }
rule head :iw { \Q[<HEAD>] <head_tag>+ \Q[<HEAD>] }
# etc.
# Implicit end of HTML grammar __END__
Note that, as with the blockless variants on
class and
module,
this form of the syntax is designed to simplify one-namespace-per-file
situations. It's a compile-time error to put two or more blockless
grammars, classes or modules in a single file.
Within the namespace, named rules are defined using the
rule
declarator. It's analogous to the
sub declarator within a
module, or the
method declarator within a class. Just like
a class method, a named rule has to be invoked through its grammar
if we refer to it outside its own namespace. That's why the actual
match became:
$text =~ /<Diff.file>/; # Invoke through grammar
If we want to match a named rule, we put the name in angle brackets.
Indeed, many of the constructs we've already seen --
<sp>,
<ws>,
<ident>,
<alpha>,
<commit> --
are really just predefined named rules that come standard with Perl 6.
Like subroutines and methods, within their own namespace, rules don't have to be qualified. Which is why we can write things like:
rule linerange { <linenum> , <linenum> | <linenum> }
instead of:
rule linerange { <Diff.linenum> , <Diff.linenum> | <Diff.linenum> }
Using named rules has several significant advantages, apart from making
the patterns look cleaner. For one thing, the compiler may be able to
optimize the embedded named rules better. For example, it could inline
the attempts to match
<linenum> within the
linerange rule. In
the
rx version:
$linerange = rx{ <$linenum> , <$linenum> | <$linenum> };
that's not possible, since the pattern matching mechanism won't know
what's in
$linenum until it actually tries to perform the match.
By the way, we can still use interpolated
<$subrule>-ish
subpatterns in a named rule, and we can use named subpatterns
in an
rx-ish rule. The difference between
rule and
rx
is just that a
rule can have a name and must use
{...} as its
delimiters, whereas an
rx doesn't have a name and can use
any allowed delimiters.
This version of the diff parser has an additional rule, named
badline.
This rule illustrates another similarity between rules and subroutines/methods:
rules can take arguments. The
badline rule factors out the error message
creation at the end of the
hunk rule. Previously that rule ended with:
| (\N*) ::: { fail "Invalid diff hunk: $1" }
but in this version it ends with:
| <badline("Invalid diff hunk")>
That's a much better abstraction of the error condition. It's easier to
understand and easier to maintain, but it does require us to be able to pass
an argument (the error message) to the new
badline subrule. To do
that, we simply declare it to have a parameter list:
rule badline($errmsg) { (\N*) ::: { fail "$errmsg: $1" }
Note the strong syntactic parallel with a subroutine definition:
sub subname($param) { ... }
The argument is passed to a subrule by placing it in parentheses after the rule name within the angle brackets:
| <badline("Invalid diff hunk")>
The argument can also be passed without the parentheses, but then it is interpreted as if it were the body of a separate rule:
rule list_of ($pattern) { <$pattern> [ , <$pattern> ]* }
# and later...
$str =~ m:w/ \[ # Literal opening square bracket <list_of \w\d+> # Call list_of subrule passing rule rx/\w\d+/ \] # Literal closing square bracket /;
A rule can take as many arguments as it needs to:
rule seplist($elem, $sep) { <$elem> [ <$sep> <$elem> ]* }
and those arguments can also be passed by name, using the standard Perl 6 pair-based mechanism (as described in Apocalypse 3).
$str =~ m:w/ \[ # literal left square bracket <seplist(sep=>":", elem=>rx/<ident>/)> # colon-separated list of identifiers \] # literal right square bracket /;
Note that the list's element specifier is itself an anonymous rule,
which the
seplist rule will subsequently interpolate as a pattern (because
the
$elem parameter appears in angle brackets within
seplist).
by Damian Conway
Editor's note: this document is out of date and remains here for historic interest. See Synopsis 5 for the current design information.
The only other change in the grammar version of the diff parser is that
the matching of the
'<' and
'>' at the start of the context
lines has been factored out. Whereas before we had:
$deleteline = rx/^^ \< <sp> (\N* \n) / $appendline = rx/^^ \> <sp> (\N* \n) /
now we have:
rule deleteline { ^^ <out_marker> (\N* \n) } rule appendline { ^^ <in_marker> (\N* \n) }
rule out_marker { \< <sp> } rule in_marker { \> <sp> }
That seems like a step backwards, since it complicated the grammar for no obvious benefit, but the benefit will be reaped later when we discover another type of diff file that uses different markers for incoming and outgoing lines.
Both the variable-based and grammatical versions of the code above do a great job of recognizing a diff, but that's all they do. If we only want syntax checking, that's fine. But, generally, if we're parsing data what we really want is to do something useful with it: transform it into some other syntax, make changes to its contents, or perhaps convert it to a Perl internal data structure for our program to manipulate.
Suppose we did want to build a hierarchical Perl data structure representing the diff that the above examples match. What extra code would we need?
None.
That's right. Whenever Perl 6 matches a pattern, it automatically builds a “result object” representing the various components of the match.
That result object is named
$0 (the program's name is now
$*PROG) and it's lexical to the scope in which the match occurs. The
result object stores (amongst other things) the complete string matched
by the pattern, and it evaluates to that string when used in a string
context. For example:
if ($text =~ /<Diff.file>/) { $difftext = $0; }
That's handy, but not really useful for extracting data structures. However, in addition, any components within a match that were captured using parentheses become elements of the object's array attribute, and are accessible through its array index operator. So, for example, when a pattern such as:
rule linenum_plus_comma { (\d+) (,?) };
matches successfully, the array element 1 of the result object
(i.e.
$0[1]) is assigned the result of the first parenthesized
capture (i.e. the digits), whilst the array element 2
(
$0[2]) receives the comma. Note that array element
zero of any result object is assigned the complete string that the pattern
matched.
There are also abbreviations for each of the array elements of
$0.
$0[1] can also be referred to as...surprise, surprise...
$1,
$0[2] can also be referred to as
$2,
$0[3] as
$3, etc.
Like
$0, each of these numeric variables is also lexical to the scope
in which the pattern match occurred.
The parts of a matched string that were matched by a named subrule become entries in the result object's hash attribute, and are subsequently accessible through its hash lookup operator. So, for example, when the pattern:
rule deleteline { ^^ <out_marker> (\N* \n) }
matches, the result object's hash entry for the key
'out_marker' (i.e.
$0{out_marker}) will contain the result object returned by the successful
nested match of the
out_marker subrule.
Named capturing into a hash is very convenient, but it doesn't work so well for a rule like:
rule linerange { <linenum> , <linenum> | <linenum> }
The problem is that the hash attribute of the rule's
$0 can only store one entry with the key
'linenum'.
So if the
<linenum> , <linenum> alternative matches,
then the result object from the second match of
<linenum> will overwrite the entry for the first
<linenum> match.
The solution to this is a new Perl 6 pattern matching feature known
as “hypothetical variables”. A hypothetical variable is
a variable that is declared and bound within a pattern match
(i.e. inside a closure within a rule).
The variable is declared, not with a
my,
our, or
temp,
but with the new keyword
let, which was chosen because it's what
mathematicians and other philosophers use to indicate a hypothetical
assumption.
Once declared, a hypothetical variable is then bound using the normal binding operator. For example:
rule checked_integer { (\d+) # Match and capture one-or-more digits { let $digits := $1 } # Bind to hypothetical var $digits - # Match a hyphen (\d) # Match and capture one digit { let $check := $2 } # Bind to hypothetical var $check }
In this example, if a sequence of digits is found, then the
$digits
variable is bound to that substring. Then, if the dash and check-digit
are matched, the digit is bound to
$check. However, if the dash or
digit is not matched, the match will fail and backtrack through the
closure. This backtracking causes the
$digits hypothetical variable
to be automatically un-bound. Thus, if a rule fails to match,
the hypothetical variables within it are not associated with any value.
Each hypothetical variable is really just another name for the
corresponding entry in the result object's hash attribute. So binding
a hypothetical variable like
$digits within a rule actually sets the
$0{digits} element of the rule's result object.
So, for example, to distinguish the two line numbers within a line range:
rule linerange { <linenum> , <linenum> | <linenum> }
we could bind them to two separate hypothetical variables -- say,
$from and
$to -- like so:
rule linerange { (<linenum>) # Match linenum and capture result as $1 { let $from := $1 } # Save result as hypothetical variable , # Match comma (<linenum>) # Match linenum and capture result as $2 { let $to := $2 } # Save result as hypothetical variable | (<linenum>) # Match linenum and capture result as $3 { let $from := $3 } # Save result as hypothetical variable }
Now our result object has a hash entry
$0{from} and (maybe) one for
$0{to} (if the first alternative was the one that matched). In fact,
we could ensure that the result always has a
$0{to}, by
setting the corresponding hypothetical variable in the second
alternative as well:
rule linerange { (<linenum>) { let $from := $1 } , (<linenum>) { let $to := $2 } | (<linenum>) { let $from := $3; let $to := $from } }
Problem solved.
But only by introducing a new problem. All that hypothesizing made our rule ugly and complex. So Perl 6 provides a much prettier short-hand:
rule linerange { $from := <linenum> # Match linenum rule, bind result to $from , # Match comma $to := <linenum> # Match linenum rule, bind result to $to | # Or... $from := $to := <linenum> # Match linenum rule, } # bind result to both $from and $to
or, more compactly:
rule linerange { $from:=<linenum> , $to:=<linenum> | $from:=$to:=<linenum> }
If a Perl 6 rule contains a variable that is immediately followed by
the binding operator (
:=), that variable is never interpolated.
Instead, it is treated as a hypothetical variable, and bound to the
result of the next component of the rule (in the above examples,
to the result of the
<linenum> subrule match).
You can also use hypothetical arrays and hashes, binding them to a component that captures repeatedly. For example, we might choose to name our set of hunks:
rule file { ^ @adonises := <hunk>* $ }
collecting all the
<hunk> matches into a single array
(which would then be available after the match as
$0{'@adonises'}. Note that
the sigil is included in the key in this case).
Or we might choose to bind a hypothetical hash:
rule config { %init := # Hypothetically, bind %init to... [ # Start of group (<ident>) # Match and capture an identifier \h*=\h* # Match an equals sign with optional horizontal whitespace (\N*) # Match and capture the rest of the line \n # Match the newline ]* }
where each repetition of the
[...]* grouping captures
two substrings on each repetition and converts them to a key/value pair,
which is then added to the hash. The first captured substring in each
repetition becomes the key, and the second captured substring becomes
its associated value. The hypothetical
%init hash is also available
through the rule's result object, as
$0{'%init'} (again, with the
sigil as part of the key).
Of course, those line number submatches in:
rule linerange { $from:=<linenum> , $to:=<linenum> | $from:=$to:=<linenum> }
will have returned their own result objects. And it's a reference to those
nested result objects that actually gets stored in
linerange's
$0{from} and
$0{to}.
Likewise, in the next higher rule:
rule hunk :i { [ <linenum> a :: <linerange> \n <appendline>+ | <linerange> d :: <linenum> \n <deleteline>+ | <linerange> c :: <linerange> \n <deleteline>+ --- \n <appendline>+ ] };
the match on
<linerange> will return its
$0 object.
So, within the
hunk rule, we could access the “from” digits
of the line range of the hunk as:
$0{linerange}{from}.
Likewise, at the highest level:
rule file { ^ <hunk>* $ }
we are matching a series of hunks, so the hypothetical
$hunk
variable (and hence
$0{hunk}) will contain a result object whose array
attribute contains the series of result objects returned by each
individual
<hunk> match.
So, for example, we could access the “from” digits of the line range of
the third hunk as:
$0{hunk}[2]{linerange}{from}.
More usefully, we could locate and print every line in the diff that was being inserted, regardless of whether it was inserted by an “append” or a “change” hunk. Like so:
my $text is from($*ARGS);
if $text =~ /<Diff.file>/ { for @{ $0{file}{hunk} } -> $hunk print @{$hunk{appendline}} if $hunk{appendline}; } }
Here, the
if statement attempts to match the text against the pattern
for a diff file. If it succeeds, the
for loop grabs the
<hunk>*
result object, treats it as an array, and then iterates each hunk match
object in turn into
$hunk. The array of append lines for each hunk
match is then printed (if there is in fact a reference to that array in
the hunk).
Because Perl 6 patterns can have arbitrary code blocks inside them, it's easy to have a pattern actually perform syntax transformations whilst it's parsing. That's often a useful technique because it allows us to manipulate the various parts of a hierarchical representation locally (within the rules that recognize them).
For example, suppose we wanted to “reverse” the diff file. That is, suppose we had a diff that specified the changes required to transform file A to file B, but we needed the back-transformation instead: from file B to file A. That's relatively easy to create. We just turn every “append” into a “delete”, every “delete” into an “append”, and reverse every “change”.
The following code does exactly that:
grammar ReverseDiff { rule file { ^ <hunk>* $ }")> }
rule badline ($errmsg) { (\N*) ::: { fail "$errmsg: $1" } }
rule linerange { $from:=<linenum> , $to:=<linenum> | $from:=$to:=<linenum> }
rule linenum { (\d+) }
rule deleteline { ^^ <out_marker> (\N* \n) } rule appendline { ^^ <in_marker> (\N* \n) }
rule out_marker { \< <sp> } rule in_marker { \> <sp> } }
# and later...
my $text is from($*ARGS);
print @{ $0{file}{hunk} } if $text =~ /<Diff.file>/;
The rule definitions for
file,
badline,
linerange,
linenum,
appendline,
deleteline,
in_marker and
out_marker are exactly
the same as before.
All the work of reversing the diff is performed in the
hunk rule.
To do that work, we have to extend each of the three main alternatives
of that rule, adding to each a closure that changes the result object
it returns.
In the first alternative (which matches “append” hunks), we match as before:
<linenum> a :: <linerange> \n <appendline>+
But then we execute an embedded closure:
{ @$appendline =~ s/<in_marker>/</; let $0 := "${linerange}d${linenum}\n" _ join "", @$appendline; }
The first line reverses the “marker” arrows on each line of data that
was previously being appended, using the smart-match operator to
apply the transformation to each line. Note too, that we reuse the
in_marker rule within the substitution.
Then we bind the result object (i.e. the hypothetical variable
$0) to
a string representing the “reversed” append hunk. That is, we reverse the
order of the line range and line number components, put a
'd' (for “delete”)
between them, and then follow that with all the reversed data:
let $0 := "${linerange}d${linenum}\n" _ join "", @$appendline;
The changes to the “delete” alternative are exactly symmetrical.
Capture the components as before, reverse the marker arrows,
reverse the
$linerange and
$linenum, change the
'd' to an
'a',
and append the reversed data lines.
In the third alternative:
$from:=<linerange> c :: $to:=<linerange> \n <deleteline>+ --- \n <appendline>+ { @$appendline =~ s/<in_marker>/</; @$deleteline =~ s/<out_marker>/>/; let $0 := "${to}c${from}\n" _ join("", @$appendline) _ "---\n" _ join("", @$deleteline); }
there are line ranges on both sides of the
'c'. So we
need to give them distinct names, by binding them to extra hypothetical
variables:
$from and
$to. We then reverse the order of two line
ranges, but leave the
'c' as it was (because we're simply changing
something back to how it was previously). The markers on both the append
and delete lines are reversed, and then the order of the two sets of
lines is also reversed.
Once those transformations has been performed on each hunk (i.e. as it's
being matched!), the result of successfully matching any
<hunk>
subrule will be a string in which the matched hunk has already been
reversed.
All that remains is to match the text against the grammar, and print out the (modified) hunks:
print @{ $0/2002/08/22/exegesis5.html{hunk} } if $text =~ /<ReverseDiff.file>/;
And, since the
file rule is now in the ReverseDiff grammar's namespace,
we need to call the rule through that grammar. Note the way the
syntax for doing that continues the parallel with methods and classes.
by Damian Conway
Editor's note: this document is out of date and remains here for historic interest. See Synopsis 5 for the current design information.
It might have come as a surprise that we were allowed to bind
the pattern's
$0 result object directly, but there's nothing magical
about it.
$0 turns out to be just another hypothetical variable...the
one that happens to be returned when the match is complete.
Likewise,
$1,
$2,
$3, etc. are all hypotheticals, and can also be
explicitly bound in a rule. That's very handy for ensuring that the
right substring always turns up in the right numbered variable. For
example, consider a Perl 6 rule to match simple Perl 5 method calls
(matching all Perl 5 method calls would, of course, require a much
more sophisticated rule):
rule method_call :w { # Match direct syntax: $var->meth(...) \$ (<ident>) -\> (<ident>) \( (<arglist>) \)
| # Match indirect syntax: meth $var (...) (<ident>) \$ (<ident>) [ \( (<arglist>) \) | (<arglist>) ] }
my ($varname, methodname, $arglist);
if ($source_code =~ / $0 := <method_call> /) { $varname = $1 // $5; $methodname = $2 // $4; $arglist = $3 // $6 // $7; }
By binding the match's
$0 to the result of the
<method_call>
subrule, we bind its
$0[1],
$0[2],
$0[3], etc. to those array
elements in
<method_call>'s result object. And thereby bind
$1,
$2,
$3, etc. as well. Then it's just a matter of sorting
out which numeric variable ended up with which bit of the method call.
That's okay, but it would be much better if we could guarantee that
the variable name was always in
$1, the method name in
$2,
and the argument list in
$3. Then we could replace the last six lines
above with just:
my ($varname, methodname, $arglist) = $source_code =~ / $0 := <method_call> /;
In Perl 5 there was no way to do that, but in Perl 6 it's relatively easy.
We just modify the
method_call rule like so:
rule method_call :w { \$ $1:=<ident> -\> $2:=<ident> \( $3:=<arglist> \) | $2:=<ident> \$ $1:=<ident> [ \( $3:=<arglist> \) | $3:=<arglist> ] }
Or, annotated:
rule method_call :w { \$ # Match a literal $ $1:=<ident> # Match the varname, bind it to $1 -\> # Match a literal -> $2:=<ident> # Match the method name, bind it to $2 \( # Match an opening paren $3:=<arglist> # Match the arg list, bind it to $3 \) # Match a closing paren | # Or $2:=<ident> # Match the method name, bind it to $2 \$ # Match a literal $ $1:=<ident> # Match the varname, bind it to $1 [ # Either... \( $3:=<arglist> \) # Match arg list in parens, bind it to $3 | # Or... $3:=<arglist> # Just match arg list, bind it to $3 ] }
Now the rule's
$1 is bound to the variable name, regardless of which
alternative matches. Likewise
$2 is bound to the method name in
either branch of the
|, and
$3 is associated with the argument
list, no matter which of the three possible ways it was matched.
Of course, that's still rather ugly (especially if we have to write all those comments just so others can understand how clever we were).
So an even better solution is just to use proper named rules (with their handy auto-capturing behaviour) for everything. And then slice the required information out of the result object's hash attribute:
rule varname { <ident> } rule methodname { <ident> }
rule method_call :w { \$ <varname> -\> <methodname> \( <arglist> \) | <methodname> \$ <varname> [ \( <arglist> \) | <arglist> ] }
$source_code =~ / <method_call> /;
my ($varname, $methodname, $arglist) = $0{method_call}{"varname","methodname","arglist"}
As the above examples illustrate, using named rules in grammars provides a cleaner syntax and a reduction in the number of variables required in a parsing program. But, beyond those advantages, and the obvious benefits of moving rule construction from run-time to compile-time, there's yet another significant way to gain from placing named rules inside a grammar: we can inherit from them.
For example, the ReverseDiff grammar is almost the same as the
normal Diff grammar. The only difference is in the
hunk rule.
So there's no reason why we shouldn't just have ReverseDiff inherit
all that sameness, and simply redefine its notion of
hunk-iness.
That would look like this:
grammar ReverseDiff is Diff {")> } }
The
ReverseDiff is Diff syntax is the standard Perl 6 way of
inheriting behaviour. Classes will use the same notation:
class Hacker is Programmer {...} class JAPH is Hacker {...} # etc.
Likewise, in the above example Diff is specified as the base grammar
from which the new ReverseDiff grammar is derived. As a result of that
inheritance relationship, ReverseDiff immediately inherits all of the
Diff grammar's rules. We then simple redefine ReverseDiff's version of
the
hunk rule, and the job's done.
Grammatical inheritance isn't only useful for tweaking the behaviour of a grammar's rules. It's also handy when two or more related grammars share some characteristics, but differ in some particulars. For example, suppose we wanted to support the “unified” diff format, as well as the “classic”.
A unified diff consists of two lines of header information, followed by a series of hunks. The header information indicates the name and modification date of the old file (prefixing the line with three minus signs), and then the name and modification date of the new file (prefixing that line with three plus signs). Each hunk consists of an offset line, followed by one or more lines representing either shared context, or a line to be inserted, or a line to be deleted. Offset lines start with two “at” signs, then consist of a minus sign followed by the old line offset and line-count, and then a plus sign followed by the nes line offset and line-count, and then two more “at” signs. Context lines are prefixed with two spaces. Insertion lines are prefixed with a plus sign and a space. Deletion lines are prefixed with a minus sign and a space.
But that's not important right now.
What is important is that we could write another complete grammar for that, like so:
grammar Diff::Unified {
rule file { ^ <fileinfo> <hunk>* $ }
rule fileinfo { <out_marker><3> $old badline ($errmsg) { (\N*) ::: { fail "$errmsg: $1" } }
rule linenum { (\d+) } rule linecount { (\d+) }
rule deleteline { ^^ <out_marker> (\N* \n) } rule appendline { ^^ <in_marker> (\N* \n) } rule contextline { ^^ <sp> <sp> (\N* \n) }
rule out_marker { \+ <sp> } rule in_marker { - <sp> } }
That represents (and can parse) the new diff format correctly, but it's a needless duplication of effort and code. Many the rules of this grammar are identical to those of the original diff parser. Which suggests we could just grab them straight from the original -- by inheriting them:
grammar Diff::Unified is Diff {
rule file { ^ <fileinfo> <hunk>* $ }
rule fileinfo { <out_marker><3> $new linecount { (\d+) }
rule contextline { ^^ <sp> <sp> (\N* \n) }
rule out_marker { \+ <sp> } rule in_marker { - <sp> } }
Note that in this version we don't need to specify the rules for
appendline,
deleteline,
linenum, etc. They're provided
automagically by inheriting from the
Diff grammar. So we only have to
specify the parts of the new grammar that differ from the original.
In particular, this is where we finally reap the reward for factoring
out the
in_marker and
out_marker rules. Because we did that
earlier, we can now just change the rules for matching those two markers
directly in the new grammar. As a result, the inherited
appendline and
deleteline rules (which use
in_marker and
out_marker as
subrules) will now attempt to match the new versions of
in_marker and
out_marker rules instead.
And if you're thinking that looks suspiciously like polymorphism, you're absolutely right. The parallels between pattern matching and OO run very deep in Perl 6.
To sum up: Perl 6 patterns and grammars extend Perl's text matching capacities enormously. But you don't have to start using all that extra power right away. You can ignore grammars and embedded closures and assertions and the other sophisticated bits until you actually need them.
The new rule syntax also cleans up much of the “line-noise” of Perl 5 regexes. But the fundamentals don't change that much. Many Perl 5 patterns will translate very simply and naturally to Perl 6.
To demonstrate that, and to round out this exploration of Perl 6 patterns, here are a few common Perl 5 regexes -- some borrowed from the Perl Cookbook, and others from the Regexp::Common module -- all ported to equivalent Perl 6 rules:
# Perl 5 $str =~ m{ /\* .*? \*/ }xs;
# Perl 6 $str =~ m{ /\* .*? \*/ };
# Perl 5 $ident =~ s/^(?:\w*::)*//;
# Perl 6 $ident =~ s/^[\w*\:\:]*//;
# Perl 5 warn "Thar she blows!: $&" if $str =~ m/.{81,}/;
# Perl 6 warn "Thar she blows!: $0" if $str =~ m/\N<81,>/;
# Perl 5 $str =~ m/ ^ m* (?:d?c{0,3}|c[dm]) (?:l?x{0,3}|x[lc]) (?:v?i{0,3}|i[vx]) $ /ix;
# Perl 6 $str =~ m:i/ ^ m* [d?c<0,3>|c<[dm]>] [l?x<0,3>|x<[lc]>] [v?i<0,3>|i<[vx]>] $ /;
# Perl 5 push @lines, $1 while $str =~ m/\G([^\012\015]*)(?:\012\015?|\015\012?)/gc;
# Perl 6 push @lines, $1 while $str =~ m:c/ (\N*) \n /;
# Perl 5 $str =~ m/ " ( [^\\"]* (?: \\. [^\\"]* )* ) " /x;
# Perl 6 $str =~ m/ " ( <-[\\"]>* [ \\. <-[\\"]>* ]* ) " /;
# Perl 5 my $quad = qr/(?: 25[0-5] | 2[0-4]\d | [0-1]??\d{1,2} )/x;
$str =~ m/ $quad \. $quad \. $quad \. $quad /x;
# Perl 6 rule quad { (\d<1,3>) :: { fail unless $1 < 256 } }
$str =~ m/ <quad> <dot> <quad> <dot> <quad> <dot> <quad> /x;
# Perl 6 (same great approach, now less syntax) rule quad { (\d<1,3>) :: <($1 < 256)> }
$str =~ m/ <quad> <dot> <quad> <dot> <quad> <dot> <quad> /x;
# Perl 5 ($sign, $mantissa, $exponent) = $str =~ m/([+-]?)([0-9]+\.?[0-9]*|\.[0-9]+)(?:e([+-]?[0-9]+))?/;
# Perl 6 ($sign, $mantissa, $exponent) = $str =~ m/(<[+-]>?)(<[0-9]>+\.?<[0-9]>*|\.<[0-9]>+)[e(<[+-]>?<[0-9]>+)]?/;
# Perl 5 my $digit = qr/[0-9]/; my $sign_pat = qr/(?: [+-]? )/x; my $mant_pat = qr/(?: $digit+ \.? $digit* | \. digit+ )/x; my $expo_pat = qr/(?: $signpat $digit+ )? /x;
($sign, $mantissa, $exponent) = $str =~ m/ ($sign_pat) ($mant_pat) (?: e ($expo_pat) )? /x;
# Perl 6 rule sign { <[+-]>? } rule mantissa { <digit>+ [\. <digit>*] | \. <digit>+ } rule exponent { [ <sign> <digit>+ ]? }
($sign, $mantissa, $exponent) = $str =~ m/ (<sign>) (<mantissa>) [e (<exponent>)]? /;
# Perl 5 our $parens = qr/ \( (?: (?>[^()]+) | (??{$parens}) )* \) /x; $str =~ m/$parens/;
# Perl 6 $str =~ m/ \( [ <-[()]> + : | <self> ]* \) /;
# Perl 5 our $parens = qr/ \( # Match a literal '(' (?: # Start a non-capturing group (?> # Never backtrack through... [^()] + # Match a non-paren (repeatedly) ) # End of non-backtracking region | # Or (??{$parens}) # Recursively match entire pattern )* # Close group and match repeatedly \) # Match a literal ')' /x;
$str =~ m/$parens/;
# Perl 6 $str =~ m/ <'('> # Match a literal '(' [ # Start a non-capturing group <-[()]> + # Match a non-paren (repeatedly) : # ...and never backtrack that match | # Or <self> # Recursively match entire pattern ]* # Close group and match repeatedly <')'> # Match a literal ')' /;
Return to the Perl.com.
Perl.com Compilation Copyright © 1998-2006 O'Reilly Media, Inc. | http://www.perl.com/lpt/a/2002/08/22/exegesis5.html | crawl-002 | refinedweb | 10,118 | 59.03 |
The 'reused' the code to calculate the distance between 2 GPS co-ords from codecodex.
Setting up
You'll need PiAware installed on your Raspberry Pi, up and running and tracking aircraft.
You'll need an LED, appropriate resistor, breadboard and a couple of Male/Female jumper cables to connect it togther.
The LED is connected to ground and pin 17 with the resistor in between.
cd ~ git clone
Launch the flightlight program passing the latitude (lat) and longitude (lon) of your PiAware station (use to find your gps location) and the range that should be used to detect if an aircraft is overhead.
usage: flightlight.py [-h] lat lon rangee.g. using GPS coords of 52.4539, -1.7481 (Birmingham, UK Airport) with a range of 10km
cd ~/flightlight/flightlight sudo python3 flightlight.py 52.4539 -1.7481 10Code
import RPi.GPIO as GPIO import argparse from flightdata import FlightData from haversine import points2distance from time import sleep #pin of the LED to light LEDPIN = 17 class LED(): def __init__(self, ledPin): self.ledPin = ledPin GPIO.setup(ledPin, GPIO.OUT) def on(self): GPIO.output(self.ledPin, True) def off(self): GPIO.output(self.ledPin, False) #read command line options parser = argparse.ArgumentParser(description="PiAware Flight Light") parser.add_argument("lat", type=float, help="The latitude of the receiver") parser.add_argument("lon", type=float, help="The longitude of the receiver") parser.add_argument("range", type=int, help="The range in km for how close an aircraft should be to turn on the led") args = parser.parse_args() #get the flight data myflights = FlightData() #set GPIO mode GPIO.setmode(GPIO.BCM) try: #create LED led = LED(LEDPIN) #loop forever while True: plane_in_range = False #loop through the aircraft and see if one is in range for aircraft in myflights.aircraft: if aircraft.validposition == 1: startpos = ((args.lat, 0, 0), (args.lon, 0, 0)) endpos = ((aircraft.lat, 0, 0), (aircraft.lon, 0, 0)) distance = points2distance(startpos, endpos) #debug #print(distance) if distance <= args.range: plane_in_range = True #turn the led on / off if plane_in_range: led.on() #print("on") else: led.off() #print("off") sleep(1) #refresh the data myflights.refresh() finally: #tidy up GPIO GPIO.cleanup()
Great stuff!
This comment has been removed by the author.
Even though request.py exists, I get lots of errors when I run: flightlight.py
Any idea's?
Hi Teddy,
Im a bit confused - there isnt a file in this project called "request.py"?
What errors do you get when you try and run flightlight.py?
Martin
When the code is run, I get a whole list of:
/usr/lib/python3.2/urllib/request.py errors.
I see. What are the errors? | https://www.stuffaboutcode.com/2015/10/piaware-aircraft-overhead-led.html | CC-MAIN-2019-35 | refinedweb | 442 | 61.83 |
I just found some notes from when I first began working with Scala, and I was working with the
yield keyword in
for loops. If you haven't worked with something like
yield before, it will help to know how it works. Here's a statement of how the
yield keyword works, from the book, Programming in Scala:
Back to topBack to top
For each iteration of your
forloop,
yieldgenerates a value which will be remembered. It's like the
forloop has a buffer you can’t see, and for each iteration of your
forloop another item is added to that buffer. When your
forloop finishes running, it will return this collection of all the yielded values. The type of the collection that is returned is the same type that you were iterating over, so a
Mapyields a
Map, a
Listyields a
List, and so on.
Also, note that the initial collection is not changed; the for/yield construct creates a new collection according to the algorithm you specify.
Basic for-loop examples
Given that background information, let’s look at a few for/yield examples. First, this example just yields a new collection that’s identical to the collection I’m looping over:
scala> for (i <- 1 to 5) yield i res10: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 2, 3, 4, 5)
Nothing too exciting there, but it’s a start. Next, let’s double every element in our initial collection:
scala> for (i <- 1 to 5) yield i * 2 res11: scala.collection.immutable.IndexedSeq[Int] = Vector(2, 4, 6, 8, 10)
As another example, here’s what the Scala modulus operator does in a for/yield loop:
scala> for (i <- 1 to 5) yield i % 2 res12: scala.collection.immutable.IndexedSeq[Int] = Vector(1, 0, 1, 0, 1)Back to top
for-loop/yield examples over a Scala Array
I mentioned in my description that the
for loop yield construct returns a collection that is the same as the collection it is given. To demonstrate this, let’s look at the same examples with a Scala
Array. Note the type of the collection that is yielded, and compare it to the previous examples:
scala> val a = Array(1, 2, 3, 4, 5) a: Array[Int] = Array(1, 2, 3, 4, 5) scala> for (e <- a) yield e res5: Array[Int] = Array(1, 2, 3, 4, 5) scala> for (e <- a) yield e * 2 res6: Array[Int] = Array(2, 4, 6, 8, 10) scala> for (e <- a) yield e % 2 res7: Array[Int] = Array(1, 0, 1, 0, 1)
As you can see, in these examples an
Array[Int] was yielded, while in the earlier examples an
IndexedSeq[Int] was returned.
for loop, yield, and guards (for-loop ‘if’ conditions)
If you’re familiar with the Scala for comprehension syntax, you know that you can add
if statements to your for loop construct. Tests like these are often referred to as “guards,” and you can combine them with the
yield syntax, as shown here:
scala> val a = Array(1, 2, 3, 4, 5) a: Array[Int] = Array(1, 2, 3, 4, 5) scala> for (e <- a if e > 2) yield e res1: Array[Int] = Array(3, 4, 5)
As you can see, adding the
if e > 2 guard condition limits the
Array we return to the three elements shown.
A real-world example
I don’t know if this will make sense out of context, but if you’d like to see a real-world use of a for/yield loop, here you go:
def getQueryAsSeq(query: String): Seq[MiniTweet] = { val queryResults = getTwitterInstance.search(new Query(query)) val tweets = queryResults.getTweets // java.util.List[Status] for (status <- tweets) yield ListTweet(status.getUser.toString, status.getText, status.getCreatedAt.toString) }
This code uses the
JavaConversions package to convert the
java.util.List[Status] I get back from Twitter4J into a
Seq[MiniTweet]. The loop actually returns a
Buffer[ListTweet], which is a
Seq[ListTweet]. A
MiniTweet is just a small version of a Twitter tweet, with the three fields shown.
Summary: Scala for-loop and yield examples
If you’re familiar with Scala’s for-loop construct, you know that there’s also much more work that can be performed in the first set of parentheses. You can add
if statements and other statements there, such as this example from the book Programming in Scala:
def scalaFiles = for { file <- filesHere if file.getName.endsWith(".scala") } yield file
I'll try to share more complicated examples like this in the future, but for today I wanted to share some simple for/yield examples, something like “An introduction to the Scala
yield keyword.”
Summary: Scala’s ‘yield’ keyword
As a quick summary of the yield keyword:
- For each iteration of your for loop, yield generates a value which is remembered by the for loop (behind the scenes, like a buffer).
- When your for loop finishes running, it returns a collection of all these yielded values.
- The type of the collection that is returned is the same type that you were iterating over.
I hope these examples have been helpful.Back to top
Add new comment | https://alvinalexander.com/scala/scala-for-loop-yield-examples-yield-tutorial | CC-MAIN-2018-30 | refinedweb | 863 | 63.83 |
the following exceptions:
- No Plugins - One of the great things about TweenLite is that you can activate plugins in order to add features (like autoAlpha, tint, blurFilter, etc.). TweenNano, however, doesn't work with plugins.
- Incompatible with TimelineLite and TimelineMax - Complex sequencing and management of groups of tweens can be much easier with TimelineLite and TimelineMax, but TweenNano instances cannot be inserted into TimelineLite or TimelineMax instances. Sequencing in TweenNano can be done using the "delay" special property.
- Fewer overwrite modes - You can either overwrite all or none of the existing tweens of the same object (overwrite:true or overwrite:false) in TweenNano.
- Fewer methods and properties- TweenNano instances aren't meant to be altered on-the-fly, so they don't have methods like pause(), resume(), reverse(), seek(), restart(), etc. The essentials are covered, though, like to(), from(), delayedCall(), killTweensOf(), and kill()
TweenNano uses exactly the same syntax as TweenLite, so all the documentation and examples for TweenLite apply to TweenNano as well (except for the features mentioned above of course).).
Getting started
If you're new to the GreenSock Tweening Platform, check out the "getting started" page. You'll be up and running in no time.
Documentation
Please see the full ASDoc documentation.
Sample AS3 code
(AS2 is identical except for property names like "x", "y", and "alpha" are "_x", "_y", "_alpha" and alpha would be 100-based instead of 1-based).
import com.greensock.*; import com.greensock.easing.*; //tweens mc's alpha property to 0.5 and x property to 120 from wherever they are currently over the course of 1.5 seconds. TweenNano.to(mc, 1.5, {alpha:0.5, x:120}); //same tween, but uses the Back.easeOut ease, delays the start time by 2 seconds, and calls the "onFinishTween" function when it completes, passing two parameters to it, 5 and "myParam2". TweenNano.to(mc, 1.5, {alpha:0.5, x:120, ease:Back.easeOut, delay:2, onComplete:onFinishTween, onCompleteParams:[5, "myParam2"]}); //tweens mc into place from 100 pixels above wherever it currently is, over the course of 1 second using the Elastic.easeOut ease. TweenNano.from(mc, 1, {y:"-100", ease:Elastic.easeOut});
- Do you plan on eventually making TweenNano compatible with plugins?
No. I am not interested in blurring the line between TweenNano and TweenLite by adding plugin capability or other features to TweenNano. The sole purpose of TweenNano is to provide an extremely lightweight engine capable of doing basic tweening, nothing more. If you want plugin-like capabilities, you can always use TweenNano's onUpdate callback to have your own function perform any action every time the tween values are updated.
- I thought TweenLite was already lightweight. Why create TweenNano if it only saves 3.1k?
Believe it or not, some developers (mostly banner ad creators) will rejoice at the thought of getting an extra 3.1k because they are forced to work within extremely tight file size constraints. That being said, if you're trying to decide whether you should use TweenNano or TweenLite, I'd recommend using TweenLite and only shifting to using TweenNano if that 3.1k becomes critical. TweenLite is definitely more flexible with its plugins and compatibility with TimelineLite and TimelineMax.
- How do I install the class? Do I have to import it on every frame?
Please refer to the "getting started" page.
- Why do my tweens keep getting overwritten? How can I prevent that?
By default, when you create a tween, TweenNano looks for all existing tweens of the same object and kills them immediately. However, you can prevent this behavior by using overwrite:false in your vars object, like
TweenNano.to(mc, 1, {x:100, overwrite:false});
- Can I set up a sequence of tweens so that they occur one after the other?
Sure. Just use the "delay" special property, like :
import com.greensock.TweenNano; TweenNano.to(mc, 2, {x:100}); TweenNano.to(mc, 1, {y:300, delay:2, overwrite:false});
-enNano.to(mc, 1, {scaleX:1.2, y:200, x:1})is the same as
TweenNano.to(mc, 1, {x:1, y:200, scaleX:1. Club GreenSock members get several useful bonus plugins, classes, update notifications, SVN access, and more. Your support keeps this project going. Please see the licensing page for details on licensing. | http://greensock.com/tweennano-as | CC-MAIN-2016-40 | refinedweb | 711 | 57.47 |
[Flex 3] One SWF, multiple Applications?motionman95 Mar 25, 2014 3:52 PM
I'm dealing with what might be a unique situation - I need to package multuple Applications within one exported SWF, and switch between which Application is loaded based on flash vars from the page the application will be in. File Size isn't a problem. Every solution I've tried so far has had no dice.
Here is what I've tried:
- Subclassing SystemManager (info/create/getDefinitionForName functions) to override what Application is loaded. This didn't work as info/create can't be overriden, and overriding getDefinitionForName and suppling the Application class I want doesn't work either (I get the 1037 getStyle error).
- Using a main Application that functions as a dummy holder, and it decides what applications are loaded into a subclassed SWFLoader that addChild()s an Application class instance I supply it with. This works, sort of, with the Application class I supply being loaded, but things like mx:Script and mx:Style aren't respected in the sub-loaded Application. Here is how my subclassed SWFLoader looks (built from cannablized code in the SWFLoader source):
package
{
import flash.display.DisplayObject;
import flash.display.DisplayObjectContainer;
import flash.display.Loader;
import mx.controls.SWFLoader;
import mx.core.mx_internal;
use namespace mx_internal;
public class AppLoader extends SWFLoader
{
public function AppLoader()
{
super();
this.percentWidth = this.percentHeight = 100;
}
public function loadAppClass(classObj:Object):DisplayObject {
var child:DisplayObject;
contentHolder = child = new classObj();
addChild(child);
try
{
if (tabChildren &&
contentHolder is Loader &&
Loader(contentHolder).content is DisplayObjectContainer)
{
Loader(contentHolder).tabChildren = true;
DisplayObjectContainer(Loader(contentHolder).content).tabChildren = true;
}
}
catch(e:Error){}
invalidateSize();
invalidateDisplayList();
return child;
}
}
}
If there are better way to do this that don't require me loading external file/modules, that would be excellent. Ideally I'd like to just be able to swap between Application classes.
1. Re: [Flex 3] One SWF, multiple Applications?Flex harUI
Mar 25, 2014 5:39 PM (in response to motionman95)1 person found this helpful
Try creating a simple application with just a SWFLoader that loads the other files. First load them externally just to make sure it all works.
Then embed each SWF in the simple app and pass the embedded SWF instead of its URL to SWFLoader.
-Alex
2. Re: [Flex 3] One SWF, multiple Applications?motionman95 Mar 25, 2014 8:30 PM (in response to Flex harUI)
Thanks for the reply! That was my 3rd idea. I don't suppose there's any way to do this without embedding the SWFs, huh? Would be less heartache for debug/release not having to worry about that embedding and whatnot
3. Re: [Flex 3] One SWF, multiple Applications?Flex harUI
Mar 25, 2014 10:33 PM (in response to motionman95)
Not if you have sub-pieces that are Applications. If you go with modules you get one more option, which is to add modules to additional frames in the SWF, but that solution doesn't truly give you random access to each module until all frames are loaded. It is better for wizard/workflow solutions.
-Alex
4. Re: [Flex 3] One SWF, multiple Applications?motionman95 Mar 26, 2014 6:35 AM (in response to Flex harUI)
Thanks for the help so far. Here's what I came up with:
Do you see any optomizations/potential improvements?
5. Re: [Flex 3] One SWF, multiple Applications?Flex harUI
Mar 26, 2014 9:45 AM (in response to motionman95)
Well, the question I have is why do these other sub-pieces need to be Applications instead of Modules or NavigatorContent. Do they really need to launch and run on their own?
-Alex
6. Re: [Flex 3] One SWF, multiple Applications?motionman95 Mar 27, 2014 10:49 AM (in response to Flex harUI)
Really specific circumstance of working on older constraints. Question: do you know if it's possible to successfully load a Flex 4 SWF into a Flex 3 one (root)? I've tried and have gotten errors.
7. Re: [Flex 3] One SWF, multiple Applications?Flex harUI
Mar 27, 2014 1:33 PM (in response to motionman95)
An older version of Flex loading a newer one is not supported.
You might be able to get it to work in specific cases but you need to isolate things via the Marshall Plan.
8. Re: [Flex 3] One SWF, multiple Applications?motionman95 Mar 27, 2014 1:36 PM (in response to Flex harUI)
That sounds interesting. How would that work?
9. Re: [Flex 3] One SWF, multiple Applications?Flex harUI
Mar 27, 2014 8:41 PM (in response to motionman95)
Search the internet for Flex Marshall Plan. | https://forums.adobe.com/thread/1436109 | CC-MAIN-2016-40 | refinedweb | 772 | 57.37 |
Four External Displays to Use With Android Things
Four External Displays to Use With Android Things
Want to learn how to select and connect different external displays on the Android Things? Check out this post to learn more!
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External displays are peripherals we can use with Android Things to show information. This article covers how to use 4 external display with Android Things. Displays are important when it is necessary to show information. When we develop smart devices based on Android Things usually it is necessary to show information to the user. Even if we could use RGB LEDs to show some kind of information, an external display connected to Android Things plays an important role when it is necessary to display messages or other kinds of information.
Android Things support several external displays and there are different drivers that we can use to interact with these external displays. This Android Things tutorial describes how to use the following external display with Android Things:
- TM1637 — This is a 4-digit display
- Max7219 — This a matrix LED, usually 8×8. It is made by 64 single LED that can be addressed. Moreover, it has an SPI interface
- LCD display (LCD 1602, LCD 2004) built on HD44780 chip and controlled with the PCF8574 chip
- SSD1306 — An OLED display with a 0.96inch screen. This OLED display has a resolution of 128×64 and each led can be controlled turning it on and off
This article will cover step by step how to connect an external display with Android Things and how to display information. Download the Android Things source code
How to Connect the TM1637 External Display to Android Things
Let us start with the simplest external display we can use with Android Things: the TM1637. It has four pins that we have to connect to Android Things:
- Vcc (+3V or +5V)
- GND
- DIO (Data)
- CLK (Clock)
The sketch to connect Android Things with TM1637 is shown below:
Where can we use this display? This external display can be used in these scenarios:
- Time display
- To display sensor data
How to Use TM1637 With Android Things
The first step is importing the right driver so that we can interact with the TM1637. The TM1637 display has a supported driver in Android Things. To use this display, it is necessary to add the following line to
build.gradle:
dependencies { implementation 'com.google.android.things.contrib:driver-tm1637:1.0' ...... }
Let us create a new class that will handle the TM1637 external display. This class is named
TM1637Display and looks like:
public class TM1637Display { private NumericDisplay display; private String DATA_PIN = "BCM4"; private String CLK_PIN = "BCM3"; private static TM1637Display me; public static TM1637Display getInstance() { if (me == null) me = new TM1637Display(); return me; } private TM1637Display() { init(); } .... }
This class is a singleton, and in the
init() method, the app initializes the driver using the Data pin and the Clock pin:
private void init() { try { display = new NumericDisplay(DATA_PIN, CLK_PIN); } catch(IOException ioe) { ioe.printStackTrace(); } }
Now, it is possible to display the data using this method:
public void display(String data) { try { display.display(data); display.setColonEnabled(true); display.setBrightness(NumericDisplay.MAX_BRIGHTNESS); } catch (IOException ioe) { ioe.printStackTrace(); } }
As you might have noticed, it is possible to change the display brightness using
setBrightness. In the
MainActivity, we can show data using the TM1637 display in this way:
private void testTM1637() { TM1637Display display = TM1637Display.getInstance(); display.display("1420"); }
The result is shown in the picture below:
This external display is very easy to use.
How to Connect Max7219 to the Android Things
The Max7219 display is a LED matrix that has 8×8 LEDs. It is possible to address each of them by turning it on or off. Usually, it is a monochrome display, but there are other variants with RGB LEDs. It is a SPI interface, and the interesting aspect is its ability to chain them. It has five different pins:
- Vcc (+5V)
- GND
- CLK (Clock>
- CS
- Data
Even if it is some limits, this external display can have several usages, and it can be used to show simple images, too.
The schema below shows how to connect Max7219 to Android Things:
How to Use Max7219 With Android Things
Before using Max7219 with Android Things, it is necessary to add the driver that handles this peripheral. Unfortunately, this display is not supported officially in Android Things. For this reason, it is necessary to find an unofficial driver. There are several drivers available; the one used in this article is this:
dependencies { implementation 'rocks.androidthings:max72xx-driver:0.2' .... }
Of course, you can use other drivers. However, be aware that the classes can change.
To handle this external display (Max7219), we can create a simple class named
Max7219Display that is a singleton, as discussed previously:
public class Max7219Display { private MAX72XX display; private static Max7219Display me; private Max7219Display() { init(); } public static Max7219Display getInstance() { if (me == null) me = new Max7219Display(); return me; } .... }
In the
init() method, the Android Things app initializes the display:
private void init() { try { display = new MAX72XX("SPI0.0", 1); // display.setIntensity(0, 13); display.shutdown(0, false); display.clearDisplay(0); } catch(IOException ioe) { ioe.printStackTrace(); } }
In the previous code, we initialized the LED intensity using the method
setIntensity. To understand how to use this external display, let us suppose we want to create a simple box. As a first step, it is necessary to create a
byte array:
private byte ROW = (byte) 0b11111111;
In this array, the 1 means that the LED is turned on while 0 is turned off. In this example, all the LEDs are on. The array size is 8 as the number of LEDs in the matrix. The next step is drawing the box borders:
public void drawBorder() { try { display.setRow(0, 0, ROW); display.setRow(0, 7, ROW); display.setColumn(0, 0, ROW); display.setColumn(0, 7, ROW); display.close(); } catch(IOException ioe) { ioe.printStackTrace(); } }
In the code above, the Android Things app uses
setRow to apply the byte array to all the LEDs in the row. In this case, we are referring to the first row (x = 0, y = 0) and the last row (x = 0, y = 7). In the same way, the app draws the border along the columns. The final result is shown in the picture below:
We can do more and show a more complex array that can be used for all the rows and columns. Add this array to the class:
private byte[] table = {(byte) 0b10101010, (byte) 0b01010101, (byte) 0b10101010, (byte) 0b01010101, (byte) 0b10101010, (byte) 0b01010101, (byte) 0b10101010, (byte) 0b01010101};
This is the method that displays the draw above:
public void drawTable() { try { for (int i=0 ; i < table.length; i++) display.setRow(0, i, table[i]); display.close(); } catch(IOException ioe) { ioe.printStackTrace(); } }
You can run it and verify the result.
How to Connect the SSD1306 External Display to Android Things
As specified before, the SSD1306 is an external display with a resolution of 128×64. It is an OLED display, and it is possible to control each pixel during it on or off. There are two different variants of this display: one with a SPI interface and the other one with I2C interface. The one used in this article has an I2C interface. Therefore, there are four different pins:
- Vcc (+3V or +5V)
- GND
- Data
- CLK
The details about how to connect the SSD external display to Android Things is shown below:
How to Use SSD1306 With Android Things
The SSD1306 external display is officially supported by Android Things. Therefore, there is a driver that we can use to connect to this external peripheral.
To use this LCD display, it is necessary to add this driver to the
build.gradle:
dependencies { implementation 'com.google.android.things.contrib:driver-ssd1306:1.0' .... }
As we did previously, let us create a new class that will handle all the details and let us call the ID as
SSD1306Display. This class looks like:
public class SSD1306Display { private static SSD1306Display me; private Ssd1306 display; private SSD1306Display() { init(); } public static SSD1306Display getInstance() { if (me == null) me = new SSD1306Display(); return me; } .. }
And, the
init() method is defined as:
private void init() { try { display = new Ssd1306("I2C1"); display.clearPixels(); } catch (IOException ioe) { ioe.printStackTrace(); } } [/code] Finally, we can start using this LCD display. The Android Things app can turn on or off each LED in this display so that using this feature, it can draw a simple line: public void drawLine(int y) { for (int x = 0; x < display.getLcdWidth(); x++) display.setPixel(x, y, true); try { display.show(); } catch (IOException ioe) { ioe.printStackTrace(); } }
Using the
setPixel, the Android Things app can select the state of each pixel. The final result is shown below (there should be a line, but it is not visible!):
Even if it can be useful to turn on or off each LED, it can be quite complex when we want to show more complex images. For this reason, it is possible to use another way as shown below:
public void drawBitmap(Resources res) { Bitmap img = BitmapFactory.decodeResource(res, R.drawable.weathersun); BitmapHelper.setBmpData(display, 0,0, img, false); try { display.show(); } catch (IOException ioe) { ioe.printStackTrace(); } }
It is possible to load directly the image and display it on the LCD display. This is very useful and easy.
That’s all.
How to Connect an LCD Display 1602 or 2004 to Android Things
The last external display we cover in this article is a simple LCD display. It can display standard characters or a custom char.
It has several sizes, but they work all in the same way. The 16×2 and 20×4 sizes are the easiest to find. The first one can display 16 chars in two lines, while the second can display 20 chars on four lines.
The image below shows how to connect Android Things with LCD 2004:
It has an I2C interface and it has the backlight, too.
How to Connect the LCD Ddisplay to Android Things
These kinds of devices are not supported natively by Android Things. There are several drivers available. The driver that we will use is shown below:
dependencies { ... implementation 'com.leinardi.android.things:driver-hd44780:1.0' }
Let us start creating a new class called
LCDDisplay that is similar to the classes previously described, the only difference is in the
init():
private void init() { try { driver = new Hd44780(I2C_PIN, I2C_ADDR, GEOMETRY); driver.cursorHome(); driver.clearDisplay(); driver.setBacklight(true); } catch(Exception e) { e.printStackTrace(); } }
where
private static final String I2C_PIN = "I2C1"; private static final int I2C_ADDR = 0x27; private static final int GEOMETRY = Hd44780.Geometry.LCD_20X4;
Tip
Please notice that the I2C_ADDR could be different from the one shown above
Let us suppose the Android Things app wants to display a message on the LCD screen. The code to use is shown below:
public void display(String data) { try { driver.clearDisplay(); driver.cursorHome(); driver.setBacklight(true); driver.setText(data); driver.close(); } catch (Exception e) { e.printStackTrace(); } }
This method at the beginning clears the display and sets the cursor to home. The next step is setting the backlight and, finally, it displays the message.
The result is shown below:
If we want to scroll the message along the display, we can use this method:
public void shift(final String word, final int speed) { final int size = 20 - word.length(); Runnable r = new Runnable() { @Override public void run() { try { driver.createCustomChar(empty, 0); for (int i = 0; i <= size; i++) { if (i > 0) { driver.setCursor(i - 1, 0); driver.writeCustomChar(0); } driver.setCursor(i, 0); driver.setText(word); Thread.sleep(speed); } } catch (Exception e) { e.printStackTrace(); } } }; Thread t = new Thread(r); t.start(); }
The important aspect to notice here is the fact that we can create a custom char. In this case, the custom char is a blank char:
int[] empty = {0b000000, 0b000000, 0b000000, 0b000000, 0b000000, 0b000000, 0b000000, 0b000000};
Summary
At the end of this article, hopefully, you have gained more knowledge on how to use an external display with Android Things. As you have learned, there are several external displays with different features. According to our needs and the scenario, we can select the best external display to use with Android Things. }} | https://dzone.com/articles/four-external-displays-to-use-with-android-things | CC-MAIN-2018-43 | refinedweb | 2,042 | 63.39 |
How I Built a Drum Machine in React, Part Two: State, Program Logic, and Failure
Michael Caveney
Updated on
・5 min read
March 22th, 2019
Note: This article contains a partial potential solution for the freeCodeCamp Drum Machine project, so please avoid this for now if you're actively working on that project and don't wish to be spoiled!
If you haven't read part one of this post, you can find that here.
Step Three: Verifying Data Flow
The first item to take care of here is to ensure that when a button is clicked, the requisite info flows from the child to the parent (from Button.js to App.js), and then from parent to child (from App.js to Display.js). That won't be so hard, right?
One hour later
...clearly, I needed some work on lifting state in React that isn't coming from a form element. Let's examine the changes I made to the App.js file first:
class App extends Component { constructor(props) { super(props); this.state = { display: "Press a key to play the drums!" }; } handleClick = (name) => console.log(name);
First, I fully expanded the class declaration to include the state inside a constructor, and wrote out a test function for the click, using the more succinct arrow function syntax. Not doing so would have involved binding the calling context of the function using the much more verbose:
this.handleClick = this.handleClick.bind(this)
....so no.
Next, I declare a handleClick prop for the button component:
<Button handleClick={this.handleClick} display={this.state.display} name={button} key={button} />
...and modify the Button component:
const Button = ({ name, handleClick }) => { return ( <button onClick={() => handleClick(name)} {name} </button> ); }
The problem I ran into was that I knew at a high-level what I needed to do, but I didn't have much practice with this pattern outside of forms. Turns out, it's really not that different, and diligent searching for other examples where someone had the same problem pointed out the solution I needed, namely utilizing an arrow function with no arguments, and it works.
Next, I'll modify the code so that it updates the display on the click thusly:
handleClick = (name) => this.setState({ display: name });
...and that works like a charm!
Step Four: Adding Audio
Hmmm. Now that I look closely at the 4th user story for this project ("Within each .drum-pad, there should be an HTML audio element which has a src attribute pointing to an audio clip, a class name of clip, and an id corresponding to the inner text of its parent .drum-pad."), I can see that I'll have to modify the button element, since it currently isn't setup up to contain the necessary
audio element that the project requires. This won't be a problem, I'll just change the
button element into a
div, and set all
button specific styles to affect
.drum-pad. I will have to add the audio files and a unique identifier to the data array, so I'll approach that by refactoring that into an array of objects.
One quick refactor later, the objects look something like this:
const drumData = [ { name: "Bdim Chord", key: "Q", src: "" },
Note that I renamed the array from data to drumData. Now that I'm refining the details of the app, I want to make sure variable names are appropriately descriptive to make the code more readable. In a minute, I'll discuss another reason to make variable names less generic.
At this point, let's have a look at the changes to the render method in the App component, which consist of feeding the new props into the Button component:
render() { return ( <div id="drum-machine"> <Display display={this.state.display} /> <div className="drum-buttons"> {drumData.map(button => ( <Button handleClick={this.handleClick} display={this.state.display} name={button.name} drumKey={button.key} src={button.src} /> ))} </div> </div> ); }
...and the resulting changes to the Button component:
const Button = ({ drumKey, handleClick, name, src }) => { return ( <div onClick={() => handleClick(name, drumKey)} {drumKey} <audio src={src} className="clip" id={drumKey} /> </div> ); };
Note that I have gone with the convention of not giving props a name that deviates from their original variable name, but here I am calling the key prop drumKey. When I first set this component up, it was didn't work and the error in Chrome Dev Tools was complaining that 'key is undefined'. I had my suspicions of what was causing the problem, and a quick search on Stack Overflow confirmed that key is a reserved word in React. One quick renaming of that prop, and everything is working as intended! That takes care of User Story #4, now time to ensure that the audio plays on click.
This is uncharted territory for me. Somebody told me that to get this working, I had to eject from create-react-app and do all these complicated things to get the audio working, and that sounds.....not correct. Usually React doesn't need to mess with the DOM proper, but an element like audio is one of those cases. The relevant documentation starts here. And this shouldn't be too bad, and.....
You may not use the ref attribute on function components because they don’t have instances:
Oh. So. I'm refactoring the Button component, I guess?
Many, many hours later:
Sometimes a project reaches a point where it can't move forward without a near total overhaul, and this project has reached that point. Here's what got me into trouble here:
I employed hasty abstractions in a slavish adherence to the idea that specific tasks/concerns needed to be broken off into components. The Display component is ONE LINE; there was literally no reason to break that off into a separate component, and doing so created more work in the long run.
I had this idea that the App component was where all handler logic needed to live, and doing so made the keypress functionality overly difficult to implement.
I didn't use React Devtools to track where and what the state and props were at any given time, introducing more guesswork into my programming process.
This is annoying, but I'm learning a lot that I clearly needed to know. Next time: I get it done!
Is “Defensive Programming” actually healthy?
I can’t solve this one, and I think I need the help of the DEV Community. So, a d...
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This was me the other day trying to make an avatar upload component using Firebase. | https://practicaldev-herokuapp-com.global.ssl.fastly.net/dylanesque/how-i-built-a-drum-machine-in-react-part-two-state-program-logic-and-failure-14od | CC-MAIN-2019-30 | refinedweb | 1,094 | 62.27 |
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