text stringlengths 454 608k | url stringlengths 17 896 | dump stringclasses 91 values | source stringclasses 1 value | word_count int64 101 114k | flesch_reading_ease float64 50 104 |
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Technical Support
On-Line Manuals
RL-ARM User's Guide (MDK v4)
#include <rtl.h>
BOOL igmp_join (
U8 *group_ip); /* IP Address of the Host Group. */
The igmp_join function requests that this host become a
member of the host group identified by group_ip. Before any
datagrams destined to a particular group can be received, an
upper-layer protocol must ask the IP module to join that group.
The igmp_join function is in the RL-TCPnet library. The
prototype is defined in rtl.h.
The igmp_join function returns __TRUE when this host
successfully joined a host group. Otherwise, the function returns
__FALSE.
igmp_leave, udp_mcast_ttl, udp_send
U8 sgroup[4] = { 238, 0, 100, 1};
..
if (igmp_join (sgroup) == __TRUE) {
printf ("This Host is a member of group: %d.%d.%d.%d\n",
sgroup[0],sgroup[1],sgroup[2],sgroup[3]);
}
else {
printf ("Failed to join a host. | http://www.keil.com/support/man/docs/rlarm/rlarm_igmp_join.htm | CC-MAIN-2020-05 | refinedweb | 142 | 68.57 |
March 2009
Volume 24# Number 03
CLR Inside Out - Isolated Storage In Silverlight 2
By Justin Van Patten | March 2009
In the August 2008 MSDN MagazineCLR Inside Out column, Andrew Pardoe gave a brief overview of isolated storage in Silverlight 2 (" Program Silverlight with the CoreCLR"). In this column, I'll provide more details on isolated storage in Silverlight along with some best practices for using it in your own apps.
Before diving into isolated storage, let me first explain what I/O functionality is available in Silverlight. Silverlight applications are partial-trust applications that run in a sandboxed environment inside a Web browser. As such, arbitrary access to the file system is not permitted. And for good reason—you wouldn't want random, potentially malicious Silverlight applications you come across while browsing the Web to be accessing your personal files or wreaking havoc with your system.
But there are valid scenarios where it is useful to allow Silverlight applications some amount of limited access to the file system, whether it's for reading files (with the end user's consent) or storing data locally on the client. Both scenarios are supported in Silverlight 2 in a limited and safe way: the former is enabled with the OpenFileDialog and the latter with isolated storage.
Like cookies, isolated storage provides the ability to store data on the client between application invocations. But unlike cookies, isolated storage is a full-fledged virtual file system, providing applications with the ability to create, read, write, delete, and enumerate files and directories inside the virtual file system. Isolated storage can be used in the same way as cookies, to maintain state and simple application settings, but it can also be used to save large amounts of data locally on the client.
Isolated storage isn't new to Silverlight; it has been part of the .NET Framework since v1.0. Today Silverlight ships with a simplified subset of the .NET Framework's isolated storage APIs, but it also includes new APIs that provide additional functionality along with some new concepts.
Isolation
As you may expect, one of the key facets of isolated storage is isolation. Isolated storage is composed of many different unique stores, each of which can be thought of as its own virtual file system. Paths cannot escape the bounds of the virtual file system, which effectively isolates the store from the rest of the file system. This prevents a malicious application from being able to access arbitrary files and directories on the disk—such as ..\..\..\..\Windows\System32—where it could cause damage or access sensitive information.
Silverlight applications have access to two different stores: a user + application store (or application store) that is isolated by user identity and application identity and a user + site store (or site store) that is isolated by user identity and site identity. Isolating stores based on the identity of the user, application, and site means that an application can only access the stores to which it is permitted access; it cannot access the stores of other applications.
The user identity that Silverlight employs is the same user identity of the underlying operating system. Silverlight isolates per user by storing all isolated storage data in the current user's local application data directory. Figure 1has more details on where isolated storage is located for each operating system.
The application store is a unique store per application. A Silverlight application can only access its application store; it cannot access any other application's application store. The application store is based on the identity of the user and the identity of the application. The identity of a Silverlight application is the full URL to the Silverlight application's XAP file. For example, is the application identity of a Silverlight application hosted at. The application identity is case insensitive, so both and have the same identity. The application store isn't new to Silverlight; it has existed in the .NET Framework since v2.0. The following code shows how to create a file in the application's application store:
try { using (var store = IsolatedStorageFile.GetUserStoreForApplication()) using (var stream = store.CreateFile("hello.txt")) using (var writer = new StreamWriter(stream)) { writer.Write("Hello World"); } } catch (IsolatedStorageException) { // Isolated storage not enabled or an error occurred }
Silverlight Isolated Storage Best Practices
When you use isolated storage, following these guidelines will help you avoid problems and make the most of the protection isolated storage provides.
- isolated storage APIs used here are located in the System.IO.IsolatedStorage namespace. You can get an instance of the application store by calling IsolatedStorageFile.GetUserStoreForApplication. If isolated storage is enabled (it is by default when Silverlight is installed), this will return an IsolatedStorageFile instance that can be used to work with the store. If the end user has disabled isolated storage, an IsolatedStorageException is thrown.
End users can enable/disable isolated storage, so it is important to always wrap the call to IsolatedStorageFile.GetUserStoreForApplication inside a try/catch block. In fact, IsolatedStorageException could be thrown from any isolated storage operation. This could happen if the end user deletes isolated storage while the application is using it (the next operation will result in an IsolatedStorageException). Plus, if multiple instances of the application are running (in multiple browser windows or tabs, for example) and one of the instances deletes the store, then the next isolated storage operation performed by one of the other application instances will throw an IsolatedStorageException.
The best practice is to wrap all calls to isolated storage inside try/catch blocks to guard against IsolatedStorageExceptions. I've wrapped this first code sample inside a try/catch block to illustrate this, but to keep things simple, the rest of the code samples will not show the try/catch block. Please consider all remaining code samples as being implicitly wrapped in a try/catch block. (For a rundown of best practices, see the sidebar "Silverlight Isolated Storage Best Practices.")
Now that you've seen the application store, let's look at the site store. The site store is a shared store to which all Silverlight applications from the same site have access. This enables applications from the same site to share data between them.
The same way Microsoft Office 2007 has common preferences across its suite of applications, you could imagine developing a suite of Silverlight applications that are all hosted on the same site and share a common set of preferences stored on the client. The site store is based on the identity of the user and the identity of the site. The site identity of a Silverlight application is similar to the application identity, but it only includes the scheme, host, and port of the URL, without the path to the XAP file. Like the application identity, the site identity is also case insensitive. The shared site store is new in Silverlight and is not available in the .NET Framework.
IsolatedStorageFile.GetUserStoreForSite can be used to get an instance of the site store. The following code shows this in action:
Another application with the same site identity could read the shared file with the following code:
To better understand how a given URL to a Silverlight application maps to an application identity and site identity, refer to Figure 2. As you can see, even though the first four URLs are different, they all map to the same application identity and site identity. This is due to the fact that identities are case insensitive, query strings are not included, and port 80 is the default port for the HTTP scheme. However, if another port is specified, such as 8080, then the identity of the application is considered different. If the leading "www" from the host is omitted, the application identity is considered different because the host is different.
The secure HTTPS URL will also yield a different identity because the scheme is different (HTTPS instead of HTTP). The last URL listed in Figure 2will have a different application identity than the first four URLs in the table, but it will have the same site identity, which means these two apps could choose to share data with each other on the client by storing data in their shared site store.
Figure 3 Isolated Storage Quota Groups
Quota
A quota is a limit on the amount of isolated storage space that can be used by an application. This includes the data stored in isolated storage as well as some additional overhead for each directory and new file created (1KB each).
Unlike the .NET Framework, Silverlight uses a concept called quota groups for managing quotas in isolated storage. A quota group is a group of isolated stores that share the same quota. In Silverlight, stores are grouped by site, so all applications that have the same site identity share the same isolated storage quota. For example, all applications hosted on microsoft.com share the same quota.
Isolated storage can have zero or more quota groups. Figure 3shows two hypothetical quota groups: one for microsoft.com and another for blogs.microsoft.com. Each quota group has at most one shared site store and zero or more application stores.
By default, each quota group is assigned a default quota of 1MB. This should be enough space for applications to store simple settings and text files in isolated storage. However, since the quota is shared across all applications from the same site, the quota can easily be reached if just one of the applications uses a lot of space. If a site hosts several Silverlight applications and each application stores data in isolated storage, the amount of free space can diminish quickly. In addition, if an application needs to save a lot of data on the client, 1MB of free space won't always be enough.
To address this, if an application needs more space in isolated storage, it can request a larger quota. When an application requests a larger quota, Silverlight prompts the end user to allow or deny the request. The following code shows how to request a larger quota:
In this code, the AvailableFreeSpace property is used to determine how much free space is available in isolated storage. The code knows it needs 5MB of free space. And if 5MB is not available, it requests a larger quota by calling IncreaseQuotaTo passing it the requested quota size in bytes (in this case the current quota plus the additional space that's needed).
The call to IncreaseQuota must be made from a user-initiated event, such as within a handler for a button-click event. If it is not called from a user-initiated event, Silverlight will not prompt the user and the request will be denied (the method will return false). If called from a user-initiated event and the end user allows the request, IncreaseQuotaTo returns true and the quota for the group is increased to the requested size.
Because quotas are per site in Silverlight, you may want to host your Silverlight application differently depending upon the needs of your site and application. For example, imagine you're creating a Silverlight video player that saves the user's top 10 favorite videos in isolated storage. Each video can be up to 10MB, which means the application will need to increase the quota to something more than 100MB. You could host the application on your main site (for example, contoso.com/player.xap), which may work fine if player.xap were the only Silverlight application hosted on the site. But if there are many other Silverlight applications on contoso.com, they'll all be competing for space in isolated storage.
To solve this, you may want to consider hosting the video player application on its own sub domain (such as player.contoso.com/player.xap). Similarly, if you plan to create a suite of Silverlight applications that need to share data, you'll want to host all of them on the same site and make sure they work well together.
Silverlight uses quota groups to make it easier for end users to manage the use of isolated storage on their computers. Instead of being presented with a laundry list of URLs to different Silverlight XAP files, end users are presented with a list of Web sites that are using isolated storage. This way, end users can quickly decide which Web sites they trust and which Web sites they do not trust to store data on their machines.
To end users, isolated storage is known as Application Storage. An end user can manage isolated storage using the Silverlight Configuration dialog. To open the dialog, right-click on any Silverlight application that's running in a Web browser and click Silverlight Configuration in the menu that pops up. Then click on the Application Storage tab in the Silverlight Configuration dialog. This tab lists the Web sites that are currently using isolated storage along with the current used size and quota for each. This list is essentially the list of quota groups. From here, end users can delete groups or enable and disable isolated storage.
Files and Directories
Creating directories and files in isolated storage is easy. Take a look at Figure 4. Here you'll see CreateDirectory, which is used to create directories. You can create top-level directories as well as subdirectories. To get a listing of the directories in a store, use GetDirectoryNames.
using (var store = IsolatedStorageFile.GetUserStoreForApplication()) { store.CreateDirectory(@"dir1"); store.CreateDirectory(@"dir1\subdir1"); store.CreateDirectory(@"dir1\subdir2"); store.CreateDirectory(@"dir2"); string[] topLevelDirs = store.GetDirectoryNames(); // { "dir1", "dir2" } string[] dir1SubDirs = store.GetDirectoryNames(@"dir1\*"); // { "subdir1", "subdir2" } store.CreateFile(@"toplevel.txt"); store.CreateFile(@"dir1\subdir1\subfile.txt"); string[] files = store.GetFileNames(); // { "toplevel.txt" } string[] subfiles = store.GetFileNames(@"dir1\subdir1\*"); // { "subfile.txt" } }
There is also an overload of GetDirectoryNames that accepts a searchPattern string that supports single-character ("?") and multi-character ("*") wild cards. Notice how a multi-character ("*") wild card is used to get the directories contained inside "dir1". Creating files is similar to creating directories: files can be created in the root of the store or inside directories.
When creating files and directories in isolated storage, keep in mind that the relative isolated storage paths are expanded to full system paths internally (Silverlight applications never see these full paths). The full paths are limited to 260 characters on both Windows and Mac. So although your relative path inside isolated storage may only be 10 characters, those 10 characters will translate into a much longer path when appended to the root system path to where isolated storage is located on the file system. If the resulting system path ends up being more than 260 characters, an exception is thrown.
The location of isolated storage depends on the current user and operating system. Back in Figure 1you saw where isolated storage is located on Windows Vista, Windows XP, and Mac OS X.
The Microsoft\Silverlight\is directory contains the internal isolated storage structure. This is where information on quota groups, stores, bookkeeping data, and so on is stored, along with the actual data, by Silverlight. The specifics of the files and directories inside this directory are not important (these are implementation details that we reserve the right to change in future releases), but it's important to note that the directory structure does add additional overhead to the length of the full path.
For example, say a Silverlight application has created a file named foo.txt in the root of its application store. On Windows Vista, the full obfuscated system path to the file will look something like this:
On Windows XP it will look something like this:
And on Mac OS X it will look something like this:
Assuming <user> is 10 characters, the full path length to foo.txt is 158 characters on Windows Vista, 190 characters on Windows XP, and 167 characters on Mac OS X. Thinking about it more generally, isolated storage paths are limited to 109 characters on Windows Vista, 77 characters on Windows XP, and 100 characters on Mac OS X assuming the current user's user name is 10 characters in length.
To be safe, the best practice is to keep isolated storage paths as small as possible to prevent the full path from reaching the 260-character limit.
One interesting thing to note about the locations listed in Figure 1is the fact that isolated storage is not part of the browser's temporary Internet files. This means that isolated storage is shared across all supported browsers, and when you (or your users, to be precise) clear out the temporary Internet files, the contents of isolated storage are not deleted.
This behavior is by design, because applications can store user-created data (such as documents and photos) in isolated storage along with other preferences and settings that a user might not want to be deleted along with the temporary Internet files. To delete the contents of isolated storage, use the Silverlight Configuration dialog as described previously.
One other thing to note is that although the location of isolated storage is obfuscated and stores are isolated from each other, the data stored in isolated storage is not protected (that is, it is not encrypted). This means that other (non-Silverlight) applications running on the machine may be able to access the data. If you need to store sensitive data in isolated storage, encrypt the data before storing it (there are encryption APIs available in Silverlight; see System.Security.Cryptographyon the MSDN library.)
IsolatedStorageSettings
Silverlight includes a new convenience class called IsolatedStorageSettings that can be used to store objects in isolated storage quickly and easily. IsolatedStorageSettings is a dictionary collection that supports saving key-value pairs in either the application store or site store. It automatically takes care of serializing the objects and saving them in isolated storage. The serialized objects are saved to a file in isolated storage called __LocalSettings.
The code in Figure 5 shows how to use IsolatedStorageSettings to save a simple object in the application store. Here I define a simple class called MySettings with three properties: Width, Height, and Color. Then I create an instance of MySettings and populate it with some values. Next, I add it to IsolatedStorageSettings.ApplicationSettings under the settings key.
Finally I call Save, which serializes the object and saves the serialized data to the application store. Retrieving the object happens to be just as easy:
MySettings settings; if (!IsolatedStorageSettings.ApplicationSettings.TryGetValue("settings", out settings)) { // Settings was not previously stored in isolated storage // create a new object initialized with default values settings = new MySettings { Width = 100, Height = 100, Color = Colors.Orange }; }
This code uses the TryGetValue method to avoid an exception if the key is not found (meaning the data had not been previously saved). The code in Figure 5saves the object to the application store. To save objects to the site store, use IsolatedStorageSettings.SiteSettings instead of IsolatedStorageSettings.ApplicationSettings.
public class MySettings { public int Width { get; set; } public int Height { get; set; } public Color Color { get; set; } } var settings = new MySettings { Width = 200, Height = 300, Color = Colors.Blue }; IsolatedStorageSettings.ApplicationSettings["settings"] = settings; IsolatedStorageSettings.ApplicationSettings.Save();
If you only need to store simple objects or settings in isolated storage, using IsolatedStorageSettings makes a lot of sense. But if you need more granular control over the format of data stored in isolated storage or if you are storing large amounts of data, you'll likely want to use the file and stream-based isolated storage APIs.
For more on isolated storage in Silverlight, see Cutting Edge in February 2009.
Send your questions and comments to clrinout@microsoft.com.
Justin Van Patten is a Program Manager on the CLR team at Microsoft where he works on the Base Class Libraries. He can be reached via the BCL team blog at blogs.msdn.com/bclteam.
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20 November 2009 17:30 [Source: ICIS news]
LONDON (ICIS news)--LyondellBasell, INEOS, BP Chemicals and Bayer MaterialScience would all be a good fit as Europe-headquartered acquisition targets for International Petroleum Investment Co (IPIC), analysts said on Friday.
Abu Dhabi-based IPIC, which earlier this week revealed it is nearing an acquisition in ?xml:namespace>
On 17 November, IPIC managing director Khadem al-Qubaisi, revealed the company is in talks with five major petrochemical players in the US and Europe, including Bayer MaterialScience, and expects to close a European acquisition by the first quarter of 2010.
IPIC plans to use technology from the new acquisition to help develop production at the Chemaweyaat chemical city in
This includes a 1.45m tonne/year ethylene plant, with further phases involving the production of aromatics and phenol, Al-Qubaisi said previously.
“As IPIC already has a pretty big polyethylene (PE) and polypropylene (PP) business with Borealis, it would make sense to optimise the benzene and phenol chain,” according to a France-based analyst.
“So clearly, polyurethanes would be a nice fit and polycarbonate a perfect fit. [Bayer MaterialScience] is number one globally in polycarbonate with 25% market share, and in the top two in polyurethanes with 30% of the market.
“IPIC’s [Chemaweyaat complex] could produce aromatics and phenol. This would offer nice backward integration for [Bayer MaterialScience's] polycarbonate and polyurethane products. Additionally, IPIC is looking for producers with cutting-edge technologies and that would fit nicely with [Bayer MaterialScience],” the France-based analyst said.
Bayer is a holding company consisting of three operating units: MaterialScience, HealthCare and CropScience. The company has always rebutted suggestions that it should split the group to make it more focused.
In 2010, however, Bayer CEO Werner Wenning and chief financial officer Klaus Kuhn are leaving the group.
Wenning’s replacement is Marijn Dekkers who has a strong background in life sciences.
“The new CEO will probably refocus the company again on the pharma side, so the polymer business could be non-core and be disposed [of]. An opportunity to sell the business now would facilitate the transition in terms of management next year, and the cash will be probably used to reduce debt or finance acquisitions in healthcare,” according to the the France-based analyst.
He added: “In terms of price, it wouldn’t be a perfect situation. We are in a downturn situation and earnings are really depressed for this business. They wouldn’t maximise the value, but from a strategic point of view it makes a lot of sense.”
The analyst said that a purchase price of €10.7bn ($15.97bn) would make sense, as it would represent eight times the company’s average 2002-2009 earnings before interest, tax, depreciation and amortisation (EBITDA), which has been the average transaction multiple in the chemicals sector in recent years.
A London-based investment banker said: “IPIC has a track record of taking stakes in groups with which they have joint ventures [for the provision of technology]. You can imagine [Bayer MaterialScience] would be a good fit with Chemaweyaat. At some point I’m sure they’ll get involved in some of these [Bayer MaterialScience] products.”
However, a London-based consultant said it would not make sense for Bayer to sell the MaterialScience unit.
“They’d be selling it because it’s not doing very well at the moment and that’s just cyclical. You miss out on the recovery potential. [Bayer MaterialScience] has made some good money,” the London-based consultant said.
UK-headquartered INEOS is also seen as a good acquisition candidate for IPIC, according to the France-based analyst.
“INEOS is carrying a lot of debt. And, in terms of product, they have a number of downstream products that could be well integrated with IPIC such as styrenics, which would be a good add-on to NOVA [Chemicals]. INEOS also has a good base in
He added: “INEOS also has polyvinyl chloride (PVC) but it’s not a great business. They are the leader in PVC in
The London-based consultant added: “They’ve got some PE through Borouge, so they might want a phenol business from INEOS Phenol, which is number one. They might want to do acrylonitrile with INEOS, too.”
According to the London-based consultant, BP Chemicals would also be a good fit for IPIC, because it has world-leading positions in purified terephthalic acid (PTA) and paraxylene (PX).
Another company that would be a good option for IPIC is LyondellBasell, according to the France-based analyst, because “it is a market leader in terms of market share and technology”.
LyondellBasell has leading positions in PP, plus refineries in the
IPIC already has stakes in the following companies with chemical interests:
($1 = €0.67) | http://www.icis.com/Articles/2009/11/20/9266131/lyondellbasell-bayer-materialscience-others-fit-ipic-analysts.html | CC-MAIN-2015-22 | refinedweb | 795 | 51.38 |
In this post, we’ll go back to the basics to uncover few interesting aspects of C# 4.0 dynamic features. Let us start with a simple experiment.
Static Typing or Early Binding
Let us start with a bare minimum program. Fire up VS2010 and try the following code.
It is obvious that this won’t compile. Simply because, the compile/design time checking ensures type safety - and as we don’t have a method named SomeStupidCall in our Human class, we can’t compile the same.
So, that is what you get.
Duck Typing or Dynamic Typing or Late BindingNow, let us take a step back, and modify the above code like this. Change the type of variable h to ‘dynamic’. And Compile. Here is a little surprise!! You got it compiled!! By using ‘dynamic’ keyword, you just told the compiler, “dude, don’t bother if SomeStupidCall() is there in the Human type”
And now, run the application. The application will break for sure. But hey, that is your fault, not the compiler’s.
By the way, why we call dynamic typing as ‘Duck typing’?
Here we go, Quoted from Wikipedia.
Now, why you need ‘dynamic’ at all?
I hope the above scenario is ‘good’ enough to give you an ‘evil’ impression about the dynamic features. But, wait. There.
How a ‘dynamic’ type is getting compiled?
Let us get back to a basic example. Consider a human class, with a Walk() method and Age property. Now, let us create a new Human and assign this to a dynamic variable ‘h’.
Let us build the above application. Fire up Reflector, open the binary executable of the app, and have a look at the same. With a bit of cleanup, this is the relevant part of the disassembled code - which is the equivalent 'statically’ typed code generated by the compiler, for the ‘dynamic’ code we wrote above.
You’ll see a ‘SiteContainer’, for keeping track of the context, and two call site fields.
And here is the disassembled code for the member invocations. It might be interesting to note that, the variable ‘h’ is compiled as a simple CLR ‘object’. Wow, from the CLR point of few, there is nothing like a ‘dynamic’ type. Instead, all member invocations to our ‘dynamic’ object are modified; in such a way that they are piped through a dynamic Call Site. The Call Site is initialized with the Binder responsible for run time binding. In this case, you may note that the C# run time binder will be used to invoke the members(Microsoft.CSharp.RuntimeBinder.Binder ‘s InvokeMember will return a CallSite binder, that’ll be used by the Call Site).
You might be thinking how the code will be generated for scenarios where, you have a method that accepts or returns a ‘dynamic’ type, or a property that gets or sets a dynamic type. Let us try this out. Change our above Human class in the above example, to something like this. Note that now Walk method accepts a dynamic type, and Age property is also modified to get/set dynamic types.
Have a sneak peak using Reflector. You’ll note that, the compiler has generated a special [Dynamic] attribute to the input parameter of Walk() method. Also, the getter and setter of the Age property is also decorated with the [Dynamic] attribute, as shown below.
Conclusion
A good follow up read is my post on ExpandoObject, which explains how to define which operations can be performed on dynamic objects and how to perform those operations. For example, you can define what happens when you try to get or set an object property, call a method, or perform standard mathematical operations such as addition and multiplication.
Also, A more interesting and useful dynamic concept I’ve recently implemented is ElasticObject, a fluent DynamicObject implementation, to deal with data formats like XML in a very easy manner.
And here is some code of the final form of our experiment. Create a Console app in C# 4.0, to play with this.
using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.CompilerServices; using Microsoft.CSharp.RuntimeBinder; namespace DynamicTest { class Human { public void Walk(dynamic place) { Console.WriteLine("I'm walking to " + place); } public dynamic Age { get; set; } } class Program { // Methods private static void Main(string[] args) { //dynamic h = new Human(); //h.Walk("Paris"); //h.Age = 10; //will get compiled to object h = new Human(); //Create the site 1 if it is null if (SiteContainer0.Site1 == null) { SiteContainer0.Site1 = CallSite<Action<CallSite, object, string>>.Create (Binder.InvokeMember(CSharpBinderFlags.ResultDiscarded, "Walk", null,1.Target(SiteContainer0.Site1, h, "Paris"); //Create the site 2 if it is null if (SiteContainer0.Site2 == null) { SiteContainer0.Site2 = CallSite<Func<CallSite, object, int, object>>.Create (Binder.SetMember(CSharpBinderFlags.None, "Age",2.Target(SiteContainer0.Site2, h, 10); } // Nested Types [CompilerGenerated] private static class SiteContainer0 { // Fields public static CallSite<Action<CallSite, object, string>> Site1; public static CallSite<Func<CallSite, object, int, object>> Site2; } } }
Enjoy, Happy Coding!! Do keep in touch, follow me In Twitter @amazedsaint Or Or Subscribe this Blog | http://www.amazedsaint.com/2010/03/c-40-dynamic-keyword-for-dummies-under.html | CC-MAIN-2016-30 | refinedweb | 851 | 58.79 |
In the original prolog of the Debugging STL Containers with WinDbg series, I started off with a simple main.cpp source, compiled it with the Visual Studio compiler, and debugged the executable with WinDbg.
A few folks mentioned that there ought to be some info that covers the steps from having an executable to seeing the debugger output. I had the assumption that if readers were interested in those blog posts they’d probably have some experiences with WinDbg. But I do agree that no matter how trivial some things might be, documenting the exact steps could be helpful one way or the other.
So here are my steps.
1. Prepare the Operating System, Compiler, and WinDbg:
a. Install Windows 8 Version 6.2 Build 9200.
b. Install Visual Studio Ultimate 2012 Version 11.0.50727.1 RTMREL.
c. Install Windows Software Development Kit (SDK) for Windows 8.
2. Open a Visual Studio command prompt.
In Windows 8, press Windows logo key +Q, and type "Developer Command Prompt for VS2012". Select the resulting app.
Here’s what my command prompt looks like where I create main.cpp:
C:\Program Files (x86)\Microsoft Visual Studio 11.0>cd\C:\>md ProjectsC:\>cd ProjectsC:\Projects>md STLC:\Projects>cd STLC:\Projects\STL>notepad main.cppC:\Projects\STL>
3. Write some code in main.cpp. Here’s an example:
#include <iostream>#include <string>#include <vector>using namespace std;int main() { vector<string> ss; ss.push_back("1"); ss.push_back("2"); ss.push_back("3"); for (int i = 0; i < (int)ss.size(); i++) cout << ss[i] << endl;}
4. Save the file, and run the following command to compile it:
C:\Projects\STL>cl /EHsc /nologo /W4 /MTd /Zi main.cpp
5. Start WinDbg. In Windows 8, press Windows logo key +Q, and type "windbg". Select "WinDbg (X86)".
6. In WinDbg, press Ctrl+E (or go to File..Open Executable), type in C:\Projects\STL\main.exe for File name, and then click the Open button. If you receive a Workspace prompt, click Yes to save information for workspace.
7. Type in the following commands, one after another, in WinDbg:
!sym noisy !symfix c:\symbols .reload /f ntdll.dll .reload /f kernel32.dll bp main!main g
At this point here’s what your WinDbg Command window might look like (I’ve highlighted the commands you need to type in):
Microsoft (R) Windows Debugger Version 6.2.9200.16384 X86Copyright (c) Microsoft Corporation. All rights reserved.CommandLine: C:\Projects\STL\main.exeSymbol search path is: *** Invalid ******************************************************************************** Symbol loading may be unreliable without a symbol search path. ** Use .symfix to have the debugger choose a symbol path. ** After setting your symbol path, use .reload to refresh symbol locations. *****************************************************************************Executable search path is: ModLoad: 00a90000 00b81000 main.exeModLoad: 772e0000 77437000 ntdll.dllModLoad: 770f0000 77220000 C:\Windows\SysWOW64\KERNEL32.DLLModLoad: 76830000 768d6000 C:\Windows\SysWOW64\KERNELBASE.dll(fac.d10): Break instruction exception - code 80000003 (first chance)*** ERROR: Symbol file could not be found. Defaulted to export symbols for ntdll.dll - eax=00000000 ebx=00000003 ecx=a0e10000 edx=00000000 esi=00000000 edi=00a900e8eip=7738054d esp=0059f4e4 ebp=0059f510 iopl=0 nv up ei pl zr na pe nccs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000246ntdll!LdrResolveDelayLoadsFromDll+0xa86:7738054d cc int 30:000> !sym noisynoisy mode - symbol prompts on0:000> !symfix c:\symbolsDBGHELP: Symbol Search Path: DBGHELP: Symbol Search Path: SRV*c:\symbols*: Symbol Search Path: SRV*c:\symbols*> .reload /f ntdll.dllDBGHELP: ntdll - public symbols c:\symbols\wntdll.pdb\2806B41638B04D8989F13322DD34573A2\wntdll.pdb0:000> .reload /f kernel32.dllDBGHELP: KERNEL32 - public symbols c:\symbols\wkernel32.pdb\CFACA818EC334A5EAD707CD86C847B4A1\wkernel32.pdb0:000> bp main!mainSYMSRV: c:\symbols\main.pdb\2AA57E80024F4D219D902A73C78FEA2D2\main.pdb not foundSYMSRV: not found*** WARNING: Unable to verify checksum for main.exeDBGHELP: main - private symbols & lines C:\Projects\STL\main.pdb0:000> gBreakpoint 0 hiteax=00d42d98 ebx=7efeb000 ecx=00000001 edx=00d45700 esi=00000000 edi=00000000eip=00a91820 esp=0059f958 ebp=0059f9a0 iopl=0 nv up ei pl zr na pe nccs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000246main!main:00a91820 55 push ebp
Here’s a sample picture of it:
Here’s what happened:
!sym noisy - Activates noisy symbol loading so that when the debugger loads symbols you get more details like exactly where the symbol was loaded.
!symfix c:\symbols (or .symfix) - Sets the symbol path to point to Microsoft symbol store. I specified c:\symbols to store downloaded symbols there.
.reload /f ntdll.dll and .reload /f kernel32.dll - Since when this debug session starts I didn’t have proper symbol path set, symbols for these two modules were not loaded. After I set the symbol path with !symfix, I’m manually reloading the symbols for these two modules. This is not necessary in this specific case but in general it’s a good practice to have symbols for these two modules.
bp main!main - Sets a breakpoint at main().
g - Go (F5), just like what you’re accustomed to in Visual Studio.
8. At this point you can just press F10 or the Step Over button on the toolbar to step over the source code until you hit the for line. This is where the code added three elements into the vector.
9. Now in the debugger’s Command window you can type commands like dt ss to look at the vector:
0:000> dt ssLocal var @ 0x59f8dc Type std::vector<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::allocator<std::basic_string<char,std::char_traits<char>,std::allocator<char> > > > +0x000 _Myproxy : 0x00b750f8 std::_Container_proxy +0x004 _Myfirst : 0x0059f8ec std::basic_string<char,std::char_traits<char>,std::allocator<char> > +0x008 _Mylast : 0x00ae3b1a std::basic_string<char,std::char_traits<char>,std::allocator<char> > +0x00c _Myend : 0x00000008 std::basic_string<char,std::char_traits<char>,std::allocator<char> >
There you go. The steps that accompany the rest of the series.
You know what, actually I’m glad I wrote these down. I might need to reference these sometime later myself.
P.S. I was tempted to go back to the prolog and add a section with an "Update" label. Sounded logical, but I didn’t want to bloat that blog post into a book. Hence this post, Prolog 2. I’ve tagged this post with the same tags as the other posts in the series, so at least the tag cloud works as it’s supposed to. There are so many other questions that could spawn from this little post, like "why not use Visual Studio to create main.cpp", "why X86 and not X64", "why c:\symbols and not d:\symbols", or even "why Windows 8 and not Windows XP or Windows 7". I’ll re-evaluate the need to expand on these points at a later time :)
P.P.S. Just a gentle reminder, if you’re still using Windows XP. Its support ends on April 8, 2014! | http://blogs.msdn.com/b/ambrosew/archive/2013/01/18/debugging-stl-containers-with-windbg-prolog-2.aspx | CC-MAIN-2014-52 | refinedweb | 1,147 | 68.87 |
nextafter - next representable double-precision floating-point number
#include <math.h> double nextafter(double x, double y);
The nextafter() function computes the next representable double-precision floating-point value following x in the direction of y. Thus, if y is less than x, nextafter() returns the largest representable floating-point number less than x.
An application wishing to check for error situations should set errno to 0 before calling nextafter(). If errno is non-zero on return, or the value NaN is returned, an error has occurred.
The nextafter() function returns the next representable double-precision floating-point value following x in the direction of y.
If x or y is NaN, then nextafter() returns NaN and may set errno to [EDOM].
If x is finite and the correct function value would overflow, HUGE_VAL is returned and errno is set to [ERANGE].
The nextafter() function will fail if:
- [ERANGE]
- The correct value would overflow.
The nextafter() function may fail if:
- [EDOM]
- The x or y argument is NaN.
None.
None.
None.
<math.h>. | http://pubs.opengroup.org/onlinepubs/7990989775/xsh/nextafter.html | CC-MAIN-2015-48 | refinedweb | 173 | 63.49 |
I'm trying to make a finite state machine chain with AASM gem. I want to check if a string is unique (not existing in the database).
I wrote:
require 'rubygems'
require 'aasm'
class Term
include AASM
aasm do
state :Beginning, :initial => true
state :CheckUniqueness
def initialize(term)
print term
end
event :UniquenessChecking do
print "Check uniqueness"
transitions :from => :Beginning, :to => :CheckUniqueness
end
end
end
term = Term.new("textstring")
term.CheckUniqueness
Term.new("textstring")
`initialize': wrong number of arguments (1 for 0) (ArgumentError)
from try.rb:24:in `new'
from try.rb:24:in `<main>'
You defined
initialize inside of the
aasm block, just move it out of that block:
require 'rubygems' require 'aasm' class Term include AASM def initialize(term) print term end aasm do # ... end end | https://codedump.io/share/dem0V4BwH4ft/1/how-to-pass-a-parameter-to-newinit-in-aasm-gem | CC-MAIN-2017-34 | refinedweb | 128 | 60.65 |
Game help 2!Wow Thanks Guys its actually working for me now!!!!
You guys have helped alot. Thankyou!!!. :D
Game help 2!it didnt work anyways. I ran the program and it just kept extending an array with random symbols. Il...
Game help 2!here it is
[code]//SDD 2012
//Tic tac toe
//l
#include <iostream>
#include <string>
usin...
Game help 2!Do you think I need to declare anything or add anything earlier in the code or something?
Game help 2!I tried ^ that format
I got a compiling error in the line 'for (int i=0; i < 9; i+=3)'
it says: "er...
This user does not accept Private Messages | http://www.cplusplus.com/user/Fallenfantasy182/ | CC-MAIN-2014-42 | refinedweb | 112 | 88.74 |
In this article, we will discuss how to use PyTorch to build custom neural network architectures, and how to configure your training loop. We will implement a ResNet to classify images from the CIFAR-10 Dataset.
Before, we begin, let me say that the purpose of this tutorial is not to achieve the best possible accuracy on the task, but to show you how to use PyTorch.
Let me also remind you that this is the Part 2 of the our tutorial series on PyTorch. Reading the first part, though not necessary for this article, is highly recommended.
- Understanding Graphs, Automatic Differentiation and Autograd
- Building Your First Neural Network
- Going Deep with PyTorch
- Memory Management and Using Multiple GPUs
- Understanding Hooks
You can get all the code in this post, (and other posts as well) in the Github repo here.
In this post, we will cover
- How to build neural networks using
nn.Moduleclass
- How to build custom data input pipelines with data augmentation using
Datasetand
Dataloaderclasses.
- How to configure your learning rate with different learning rate schedules
- Training a Resnet bases image classifier to classify images from the CIFAR-10 dataset.
Prerequisites
- Chain rule
- Basic Understanding of Deep Learning
- PyTorch 1.0
- Part 1 of this tutorial
You can get all the code in this post, (and other posts as well) in the Github repo here.
A Simple Neural Network
In this tutorial, we will be implementing a very simple neural network.
Building the Network
The
torch.nn module is the cornerstone of designing neural networks in PyTorch. This class can be used to implement a layer like a fully connected layer, a convolutional layer, a pooling layer, an activation function, and also an entire neural network by instantiating a
torch.nn.Module object. (From now on, I'll refer to it as merely
nn.module)
Multiple
nn.Module objects can be strung together to form a bigger
nn.Module object, which is how we can implement a neural network using many layers. In fact,
nn.Module can be used to represent an arbitrary function f in PyTorch.
The
nn.Module class has two methods that you have to override.
__init__function. This function is invoked when you create an instance of the
nn.Module. Here you will define the various parameters of a layer such as filters, kernel size for a convolutional layer, dropout probability for the dropout layer.
forwardfunction. This is where you define how your output is computed. This function doesn't need to be explicitly called, and can be run by just calling the
nn.Moduleinstance like a function with the input as it's argument.
# Very simple layer that just multiplies the input by a number class MyLayer(nn.Module): def __init__(self, param): super().__init__() self.param = param def forward(self, x): return x * self.param myLayerObject = MyLayer(5) output = myLayerObject(torch.Tensor([5, 4, 3]) ) #calling forward inexplicitly print(output)
Another widely used and important class is the
nn.Sequential class. When initiating this class we can pass a list of
nn.Module objects in a particular sequence. The object returned by
nn.Sequential is itself a
nn.Module object. When this object is run with an input, it sequentially runs the input through all the
nn.Module object we passed to it, in the very same order as we passed them.
combinedNetwork = nn.Sequential(MyLayer(5), MyLayer(10)) output = combinedNetwork([3,4]) #equivalent to.. # out = MyLayer(5)([3,4]) # out = MyLayer(10)(out)
Let us now start implementing our classification network. We will make use of convolutional and pooling layers, as well as a custom implemented residual block.
While PyTorch provided many layers out of the box with it's
torch.nn module, we will have to implement the residual block ourselves. Before implementing the neural network, we implement the ResNet Block.
class ResidualBlock(nn.Module): def __init__(self, in_channels, out_channels, stride=1): super(ResidualBlock, self).__init__() # Conv Layer 1 self.conv1 = nn.Conv2d( in_channels=in_channels, out_channels=out_channels, kernel_size=(3, 3), stride=stride, padding=1, bias=False ) self.bn1 = nn.BatchNorm2d(out_channels) # Conv Layer 2 self.conv2 = nn.Conv2d( in_channels=out_channels, out_channels=out_channels, kernel_size=(3, 3), stride=1, padding=1, bias=False ) self.bn2 = nn.BatchNorm2d(out_channels) # Shortcut connection to downsample residual # In case the output dimensions of the residual block is not the same # as it's input, have a convolutional layer downsample the layer # being bought forward by approporate striding and filters self.shortcut = nn.Sequential() if stride != 1 or in_channels != out_channels: self.shortcut = nn.Sequential( nn.Conv2d( in_channels=in_channels, out_channels=out_channels, kernel_size=(1, 1), stride=stride, bias=False ), nn.BatchNorm2d(out_channels) ) def forward(self, x): out = nn.ReLU()(self.bn1(self.conv1(x))) out = self.bn2(self.conv2(out)) out += self.shortcut(x) out = nn.ReLU()(out) return out
As you see, we define the layers, or the components of our network in the
__init__ function. In the
forward function, how are we going to string together these components to compute the output from our input.
Now, we can define our full network.
class ResNet(nn.Module): def __init__(self, num_classes=10): super(ResNet, self).__init__() # Initial input conv self.conv1 = nn.Conv2d( in_channels=3, out_channels=64, kernel_size=(3, 3), stride=1, padding=1, bias=False ) self.bn1 = nn.BatchNorm2d(64) # Create blocks self.block1 = self._create_block(64, 64, stride=1) self.block2 = self._create_block(64, 128, stride=2) self.block3 = self._create_block(128, 256, stride=2) self.block4 = self._create_block(256, 512, stride=2) self.linear = nn.Linear(512, num_classes) # A block is just two residual blocks for ResNet18 def _create_block(self, in_channels, out_channels, stride): return nn.Sequential( ResidualBlock(in_channels, out_channels, stride), ResidualBlock(out_channels, out_channels, 1) ) def forward(self, x): # Output of one layer becomes input to the next out = nn.ReLU()(self.bn1(self.conv1(x))) out = self.stage1(out) out = self.stage2(out) out = self.stage3(out) out = self.stage4(out) out = nn.AvgPool2d(4)(out) out = out.view(out.size(0), -1) out = self.linear(out) return out
Input Format
Now that we have our network object, we turn our focus to the input. We come across different types of input while working with Deep Learning. Images, audio or high dimensional structural data.
The kind of data we are dealing with will dictate what input we use. Generally, in PyTorch, you will realise that batch is always the first dimension. Since we are dealing with Images here, I will describe the input format required by images.
The input format for images is
[B C H W]. Where
B is the batch size,
C are the channels,
H is the height and
W is the width.
The output of our neural network is gibberish right now since we have used random weights. Let us now train our network.
Let us now load the data. We will be making the use of
torch.utils.data.Dataset and
torch.utils.data.Dataloader class for this.
We first start by downloading the CIFAR-10 dataset in the same directory as our code file.
Fire up the terminal,
cd to your code directory and run the following commands.
wget tar xzf cifar.tgz
You might need to use
curl if you're on macOS or manually download it if you're on windows.
We now read the labels of the classes present in the CIFAR dataset.
data_dir = "cifar/train/" with open("cifar/labels.txt") as label_file: labels = label_file.read().split() label_mapping = dict(zip(labels, list(range(len(labels)))))
We will be reading images using
PIL library. Before we write the functionality to load our data, we write a preprocessing function that does the following things.
- Randomly horizontally the image with a probability of 0.5
- Normalise the image with mean and standard deviation of CIFAR dataset
- Reshape it from
W H Cto
C H W.
def preprocess(image): image = np.array(image) if random.random() > 0.5: image = image[::-1,:,:] cifar_mean = np.array([0.4914, 0.4822, 0.4465]).reshape(1,1,-1) cifar_std = np.array([0.2023, 0.1994, 0.2010]).reshape(1,1,-1) image = (image - cifar_mean) / cifar_std image = image.transpose(2,1,0) return image
Normally, there are two classes PyTorch provides you in relation to build input pipelines to load data.
torch.data.utils.dataset, which we will just refer as the
datasetclass now.
torch.data.utils.dataloader, which we will just refer as the
dataloaderclass now.
torch.utils.data.dataset
dataset is a class that loads the data and returns a generator so that you iterate over it. It also lets you incorporate data augmentation techniques into the input Pipeline.
If you want to create a
dataset object for your data, you need to overload three functions.
__init__function. Here, you define things related to your dataset here. Most importantly, the location of your data. You can also define various data augmentations you want to apply.
__len__function. Here, you just return the length of the dataset.
__getitem__function. The function takes as an argument an index
iand returns a data example. This function would be called every iteration during our training loop with a different
iby the
datasetobject.
Here is a implementation of our
dataset object for the CIFAR dataset.
class Cifar10Dataset(torch.utils.data.Dataset): def __init__(self, data_dir, data_size = 0, transforms = None): files = os.listdir(data_dir) files = [os.path.join(data_dir,x) for x in files] if data_size < 0 or data_size > len(files): assert("Data size should be between 0 to number of files in the dataset") if data_size == 0: data_size = len(files) self.data_size = data_size self.files = random.sample(files, self.data_size) self.transforms = transforms def __len__(self): return self.data_size def __getitem__(self, idx): image_address = self.files[idx] image = Image.open(image_address) image = preprocess(image) label_name = image_address[:-4].split("_")[-1] label = label_mapping[label_name] image = image.astype(np.float32) if self.transforms: image = self.transforms(image) return image, label
We also use the
__getitem__ function to extract the label for an image encoded in its file name.
Dataset class allows us to incorporate the lazy data loading principle. This means instead of loading all data at once into the memory (which could be done by loading all the images in memory in the
__init__ function rather than just addresses), it only loads a data example whenever it is needed (when
__getitem__ is called).
When you create an object of the
Dataset class, you basically can iterate over the object as you would over any python iterable. Each iteration,
__getitem__ with the incremented index
i as its input argument.
Data Augmentations
I've passed a
transforms argument in the
__init__ function as well. This can be any python function that does data augmentation. While you can do the data augmentation right inside your preprocess code, doing it inside the
__getitem__ is just a matter of taste.
Here, we can also add data augmentation. These data augmentations can be implemented as either functions or classes. You just have to make sure that you are able to apply them to your desired outcome in the
__getitem__ function.
We have a plethora of data augmentation libraries that can be used to augment data.
For our case,
torchvision library provides a lot of pre-built transforms along with the ability to compose them into one bigger transform. But we are going to keep our discussion limited to PyTorch here.
torch.utils.data.Dataloader
The
Dataloader class facilitates
- Batching of Data
- Shuffling of Data
- Prefetching, that is, while GPU crunches the current batch,
Dataloadercan load the next batch into memory in meantime. This means GPU doesn't have to wait for the next batch and it speeds up training.
You instantiate a
Dataloader object with a
Dataset object. Then you can iterate over a
Dataloader object instance just like you did with a
dataset instance.
However you can specify various options that can let you have more control on the looping options.
trainset = Cifar10Dataset(data_dir = "cifar/train/", transforms=None) trainloader = torch.utils.data.DataLoader(trainset, batch_size=128, shuffle=True, num_workers=2) testset = Cifar10Dataset(data_dir = "cifar/test/", transforms=None) testloader = torch.utils.data.DataLoader(testset, batch_size=128, shuffle=True, num_workers=2)
Both the
trainset and
trainloader objects are python generator objects which can be iterated over in the following fashion.
for data in trainloader: # or trainset img, label = data
However, the
Dataloader class makes things much more convenient than
Dataset class. While on each iteration the
Dataset class would only return us the output of the
__getitem__ function,
Dataloader does much more than that.
- Notice that the our
__getitem__method of
trainsetreturns a numpy array of shape
3 x 32 x 32.
Dataloaderbatches the images into Tensor of shape
128 x 3 x 32 x 32. (Since
batch_size= 128 in our code).
- Also notice that while our
__getitem__method outputs a numpy array,
Dataloaderclass automatically converts it into a
Tensor
- Even if the
__getitem__method returns a object which is of non-numerical type, the
Dataloaderclass turns it into a list / tuple of size
B(128 in our case). Suppose that
__getitem__also return the a string, namely the label string. If we set batch = 128 while instantiating the dataloader, each iteration,
Dataloaderwill give us a tuple of 128 strings.
Add prefetching, multiple threaded loading to above benefits, using
Dataloader class is preferred almost every time.
Training and Evaluation
Before we start writing our training loop, we need to decide our hyperparameters and our optimisation algorithms. PyTorch provides us with many pre-built optimisation algorithms through its
torch.optim .
torch.optim
torch.optim module provides you with multiple functionalities associated with training / optimisation like.
- Different optimisation algorithms (like
optim.SGD,
optim.Adam)
- Ability to schedule the learning rate (with
optim.lr_scheduler)
- Ability to having different learning rates for different parameters (we will not discuss this in this post though).
We use a cross entropy loss, with momentum based SGD optimisation algorithm. Our learning rate is decayed by a factor of 0.1 at 150th and 200th epoch.
device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu") #Check whether a GPU is present. clf = ResNet() clf.to(device) #Put the network on GPU if present criterion = nn.CrossEntropyLoss() optimizer = optim.SGD(clf.parameters(), lr=0.1, momentum=0.9, weight_decay=5e-4) scheduler = torch.optim.lr_scheduler.MultiStepLR(optimizer, milestones=[150, 200], gamma=0.1)
In the first line of code,
device is set to
cuda:0 if a GPU number 0 if it is present and
cpu if not.
By default, when we initialise a network, it resides on the CPU.
clf.to(device) moves the network to GPU if present. We will cover how to use multiple GPUs in more detail in the another part. We can alternatively use
clf.cuda(0) to move our network
clf to GPU
0 . (Replace
0 by index of the GPU in general case)
criterion is basically a
nn.CrossEntropy class object which, as the name suggests, implements the cross entropy loss. It basically subclasses
nn.Module.
We then define the variable
optimizer as an
optim.SGD object. The first argument to
optim.SGD is
clf.parameters(). The
parameters() function of a
nn.Module object returns it's so called
parameters (Implemented as
nn.Parameter objects, we will learn about this class in a next part where we explore advanced PyTorch functionality. For now, think of it as a list of associated
Tensors which are learnable).
clf.parameters() are basically the weights of our neural network.
As you will see in the code, we will call
step() function on
optimizer in our code. When
step() is called, the optimizer updates each of the
Tensor in
clf.parameters() using the gradient update rule equation. The gradients are accessed by using the
grad attribute of each
Tensor
Generally, the first argument to any optimiser whether it be SGD, Adam or RMSprop is the list of
Tensors it is supposed to update. The rest of arguments define the various hyperparameters.
scheduler , as the name suggests, can schedule various hyperparameters of the
optimizer.
optimizer is used to instantiate
scheduler. It updates the hyperparameters everytime we call
scheduler.step()
Writing the training loop
We finally train for 200 epochs. You can increase the number of epochs. This might take a while on a GPU. Again the idea of this tutorial is to show how PyTorch works and not to attain the best accuracy.
We evaluate classification accuracy every epoch.
for epoch in range(10): losses = [] scheduler.step() # Train start = time.time() for batch_idx, (inputs, targets) in enumerate(trainloader): inputs, targets = inputs.to(device), targets.to(device) optimizer.zero_grad() # Zero the gradients outputs = clf(inputs) # Forward pass loss = criterion(outputs, targets) # Compute the Loss loss.backward() # Compute the Gradients optimizer.step() # Updated the weights losses.append(loss.item()) end = time.time() if batch_idx % 100 == 0: print('Batch Index : %d Loss : %.3f Time : %.3f seconds ' % (batch_idx, np.mean(losses), end - start)) start = time.time() # Evaluate clf.eval() total = 0 correct = 0 with torch.no_grad(): for batch_idx, (inputs, targets) in enumerate(testloader): inputs, targets = inputs.to(device), targets.to(device) outputs = clf(inputs) _, predicted = torch.max(outputs.data, 1) total += targets.size(0) correct += predicted.eq(targets.data).cpu().sum() print('Epoch : %d Test Acc : %.3f' % (epoch, 100.*correct/total)) print('--------------------------------------------------------------') clf.train()
Now, the above is a large chunk of code. I didn't break it into smaller ones so as to not risk continuity. While I've added comments in the code to inform the reader what's going on, I will now explain the not so trivial parts in the code.
We first call
scheduler.step() at the beginning of epoch to make sure that
optimizer will use the correct learning rate.
The first thing inside the loop we do is that we move our
input and
target to GPU 0. This should be the same device on which our model resides, otherwise PyTorch will throw up and error and halt.
Notice we call
optimizer.zero_grad() before our forward pass. This is because a leaf
Tensors (which are weights are) will retain the gradients from previous passes. If
backward is called again on the loss, the new gradients would simply be added to the earlier gradients contained by the
grad attribute. This functionality comes handy when working with RNNs, but for now, we need to set the gradients to zero so the gradients don't accumulate between subsequent passes.
We also put our evaluation code inside
torch.no_grad context, so that no graph is created for evaluation. If you find this confusing, you can go back to part 1 to refresh your autograd concepts.
Also notice, we call
clf.eval() on our model before evaluation, and then
clf.train() after it. A model in PyTorch has two states
eval() and
train(). The difference between the states is rooted in stateful layers like Batch Norm (Batch statistics in training vs population statistics in inference) and Dropout which behave different during inference and training.
eval tells the
nn.Module to put these layers in inference mode, while training tells
nn.Module to put it in the training mode.
Conclusion
This was an exhaustive tutorial where we showed you how to build a basic training classifier. While this is only a start, we have covered all the building blocks that can let you get started with developing deep networks with PyTorch.
In the next part of this series, we will look into some of the advanced functionality present in PyTorch that will supercharge your deep learning designs. These include ways to create even more complex architectures, how to customise training such as having different learning rates for different parameters.
Further Reading
Add speed and simplicity to your Machine Learning workflow today | https://blog.paperspace.com/pytorch-101-building-neural-networks/ | CC-MAIN-2022-27 | refinedweb | 3,278 | 51.55 |
101282/how-do-i-check-if-a-variable-exists-in-python
I want to check if a variable exists. Now I'm doing something like this:
try:
myVar
except NameError:
# Do something.
Are there other ways without exceptions?
Variables in Python can be defined locally or globally. There are two types of the variable first one is a local variable that is defined inside the function and the second one are global variable that is defined outside the function.
To check the existence of the variable locally we are going to use the locals() function to get the dictionary of the current local symbol table.
Example:
Examples: Checking local variable existence
def func():
# defining local variable
a_variable = 0
# using locals() function
# for checking existence in symbol table
is_local_var = "a_variable" in locals()
# printing result
print(is_local_var)
# driver code
func()
Output:
True
Python doesn’t have a specific function to test whether a variable is defined, since all variables are expected to have been defined before use, even if initially assigned the None object.
Hi. Good question! Well, just like what ...READ MORE
Hey @Vedant, that's pretty simple and straightforward:
if ...READ MORE
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import urllib.request, ...READ MORE
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mylist = ...READ MORE
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1886
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Greetings everybody. I am building a small project around a custom made SAMD21G board that doesn't use the standard SPI pins (they're not even soldered...) . I can define a new SPI interface using SERCOM5 on pins 11, 12, 13 (using Adafruit's guide) because I want to use an ILI9341 display that I have laying around. The problem is how to force a library that uses SPI to talk to the display, use my own defined mySPI interface.
#include "SPI.h" #include "wiring_private.h" // pinPeripheral() function SPIClass mySPI (&sercom1, 12, 13, 11, SPI_PAD_0_SCK_1, SERCOM_RX_PAD_3); #include "Adafruit_GFX.h" #include "Adafruit_ILI9341.h" // For the Adafruit shield, these are the default. #define TFT_DC 9 #define TFT_CS 10 Adafruit_ILI9341 tft = Adafruit_ILI9341(TFT_CS, TFT_DC); void setup() { mySPI.begin(); // Assign pins 11, 12, 13 to SERCOM functionality pinPeripheral(11, PIO_SERCOM); pinPeripheral(12, PIO_SERCOM); pinPeripheral(13, PIO_SERCOM); tft.begin(); }
As you can see, I instantiated mySPI but I assume that tft.begin() uses the default SPI ports (which as I said, in my case are not even soldered). Is it possible to pass mySPI as a parameter to tft.begin()? Any other thoughts?
Thanks a lot.
EDIT: I solved it. I had to instantiate my tft object with my new defined mySPI interface as a parameter.
The right code is:
Adafruit_ILI9341 tft = Adafruit_ILI9341(&mySPI, TFT_DC, TFT_CS, RST); | https://forum.arduino.cc/t/solved-new-sercom-interface-and-how-to-force-spi-devices-use-it/683769 | CC-MAIN-2022-40 | refinedweb | 222 | 67.65 |
@laribee on Twitter
I've written about the template method pattern before. For my money it's still a very useful pattern for building super lightweight frameworks and enabling the open-closed principle which states:
Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification.
So let's review quickly what a template method looks like and what it can do for our code:
public abstract class PriceCalculator
{
public Money Calculate(Product product)
{
Money retailPrice = GetRetailPrice();
Discount discount = CalculateDiscount(product);
return discount.Apply(retailPrice);
}
public abstract Discount CalculateDiscount(Product product);
public Rate GetRetailPrice() { //... }
}
public class GoldCustomerPriceCalculator : PriceCalculator
{
public override Discount CalculateDiscount(Product product)
{
// Gold customers get 20% off, OR
// We could use per-product discounts.
return new Discount(20);
}
}
public class StandardCustomerPriceCalculator : PriceCalculator
{
public override Discount CalculateDiscount(Product product)
{
// Standard customers receive no discount
return new Discount(0);
}
}
It's pretty easy to see we've gotten some variation. This is a simple example off the top of my head and there's probably a better way to tackle this domain problem, but it shows template method in action so I'll leave it alone.
This is all well and good, but what if we encountered a scenario where our class could function autonomously but we want to provide an hook or extensibility point for edge cases or later extension (beware of YAGNI on the latter). I'll call this technique a hook method.
What's a hook method? By playing with the physics of template method a bit to we can make derivations elective by lifting the abstract constraint on our base class and making the template method virtual. The former move is optional and the later is required. Your solution will dictate whether or not the base class should or should not be declared abstract.
Let's consider an example where we want a start/finish semantic for an implementation of model view presenter. In this example I want to have a base presenter that provides some common functionality: attaching the presenter to the view and raising events to signify the presenter has been started. I want to provide a hook so my presenter implementations can do some processing, call services, obtain reference data, etc. I can accomplish this with a hook method style of template method like so:
public abstract class Presenter : IPresenter
{
public void Start()
{
if (Starting != null) Starting(this, EventArgs.Empty);
View.Attach(this);
Startup();
if (Started != null) Started(this, EventArgs.Empty);
}
protected virtual void Startup() {};
public event EventHandler Starting;
public event EventHandler Started;
}
Or we can return to the contrived example of the price calculator to illustrate a non-abstract class:
public class PriceCalculator
{
public Money Calculate(Product product)
{
Money retailPrice = GetRetailPrice();
Discount discount = CalculateDiscount(product);
return discount.Apply(retailPrice);
}
public virtual Discount CalculateDiscount(Product product)
{
return new Discount(0);
}
public Rate GetRetailPrice() { //... }
}
public class GoldCustomerPriceCalculator : PriceCalculator
{
public override Discount CalculateDiscount(Product product)
{
// Gold customers get 20% off, OR
// We could use per-product discounts.
return new Discount(20);
}
}
Money price = new PriceCalculator.Calculate(someProduct);
// or
Money price = new GoldCutomerPriceCalculator.Calculate(someProduct);
I'm sure many of you have seen examples of this in the wild. I'd file this under "pattern life hack." That is, a simple and subtle shift in thinking around template method that expands its many uses in DRYing up your codebase.
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Your standardcustomer class has the same discount as your gold one. HTH
Thanks for catching that. Fixed!
I think:
if (Started != null) Starting(this, EventArgs.empty);
should be:
if (Started != null) Started(this, EventArgs.empty);
The Design Patterns in Ruby book also has an excellent example and explanation of the Hook Methods.
I prefer Strategy to avoid inheritence, but you can't avoid it sometimes.
Good post David.
@Michael - Wow, I'm batting a thousand today. Thanks for the heads up. It's corrected now.
@Jason - RE: your preference. I hear you loud and clear. Where template method can really shine (and inheritance in general) is in layer supertypes. For types with more diverse variation I go with the conventional "favor composition" wisdom. I bought the book you mentioned but haven't read it yet. Will have to dig in a bit more...
It should be Empty not empty :)
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Nice description. I find this funny because we (mvc team) get chastised for following this pattern. Someone would come along and say, "Hey, public Money Calculate(Product product) should be virtual!!!" which defeats the whole point of the Template method pattern. ;)
@Phil - Maybe. It depends :) I can see their point; why not let the "main" method of the pattern be overridden? Obviously you know this, but virtual means proxy-able and testable...
The virtual method approach, with a do-nothing implementation in the base class, we've used that a lot. Very useful approach
@David
Since you're blogging again are you thinking of doing posts on your domain model, for example the way you structure your different sub domains and use anti-corruption layers between them. You've only alluded to this stuff in the past and it seems quite interesting to me.
@Colin
Blogging again?! Okay, okay, so I slowed way down there for a while ;)
I can tackle that problem in an upcoming post, sure. I'm not done with specifications yet, so let me clear that. I had in mind this technique about anti-corruption layers and the visitor pattern for pulling stuff in your model which I'll get to (probably) next week.
This is a good pattern to follow, but I would argue that you should typically favor composition over inheritance. In a lot of cases, this problem can be solved via dependency injection (really just the strategy pattern) -- by introducing a DiscountCalculator dependency, for example, which can be injected into the PriceCalculator.
Sometimes, when using the template method pattern, you might just be giving the *appearance* of extensibility. For example, if PriceCalculator had a bunch of different template methods rather than just the one for calculating discounts, you would be forced to implement each of these in a subtype just to alter the discount calculation. If you instead create a dependency that fulfills each of those concerns, you might end up making your type easier to extend.
@Nate - Sure. I've got a bad example here. Where inheritance is a natural choice is layer supertypes. The presenter example is a better application and these kinds of things tend to be the exception to the "favor composition over inheritance" rule.
On the composition argument, even if you did use composition you might well use a template method approach if all the strategies share some aspects of their behavior.
Good point. Another: template method *can* really limit testing liability (as testing goes into the supertype).
@Dave
Excellent, looking forward to the visitor/anti-corruption entries.
Wonderful. I wish everyone posted such great content. Thanks. Sam.
The next leg of our quest to uncover the deeper driving forces behind SOLID principles brings us to the
Pingback from Why SOLID? GIMME AN O! - | http://codebetter.com/blogs/david_laribee/archive/2008/06/16/hook-methods.aspx | crawl-002 | refinedweb | 1,195 | 55.95 |
"Nicholas J. Leon" <nicholas@binary9.net> writes:> This is precisely what I was thinking. Except that unlike you, who don't> think these minimal headers should be distributed with the kernel, I do.I don't.1) Any changes would have to go through Linus; Linus doesn't wantthat, and we don't want Linus' time taken with this.2) Some people want to use old kernels ("It does what I want"), but we still want them to compile their programs using the latest version ofthis "header package" (aka "LKILP" aka ?), so that that person'sprograms will work even on very recent kernels.3) People shouldn't have to keep the whole linux source tree on theirdisk just to keep an up-to-date version of the LKILP.(However, maybe 2 and 3 are non-issues for people who usedistributions.)I think part of the reason for our disagreement is that I expect agreater difference between the LKILP headers and the kernel headersthan you do.I'm thinking that anything that #include's <linux/config.h> from userspace (as most kernel headers do) is wrong: the result of gcc foo.cshould be the same regardless of my current kernel config.I hear a lot of people talking about namespace issues, and, to me,this implies that name changes are required. (Note that I'm largelyignorant of the namespace requirements, so maybe I overestimate them.)pjm.-To unsubscribe from this list: send the line "unsubscribe linux-kernel" inthe body of a message to majordomo@vger.rutgers.edu | http://lkml.org/lkml/1998/6/24/23 | CC-MAIN-2014-52 | refinedweb | 256 | 63.7 |
/* ** (c) COPYRIGHT MIT 1995. ** Please first read the full copyright statement in the file COPYRIGH. */
The. The general return codes from the methods are:
It is in general not relevant to return how much data has been written in
the stream, as there often will be a relationship other than 1:1 between
indata and outdata. However, it is important that a stream keeps state (either
on the incoming data or the outgoing data stream) so that it can accept a
HT_WOULD_BLOCK and continue at a later time when the blocking
situation has stopped.
This module is implemented by HTStream.c, and it is a part of the W3C Sample Code Library.
#ifndef HTSTREAM_H #define HTSTREAM_H #include "HTList.h" typedef struct _HTStream HTStream; typedef struct _HTStreamClass { char * name;
This field is for diagnostics only
int (*flush) (HTStream * me);
The free method is like the
flush method but it also
frees the current stream object and all stream objects down stream. When
the
free method has been called, the whole stream pipe
(not only this obejct) should not accept any more data.
int (*abort) (HTStream * me, HTList * errorlist);
The abort method should only be used if a stream is interrupted, for example by the user, or an error occurs.
int (*put_character)(HTStream * me, char ch); int (*put_string) (HTStream * me, const char * str); int (*put_block) (HTStream * me, const char * str, int len);
These methods are for actually putting data down the stream. It is important
that the most efficient method is chosen (often put_block). There is no guarantee
that a stream won't change method, for example from
put_character to
put_block
} HTStreamClass;
These streams can be plugged in everywhere in a stream pipe.
This stream simply absorbs data without doing anything what so ever.
extern HTStream * HTBlackHole (void);
The Error stream simply returns
HT_ERROR on all methods. This
can be used to stop a stream as soon as data arrives, for example from the
network.
extern HTStream * HTErrorStream (void);
#endif /* HTSTREAM_H */ | http://www.w3.org/Library/src/HTStream.html | CC-MAIN-2015-06 | refinedweb | 329 | 69.01 |
This article will describe how to embed a .NET Windows Forms application in a web browser using a WPF browser application. Basically, this article will show you how to web enable any Windows Forms .NET application with very few modifications to your project and no code modifications to your WinForms app.
Now, I realize that this is cheating, this article does not actually show you how to convert a .NET Windows Forms application to WPF. If you want to take advantage of all the features that come with WPF, eventually, you will need to re-write your GUI into WPF. However, if in the short term it is not feasible to convert all of your GUI code into WPF, then this solution is a primitive workaround that enables you to host your applications online.
The first step in this article will be to create a simple Windows Forms C# application. This can be any WinForms application, but for the purpose of this article, I will create a small application that calculates a Fibonacci number and displays it on the user interface. This WinForms application can be in either .NET 2.0 or 3.5.
My application will have a form called MainForm, a button called btnCalculate, and a text box called txtResult.
MainForm
btnCalculate
txtResult
Here is the code for the button click event and the Fibonacci calculation:
static int Fibonacci(int x)
{
if (x <= 1)
{
return 1;
}
return Fibonacci(x - 1) + Fibonacci(x - 2);
}
private void btnCalculate_Click(object sender, EventArgs e)
{
txtResult.Text = Fibonacci(10).ToString();
}
Now that we have our sample application, the next step is to convert it to a Class Library. Right click on your project and choose Properties. Under the Application tab in the Output type combo box, choose Class Library, save, and rebuild.
Note, in order to have your application be referenced in WPF, this is the only change you will have to make to your Windows Forms project.
The next step will be to create a WPF browser application. You can do this within the same solution as your Windows Forms application, or in a new solution. In this sample, I am simply going to add the WPF browser application project to the same solution. I have called this new project WPFHost.
The first thing we are going to do is add a reference from our WPFHost project to our WinForms Fibonacci application.
Since the WinForms project is in the same solution, we will add the reference to the Fibonacci project. If the WinForms application was in a different solution, we would browse to the created DLL and add a reference to it.
We will also need to add a reference to the Windows Forms Integration and System Windows Forms Component in the .NET tab.
The next step will be to add a StackPanel to our Page1 XAML window.
StackPanel
Page1
The full XAML for Page1.xaml is:
<Page x:Class="WPFHost.Page1"
xmlns=""
xmlns:
<Grid>
<StackPanel Margin="0,0,0,0" Name="stackPanel"
HorizontalAlignment="Left" VerticalAlignment="Top" />
</Grid>
</Page>
OK, we are almost there. The next step will be to add some code to Page1.xaml.cs in our project. The magic will happen in the Page1 constructor. Our code will create a WindowsFormHost object and assign the previously created MainForm object from our Fibonacci assembly as the child. The WindowsFormHost will then be added as a child to our WPF StackPanel. The only other obscure line of code sets the TopLevel property of the MainForm object to false. I am not sure why this is required, but you will get a compile error if you do not add this step.
WindowsFormHost
TopLevel
false
The code looks as follows:
using System.Windows.Controls;
using System.Windows.Forms.Integration;
using Fibonacci;
namespace WPFHost
{
/// <summary>
/// Interaction logic for Page1.xaml
/// </summary>
public partial class Page1 : Page
{
private readonly MainForm mainForm = new MainForm();
public Page1()
{
InitializeComponent();
//Create a Windows Forms Host to host a form
WindowsFormsHost windowsFormsHost = new WindowsFormsHost();
stackPanel.Width = mainForm.Width;
stackPanel.Height = mainForm.Height;
windowsFormsHost.Width = mainForm.Width;
windowsFormsHost.Height = mainForm.Height;
mainForm.TopLevel = false;
windowsFormsHost.Child = mainForm;
stackPanel.Children.Add(windowsFormsHost);
}
}
}
Don’t forget to Save.
OK, this is the last step, I promise. It is also the most obscure one that took me some time to figure out. When I first created the WPF project, I could get this code to work in a regular WPF application, but I always received a weird error when I tried it in a WPF browser application. I almost gave up, thinking that maybe it is not possible to host a Windows Forms application in a web browser. At the end, I found a post on Google groups that gave me the solution. The last step is to right click on the WPFHost project, choose Properties, and navigate to the Security tab. In the tab, change the radio button from “This is a partial trust application” to “This is a full trust application”.
OK, I lied, there is one more step. Right click on your WPFHost project and choose “Set as Startup Project”.
Save, Compile, and Run. You should see your default web browser open with the following page:
That’s it. If you wish to embed the created .xbap in an HTML web page, you can use the <iframe> tag as follows:
<iframe>
<iframe src="WPFHost.xbap" width="329" height="443" />. | https://www.codeproject.com/articles/31429/embedding-a-net-winforms-application-in-an-interne?fid=1531950&df=90&mpp=10&sort=position&spc=none&tid=3244296 | CC-MAIN-2017-13 | refinedweb | 898 | 65.01 |
C++ Program for DFS Traversal
Hello Everyone!
In this tutorial, we will learn how to implement the DFS Traversal on a Graph, in the C++ programming language.
What is DFS Traversal?
As the name suggests, Depth first search (DFS) algorithm starts with the starting node, and then travers each branch of the graph until we find the leaf node which is a node that has no children. The algorithm, then backtracks towards the most recent nodes that is yet to be completely explored. This process is repeated until all the nodes of the graphs are visited or explored.
The data structure used in DFS is Stack. To learn more about the Stack data structure, we will recommend you to visit, where we have explained these concepts in detail.
For better understanding, refer to the well-commented C++ code given below.
Code:
#include <iostream> #include<vector> using namespace std; int main() { cout << "\n\nWelcome to Studytonight :-)\n\n\n"; cout << " ===== Program to demonstrate the DFS Traversal on a Graph, in CPP ===== \n\n"; //variable declaration int cost[10][10], i, j, k, n, e, top, v, stk[10], visit[10], visited[10]; cout << "Enter the number of vertices in the Graph: "; cin >> n; cout << "\nEnter the number of edges in the Graph : "; cin >> e; cout << "\nEnter the start and end vertex of the edges: \n"; for (k = 1; k <= e; k++) { cin >> i >> j; cost[i][j] = 1; } cout << "\nEnter the initial vertex to start the DFS traversal with: "; cin >> v; cout << "\nThe DFS traversal on the given graph is : \n"; cout << v << " "; //As we start with the vertex v, marking it visited to avoid visiting again visited[v] = 1; k = 1; //The DFS Traversal Logic while (k < n) { for (j = n; j >= 1; j--) { if (cost[v][j] != 0 && visited[j] != 1 && visit[j] != 1) { visit[j] = 1; //put all the vertices that are connected to the visited vertex into a stack stk[top] = j; top++; } } //output all the connected vertices one at a time v = stk[--top]; cout << v << " "; k++; //as v is visited so it is not a valid candidate to visit in future so visit[v]=0 and visited[v]=1 visit[v] = 0; //to mark it visited visited[v] = 1; } cout << "\n\n\n"; return 0; }
Output:
We hope that this post helped you develop a better understanding of the concept of DFS Traversal and its implementation 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-program-for-dfs-traversal | CC-MAIN-2021-04 | refinedweb | 421 | 55.2 |
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- Can't solve the problem :( | https://www.sencha.com/forum/archive/index.php/f-87-p-29.html | CC-MAIN-2016-30 | refinedweb | 1,842 | 54.73 |
The American company Electronic Arts Inc (EA) has opened the source code of the games Command & Conquer: Tiberian Dawn and Command & Conquer: Red Alert publicly available. Several dozen errors were detected in the source code using the PVS-Studio analyzer, so, please, welcome the continuation of found defects review. and potential vulnerabilities in the source code of programs, written in C, C++, C#, and Java.
Link to the first error overview: "The Code of the Command & Conquer Game: Bugs from the 90's. Volume one"
V583 The '?:' operator, regardless of its conditional expression, always returns one and the same value: 3072. STARTUP.CPP 1136
void Read_Setup_Options( RawFileClass *config_file ) { .... ScreenHeight = ini.Get_Bool("Options", "Resolution", false) ? 3072 : 3072; .... }
It turns out that users couldn't configure some settings. Or, rather, they did something but due to the fact that the ternary operator always returns a single value, nothing has actually changed.
V590 Consider inspecting the 'i < 8 && i < 4' expression. The expression is excessive or contains a misprint. DLLInterface.cpp 2238
// Maximum number of multi players possible. #define MAX_PLAYERS 8 // max # of players we can have for (int i = 0; i < MAX_PLAYERS && i < 4; i++) { if (GlyphxPlayerIDs[i] == player_id) { MultiplayerStartPositions[i] = XY_Cell(x, y); } }
Due to an incorrect loop, the position is not set for all players. On the one hand, we see the constant MAX_PLAYERS 8 and assume that this is the maximum number of players. On the other hand, we see the condition i < 4 and the operator &&. So the loop never makes 8 iterations. Most likely, at the initial stage of development, the programmer hadn't used constants. When he started, he forgot to delete the old numbers from the code.
V648 Priority of the '&&' operation is higher than that of the '||' operation. INFANTRY.CPP 1003
void InfantryClass::Assign_Target(TARGET target) { .... if (building && building->Class->IsCaptureable && (GameToPlay != GAME_NORMAL || *building != STRUCT_EYE && Scenario < 13)) { Assign_Destination(target); } .... }
You can make the code non-obvious (and most likely erroneous) simply by not specifying the priority of operations for the || and && operators. Here I can't really get if it's an error or not. Given the overall quality of the code for these projects, we can assume that here and in several other places, we will find errors related to operations priority:
V617 Consider inspecting the condition. The '((1L << STRUCT_CHRONOSPHERE))' argument of the '|' bitwise operation contains a non-zero value. HOUSE.CPP 5089
typedef enum StructType : char { STRUCT_NONE=-1, STRUCT_ADVANCED_TECH, STRUCT_IRON_CURTAIN, STRUCT_WEAP, STRUCT_CHRONOSPHERE, // 3 .... } #define STRUCTF_CHRONOSPHERE (1L << STRUCT_CHRONOSPHERE) UrgencyType HouseClass::Check_Build_Power(void) const { .... if (State == STATE_THREATENED || State == STATE_ATTACKED) { if (BScan | (STRUCTF_CHRONOSPHERE)) { // <= urgency = URGENCY_HIGH; } } .... }
To check whether certain bits are set in a variable, use the & operator, not |. Due a typo in this code snippet, we have a condition that is always true here.
V768 The enumeration constant 'WWKEY_RLS_BIT' is used as a variable of a Boolean-type. KEYBOARD.CPP 286
typedef enum { WWKEY_SHIFT_BIT = 0x100, WWKEY_CTRL_BIT = 0x200, WWKEY_ALT_BIT = 0x400, WWKEY_RLS_BIT = 0x800, WWKEY_VK_BIT = 0x1000, WWKEY_DBL_BIT = 0x2000, WWKEY_BTN_BIT = 0x8000, } WWKey_Type; int WWKeyboardClass::To_ASCII(int key) { if ( key && WWKEY_RLS_BIT) return(KN_NONE); return(key); }
I think, in the key parameter, the intention was to check a certain bit set by the WWKEY_RLS_BIT mask, but the author made a typo. They should have used the & bitwise operator instead of && to check the key code.
V523 The 'then' statement is equivalent to the 'else' statement. RADAR.CPP 1827
void RadarClass::Player_Names(bool on) { IsPlayerNames = on; IsToRedraw = true; if (on) { Flag_To_Redraw(true); // Flag_To_Redraw(false); } else { Flag_To_Redraw(true); // force drawing of the plate } }
A developer once commented on code for debugging. Since then, a conditional operator with the same operators in different branches has remained in the code.
Exactly the same two places were found:
V705 It is possible that 'else' block was forgotten or commented out, thus altering the program's operation logics. NETDLG.CPP 1506
static int Net_Join_Dialog(void) { .... /*............................................................... F4/SEND/'M' = edit a message ...............................................................*/ if (Messages.Get_Edit_Buf()==NULL) { .... } else /*............................................................... If we're already editing a message and the user clicks on 'Send', translate our input to a Return so Messages.Input() will work properly. ...............................................................*/ if (input==(BUTTON_SEND | KN_BUTTON)) { input = KN_RETURN; } .... }
Due to a large comment, the developer hasn't seen the above unfinished conditional operator. The remaining else keyword forms the else if construction with the condition below, which most likely changes the original logic.
V519 The 'ScoresPresent' variable is assigned values twice successively. Perhaps this is a mistake. Check lines: 539, 541. INIT.CPP 541
bool Init_Game(int , char *[]) { .... ScoresPresent = false; //if (CCFileClass("SCORES.MIX").Is_Available()) { ScoresPresent = true; if (!ScoreMix) { ScoreMix = new MixFileClass("SCORES.MIX"); ThemeClass::Scan(); } //}
Another potential defect due to incomplete refactoring. Now it is unclear whether the ScoresPresent variable should be set to true or false.
V611 The memory was allocated using 'new T[]' operator but was released using the 'delete' operator. Consider inspecting this code. It's probably better to use 'delete [] poke_data;'. CCDDE.CPP 410
BOOL Send_Data_To_DDE_Server (char *data, int length, int packet_type) { .... char *poke_data = new char [length + 2*sizeof(int)]; // <= .... if(DDE_Class->Poke_Server( .... ) == FALSE) { CCDebugString("C&C95 - POKE failed!\n"); DDE_Class->Close_Poke_Connection(); delete poke_data; // <= return (FALSE); } DDE_Class->Close_Poke_Connection(); delete poke_data; // <= return (TRUE); }
The analyzer found an error related to the fact that memory can be allocated and released in incompatible ways. To free up memory allocated for an array, the delete[] operator should have been used instead of delete.
There were several such places, and all of them gradually harm the running application (game):
V772 Calling a 'delete' operator for a void pointer will cause undefined behavior. ENDING.CPP 254
void GDI_Ending(void) { .... void * localpal = Load_Alloc_Data(CCFileClass("SATSEL.PAL")); .... delete [] localpal; .... }
The delete and delete[] operators are separated for a reason. They perform different tasks to clear memory. When using an untyped pointer, the compiler doesn't know which data type the pointer is pointing to. In the C++ standard, the behavior of the compiler is uncertain.
There was also a number of analyzer warnings of this kind:
V773 The function was exited without releasing the 'progresspalette' pointer. A memory leak is possible. MAPSEL.CPP 258
void Map_Selection(void) { .... unsigned char *grey2palette = new unsigned char[768]; unsigned char *progresspalette = new unsigned char[768]; .... scenario = Scenario + ((house == HOUSE_GOOD) ? 0 : 14); if (house == HOUSE_GOOD) { lastscenario = (Scenario == 14); if (Scenario == 15) return; } else { lastscenario = (Scenario == 12); if (Scenario == 13) return; } .... }
The developer might have thought: ''If I don't free memory at all, I will definitely not make a mistake and will choose the correct operator''.
But it results in a memory leak, which is also an error. Somewhere at the end of the function, memory gets released. Before that, there are many places with a conditional exit of the function, and memory by the grey2palette and progresspalett pointers isn't released.
V570 The 'hdr->MagicNumber' variable is assigned to itself. COMBUF.CPP 806
struct CommHdr { unsigned short MagicNumber; unsigned char Code; unsigned long PacketID; } *hdr; void CommBufferClass::Mono_Debug_Print(int refresh) { .... hdr = (CommHdr *)SendQueue[i].Buffer; hdr->MagicNumber = hdr->MagicNumber; hdr->Code = hdr->Code; .... }
Two fields in the CommHdr structure are initialized with their own values. In my opinion, it's a meaningless operation, but it is executed many times:
V591 Non-void function should return a value. HEAP.H 123
int FixedHeapClass::Free(void * pointer); template<class T> class TFixedHeapClass : public FixedHeapClass { .... virtual int Free(T * pointer) {FixedHeapClass::Free(pointer);}; };
In the Freefunction of the TFixedHeapClass class there is no return operator. What's interesting is that the called FixedHeapClass::Free function also has a return value of the int type. Most likely, the programmer just forgot to write the return statement and now the function returns an incomprehensible value.
V672 There is probably no need in creating the new 'damage' variable here. One of the function's arguments possesses the same name and this argument is a reference. Check lines: 1219, 1278. BUILDING.CPP 1278
ResultType BuildingClass::Take_Damage(int & damage, ....) { .... if (tech && tech->IsActive && ....) { int damage = 500; tech->Take_Damage(damage, 0, WARHEAD_AP, source, forced); } .... }
The damage parameter is passed by reference. Therefore, the function body is expected to change the value of this variable. But at one point, the developer declared a variable with the same name. Because of this, the 500 value instead of the function parameter is stored in the local damage variable . Perhaps different behavior was intended.
One more similar fragment:
V762 It is possible a virtual function was overridden incorrectly. See first argument of function 'Occupy_List' in derived class 'BulletClass' and base class 'ObjectClass'. BULLET.H 90
class ObjectClass : public AbstractClass { .... virtual short const * Occupy_List(bool placement=false) const; // <= virtual short const * Overlap_List(void) const; .... }; class BulletClass : public ObjectClass, public FlyClass, public FuseClass { .... virtual short const * Occupy_List(void) const; // <= virtual short const * Overlap_List(void) const {return Occupy_List();}; .... };
The analyzer detected a potential error in overriding the virtual Occupy_List function. This may cause the wrong functions to be called at runtime.
Some other suspicious fragments:
V763 Parameter 'coord' is always rewritten in function body before being used. DISPLAY.CPP 4031
void DisplayClass::Set_Tactical_Position(COORDINATE coord) { int xx = 0; int yy = 0; Confine_Rect(&xx, &yy, TacLeptonWidth, TacLeptonHeight, Cell_To_Lepton(MapCellWidth) + GlyphXClientSidebarWidthInLeptons, Cell_To_Lepton(MapCellHeight)); coord = XY_Coord(xx + Cell_To_Lepton(MapCellX), yy + Cell_To_Lepton(....)); if (ScenarioInit) { TacticalCoord = coord; } DesiredTacticalCoord = coord; IsToRedraw = true; Flag_To_Redraw(false); }
The coord parameter is immediately overwritten in the function body. The old value was not used. This is very suspicious when a function has arguments and it doesn't depend on them. In addition, some coordinates are passed as well.
So this fragment is worth checking out:
V507 Pointer to local array 'localpalette' is stored outside the scope of this array. Such a pointer will become invalid. MAPSEL.CPP 757
extern "C" unsigned char *InterpolationPalette; void Map_Selection(void) { unsigned char localpalette[768]; .... InterpolationPalette = localpalette; .... }
There are a lot of global variables in the game code. Perhaps, it used to be a common approach to writing code back then. However, now it is considered bad and even dangerous.
The InterpolationPalette pointer is stored in the local array localpalette, which will become invalid after exiting the function.
A couple more dangerous places:
As I wrote in the first report, let's hope that new Electronic Arts projects are of better quality. By the way, game developers are currently actively purchasing PVS-Studio. Now the game budgets are quite large, so no one needs extra expenses to fix bugs in production. Speaking of which, fixing an error at an early stage of code writing does not take up much time and other resources.
You are welcome to visit our site to download and try PVS-Studio on all projects. ... | https://www.viva64.com/en/b/0748/ | CC-MAIN-2021-04 | refinedweb | 1,754 | 50.02 |
NAME¶top - display Linux processes
SYNOPSIS¶top -hv|-bcHiOSs -d secs -n max -u|U user - p pid -o fld -w [cols]
DESCRIPTION¶.
OVERVIEW¶
Documentation¶The remaining Table of Contents
OVERVIEW Operation Startup Defaults. SYSTEM Configuration File b. PERSONAL Configuration File c. ADDING INSPECT Entries 7. STUPID TRICKS Sampler a. Kernel Magic b. Bouncing Windows c. The Big Bird Window d. The Ol' Switcheroo 8. BUGS, 9. SEE Also
Operation¶When operating top, the two most important keys are the help (h or ?) key and quit (`q') key. Alternatively, you could simply use the traditional interrupt key (^C) when you're done.
key/cmd objective ^Z suspend top fg resume top <Left> force a screen redraw (if necessary)
key/cmd objective reset restore your terminal settings
key special-significance Up recall older strings for re-editing Down recall newer strings or erase entire line Insert toggle between insert and overtype modes Delete character removed at cursor, moving others left Home jump to beginning of input line End jump to end of input line
Startup Defaults¶The following startup defaults assume no configuration file, thus no user customizations. Even so, items shown with an asterisk (`*') could be overridden through the command-line. All are explained in detail in the sections that follow.
Global-defaults A - Alt display Off (full-screen) * d - Delay time 1.5 seconds * H - Threads mode Off (summarize as tasks) I - Irix mode On (no, `solaris' smp) * p - PID monitoring Off (show all processes) * s - Secure mode Off (unsecured) B - Bold enable On (yes, bold globally) Summary-Area-defaults l - Load Avg/Uptime On (thus program name) t - Task/Cpu states On (1+1 lines, see `1') m - Mem/Swap usage On (2 lines worth) 1 - Single Cpu Off (thus multiple cpus) Task-Area-defaults b - Bold hilite Off (use `reverse') * c - Command line Off (name, not cmdline) * i - Idle tasks On (show all tasks) J - Num align right On (not left justify) j - Str align right Off (not right justify) R - Reverse sort On (pids high-to-low) * S - Cumulative time Off (no, dead children) * u - User filter Off (show euid only) * U - User filter Off (show any uid) V - Forest view On (show as branches) x - Column hilite Off (no, sort field) y - Row hilite On (yes, running tasks) z - color/mono On (show colors)
Linux Memory Types¶
Private | Shared 1 | 2 Anonymous . stack | . malloc() | . brk()/sbrk() | . POSIX shm* . mmap(PRIVATE, ANON) | . mmap(SHARED, ANON) -----------------------+---------------------- . mmap(PRIVATE, fd) | . mmap(SHARED, fd) File-backed . pgms/shared libs | 3 | 4
)
1. COMMAND-LINE Options¶The command-line syntax for top consists of:
- hv|-bcHiOSs -d secs -n max -u|U user - p pid -o fld -w [cols]
- .
- -O :Output-field-names
- This option acts as a form of help for the above -o option. It will cause top to print each of the available field names on a separate line, then quit. Such names are subject to nls.
- -s :Secure-mode operation
- Starts top with secure mode forced, even for root. This mode is far better controlled through.
2. SUMMARY Display¶Each of the following three areas are individually controlled through one or more interactive commands. See topic 4b. SUMMARY AREA Commands for additional information regarding these provisions.
2a. UPTIME and LOAD Averages¶This portion consists of a single line containing:
program or window name, depending on display mode current time and length of time since last boot total number of users system load avg over the last 1, 5 and 15 minutes
2b. TASK and CPU States¶This portion consists of a minimum of two lines. In an SMP environment, additional lines can reflect individual CPU state percentages.
running; sleeping; stopped; zombie
a b c d %Cpu(s): 75.0/25.0 100[ ...
2c. MEMORY Usage¶This portion consists of two lines which may express values in kibibytes (KiB) through exbibytes (EiB) depending on the scaling factor enforced with the `E' interactive command.
total, free, used and buff/cache
total, free, used and avail (which is physical memory)
a b c GiB Mem : 18.7/15.738 [ ... GiB Swap: 0.0/7.999 [ ...¶
3a. DESCRIPTIONS of Fields¶Listed below are top's available process fields (columns). They are shown in strict ascii alphabetical order. You may customize their position and whether or not they are displayable with the `f' or `F' (Fields Management) interactive commands.
1. %CPU -- CPU Usage
- The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.
2. %MEM -- Memory Usage (RES)
- A task's currently resident share of available physical memory.
3. CGNAME -- Control Group Name
- The name of the control group to which a process belongs, or `-' if not applicable for that process.
4. CGROUPS -- Control Groups
- The names of the control group(s) to which a process belongs, or `-' if not applicable for that process.
5. CODE -- Code Size (KiB)
- The amount of physical memory currently devoted to executable code, also known as the Text Resident Set size or TRS.
6. COMMAND -- Command Name or Command Line
- Display the command line used to start a task or the name of the associated program. You toggle between command line and name with `c', which is both a command-line option and an interactive command.
[kthreadd].
8. ENVIRON -- Environment variables
- Display all of the environment variables, if any, as seen by the respective processes. These variables will be displayed in their raw native order, not the sorted order you are accustomed to seeing with an unqualified `set'.. OOMa -- Out of Memory Adjustment Factor
- The value, ranging from -1000 to +1000, added to the current out of memory score (OOMs) which is then used to determine which task to kill when memory is exhausted.
- 15. OOMs -- Out of Memory Score
- The value, ranging from 0 to +1000, used to select task(s) to kill when memory is exhausted. Zero translates to `never kill' whereas 1000 means `always kill'.
- 16.).
- 17..
- 18. PID -- Process Id
- The task's unique process ID, which periodically wraps, though never restarting at zero. In kernel terms, it is a dispatchable entity defined by a task_struct.
- 19. PPID -- Parent Process Id
- The process ID (pid) of a task's parent.
- 20. PR -- Priority
- The scheduling priority of the task. If you see `rt' in this field, it means the task is running under real time scheduling priority.
- 21. RES -- Resident Memory Size (KiB)
- A subset of the virtual address space (VIRT) representing the non-swapped physical memory a task is currently using. It is also the sum of the RSan, RSfd and RSsh fields.
- 22. RSan -- Resident Anonymous Memory Size (KiB)
- A subset of resident memory (RES) representing private pages not mapped to a file.
- 23. RSfd -- Resident File-Backed Memory Size (KiB)
- A subset of resident memory (RES) representing the implicitly shared pages supporting program images and shared libraries. It also includes explicit file mappings, both private and shared.
- 24. RSlk -- Resident Locked Memory Size (KiB)
- A subset of resident memory (RES) which cannot be swapped out.
- 25. RSsh -- Resident Shared Memory Size (KiB)
- A subset of resident memory (RES) representing the explicitly shared anonymous shm*/mmap pages.
- 26. RUID -- Real User Id
- The real user ID.
- 27. RUSER -- Real User Name
- The real user name.
- 28. S -- Process Status
- The status of the task which can be one of:
D = uninterruptible sleep
R = running
S = sleeping
T = stopped by job control signal
t = stopped by debugger during trace
Z = zombie
- 29. SHR -- Shared Memory Size (KiB)
- A subset of resident memory (RES) that may be used by other processes. It will include shared anonymous pages and shared file-backed pages. It also includes private pages mapped to files representing program images and shared libraries.
- 30..
- 31. SUID -- Saved User Id
- The saved user ID.
- 32. SUPGIDS -- Supplementary Group IDs
- The IDs of any supplementary group(s) established at login or inherited from a task's parent. They are displayed in a comma delimited list.
- 33. SUPGRPS -- Supplementary Group Names
- The names of any supplementary group(s) established at login or inherited from a task's parent. They are displayed in a comma delimited list.
- 34. SUSER -- Saved User Name
- The saved user name.
- 35. SWAP -- Swapped Size (KiB)
- The formerly resident portion of a task's address space written to the swap file when physical memory becomes over committed.
- 36. TGID -- Thread Group Id
- The ID of the thread group to which a task belongs. It is the PID of the thread group leader. In kernel terms, it represents those tasks that share an mm_struct.
- 37..
- 38. TIME+ -- CPU Time, hundredths
- The same as TIME, but reflecting more granularity through hundredths of a second.
- 39.).
- 40..
- 41. UID -- User Id
- The effective user ID of the task's owner.
- 42. USED -- Memory in Use (KiB)
- This field represents the non-swapped physical memory a task is using (RES) plus the swapped out portion of its address space (SWAP).
- 43. USER -- User Name
- The effective user name of the task's owner.
- 44. VIRT -- Virtual Memory Size (KiB)
- The total amount of virtual memory used by the task. It includes all code, data and shared libraries plus pages that have been swapped out and pages that have been mapped but not used.
- 45. WCHAN -- Sleeping in Function
- This field will show the name of the kernel function in which the task is currently sleeping. Running tasks will display a dash (`-') in this column.
- 46. nDRT -- Dirty Pages Count
- The number of pages that have been modified since they were last written to auxiliary storage. Dirty pages must be written to auxiliary storage before the corresponding physical memory location can be used for some other virtual page.
- 47..
- 48..
- 48. nTH -- Number of Threads
- The number of threads associated with a process.
- 50. nsIPC -- IPC namespace
- The Inode of the namespace used to isolate interprocess communication (IPC) resources such as System V IPC objects and POSIX message queues.
- 51. nsMNT -- MNT namespace
- The Inode of the namespace used to isolate filesystem mount points thus offering different views of the filesystem hierarchy.
- 52. nsNET -- NET namespace
- The Inode of the namespace used to isolate resources such as network devices, IP addresses, IP routing, port numbers, etc.
- 53. nsPID -- PID namespace
- The Inode of the namespace used to isolate process ID numbers meaning they need not remain unique. Thus, each such namespace could have its own `init/systemd' (PID #1) to manage various initialization tasks and reap orphaned child processes.
- 54. nsUSER -- USER namespace
- The Inode of the namespace used to isolate the user and group ID numbers. Thus, a process could have a normal unprivileged user ID outside a user namespace while having a user ID of 0, with full root privileges, inside that namespace.
- 55. nsUTS -- UTS namespace
- The Inode of the namespace used to isolate hostname and NIS domain name. UTS simply means "UNIX Time-sharing System".
- 56. vMj -- Major Page Fault Count Delta
- The number of major page faults that have occurred since the last update (see nMaj).
- 57. vMn -- Minor Page Fault Count Delta
- The number of minor page faults that have occurred since the last update (see nMin).
3b. MANAGING Fields¶.
- •
- As the on screen instructions indicate, you navigate among the fields with the Up and Down arrow keys. The PgUp, PgDn, Home and End keys can also be used to quickly reach the first or last available field.
- •
- The Right arrow key selects a field for repositioning and the Left arrow key or the <Enter> key commits that field's placement.
- •
- The `d' key or the <Space> bar toggles a field's display status, and thus the presence or absence of the asterisk.
- •
- The `s' key designates a field as the sort field. See topic 4c. TASK AREA Commands, SORTING for additional information regarding your selection of a sort field.
- •
- The `a' and `w' keys can be used to cycle through all available windows and the ` q' or <Esc> keys exit Fields Management.
4. INTERACTIVE Commands¶ Commands¶The global interactive commands are always available in both full-screen mode and alternate-display mode. However, some of these interactive commands are not available when running in Secure mode.
- <Enter> or <Space> : Refresh-Display
- These commands awaken top and following receipt of any input the entire display will be repainted. They also force an update of any hotplugged cpu or physical memory changes.
- ? | h : Help
- There are two help levels available. The first will provide a reminder of all the basic interactive commands. If top is secured, that screen will be abbreviated.
- = .
- * d | s :Change-Delay-Time-interval
- You will be prompted to enter the delay time, in seconds, between display updates.
-.
1) at the pid prompt, type an invalid number 2) at the signal prompt, type 0 (or any invalid signal) 3) at any prompt, type <Esc>
- q :Quit
- * r :Renice-a-Task
- You will be prompted for a PID and then the value to nice it to. Commands¶The summary area interactive commands are always available in both full-screen mode and alternate-display mode. They affect the beginning lines of your display and will determine the position of messages and prompts.
-.
1. detailed percentages by category 2. abbreviated user/system and total % + bar graph 3. abbreviated user/system and total % + block graph 4. turn off task and cpu states display
- m :Memory/Swap-Usage toggle
- This command affects the two summary area lines dealing with physical and virtual memory..
4c. TASK AREA Commands¶The task area interactive commands are always available in full-screen.
The following commands will also be influenced by the state of the global `B' (bold enable) toggle.
CONTENT of task window
SIZE of task window
SORTING of task window
-
- y :Row-Highlight toggle
- Changes highlighting for "running" tasks. For additional insight into this task state, see topic 3a. DESCRIPTIONS of Fields, the `S' field (Process Status).
-.
- S :Cumulative-Time-Mode toggle
- When Cumulative mode is On, each process is listed with the cpu time that it and its dead children have used.
- u | U : Show-Specific-User-Only
- You will be prompted for the uid or name of the user to display. The -u option matches on effective user whereas the -U option matches on any user (real, effective, saved, or filesystem).
-.
- n | # : Set-Maximum-Tasks
- You will be prompted to enter the number of tasks to display. The lessor of your number and available screen rows will be used.
For compatibility, this top supports most of the former top sort keys. Since this is primarily a service to former top users, these commands do not appear on any help screen.
Note: Field sorting uses internal values, not those in column display.
Thus, the TTY and WCHAN fields will violate strict ASCII collating
sequence.
command sorted-field supported A start time (non-display) No M %MEM Yes N PID Yes P %CPU Yes T TIME+ Yes.
4d. COLOR Mapping¶When you issue the `Z' interactive command, you will be presented with a separate screen. That screen can be used to change the colors in just the `current' window or in all four windows before returning to the top display.
5. ALTERNATE-DISPLAY Provisions¶
5a. WINDOWS Overview¶
-.
- Current Window:
- The `current' window is the window associated with the summary area and the window to which task related commands are always directed. Since in alternate-display mode you can toggle the task display Off, some commands might be restricted for the `current' window.
5b. COMMANDS for Windows¶
- - | _ :.
- * A :Alternate-Display-Mode toggle
- This command will switch between full-screen mode and alternate-display mode.
- * a | w :Next-Window-Forward/Backward
- This will change the `current' window, which in turn changes the window to which commands are directed. These keys act in a circular fashion so you can reach any desired window using either key.
- * g :Choose-Another-Window/Field-Group
- You will be prompted to enter a number between 1 and 4 designating the field group which should be made the `current' window.
-¶.
- Home :Jump-to-Home-Position
- Reposition the display to the un-scrolled coordinates.
- End :Jump-to-End-Position
- Reposition the display so that the rightmost column reflects the last displayable field and the bottom task row represents the last.
5d. SEARCHING in a Window¶You can use these interactive commands to locate a task row containing a particular value.
- L :Locate-a-string
- You will be prompted for the case-sensitive string to locate starting from the current window coordinates. There are no restrictions on search string content.
- & :Locate-next
- Assuming a search string has been established, top will attempt to locate the next occurrence.
-.
5e. FILTERING in a Window¶You can use this Other Filter feature to establish selection criteria which will then determine which tasks are shown in the `current' window.
-..Either of these RES filters might yield inconsistent and/or misleading results, depending on the current memory scaling factor. Or both filters could produce the exact same results.Potential Solutions
GROUP=root ( only the same results when ) GROUP=ROOT ( invoked via lower case `o' )
RES>9999 ( only the same results when ) !RES<10000 ( memory scaling is at `KiB' )
nMin>9999 ( always a blank task window ).With Forest View mode active and the COMMAND column in view, this filter effectively collapses child processes so that just 3 levels are shown.
!nTH=` 1 ' ( ' for clarity only ) nTH>1 ( same with less i/p )
!COMMAND=` `- ' ( ' for clarity only )
`PR>20' + `!PR=-' ( 2 for right result ) `!nMin=0 ' + `!nMin=1 ' + `!nMin=2 ' + `!nMin=3 ' ...
6. FILES¶
6a. SYSTEM Configuration File¶
s # line 1: secure mode switch 5.0 # line 2: delay interval in seconds
6b. PERSONAL Configuration File¶This file is written as `$HOME/.your-name-4-top' + `rc'. Use the `W' interactive command to create it or update it.
6c. ADDING INSPECT Entries¶To exploit the `Y' interactive command, you must add entries at the end of the top personal configuration file. Such entries simply reflect a file to be read or command/pipeline to be executed whose results will then be displayed in a separate scrollable, searchable window.
.type: literal `file' or `pipe' .name: selection shown on the Inspect screen .fmts: string representing a path or command
.fmts= /proc/ %d/numa_maps .fmts= lsof -P -p %d
.fmts= pmap -x %d 2>
"pipe\tOpen Files\tlsof -P -p %d 2>&1" >> ~/.toprc "file\tNUMA Info\t/proc/%d/numa_maps" >> ~/.toprc "pipe\tLog\ttail -n200 /var/log/syslog | sort -Mr" >> ~/.toprc
# next would have contained `\t' ... # file ^I <your_name> ^I /proc/%d/status # but this will eliminate embedded `\t' ... pipe ^I <your_name> ^I cat /proc/%d/status | expand -
Inspection Pause at pid ... Use: left/right then <Enter> ... Options: help 1 2 3 4 5 6 7 8 9 10 11 ...
7. STUPID TRICKS Sampler¶Many of these tricks work best when you give top a scheduling boost. So plan on starting him with a nice value of -10, assuming you've got the authority.
7a. Kernel Magic¶For these stupid tricks, top needs full-screen mode.
- •
- The user interface, through prompts and help, intentionally implies that the delay interval is limited to tenths of a second. However, you're free to set any desired delay. If you want to see Linux at his scheduling best, try a delay of .09 seconds or less.
.
- •
- Under an xterm using `white-on-black' colors, on top's Color Mapping screen set the task color to black and be sure that task highlighting is set to bold, not reverse. Then set the delay interval to around .3 seconds.
- •
- Delete the existing rcfile, or create a new symlink. Start this new version then type `T' (a secret key, see topic 4c. Task Area Commands, SORTING) followed by `W' and `q'. Finally, restart the program with -d0 (zero delay).
7b. Bouncing Windows¶For these stupid tricks, top needs alternate-display mode.
- •
-.
- •
- Set each window's summary lines differently: one with no memory (`m'); another with no states (`t'); maybe one with nothing at all, just the message line. Then hold down `a' or `w' and watch a variation on bouncing windows -- hopping windows.
- •
- Display all 4 windows and for each, in turn, set idle processes to Off using the `i' command toggle. You've just entered the "extreme bounce" zone.
7c. The Big Bird Window¶This stupid trick also requires alternate-display mode.
- •
- Display all 4 windows and make sure that 1:Def is the `current' window. Then, keep increasing window size with the `n' interactive command until all the other task displays are "pushed out of the nest".
is top fibbing or telling honestly your imposed truth?
7d. The Ol' Switcheroo¶This.
some lines travel left, while others travel right
eventually all lines will Switcheroo, and move right | https://manpages.debian.org/stretch/procps/top.1.en.html | CC-MAIN-2018-17 | refinedweb | 3,475 | 63.8 |
On Sat, 2005-12-10 at 02:23 -0700, Mike Sparr - wrote:
> If I have a document (note the content element referencing external
> namespace):
>
>
>
> Some name of a document
> A brief description of a quotable phrase from
> document
>
> This is the heading of the document
> This is the sub-heading of the
> document
>
> This is the body content of the document
> and I can have some text that references a
> term that may require more explaination so
> I add a strangeword and this footnote will appear at
> the bottom of the document.
>
>
>
>
> I am new to digester but understand I have to write getter/setter
> classes to represent the different elements. Can someone help with
> writing the rules to digest this? I would like some flexibility to have
> zero, one or more namespaces declared in my element and the
> digester will "digest" the elements within these.
>
> For example, this instance uses a namespace and scheme defined by myco,
> but we may want just text with no namespaces, or use
> xmlns:xhtml="" and embed html in the
> document.
>
> Where do I start?
There are a number of good resources for learning Digester.
There is a list of articles availabel on the wiki:
There is a general overview of digester in the javadoc:
There are also a number of example applications available. They are
included in the source downloads for digester, or can be browsed
directly from the subversion repository:
Note that Digester's support for xml namespaces is quite weak; it was
originally written before namespaces existed and that shows. A rule can
be associated with a namespace; this ensures that the *last* element in
the match path is in the specified namespace. However there is no
control over namespace-matching for the other parts of the path. As am
example, a rule with path "foo/bar/baz" and namespace "urn:ns1" will
only match baz elements in the specified namespace, but foo and bar will
match elements in any namespace. This looks like it will be acceptable
for your purposes though.
Once you have read the available info, I'm happy to answer any specific
questions you may have...
Regards,
Simon
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CodeS.
# Table of Contents - What is CodeSandbox - What is Netlify - Clients Templates on CodeSandbox - File Structure - File Structure Content - Claim your site - Closing Thoughts - Resources
What is CodeSandbox
CodeSandbox is an online VSCode-like editor built for web applications development, It was built with a mindset to make projects sharing easy across teams and people. Get started with CodeSandbox here.
What is Netlify
Netlify is a developers platform that automates codes, built in a way users will be able to simply push their code and the platform handles the rest.
Let's get started
Firstly, visit your dashboard and create a simple static site from one of the client templates.
List of client Templates on CodeSandbox
- React.js (create-react-app)
- Vue.js (vue-cli)
- Angular.js (angular-cli)
- Preact.js (preact-cli)
- Vanilla (parcel)
- Cx.js (cxjs)
- Dojo (dojo/cli-create-app)
- Reason (reason)
- Svelte (svelte)
- Static (static)
In this scenario, we would be using the React create-react-app template.
File Structure
my-app/ package.json public/ index.html src/ index.js index.css
For the project to build, these files must exist with exact filenames:
public/index.htmlis the page template;
src/index.js isthe JavaScript entry point.
You can delete or rename the other files.
File Structure Content
src/index.js
import React from "react"; import ReactDOM from "react-dom"; import "./styles.css"; function App() { return ( <div className="App"> <h2>CodeSandbox X Netlify</h2> <h3>Deploying Static Sites to Netlify from CodeSandbox.</h3> </div> ); } const rootElement = document.getElementById("root"); ReactDOM.render(<App />, rootElement);
src/index.css
.App { font-family: sans-serif; text-align: center; }
public/index.html
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"> <meta name="theme-color" content="#000000"> <link rel="manifest" href="%PUBLIC_URL%/manifest.json"> <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico"> <title>CodeSandbox X Netlify</title> </head> <body> <noscript> You need to enable JavaScript to run this app. </noscript> <div id="root"></div> </body> </html>
You can create other files inside the
src folder for faster rebuilds because only files inside the
src folder are processed by Webpack. You need to put any JavaScript and CSS files inside
src, otherwise, Webpack won’t see them.
Next, you would have to click on file and Fork the Sandbox, Awesome! Now you have it all to yourself. you can customize it whichever way you desire.
Deploy to Netlify
Once that's done you should have something similar to what I have below.
Now, let's create our GitHub repository directly from our CodeSandbox dashboard, click on the GitHub icon on the icon tag across your left.
Put in your desired name of repo and then click create repository, you should get the below, but then wait a few seconds for it to deploy.
You should get a loading screen like the below for some seconds.
Once that's done, click on the Plus sign and refork the repo, Click again on the rocket button and click deploy on Netlify.
Once deploy is clicked on Netlify, you will get a unique domain like csb-mqpoxl7wjx wait few seconds for it to build and deploy.
Awesome🔥🔥🔥, You should get two buttons Visit and Claim Site click Visit to view the deployed site.
Your deployed site should look like the image below if all steps were followed.
Claim your site
Once deployed you would see a blue button named Claim Site click it,
Once that's clicked, you would be redirected to a new page on Netlify that looks like the image below, you just have to add it to your netlify dashboard.
Your CodeSandbox site has successfully been added to the list of your site's hosted on Netlify
Closing Thoughts
We’ve only scratched the surface with this Deploying Static Sites from CodeSandbox to netlify article. I hope you've enjoyed learning how to Deploying Static Sites from CodeSandbox to netlify.
Read more on Netlify via the official Netlify Docs and use CodeSandbox as your default live editor its amazing if you are looking forward to collaborating with multiple people on a single project. Read more here, Documentation - CodeSandbox Documentation
Thanks to Ives van Hoorne, Sara Vieira and others behind this helping us maintain and improve this amazing platfrom.
Resources
Link to GitHub
Link to CodeSandbox
CodeSandbox-client on GitHub.
Discussion | https://dev.to/developerayo/deploying-static-sites-to-netlify-from-codesandbox-1jnl | CC-MAIN-2020-45 | refinedweb | 733 | 56.86 |
Important: Please read the Qt Code of Conduct -
Starting pains with Necessitas on Windows 7
Finally I am trying to start with Necessitas and got stuck with my first "hello world" program already.
I have installed Necessitas on Windows 7 with Qt creator 2.5. I followed the steps on the "Wiki article.":
here are the few lines of my test program:
@
#include <QtCore/QCoreApplication>
#include <qDebug>
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
qDebug() << "hello world" << endl; return a.exec();
}
@
It builds ok, but trying to run following error message will appear:
@
Packaging Error: Command 'C:/Program Files (x86)/WinAnt/bin/ant.bat clean debug' failed.Exit code: 1
Error while building project test1 (target: Android)
When executing build step 'Packaging for Android'
@
My guess is that it is trying to deploy on the device which is not connected. However, I like to start out with deploying on the simulator, but I do not find a place in Qt creator where to select.
Any hints?
- sierdzio Moderators last edited by
You should use QtCreator bundled with Necessitas SDK. Other than that - I'm using Linux only, so I can't help much more.
[quote author="sierdzio" date="1342101941"]You should use QtCreator bundled with Necessitas SDK. Other than that - I'm using Linux only, so I can't help much more.[/quote]
Thanks for feedback.
I have done both with the same result.
Hmm I wasn't even aware you could deploy with Necessitas on a non-Linux host.
Hi Koahnig,
I wrote that wiki page about a year ago because there were no installation instructions for windows at that time.
Things have changed since then. The maintainers have made "this installation page":
I'm planning to test necessitas out again in the near future.
I've changed the wiki page and added a remark : the installation instructions are obsolete now.
Good luck,
Eddy
Hi Eddy
thanks for reply. Actually your wiki page was a good guidance. The only major difference was that some part are now already in the necessitas bundle included. However, it did not make any difference.
I had found the installation page a little later. Actually the scheme is not too different.
However, there is one thing mentioned there. The paths should have no spaces. Even though, the picture above shows a space in "Open JDK folder". I have made an installation with no spaces in all java related folders, but that seems to have messed up more.
Another options I have tried is the installation under Ubuntu Linux on VirtualBox. However, there seem to be many emulators in the way now. It is awful slow (and it does not run either ;-( )
Thanks for the feedback, Koahnig
I'll keep that in mind when i try to install the latest version. But i don't see a picture above, can you tell me which image you are pointing to?
If I succeed I will adapt the wiki again.
Maybe I can give it a try this weekend
Sorry, was a bit imprecise ;-)
On the installation page there is a section for "common problems and issues (Windows)": I meant the screenshot above this section. There is the "Open JDK location" and it points to something on "c:/Program Files/Java/...". There is certainly at least one space. So the comment below in problems and issues may be a bit misleading.
Looking forward hearing from you on your success. May be you can give me then a hint where I am failing.
Thanks, Koahnig,
I will keep that in mind and install the jdk on the C:/ drive to avoid it. It seems to me at first glance this is the only one we have to choose ourselves.
I'll be back ;-)
Hi Koahnig,
I finally got necessitas working.
I had the same issues you described, so hopefully I can help you out, if you're still interested ;-)
firstly i installed the jdk using jdk-7u5-windows-x64.exe in C:\Program Files\Java\ (with a space!)
then i installed necessitas in C:\necessitas.
then i tested the AVD manager installed by necessitas, but that didn't work out. so i googled the android web pages and found some solutions. I had to set some environment variables on my own. Here they are :
User variables
ANT_HOME : Points to the folder containing: /bin/ant.bat
C:\necessitas\apache-ant-1.8.2
JAVA_HOME
C:\Program Files\Java\jdk1.7.0_05
PATH
C:\necessitas\android-sdk\platform-tools;C:\necessitas\android-sdk\tools; C:\necessitas\QtCreator\bin;C:\QtSDK\mingw\bin;C:\QtSDK\Desktop\Qt\4.7.4\mingw\bin;
C:\Program Files\Java\jdk1.7.0_05\bin\java.exe;
C:\Program Files\Java\jdk1.7.0_05\bin;C:\necessitas\apache-ant-1.8.2\bin
ANDROID_SDK_HOME set it to the same location as your HOME environment variable
In my case it is C:\Users\eddy
then I followed the same steps as the wiki page and my hello world app is running both on the emulator and on an android device. I tried a QML test app, but sometimes it succeeds and sometimes not. I'll have to dig some more there...
I hope this helps, if you have some more specific questions, I will be glad to be of your assistance.
I'm going to adapt the wiki page to reflect the new changes and let the maintainers know about my findings.
Cheers,
Eddy
Thanks Eddy for your summary.
I will give it another shot. At the moment I had to push it back for other priorities, but I am still interested. Certainly I have to make fresh start. Something has been messed up completely.
I'll keep you posted.
Cheers,
koahnig
you're welcome
Eddy.
- sierdzio Moderators last edited by
[quote author="qtandroid" date="1391581516".
[/quote]
In Qt 5.2, android port is fully integrated, you do not need to install Necessitas anymore. I suggest upgrading.
Thanks sierdzio!
I'll try Qt 5.2
Still same error :( | https://forum.qt.io/topic/18230/starting-pains-with-necessitas-on-windows-7 | CC-MAIN-2021-04 | refinedweb | 1,004 | 67.35 |
PopupCalcButton
TextBox calcTextBox = new TextBox();
Button showCalcBtn = new Button("Show Calc");
PopupCalcPanel calc =
new PopupCalcPanel(calcTextBox, showCalcBtn);
RootPanel.get().add(calcTextBox);
RootPanel.get().add(showCalcBtn);
RootPanel.get().add(calc);
We need to create a TextBox widget to recieve the calculated value, and a Button to activate the pop-up calculator. The flow of events starts when a user clicks the "Show Calc" button, which will display the calculator just below the TextBox widget. The user can use the calculator to calculate a result, then clicks a button in the calcluator labeled "DONE" to close the calculator and copy the result to our TextArea.
The PopupCalcPanel requires a reference to both the TextBox and Botton widgets. It will add event handlers to the Button for the calculator to appear, and uses the TextBox for positioning and to place the calculated total. The PopupCalcPanel provides no other options other than CSS tweaks.
The GWT-WL includes a single default CSS stylesheet for all calculator widgets shipped with the library. The stylesheet includes all of the style classes used by the widgets. To use the default you will need to add the following in the of your HTML code.
<link rel="stylesheet" type="text/css"
href="style/gwl-calcPanel.css">
SimpleCalcPanel
SimpleCalcPanel calcPanel = new SimpleCalcPanel();
RootPanel.get("example").add(calcPanel);
The SimpleCalcPanel has two public methods, getValue() and clearValue(). All other methods are protected, and cannot be accessed without subclassing the widget.
Extending SimpleCalcPanel
You can customize the SimpleCalcPanel by subclassing it and overriding one or more of it's methods. When the class is created it internally calls the init() method. You may override the init method, but in most case this is not recommended. The init() method for SimpleCalcPanel is below.
protected void init ()
{
TextBox textDisplay = createTextDisplay();
createCalc(createDisplayListener(textDisplay), textDisplay);
setKeyboardListener(textDisplay);
initComplete();
}
The init() method itself does very little work, and delegates the setup work to other methods in the class. Depending on what you are trying to do, you will override the methods that init() calls so that you can customize some part of the setup. You may, for example, want to use your own KeyboardListener for custom shortcuts, or use a text display other then a simple TextBox so that you can color the output red for negative numbers.
One of the methods that can be overridden is the buildCalcLayout(CalcEngine, TextBox) method. This method is called as part of the initialization, but not by init() directly. It is called as part of the createCalc() call. This method allows you to create the widgets that make up the display, including buttons, panels, and any other widgets you need. The only widget that you won't create is the TextBox calculator display, which is passed to the method. If you override this method you will need to add the TextBox to the panel yourself, or call the method in the super class.
package org.hanson.gwt.client;
import org.gwtwidgets.client.ui.SimpleCalcPanel;
import org.gwtwidgets.client.util.CalcEngine;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.ClickListener;
import com.google.gwt.user.client.ui.HorizontalPanel;
import com.google.gwt.user.client.ui.RadioButton;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.TextBox;
import com.google.gwt.user.client.ui.Widget;
public class MyApplication implements EntryPoint
{
public void onModuleLoad ()
{
RootPanel.get().add(new HexCalcPanel());
}
class HexCalcDisplay extends TextBox
{
public boolean isHexMode = false;
public void setText (String text)
{
if (isHexMode) {
double num = Double.parseDouble(text);
String hexString = Integer.toHexString((int) num);
hexString = hexString.toUpperCase();
super.setText(hexString);
}
else {
super.setText(text);
}
}
}
class HexCalcPanel extends SimpleCalcPanel
{
private HexCalcDisplay textBox;
protected TextBox createTextDisplay ()
{
textBox = new HexCalcDisplay();
textBox.setStyleName("simpleCalcDisplay");
return textBox;
}
protected void buildCalcLayout (
final CalcEngine calcEngine,
TextBox textDisplay)
{
RadioButton dec = new RadioButton("output", "Dec");
dec.setChecked(true);
dec.addClickListener(new ClickListener(){
public void onClick (Widget sender)
{
textBox.isHexMode = false;
calcEngine.refreshDisplay();
}
});
RadioButton hex = new RadioButton("output", "Hex");
hex.addClickListener(new ClickListener(){
public void onClick (Widget sender)
{
textBox.isHexMode = true;
calcEngine.refreshDisplay();
}
});
HorizontalPanel opts = new HorizontalPanel();
opts.add(dec);
opts.add(hex);
add(opts);
super.buildCalcLayout(calcEngine, textDisplay);
}
}
}
The CalcEngine
In some cases you will need to customize the control beyond what the SimpleCalcPanel allows. At the very heart of the calculator is the CalcEngine. The CalcEngine keeps track of the state of the calculator, the contents of the display, and the contents of the total register. It allows you to override methods for many of the operators, and gives you a programmatic way to refresh the display. It also has utility methods to adding number and operator buttons to your display. It is in every sense the heart of the system.
I believe that in most cases you will not need to override any of the CalcEngine methods, more likely you will use it as the core of your own calculator panel. In the future you can expect to see new functions added here in the core, which can then be used by calculator panels. The obvious enhancements include the addition of trigonometric and algebraic functions.
Conclusion
The calculator widget and engine set allows for ease of use, ease of extension, and the ability to create highly customized calculators. Future extensions will expand on it's potential, hopefully leading to productive components.
15 comments:
Probably title shoud be "Calculator..."
How about using some tool that can add colors for Java source? For example Colorer. It is hard to read plain text.
> Probably title shoud be "Calculator..."
Err... yeah... oops.
My Ti-92 is way better.
Hi,
Nothing beats a minature solid gold abacus.
Coral
Try 3+2*3 and see the result ... you should not rely so much on this "calculator" !
Is that your idea of a bug report? If it is, there is a facility for submitting these,. You also forgot to mention what you feel is the right answer? Is it 11 or 15?
Seriously "Anonymous", if you are interested in using an open source beta product it is more productive to help solve problems than it is to dismiss the product.
I think you're making a worse mistake in being dismissive of Anonymous's very valid point - this calculator does NOT behave like a 'normal' calculator, so why trust or use it? A normal (non-RPN anyway) calculator will obviously compute 3+2*3 as: 3+2 makes 5, times 3 is 15. Also, why not allow the user to simply type a number and press DONE, and why not allow them to type a number, hit equal and type DONE? It is still a textbox - an input field after all. P.S. I'm not the same anonymous, and certainly don't see why you can't make use of (I think) constructive comments entered here rather than 'through the right channels'.
I wasn't trying to be dismissive, and I don't even disagree. I just didn't really like the tone.
From my point of view I spent a lot of time building something and gave it away for free.
I appreciate *constructive* comments, bug reports, and patches. I don't believe the comment in question falls into any of these categories.
As for your commets, I can't say that I disagree. It has been a long time since I even looked at that code, and it probably needs some fixing.
Currently I am ankle deep in Gears ORM, viewports, book promotion, my regular job, and then the "family" time on top of all of that, so it may be some time before I get to look at it.
But this leads me back to what I said before... patches are always welcome, and I always attribute the patch to the patch author.
I will be uploading the first release of "algebrain" to sourceforge.net over the weekend. I think it would make a real powerful "CalcEngine" for this widget. I don't have the GWT experience to do it but maybe someone who does have that experience might give it a try.
Thanks for the info Chris, but I think that might be problematic. The issue is that algebrain is released under the GPL, and the GWT-WL is under Apache 2. The two are pretty incompitable, and I am not sure I want to get involved with dual licensing.
At the beginning of this post, "set of calendar tools" should be "set of calculator tools".
Also, in the last paragraph of your demo page, "customize your calendar" should be "customize your calendar".
Thanks Damon, noted and fixed. | http://blog.mental.ninja/2006/07/calculator-widgets-for-gwt.html | CC-MAIN-2017-34 | refinedweb | 1,430 | 58.38 |
Inside guide came from PyImageSearch reader, Igor, who emailed me a few weeks ago and asked:
Hey Adrian, thanks for the PyImageSearch blog. I’ve noticed that nearly every “getting started” guide I come across for Keras and image classification uses either the MNIST or CIFAR-10 datasets which are built into Keras. I just call one of those functions and the data is automatically loaded for me.
But how do I go about using my own image dataset with Keras?
What steps do I have to take?
Igor has a great point — most Keras tutorials you come across will try to teach you the basics of the library using an image classification dataset such MNIST (handwriting recognition) or CIFAR-10 (basic object recognition).
These image datasets are standard benchmarks in the computer vision and deep learning literature, and sure, they will absolutely get you started using Keras…
…but they aren’t necessarily practical in the sense that they don’t teach you how to work with your own set of images residing on disk. Instead, you’re just calling helper functions to load pre-compiled datasets.
I’m going with a different take on an introductory Keras tutorial.
Instead of teaching you how to utilize one of these pre-compiled datasets, I’m going to teach you how to train your first neural network and Convolutional Neural Network using a custom dataset — because let’s face it, your goal is to apply deep learning to your own dataset, not one built into Keras, am I right?
To learn how to get started with Keras, Deep Learning, and Python, just keep reading!
Keras Tutorial: How to get started with Keras, Deep Learning, and Python
2020-05-13 Update: This blog post is now TensorFlow 2+ compatible!
Today’s Keras tutorial is designed with the practitioner in mind — it is meant to be a practitioner’s approach to applied deep learning.
That means that we’ll learn by doing.
We’ll be getting our hands dirty.
Writing some Keras code.
And then training our networks on our custom datasets.
This tutorial is not meant to be a deep dive into the theory surrounding deep learning.
If you’re interested in studying deep learning in odepth, including both (1) hands-on implementations and (2) a discussion of theory, I would suggest you check out my book, Deep Learning for Computer Vision with Python.
Overview of what’s going to be covered
Training your first simple neural network with Keras doesn’t require a lot of code, but we’re going to start slow, taking it step-by-step, ensuring you understand the process of how to train a network on your own custom dataset.
The steps we’ll cover today include:
- Installing Keras and other dependencies on your system
- Creating your training and testing splits
- Defining your Keras model architecture
- Compiling your Keras model
- Training your model on your training data
- Evaluating your model on your test data
- Making predictions using your trained Keras model
I’ve also included an additional section on training your first Convolutional Neural Network.
This may seem like a lot of steps, but I promise you, once we start getting into the example you’ll see that the examples are linear, make intuitive sense, and will help you understand the fundamentals of training a neural network with Keras.
Our example dataset
Most Keras tutorials you come across for image classification will utilize MNIST or CIFAR-10 — I’m not going to do that here.
To start, MNIST and CIFAR-10 aren’t very exciting examples.
These tutorials don’t actually cover how to work with your own custom image datasets. Instead, they simply call built-in Keras utilities that magically return the MNIST and CIFAR-10 datasets as NumPy arrays. In fact, your training and testing splits have already been pre-split for you!
Secondly, if you want to use your own custom datasets you really don’t know where to start. You’ll find yourself scratching your head and asking questions such as:
- Where are those helper functions loading the data from?
- What format should my dataset on disk be?
- How can I load my dataset into memory?
- What preprocessing steps do I need to perform?
Let’s be honest — your goal in studying Keras and deep learning isn’t to work with these pre-baked datasets.
Instead, you want to work with your own custom datasets.
And those introductory Keras tutorials you’ve come across only take you so far.
That’s why, inside this Keras tutorial, we’ll be working with a custom dataset called the “Animals dataset” I created for my book, Deep Learning for Computer Vision with Python:
The purpose of this dataset is to correctly classify an image as containing either:
- Cats
- Dogs
- Pandas
Containing only 3,000 images, the Animals dataset is meant to be an introductory dataset that we can quickly train a deep learning model on using either our CPU or GPU (and still obtain reasonable accuracy).
Furthermore, using this custom dataset enables you to understand:
-
By following the steps in this Keras tutorial you’ll be able to swap out my Animals dataset for any dataset of your choice, provided you utilize the project/directory structure detailed below.
Need data? If you need to scrape images from the internet to create a dataset, check out how to do it the easy way with Bing Image Search, or the slightly more involved way with Google Images.
Project structure
There are a number of files associated with this project. Grab the zip from the “Downloads” section and then use the
tree command to show the project structure in your terminal (I’ve provided two command line argument flags to
tree to make the output nice and clean):
$ tree --dirsfirst --filelimit 10 . ├── animals │ ├── cats [1000 entries exceeds filelimit, not opening dir] │ ├── dogs [1000 entries exceeds filelimit, not opening dir] │ └── panda [1000 entries exceeds filelimit, not opening dir] ├── images │ ├── cat.jpg │ ├── dog.jpg │ └── panda.jpg ├── output │ ├── simple_nn.model │ ├── simple_nn_lb.pickle │ ├── simple_nn_plot.png │ ├── smallvggnet.model │ ├── smallvggnet_lb.pickle │ └── smallvggnet_plot.png ├── pyimagesearch │ ├── __init__.py │ └── smallvggnet.py ├── predict.py ├── train_simple_nn.py └── train_vgg.py 7 directories, 14 files
As previously discussed, today we’ll be working with the Animals dataset. Notice how
animals is organized in the project tree. Inside of
animals/ , there are three class directories:
cats/ ,
dogs/ ,
panda/ . Within each of those directories is 1,000 images pertaining to the respective class.
If you work with your own dataset, just organize it the same way! Ideally you’ll gather 1,000 images per class at a minimum. This isn’t always possible, but you should at least have class balance. Significantly more images in one class folder could cause model bias.
Next is the
images/ directory. This directory contains three images for testing purposes which we’ll use to demonstrate how to (1) load a trained model from disk and then (2) classify an input image that is not part of our original dataset.
The
output/ folder contains three types of files which are generated by training:
.model: A serialized Keras model file is generated after training and can be used in future inference scripts.
.pickle: A serialized label binarizer file. This file contains an object which contains class names. It accompanies a model file.
.png: I always place my training/validation plot images in the output folder as it is an output of the training process.
The
pyimagesearch/ directory is a module. Contrary to the many questions I receive,
pyimagesearch is not a pip-installable package. Instead it resides in the project folder and classes contained within can be imported into your scripts. It is provided in the “Downloads” section of this Keras tutorial.
Today we’ll be reviewing four .py files:
- In the first half of the blog post, we’ll train a simple model. The training script is
train_simple_nn.py.
- We’ll advance to training
SmallVGGNetusing the
train_vgg.pyscript.
- The
smallvggnet.pyfile contains our
SmallVGGNetclass, a Convolutional Neural Network.
- What good is a serialized model unless we can deploy it? In
predict.py, I’ve provided sample code for you to load a serialized model + label file and make an inference on an image. The prediction script is only useful after we have successfully trained a model with reasonable accuracy. It is always useful to run this script to test with images that are not contained within the dataset.
Configuring your development environment
.
2. Load your data from disk
Now that Keras is installed on our system we can start implementing our first simple neural network training script using Keras. We’ll later implement a full-blown Convolutional Neural Network, but let’s start easy and work our way up.
Open up
train_simple_nn.py and insert the following code:
# set the matplotlib backend so figures can be saved in the background import matplotlib matplotlib.use("Agg") # import the necessary packages from sklearn.preprocessing import LabelBinarizer from sklearn.model_selection import train_test_split from sklearn.metrics import classification_report from tensorflow.keras.models import Sequential from tensorflow.keras.layers import Dense from tensorflow.keras.optimizers import SGD from imutils import paths import matplotlib.pyplot as plt import numpy as np import argparse import random import pickle import cv2 import os
Lines 2-19 import our required packages. As you can see there are quite a few tools this script is taking advantage of. Let’s review the important ones:
matplotlib: This is the go-to plotting package for Python. That said, it does have its nuances, and if you’re having trouble with it, refer to this blog post. On Line 3, we instruct
matplotlibto use the
"Agg"backend enabling us to save plots to disk — that’s your first nuance!
sklearn: The scikit-learn library will help us with binarizing our labels, splitting data for training/testing, and generating a training report in our terminal.
tensorflow.keras: You’re reading this tutorial to learn about Keras — it is our high level frontend into TensorFlow and other deep learning backends.
imutils: My package of convenience functions. We’ll use the
pathsmodule to generate a list of image file paths for training.
numpy: NumPy is for numerical processing with Python. It is another go-to package. If you have OpenCV for Python and scikit-learn installed, then you’ll have NumPy as it is a dependency.
cv2: This is OpenCV. At this point, it is both tradition and a requirement to tack on the 2 even though you’re likely using OpenCV 3 or higher.
- …the remaining imports are built into your installation of Python!
Wheww! That was a lot, but having a good idea of what each import is used for will aid your understanding as we walk through these scripts.
Let’s parse our command line arguments with argparse:
#())
Our script will dynamically handle additional information provided via the command line when we execute our script. The additional information is in the form of command line arguments. The
argparse module is built into Python and will handle parsing the information you provide in your command string. For additional explanation, refer to this blog post.
We have four command line arguments to parse:
--dataset: The path to our dataset of images on disk.
--model: Our model will be serialized and output to disk. This argument contains the path to the output model file.
-.
With the dataset information in hand, let’s load our images and class labels:
# the image to be 32x32 pixels (ignoring # aspect ratio), flatten the image into 32x32x3=3072 pixel image # into a list, and store the image in the data list image = cv2.imread(imagePath) image = cv2.resize(image, (32, 32)).flatten() data.append(image) # extract the class label from the image path and update the # labels list label = imagePath.split(os.path.sep)[-2] labels.append(label)
Here we:
- Initialize lists for our
dataand
labels(Lines 35 and 36). These will later become NumPy arrays.
- Grab
imagePathsand randomly shuffle them (Lines 39-41). The
paths.list_imagesfunction conveniently will find all the paths to all input images in our
--datasetdirectory before we sort and
shufflethem. I set a
seedso that the random reordering is reproducible.
- Begin looping over all
imagePathsin our dataset (Line 44).
For each
imagePath , we proceed to:
- Load the
imageinto memory (Line 48).
- Resize the
imageto
32x32pixels (ignoring aspect ratio) as well as
flattenthe image (Line 49). It is critical to
resizeour images properly because this neural network requires these dimensions. Each neural network will require different dimensions, so just be aware of this. Flattening the data allows us to pass the raw pixel intensities to the input layer neurons easily. You’ll see later that for VGGNet we pass the volume to the network since it is convolutional. Keep in mind that this example is just a simple non-convolutional network — we’ll be looking at a more advanced example later in the post.
- Append the resized image to
data(Line 50).
- Extract the class
labelof the image from the path (Line 54) and add it to the
labelslist (Line 55). The
labelslist contains the classes that correspond to each image in the data list.
Now in one fell swoop, we can apply array operations to the data and labels:
# scale the raw pixel intensities to the range [0, 1] data = np.array(data, dtype="float") / 255.0 labels = np.array(labels)
On Line 58 we scale pixel intensities from the range [0, 255] to [0, 1] (a common preprocessing step).
We also convert the
labels list to a NumPy array (Line 59).
3. Construct your training and testing splits
Now that we have loaded our image data from disk, next we need to construct our training and testing splits:
# partition the data into training and testing splits using 75% of # the data for training and the remaining 25% for testing (trainX, testX, trainY, testY) = train_test_split(data, labels, test_size=0.25, random_state=42)
It is typical to allocate a percentage of your data for training and a smaller percentage of your data for testing. The scikit-learn provides a handy
train_test_split function which will split the data for us.
Both
trainX and
testX make up the image data itself while
trainY and
testY make up the labels.
Our class labels are currently represented as strings; however, Keras will assume that both:
- Labels are encoded as integers
- And furthermore, one-hot encoding is performed on these labels making each label represented as a vector rather than an integer
To accomplish this encoding, we can use the
LabelBinarizer class from scikit-learn:
#)
On Line 70, we initialize the
LabelBinarizer object.
A call to
fit_transform finds all unique class labels in
trainY and then transforms them into one-hot encoded labels.
A call to just
.transform on
testY performs just the one-hot encoding step — the unique set of possible class labels was already determined by the call to
.fit_transform .
Here’s an example:
[1, 0, 0] # corresponds to cats [0, 1, 0] # corresponds to dogs [0, 0, 1] # corresponds to panda
Notice how only one of the array elements is “hot” which is why we call this “one-hot” encoding.
4. Define your Keras model architecture
The next step is to define our neural network architecture using Keras. Here we will be using a network with one input layer, two hidden layers, and one output layer:
# define the 3072-1024-512-3 architecture using Keras model = Sequential() model.add(Dense(1024, input_shape=(3072,), activation="sigmoid")) model.add(Dense(512, activation="sigmoid")) model.add(Dense(len(lb.classes_), activation="softmax"))
Since our model is really simple, we go ahead and define it in this script (typically I like to make a separate class in a separate file for the model architecture).
The input layer and first hidden layer are defined on Line 76. will have an
input_shape of
3072 as there are
32x32x3=3072 pixels in a flattened input image. The first hidden layer will have
1024 nodes.
The second hidden layer will have
512 nodes (Line 77).
Finally, the number of nodes in the final output layer (Line 78) will be the number of possible class labels — in this case, the output layer will have three nodes, one for each of our class labels (“cats”, “dogs”, and “panda”, respectively).
5. Compile your Keras model
Once we have defined our neural network architecture, the next step is to “compile” it:
# initialize our initial learning rate and # of epochs to train for INIT_LR = 0.01 EPOCHS = 80 # compile the model using SGD as our optimizer and categorical # cross-entropy loss (you'll want to use binary_crossentropy # for 2-class classification) print("[INFO] training network...") opt = SGD(lr=INIT_LR) model.compile(loss="categorical_crossentropy", optimizer=opt, metrics=["accuracy"])
First, we initialize our learning rate and total number of epochs to train for (Lines 81 and 82).
Then we
compile our model using the Stochastic Gradient Descent (
SGD ) optimizer with
"categorical_crossentropy" as the
loss function.
Categorical cross-entropy is used as the loss for nearly all networks trained to perform classification. The only exception is for 2-class classification where there are only two possible class labels. In that event you would want to swap out
"categorical_crossentropy" for
"binary_crossentropy" .
6. Fit your Keras model to the data
Now that our Keras model is compiled, we can “fit” (i.e., train) it on our training data:
# train the neural network H = model.fit(x=trainX, y=trainY, validation_data=(testX, testY), epochs=EPOCHS, batch_size=32)
We’ve discussed all the inputs except
batch_size . The
batch_size controls the size of each group of data to pass through the network. Larger GPUs would be able to accommodate larger batch sizes. I recommend starting with
32 or
64 and going up from there.
7. Evaluate your Keras model
We’ve trained our actual model but now we need to evaluate it on our testing data.
It’s important that we evaluate on our testing data so we can obtain an unbiased (or as close to unbiased as possible) representation of how well our model is performing with data it has never been trained on.
To evaluate our Keras model we can use a combination of the
.predict method of the model along with the
classification_report from scikit-learn:
# (Simple NN)") plt.xlabel("Epoch #") plt.ylabel("Loss/Accuracy") plt.legend().
When running this script you’ll notice that our Keras neural network will start to train, and once training is complete, we’ll evaluate the network on our testing set:
$ python train_simple_nn.py --dataset animals --model output/simple_nn.model \ --label-bin output/simple_nn_lb.pickle --plot output/simple_nn_plot.png Using TensorFlow backend. [INFO] loading images... [INFO] training network... Train on 2250 samples, validate on 750 samples Epoch 1/80 2250/2250 [==============================] - 1s 311us/sample - loss: 1.1041 - accuracy: 0.3516 - val_loss: 1.1578 - val_accuracy: 0.3707 Epoch 2/80 2250/2250 [==============================] - 0s 183us/sample - loss: 1.0877 - accuracy: 0.3738 - val_loss: 1.0766 - val_accuracy: 0.3813 Epoch 3/80 2250/2250 [==============================] - 0s 181us/sample - loss: 1.0707 - accuracy: 0.4240 - val_loss: 1.0693 - val_accuracy: 0.3533 ... Epoch 78/80 2250/2250 [==============================] - 0s 184us/sample - loss: 0.7688 - accuracy: 0.6160 - val_loss: 0.8696 - val_accuracy: 0.5880 Epoch 79/80 2250/2250 [==============================] - 0s 181us/sample - loss: 0.7675 - accuracy: 0.6200 - val_loss: 1.0294 - val_accuracy: 0.5107 Epoch 80/80 2250/2250 [==============================] - 0s 181us/sample - loss: 0.7687 - accuracy: 0.6164 - val_loss: 0.8361 - val_accuracy: 0.6120 [INFO] evaluating network... precision recall f1-score support cats 0.57 0.59 0.58 236 dogs 0.55 0.31 0.39 236 panda 0.66 0.89 0.76 278 accuracy 0.61 750 macro avg 0.59 0.60 0.58 750 weighted avg 0.60 0.61 0.59 750 [INFO] serializing network and label binarizer...
This network is small, and when combined with a small dataset, takes only 2 seconds per epoch on my CPU.
Here you can see that our network is obtaining 60% accuracy.
Since we would have a 1/3 chance of randomly picking the correct label for a given image we know that our network has actually learned patterns that can be used to discriminate between the three classes.
We also save a plot of our:
- Training loss
- Validation loss
- Training accuracy
- Validation accuracy
…ensuring that we can easily spot overfitting or underfitting in our results.
Looking at our plot we see a small amount of overfitting start to occur past epoch ~45 where our training and validation losses start to diverge and a pronounced gap appears.
Finally, we can save our model to disk so we can reuse it later without having to retrain it:
# save the model and label binarizer to disk print("[INFO] serializing network and label binarizer...") model.save(args["model"], save_format="h5") f = open(args["label_bin"], "wb") f.write(pickle.dumps(lb)) f.close()
8. Make predictions on new data using your Keras model
At this point our model is trained — but what if we wanted to make predictions on images after our network has already been trained?
What would we do then?
How would we load the model from disk?
How can we load an image and then preprocess it for classification?
Inside the
predict.py script, I’ll show you how, so open it and insert the following code:
# import the necessary packages from tensorflow.keras.models import load_model import argparse import pickle import cv2 # construct the argument parser and parse the arguments ap = argparse.ArgumentParser() ap.add_argument("-i", "--image", required=True, help="path to input image we are going to classify") ap.add_argument("-m", "--model", required=True, help="path to trained Keras model") ap.add_argument("-l", "--label-bin", required=True, help="path to label binarizer") ap.add_argument("-w", "--width", type=int, default=28, help="target spatial dimension width") ap.add_argument("-e", "--height", type=int, default=28, help="target spatial dimension height") ap.add_argument("-f", "--flatten", type=int, default=-1, help="whether or not we should flatten the image") args = vars(ap.parse_args())
First, we’ll import our required packages and modules.
You’ll need to explicitly import
load_model from
tensorflow.keras.models whenever you write a script to load a Keras model from disk. OpenCV will be used for annotation and display. The
pickle module will be used to load our label binarizer.
Next, let’s parse our command line arguments:
--image: The path to our input image.
--model: Our trained and serialized Keras model path.
--label-bin: Path to the serialized label binarizer.
--width: The width of the input shape for our CNN. Remember — you can’t just specify anything here. You need to specify the width that the model is designed for.
--height: The height of the image input to the CNN. The height specified must also match the network’s input shape.
--flatten: Whether or not we should flatten the image. By default, we won’t flatten the image. If you need to flatten the image, you should pass a
1for this argument.
Next, let’s load the image and resize it based on the command line arguments:
# load the input image and resize it to the target spatial dimensions image = cv2.imread(args["image"]) output = image.copy() image = cv2.resize(image, (args["width"], args["height"])) # scale the pixel values to [0, 1] image = image.astype("float") / 255.0
And then we’ll
flatten the image if necessary:
# check to see if we should flatten the image and add a batch # dimension if args["flatten"] > 0: image = image.flatten() image = image.reshape((1, image.shape[0])) # otherwise, we must be working with a CNN -- don't flatten the # image, simply add the batch dimension else: image = image.reshape((1, image.shape[0], image.shape[1], image.shape[2]))
Flattening the image for standard fully-connected networks is straightforward (Lines 33-35).
In the case of a CNN, we also add the batch dimension, but we do not flatten the image (Lines 39-41). An example CNN is covered in the next section.
From there, let’s load the model + label binarizer into memory and make a prediction:
# load the model and label binarizer print("[INFO] loading network and label binarizer...") model = load_model(args["model"]) lb = pickle.loads(open(args["label_bin"], "rb").read()) # make a prediction on the image preds = model.predict(image) # find the class label index with the largest corresponding # probability i = preds.argmax(axis=1)[0] label = lb.classes_[i]
Our model and label binarizer are loaded via Lines 45 and 46.
We can make predictions on the input
image by calling
model.predict (Line 49).
What does the
preds array look like?
(Pdb) preds array([[5.4622066e-01, 4.5377851e-01, 7.7963534e-07]], dtype=float32)
The 2D array contains (1) the index of the image in the batch (here there is only one index as there was only one image passed into the NN for classification) and (2) percentages corresponding to each class label, as shown by querying the variable in my Python debugger:
- cats: 54.6%
- dogs: 45.4%
- panda: ~0%
In other words, our network “thinks” that it sees “cats” and it sure as hell “knows” that it doesn’t see a “panda”.
Line 53 finds the index of the max value (the 0-th “cats” index).
And Line 54 extracts the “cats” string label from the label binarizer.
Easy right?
Now let’s display the results:
# draw the class label + probability on the output image text = "{}: {:.2f}%".format(label, preds[0][i] * 100) cv2.putText(output, text, (10, 30), cv2.FONT_HERSHEY_SIMPLEX, 0.7, (0, 0, 255), 2) # show the output image cv2.imshow("Image", output) cv2.waitKey(0)
We format our
text string on Line 57. This includes the
label and the prediction value in percentage format.
Then we place the
text on the
output image (Lines 58 and 59).
Finally, we show the output image on the screen and wait until the user presses any key on Lines 62 and 63 (watch Homer Simpson try to locate the “any” key).
Our prediction script was rather straightforward.
Once you’ve used the “Downloads” section of this tutorial to download the code, you can open up a terminal and try running our trained network on custom images:
$ python predict.py --image images/cat.jpg --model output/simple_nn.model \ --label-bin output/simple_nn_lb.pickle --width 32 --height 32 --flatten 1 Using TensorFlow backend. [INFO] loading network and label binarizer...
Be sure that you copy/pasted or typed the entire command (including command line arguments) from within the folder relative to the script. If you’re having trouble with the command line arguments, give this blog post a read.
Here you can see that our simple Keras neural network has classified the input image as “cats” with 55.87% probability, despite the cat’s face being partially obscured by a piece of bread.
9. BONUS: Training your first Convolutional Neural Network with Keras
Admittedly, using a standard feedforward neural network to classify images is not a wise choice.
Instead, we should leverage Convolutional Neural Networks (CNNs) which are designed to operate over the raw pixel intensities of images and learn discriminating filters that can be used to classify images with high accuracy.
The model we’ll be discussing here today is a smaller variant of VGGNet which I have named “SmallVGGNet”.
VGGNet-like models share two common characteristics:
- Only 3×3 convolutions are used
- Convolution layers are stacked on top of each other deeper in the network architecture prior to applying a destructive pooling operation
Let’s go ahead and implement SmallVGGNet now.
Open up the
smallvggnet.py file
As you can see from the imports on Lines 2-10, everything needed for the
SmallVGGNet comes from
keras . I encourage you to familiarize yourself with each in the Keras documentation and in my deep learning book.
We then begin to define our
SmallVGGNet class and the
build method:
class SmallV class is defined on Line 12 and the sole
build method is defined on Line 14.
Four parameters are required for
build : the
width of the input images, the height of the
height input images, the
depth , and number of
classes .
The
depth can also be thought of as the number of channels. Our images are in the RGB color space, so we’ll pass a
depth of
3 when we call the
build method.
First, we initialize a
Sequential model (Line 17).
Then, we determine channel ordering. Keras supports
"channels_last" (i.e. TensorFlow) and
"channels_first" (i.e. Theano) ordering. Lines 18-25 allow our model to support either type of backend.
Now, let’s add some layers to the network:
# CONV => RELU => POOL layer set model.add(Conv2D(32, (3, 3), padding="same", input_shape=inputShape)) model.add(Activation("relu")) model.add(BatchNormalization(axis=chanDim)) model.add(MaxPooling2D(pool_size=(2, 2))) model.add(Dropout(0.25))
Our first
CONV => RELU => POOL layers are added by this block.
Our first
CONV layer has
32 filters of size
3x3 .
It is very important that we specify the
inputShape for the first layer as all subsequent layer dimensions will be calculated using a trickle-down approach.
We’ll use the ReLU (Rectified Linear Unit) activation function in this network architecture. There are a number of activation methods and I encourage you to familiarize yourself with the popular ones inside Deep Learning for Computer Vision with Python where pros/cons and tradeoffs are discussed.
Batch Normalization, MaxPooling, and Dropout are also applied.
Batch Normalization is used to normalize the activations of a given input volume before passing it to the next layer in the network. It has been proven to be very effective at reducing the number of epochs required to train a CNN as well as stabilizing training itself.
POOL layers have a primary function of progressively reducing the spatial size (i.e. width and height) of the input volume to a layer. It is common to insert POOL layers between consecutive CONV layers in a CNN architecture.
Dropout is an interesting concept not to be overlooked. In an effort to force the network to be more robust we can apply dropout, the process of disconnecting random neurons between layers. This process is proven to reduce overfitting, increase accuracy, and allow our network to generalize better for unfamiliar images. As denoted by the parameter, 25% of the node connections are randomly disconnected (dropped out) between layers during each training iteration.
Note: If you’re new to deep learning, this may all sound like a different language to you. Just like learning a new spoken language, it takes time, study, and practice. If you’re yearning to learn the language of deep learning, why not grab my highly rated book, Deep Learning for Computer Vision with Python? I promise that I break down these concepts in the book and reinforce them via practical examples.
Moving on, we reach our next block of
(CONV => RELU) * 2 => POOL layers:
# (CONV => RELU) * 2 => POOL layer set))
Notice that our filter dimensions remain the same (
3x3 , which is common for VGG-like networks); however, we’re increasing the total number of filters learned from 32 to 64.
This is followed by a
(CONV => RELU => POOL) * 3 layer set:
# (CONV => RELU) * 3 => POOL layer set))
Again, notice how all CONV layers learn
3x3 filters but the total number of filters learned by the CONV layers has doubled from 64 to 128. Increasing the total number of filters learned the deeper you go into a CNN (and as your input volume size becomes smaller and smaller) is common practice.
And finally we have a set of
FC => RELU layers:
# first (and only) set of FC => RELU layers model.add(Flatten()) model.add(Dense(512)) model.add(Activation("relu")) model.add(BatchNormalization()) model.add(Dropout(0.5)) # softmax classifier model.add(Dense(classes)) model.add(Activation("softmax")) # return the constructed network architecture return model
Fully connected layers are denoted by
Dense in Keras. The final layer is fully connected with three outputs (since we have three
classes in our dataset). The
softmax layer returns the class probabilities for each label.
Now that
SmallVGGNet is implemented, let’s write the driver script that will be used to train it on our Animals dataset.
Much of the code here will be similar to the previous example, but I’ll:
- Review the entire script as a matter of completeness
- And call out any differences along the way
Open up the
train_vgg.py script and let’s get started:
# set the matplotlib backend so figures can be saved in the background import matplotlib matplotlib.use("Agg") # import the necessary packages from pyimagesearch.smallvggnet import SmallVGGNet from sklearn.preprocessing import LabelBinarizer from sklearn.model_selection import train_test_split from sklearn.metrics import classification_report from tensorflow.keras.preprocessing.image import ImageDataGenerator from tensorflow.keras.optimizers import SGD from imutils import paths import matplotlib.pyplot as plt import numpy as np import argparse import random import pickle import cv2 import os
The imports are the same as our previous training script with two exceptions:
- Instead of
from keras.models import Sequential, this time we import
SmallVGGNetvia
from pyimagesearch.smallvggnet import SmallVGGNet. Scroll up slightly to see the SmallVGGNet implementation.
- We will be augmenting our data with
ImageDataGenerator. Data augmentation is almost always recommended and leads to models that generalize better. Data augmentation involves adding applying random rotations, shifts, shears, and scaling to existing training data. You won’t see a bunch of new .png and .jpg files — it is done on the fly as the script executes.
You should recognize the other imports at this point. If not, just refer to the bulleted list above.
Let’s parse our command line arguments:
#())
We have four command line arguments to parse:
--dataset: The path to our dataset of images on disk. This can be the path to
animals/or another dataset organized the same way.
--model: Our model will be serialized and output to disk. This argument contains the path to the output model file. Be sure to name your model accordingly so you don’t overwrite any previously trained models (such as the simple neural network one).
-. Each time you train your model with changes to parameters, you should specify a different plot filename in the command line so that you’ll have a history of plots corresponding to training notes in your notebook or notes file. This tutorial makes deep learning seem easy, but keep in mind that I went through several iterations of training before I settled on all parameters to share with you in this script.
Let’s load and preprocess our data:
# it to 64x64 pixels (the required input # spatial dimensions of SmallVGGNet), and store the image in the # data list image = cv2.imread(imagePath) image = cv2.resize(image, (64, 64)) data.append(image) # extract the class label from the image path and update the # labels list label = imagePath.split(os.path.sep)[-2] labels.append(label) # scale the raw pixel intensities to the range [0, 1] data = np.array(data, dtype="float") / 255.0 labels = np.array(labels)
Exactly as in the simple neural network script, here we:
- Initialize lists for our
dataand
labels(Lines 35 and 36).
- Grab
imagePathsand randomly
shufflethem (Lines 39-41). The
paths.list_imagesfunction conveniently will find all images in our input dataset directory before we sort and
shufflethem.
- Begin looping over all
imagePathsin our dataset (Line 44).
As we loop over each
imagePath , we proceed to:
- Load the
imageinto memory (Line 48).
- Resize the image to
64x64, the required input spatial dimensions of
SmallVGGNet(Line 49). One key difference is that we are not flattening our data for neural network, because it is convolutional.
- Append the resized
imageto
data(Line 50).
- Extract the class
labelof the image from the
imagePathand add it to the
labelslist (Lines 54 and 55).
On Line 58 we scale pixel intensities from the range [0, 255] to [0, 1] in array form.
We also convert the
labels list to a NumPy array format (Line 59).
Then we’ll split our data and binarize our labels:
# partition the data into training and testing splits using 75% of # the data for training and the remaining 25% for testing (trainX, testX, trainY, testY) = train_test_split(data, labels, test_size=0.25, random_state=42) #)
We perform a 75/25 training and testing split on the data (Lines 63 and 64). An experiment I would encourage you to try is to change the training split to 80/20 and see if the results change significantly.
Label binarizing takes place on Lines 70-72. This allows for one-hot encoding as well as serializing our label binarizer to a pickle file later in the script.
Now comes the data augmentation:
# construct the image generator for data augmentation aug = ImageDataGenerator(rotation_range=30, width_shift_range=0.1, height_shift_range=0.1, shear_range=0.2, zoom_range=0.2, horizontal_flip=True, fill_mode="nearest") # initialize our VGG-like Convolutional Neural Network model = SmallVGGNet.build(width=64, height=64, depth=3, classes=len(lb.classes_))
On Lines 75-77, we initialize our image data generator to perform image augmentation.
Image augmentation allows us to construct “additional” training data from our existing training data by randomly rotating, shifting, shearing, zooming, and flipping.
Data augmentation is often a critical step to:
- Avoiding overfitting
- Ensuring your model generalizes well
I recommend that you always perform data augmentation unless you have an explicit reason not to.
To build our
SmallVGGNet , we simply call
SmallVGGNet.build while passing the necessary parameters (Lines 80 and 81).
Let’s compile and train our model:
# initialize our initial learning rate, # of epochs to train for, # and batch size INIT_LR = 0.01 EPOCHS = 75 BS = 32 # initialize the model and optimizer (you'll want to use # binary_crossentropy for 2-class classification) print("[INFO] training network...") opt = SGD(lr=INIT_LR, decay=INIT_LR / EPOCHS) model.compile(loss="categorical_crossentropy", optimizer=opt, metrics=["accuracy"]) # train the network H = model.fit(x=aug.flow(trainX, trainY, batch_size=BS), validation_data=(testX, testY), steps_per_epoch=len(trainX) // BS, epochs=EPOCHS)
First, we establish our learning rate, number of epochs, and batch size (Lines 85-87).
Then we initialize our Stochastic Gradient Descent (SGD) optimizer (Line 92).
We’re now ready to compile and train our model (Lines 93-99). Our
model.fit call handles both training and on-the-fly data augmentation. We must pass the generator with our training data as the first parameter. The generator will produce batches of augmented training data according to the settings we previously made..
Finally, we’ll evaluate our model, plot the loss/accuracy curves, and save the model:
# (SmallVGGNet)") plt.xlabel("Epoch #") plt.ylabel("Loss/Accuracy") plt.legend() plt.savefig(args["plot"]) # save the model and label binarizer to disk print("[INFO] serializing network and label binarizer...") model.save(args["model"], save_format="h5") f = open(args["label_bin"], "wb") f.write(pickle.dumps(lb)) f.close()
We make predictions on the testing set, and then scikit-learn is employed to calculate and print our
classification_report (Lines 103-105).
Matplotlib is utilized for plotting the loss/accuracy curves — Lines 108-118 demonstrate my typical plot setup. Line 119 saves the figure to disk..
Finally, we save our model and label binarizer to disk (Lines 123-126).
Let’s go ahead and train our model.
Make sure you’ve used the “Downloads” section of this blog post to download the source code and the example dataset.
From there, open up a terminal and execute the following command:
$ python train_vgg.py --dataset animals --model output/smallvggnet.model \ --label-bin output/smallvggnet_lb.pickle \ --plot output/smallvggnet_plot.png Using TensorFlow backend. [INFO] loading images... [INFO] training network... Train for 70 steps, validate on 750 samples Epoch 1/75 70/70 [==============================] - 13s 179ms/step - loss: 1.4178 - accuracy: 0.5081 - val_loss: 1.7470 - val_accuracy: 0.3147 Epoch 2/75 70/70 [==============================] - 12s 166ms/step - loss: 0.9799 - accuracy: 0.6001 - val_loss: 1.6043 - val_accuracy: 0.3253 Epoch 3/75 70/70 [==============================] - 12s 166ms/step - loss: 0.9156 - accuracy: 0.5920 - val_loss: 1.7941 - val_accuracy: 0.3320 ... Epoch 73/75 70/70 [==============================] - 12s 166ms/step - loss: 0.3791 - accuracy: 0.8318 - val_loss: 0.6827 - val_accuracy: 0.7453 Epoch 74/75 70/70 [==============================] - 12s 167ms/step - loss: 0.3823 - accuracy: 0.8255 - val_loss: 0.8157 - val_accuracy: 0.7320 Epoch 75/75 70/70 [==============================] - 12s 166ms/step - loss: 0.3693 - accuracy: 0.8408 - val_loss: 0.5902 - val_accuracy: 0.7547 [INFO] evaluating network... precision recall f1-score support cats 0.66 0.73 0.69 236 dogs 0.66 0.62 0.64 236 panda 0.93 0.89 0.91 278 accuracy 0.75 750 macro avg 0.75 0.75 0.75 750 weighted avg 0.76 0.75 0.76 750 [INFO] serializing network and label binarizer...
When you paste the command, ensure that you have all the command line arguments to avoid a “usage” error. If you are new to command line arguments, make sure you read about them before continuing.
Training on a CPU will take some time — each of the 75 epochs requires over one minute. Training will take well over an hour.
A GPU will finish the process in a matter of minutes as each epoch requires only 2sec, as demonstrated!
Let’s take a look at the resulting training plot that is in the
output/ directory:
As our results demonstrate, you can see that we are achieving 76% accuracy on our Animals dataset using a Convolutional Neural Network, significantly higher than the previous accuracy of 60% using a standard fully-connected network.
We can also apply our newly trained Keras CNN to example images:
$ python predict.py --image images/panda.jpg --model output/smallvggnet.model \ --label-bin output/smallvggnet_lb.pickle --width 64 --height 64 Using TensorFlow backend. [INFO] loading network and label binarizer...
Our CNN is very confident that this a “panda”. I am too, but I just wish he would stop staring at me!
Let’s try a cute little beagle:
$ python predict.py --image images/dog.jpg --model output/smallvggnet.model \ --label-bin output/smallvggnet_lb.pickle --width 64 --height 64 Using TensorFlow backend. [INFO] loading network and label binarizer...
A couple beagles have been part of my family and childhood. I’m glad that this beagle picture I found online is recognized as a dog!
I could use a similar CNN to find dog photos of my beagles on my computer.
In fact, in Google Photos, if you type “dog” in the search box, pictures of dogs in your photo library will be returned — I’m pretty sure a CNN has been used for that image search engine feature. Image search engines aren’t the only use case for CNNs — I bet your mind is starting to come up with all sorts of ideas upon which to apply deep learning.
Frustrated with your progress in deep learning?
You can develop your first neural network in minutes…with just a few lines of Python as I demonstrated today.
But designing more advanced networks and tuning training parameters takes studying, time, and practice. Many people find tutorials online that work, but when they try to train their own models, they are left struggling.
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Summary
In today’s tutorial, you learned how to get started with Keras, Deep Learning, and Python.
Specifically, you learned the seven key steps to working with Keras and your own custom datasets:
- How to load your data from disk
-
From there you also learned how to implement a Convolutional Neural Network, enabling you to obtain higher accuracy than a standard fully-connected network.
If you have any questions regarding Keras be sure to leave a comment — I’ll do my best to answer.
And to be notified when future Keras and deep learning posts are published here on PyImageSearch, be sure to enter your email address in the form below!
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163 responses to: Keras Tutorial: How to get started with Keras, Deep Learning, and Python
Great: Adrian!
always forward
Thank you and thank you Igor
I have a suggestion as to how to apply some basic concepts of deep learning.
About how to write those equations in Python.
Many people know the concepts but there is a barrier between them and the application.
Hey Mohamed — is there a particular algorithm/equation that you’re struggling with? Or are you speaking in more general terms? If you’re speaking more generically, then Deep Learning for Computer Vision with Python covers the basic concepts of both machine learning and deep learning, including some basic equations and theory before moving into actual applications and code.
Thanks Adrian Yes, there are certain things that are facing me. But anyway I meant in general
The book is really wonderful I will work on getting the rest of the versions of it.
Not Working, here, different numbers on training, and a lot of wrong detection.
first:
precision recall f1-score support
cats 0.46 0.66 0.54 244
dogs 0.49 0.22 0.30 242
panda 0.69 0.78 0.73 264
avg / total 0.55 0.56 0.53 750
second method:
precision recall f1-score support
cats 0.66 0.77 0.71 244
dogs 0.76 0.55 0.63 242
panda 0.85 0.95 0.90 264
avg / total 0.76 0.76 0.75 750
everything seems fine but not the results.
Could you share which version of Keras and TensorFlow (assuming a TF backend) you are running? Secondly, keep in mind that NNs are stochastic algorithms — there will naturally be variations in results and you should not expect your results to 100% match mine. The effects are random weight initializations are even more pronounced due the fact that we’re working with such a small dataset.
Hi Adrian:
I test an image like this, however the result shown is “Panda 100%”. Why happend this?
Pandas are largely white and black and the dog itself is dark brown and white. The network could have overfit to the panda class. The example used here is just that — an example. It’s not meant to be a model that can correctly classify each image class 100% of the time. For that, you will need more data and more advanced techniques. I would encourage you to take a look at Deep Learning for Computer Vision with Python for more information.
Brilliant post Adrian!
Thanks Aiden, I’m glad you liked it!
Amazing tutorial! So clear!
Thanks so much, Aline! I’m glad you found it helpful 🙂
Hi, Adrian
Excellent post.
Can we improve its accuracy?
You could improve the accuracy by:
1. Using more images
2. Applying transfer learning
Models trained on ImageNet already have a panda, dog, and cat class as well so you could even use an out-of-the-box classifier.
Hello! How can I download the Animals dataset?
Just use the “Downloads” section of the blog post and you will be able to download the code and “Animals” dataset.
Great Video Adrian. Thanks
Nice one Adrian ! I really appreciate it .
Such a wonderful post with elegant and simple explanation .
I wonder if increasing the no.of hidden layers and making dropout to 0.5 would further increase the accuracy from 78
It may as those are hyperparameters. Give it a try and see!
My friend, this is the best tutorial so far I have ever seen!! thank you so much.
I am struggling just in one point: I have a binary problem and have to use the to_categorical function from keras. As I am seeing, I can just use it with integers categories, not strings. Is this true?
And how do I use the pickle file to write this integer binary categories (from to_categorical) and also how do I use it in the classification_report (the code uses the “lb”)?
Thank you again and congratulations for such good and complete explanations!
Thanks Marcelo, I’m glad you found the tutorial helpful!
For a binary problem you should use the
LabelEncoderclass instead of
LabelBinarizer. The
LabelBinarizerwill integer-encode the labels which you can then pass into
to_categoricalto obtain the vector representation of the labels.
The
LabelEncodercan be serialized to disk and convert labels just like the
LabelBinarizerdoes.
Hi Adrian,
Range of the pixels are same. Every pixel gets values between 0-255. Why we need to scale it between 0 and 1 ?
Most (but not all) neural networks expect inputs to be in the range [0, 1]. You may see other scaling and normalization techniques, such as mean subtraction, but those are more advanced methods. Your goal here is to bring every input to a common range. Exactly which range you use may depend on:
1. Weight initialization techniqu
2. Activation technique
3. Whether or not you are performing mean subtraction
In general, scaling to [0, 1] gives your variables less “freedom” and less likely of causing gradient or overflow errors if you keep larger value ranges (such as [0, 255]). [0, 1] scaling is typically your “first” scaling technique that you’ll see.
Hi Adrian,
Great tutorial as always! I’m wondering though, isn’t this almost the same tutorial as the Pokemon one? The where you classify different 5 pokemons in images? The code seems mostly the same 🙂
I do see some small differences though, for example in the Pokemon on you use the Adam optimizer instead of SGD, and the initial learning rate is 0.001 instead of 0.01.
Are these changes things you’ve learned these past months to achieve better results? Or were these randomly chosen?
The code is similar but not the same. This tutorial is meant to be significantly more introductory and is intended for readers with little to no experience with Keras and deep learning.
The parameters were also not randomly chosen. They were determined via experiments to find the optimal values for this particular post.
Ah ok, good to know, thanks! I wasn’t trying to be offensive or anything, just curious. Apologies if I came across that way!
You certainly were not being offensive, Bob. I just wanted to clarify, that’s all 🙂 Have a great day, friend!
Hi Adrian,
What is chanDim = -1 and chanDim = 1 in beginning of the smallVGGNET?
Great tutorial BTW.
It’s the dimension of the channel. For channels-first ordering (ex. Thenano) the channels are ordered first but with channels-last ordering (like TensorFlow) the channels are ordered last — a “-1” value when indexing with Python means the “last dimension/value”.
Hi Adrain,
Thank you for the excellent tutorial.
I have a basic question:
During validation, we are considering train, test split as 75% and 25%respectively.
So while testing, the network randomly picks 25% of images.
But if I want to find out which images are used for testing, how can I find out?
I want to know the names of the images used for testing.
Please help me
The names of the images won’t be returned by scikit-learn. Instead, if you want the exact image names I would suggest you split your image paths rather than the raw images/labels. That will enable you to still perform the split and have the image paths.
Hi Adrian,
This was an excellent tutorial, very well presented and clear. I have a question, how would I add the bounding box using either nms or my own algorithm to show boxes around a image, like what is done in face detection?
Thanks,
Andreas
We are performing image classification in this post. What you are looking to perform is called object detection. I would suggest you read this tutorial to get you started.
never seen a simple and better tutorial..
Thank you for the kind words Merly 🙂 Congratulations on getting your start with Keras!
UserWarning: Trying to unpickle estimator LabelBinarizer from version 0.19.1 when using version 0.19.2. This might lead to breaking code or invalid results. Use at your own risk.
I am getting this error ..what should i do?
Hey there, it’s not an error, it’s a warning. I would suggest you train the model first before you try to run it and make predictions.
hi adrien,
This blog was awsome . i really appreciate you for this great effort and am your big fan.
After reading this keras + tf tutorial i understood lots of things. But i have to initialize my model or weights manually by using my own method like random initialization. so what step should i do in order to initialize this model manually…
Thanks in advance
The model weights are automatically initialized during the call to
.compile. You can change the initialization method by choosing one of the Keras initializers.
Thanx Adrian
Can we use this technique for activity reconization or this technique is only for static object detection
The method covered here is only for image classification, not activity recognition or object detection.
Trained using keras 2.2.2 and tensorflow 1.10.0
Prediction for both simple_nn and smallvggnet failed on the dog.jpg image.
My question: How do you analyze/understand what went wrong? Is it overfitting, too few training images, poor training image selection, overfitting or something else?
In order to help get everyone up and running with Keras and deep learning we used a very small dataset for this example. Typically, we would have at least 1,000 images per class. Our network is also far from perfect. We can increase the accuracy of our model by introducing regularization methods, such as L2 weighting, additional data augmentation, etc. If you’re interested in learning more about overfitting/underfitting, including how to detect them, I would suggest you read through Deep Learning for Computer Vision with Python.
Hi Adrian,
After many issues with installing opencv, finally i got started with opencv.
I was trying this tutorial and when i launch the program with this command
python train_vgg.py –dataset animals –model output/smallvggnet.model \
–label-bin output/smallvggnet_lb.pickle \
–plot output/smallvggnet_plot.png
this is the result:
> /home/luca/Scrivania/keras-tutorial/train_simple_nn.py(78)()
-> model = Sequential()
(Pdb)
And it doesn’ t move on,
what should i do?
How are you trying to execute the script? Via the command line?
Got same problem. Run via command line (using fish, virtualenv, python 3.6.5, mac)
Does bash produce the same error as fish?
just execute “continue” command
Hhi adrian,
so using the vgg train as you describe everything goes smoothly and i’m getting the 70% plus accuracy, but when i try to predict something using the predict.py I’m always getting the panda prediction.
After doing some research I think it might be something related to the preprocessing of images??
But i’m not sure. One thing is clear when I add:
image = image.astype(‘float32’)
image = image/255
after the image read I start to have some better results, but not sure if this is the way, can you help me?
Thanks
It sounds like the network is overfitting to the “panda” class. One method to increase accuracy would be to introduce more regularization, including additional data augmentation.
Thanks for the great tutorial! Can I add more classes into the file structure, say, adding cow class?
There should be no changes in the code for this code to recognize dogs, cats, pandas, and cow, correct?
Thanks
Stonez
As long as you follow my directory structure for the project and add a directory named “cow” with “cow” images to the
datasetdirectory then yes, no code changes are required.
Hi,
I am getting following error when i try run predict script.
…
line 294, in from_config
model = cls(name=name)
UnboundLocalError: local variable ‘name’ referenced before assignment
Hi Balaji, could you clarify which version of Keras and TensorFlow you are using? Additionally, did you train your model before trying to run the prediction script?
Hi Adrian.
I am with the same problem using tensorflow 1.5.0 (because my computer does not support AVX instructions) and Keras 2.2.3, and tensorflow 1.10.0 and Keras 2.2.3 in other machine.
I am trying:
python predict.py –image images/cat.jpg –model output/simple_nn.model \
–label-bin output/simple_nn_lb.pickle –width 32 –height 32 –flatten 1
python predict.py –image images/panda.jpg –model output/smallvggnet.model \
–label-bin output/smallvggnet_lb.pickle –width 64 –height 64
python predict.py –image images/dog.jpg –model output/smallvggnet.model \
–label-bin output/smallvggnet_lb.pickle –width 64 –height 64
Do I need train the model? I have download your files and I am trying execute them without train.
Thanks.
Yes, make sure you train the model before you try to make predictions on images.
Hello Adrian,
Every article that i check out on pyImageSearch always leaves me impressed. Great work.
I noticed that in every tutorial you use “argparse”. I wish to know if it makes any difference if we directly load our image into a variable directly instead of using argparse. If so, can you let me know what the difference is?
Thanks.
Hey Niranjan — I think your confusion can be resolved by reading this guide on how argparse works. As you’ll find out, argparse just allows us to supply arguments via the command line instead of manually hardcoding them 🙂
hi adrian,
can you give me an example of a path that can be add in help”……” ?
Because when I start the train simple example it arrives to “[INFO] loading images…”
and then it doesn’t go on!
Ah , thanks for these amazing tutorials!!!!!!
Hey Jacob, I think your confusion is related to how command line arguments work. Make sure you read this tutorial to help you clear up your confusion.
hi adrian,
I dont understand when training train_vgg.py there is 70/70 [==================]
Where 70 come from? What does 70 mean? 70 pictures every epoch?
Thanks for your articles!
That is actually the number of batches per epoch. There are 70 batches of images per epoch.
Hi Adrian,
Could you please explain further about how the 70 is calculated?
I assume is from this line of code, right?
model.fit_generator(aug.flow(trainX, trainY, batch_size=BS), validation_data=(testX, testY), steps_per_epoch=len(trainX) // BS, epochs=EPOCHS)
What specifically in Line 70 are you asking how is calculated? The steps_per_epoch value?
Hello Adrian. Thank you very much for this excellent tutorial. I have a little question. Could you please describe what would be the architecture in keras code of the convolutional network if the dataset only had two categories? for example cats and dogs (eliminating the pandas folder) and always in the RGB color space. If you could make a parallel with the code of this tutorial for the three categories. I know it is a question that may be basic but it would help me to understand the architecture of the cnn in keras that I still do not have very clear. Thank you very much for your excellent work and congratulations for your wedding. Jorge from Argentina.
The architecture itself would not change except for the final FC layer where there will be two nodes rather than three nodes. Other than that, there will be no other changes to the architecture itself. If you want to train a network for binary classification just make sure you use “binary_crossentropy” for your loss.
Hi Adrian,
Thanks for the amazing explanation. I have few doubts.
If we try implementing with another dataset, is it supposed to be organized in the way you have organized?
And also, what does 32x32x3=3072 pixels in a flattened input image mean I am not able to understand the multiplication of 3?
I would recommend you use the same directory structure that I use in the blog post. It will ensure that the code doesn’t have to be changed at all and you can just run the script to train on your own custom dataset.
As for your second question, images are represented as a 3 channel RGB image. Thus, for a 32×32 RGB image there are a total of 32x32x3=3072 values.
Hi, this tutorial is self-explanatory I have just started learning machine learning and this image recognition sounds really interesting and cool. I have downloaded all the required files and code from your site. I have Spyder install on Anaconda. I want to run these files. I need help in how can i start integrating these scripts.
How can i run this model on Spyder?
Thank You.
Hey Nick, you can certainly use an IDE if you would like but I don’t recommend if you are new to computer vision and deep learning. Take the time to invest in your ability to execute the scripts via the command line. We use the command line quite a bit so become comfortable with it now. Additionally, while I don’t use the Spyder IDE you can use this tutorial on how to use an IDE with Python.
In Section 9, how do you choose 512 in the model.add(Dense(512)) line 60 of code after you’re done the CONV –> RELU steps?
It’s a hyperparameter to the model architecture. You run experiments to tune the hyperparameters of the network. I discuss my best practices, tips, and suggestions to hyperparameter tuning inside my book, Deep Learning for Computer Vision with Python.
Hi Adrian. Thanks for nice explanation. Is there any way to create a CNN model from scratch for object detection or object localization using keras? Can keras do it at all? I searched many posts in websites and all of them used keras for image classification only. If yes, I hope you publish a blog post tutorial about object detection by keras. Thanks for your amazing works.
Great question, thanks for asking Farshad. I actually cover how to train your own custom Keras object detector inside Deep Learning for Computer Vision with Python.
Great post, but there is one thing missing which is making the predictions fail.
The same way we divide the inputs by 255.0, we need to do the same thing on the predictor before providing image as input on the NN.
Thanks so much for pointing this out, Juanlu! It was a typo on my part. I have fixed the typo as well as the code download so the issue no longer exists.
Hi Adrian,
How do we add the object detection bounding boxes to the images?
You cannot use a model trained for image classification as an object detector. I would suggest you read this tutorial on deep learning object detection so you can learn the fundamentals.
Hi Adrian,
I get this error..any suggestions?
(-215) ssize.width > 0 && ssize.height > 0 in function cv::resize
Double-check the path to your input dataset. Your path is likely incorrect and the
cv2.imreadfunction is returning “None”.
Hi Adrian.
Thank you for your excellent tutorial. But it’s just for pictures. How could cnn be used to recognize sounds?
Sorry, I don’t have any experience with deep learning for audio applications. I only work with computer vision here. Sorry I couldn’t be of more help!
This is by far the most simple to understand and useful tutorial on Keras that I have ever seen. You do a great job of explaining BOTH the concepts behind how the neural network works and what the different functions in the libraries are doing for us (the last part is often left out). Thank you so much!
Thank you so much for the kind words, Zachary — I really appreciate that 🙂
Hi, Adrian
Excellent work
If I have 1 channel images (ex medical images) and I wanted to apply this program to classify them, what should I change in this program especially the input_shape ?
First, convert your images to grayscale when you load them:
image = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
Secondly, change your
depth=1when initializing SmallVGGNet.
please send me source code of this post..
You can use the “Downloads” section of the post to download the source code.
where can I find the dataset for this tutorial?
You can use the “Downloads” section of this post to download the source code and dataset.
Hi Adrian
Thank you for this tutorial.
I have two doubts :
1. At the data =np.array(data, dtype=”float”)
i am getting a sequence error , in short I am not able to convert the data dtype(‘O’) into float.
I got rid of this error by copying it into another float array. But after trying for many hours I could’nt solve this error.
2. I am getting loss =NaN
I have checked my input data and I am sure that none of the input values have nan value.
Any help will be appreciated.
thank you
Are you using the exact code and datasets from this tutorial? Or are you working with your own custom dataset?
Hi thanks Adrian for the post again.
I figured the errors myself. I was using a custom dataset and some of the images were corrupted due to which i was getting these errors.
Congrats on resolving the issue!
Hi Adrian,
I managed to run it. But after 1200 epoch and 0.01 learning rate, my training accuracy is ~1.0 and validation accuracy is ~0.50!
What’s happening??!!
Your network is overfitting to the data. Training for longer isn’t necessarily going to give you better accuracy. Instead, you need to learn how to properly set the hyperparameters of the network. To improve your accuracy and learn my tips, suggestions, and best practices to improve the accuracy of your networks, make sure you refer to Deep Learning for Computer Vision with Python.
Hey! Loved the tutorial.
Can the same VGG network be used for a hand gesture recognition system for classifying gestures from A-Z (26 classes)?
Not as it stands. VGG is a classification network and presuming you are referring to the pre-trained VGG network on ImageNet there is no hand gesture classes. You would need to fine-tune VGG to recognize hand gestures. For what it’s worth I cover tranfer learning and fine-tuning inside my book, Deep Learning for Computer Vision with Python.
Is it possible know where the cat/dog/panda are into image?
is it possible running this process in real time with a video streaming?
Thanks
What you are referring to is called “object detection”. See this most for more details on object detection.
can you do the same problem for binary classification.. i got stuck at doing that… i have 2 classes only.. and i want to save the model also
You’ll want to change your loss function to “binary_crossentropy” for 2-class, binary classification. This tutorial covers how to save and load your models with Keras. For more details on deep learning, including how to get started, I would suggest working through Practical Python and OpenCV.
Hi,
i didn’t understand how feature extraction is done in this code. I have applied the same code for gender recognition and the only difference from your code is the training set images. I would like to know how feature extraction is done and what features have been extracted.
If you’re interested in feature extraction via pre-trained CNNs (including gender recognition) then definitely take a look at Deep Learning for Computer Vision with Python where I cover the topic in detail.
I have used this exact same code for gender recogniton. It is working but i would like to know what feature are being extracted as well as how feature extraction is done. Can you please reply asap.The only difference from your code is the dataset used.
I cover that exact topic inside Deep Learning for Computer Vision — my suggest is to start there.
Hi Adrian,
I only want to classify dog and cat, so I change “caterogry_crossentropy” to “binary_crossentropy, then it has error:
“expected activation_2 to have shape (2 ) but got array with shape (1 )”
then I change to “spare_category_crossentropy” and it works.
But if I want to classify gray images, for examples “number 0” and “number 1” in MINST dataset, I do “binary_crossentropy” and change the input_shape to:
“model = SmallVGGNet.build(width=28, height=28, depth=1, classes=len(lb.classes_))
then it shows similar error as:
“expected activation_2 to have shape (2 ) but got array with shape (1 )”
Could you help me?
Thank you very much.
1. See my note on Lines 66-69 about using Keras’ “to_categorical” function.
2. You should be using “binary_crossentropy” as your loss.
Once you switch both of those you will be able to train the network.
Adrian,
how do you use the “to_categorical” function in this context? I don’t have a lot of coding experience with python. I googled for examples but it did not work for me.
Also, in previous related questions you mentioned to change to LabelEncoder (instead of LabelBinarizer). I tried my hand at that but did not work:
I changed:
lb = LabelBinarizer() to lb = LabelEncoder()
I also change to the binary_crossentropy as a loss function. But I am getting an error like Nguyen mentioned above.
Many thanks for the tutorial. It is REALLY helpful.
You first encode using LabelEncoder and then call to_categorical, similar to the following:
hi adriand thank you for your explanation , but can you explain me what is numClasses is ? thank you so much
The “numClasses” is the total number of unique class labels. For example, suppose you had a three class dataset: dogs, cats, and pandas. Then “numClasses=3” since you have three total classes.
Hello Adrain Brother, Being in final Year of college i found your resources are quite awesome.
>>>>I have a Doubt in using No. of classes <<<<
You have used 3 classes(cat,dog,panda) and you vectorized to trainY and testY as below…
lb = LabelBinarizer()
trainY = lb.fit_transform(trainY)
testY = lb.transform(testY)
and in comments you mentioned if 2 classes is used then, LabelEncoder is used instead of LabelBinarizer and fit_transform and to_categorical is applied for labels, as below
le = LabelEncoder()
labels = le.fit_transform(labels)
labels = to_categorical(labels, numClasses)
Could you please explain me When to binarize the labels, When to binarize the trainY and testY, and when to use LabelBinarizer, LabelEncoder and to_categorical?
Hey Parvez — I address that exact question inside Deep Learning for Computer Vision with Python. I suggest you start there.
Did you get this working? I check this out today but obviously, I do not understand exactly what is going on. I keep on getting errors even after using well-explained code on this.
Hi Beatrice — did you see my previous comment? I provided you with code you could use.
Hi
This is a great tutorial.
I’ve purchased your book and it’s supporting material and look forward to reading and learning even more about this topic.
Keep up the good work.
Robert.
Thanks so much, Robert! I hope you are enjoying. By all means, feel free to reach out if you have any questions on it 🙂
Hi
Yes, I did. I made the modifications but then get an error when training the neural net needs to happen. The shape of the array is not what it is expecting any more.
Hello and nice guide!
I got a question, is this tutorial for windows or linux?
Provided you have Keras properly installed this tutorial will work on Linux, macOS, and Windows.
Thank you for the response!
I have another question, I tried running the train_vgg script and it takes about 3-4 minutes per epoch on my computer. How do I tell Tensorflow to use my GPU instead of my CPU? I assume it uses my CPU since the timers are well over 1 minute.
You can use the “nvidia-smi” command to check and see if your GPU is being utilized. You’ll also want to ensure the “tensorflow-gpu” package is installed.
I learned that the evaluation dataset is used to tunning the hyperparameters.
In this blog, what are the hyperparameters?
The hyperparameters include the learning rate, number of nodes/filters for each layer, and any regularization. I would definitely suggest reading through Deep Learning for Computer Vision with Python where I cover hyperparameters (and how to properly tune them) in detail.
Great tutorial!
Can you give me some hints on how to deploy this on a Flask Web App ? It would be great!
See this tutorial.
Thank you for sharing this with us. I found it to be of great benefit for me.
# do you have a similar tutorial for RGB-D data? I know you add the extra channel but I suppose my struggle is even before that, with the per processing of the data. I recorded a ROS bag with the RGB-D data then I can extract the RGB in a folder and the D in another, then I get confused when trying to give it as an input to the convnet. (I struggle with the coding).
Sorry, I Do not have any tutorials for RGB-D data.
Hello! thank you for sharing this with us!!!
I still do not understand how you label dogs, cats and pandas? Please explain to me the label?
I manually labeled those images themselves. I created a directory for each of the dogs, cats, and pandas images, then placed each into their corresponding directory.
Thank you.
No problem, I’m glad you found it helpful!
hey this tutorial is awesome,the code for non CNN worked just fine but when i ran it for CNN with smallvggnet it gave me the error:
Import Error: No module named ‘pyimagesearch’
how to resolve this?
and secondly if i use the this line : image = cv2.resize(image, (64, 64))
will it resize all my images into 64×64 no matter what the original size? plus how do i know that the images being fed into the neural network are fine for training,wont the larger images be distorted like that?(the details are unable to be observed for training)
My last question,for this line in smallvggnet script:inputShape = (width, height,depth )
do i write the dimensions which i want the image in or what the image already has?(in a dataset how can i tell about 1 image it has many images!)
Hey Mary — make sure you use the “Downloads” section of the code to download the source code. It sounds like you may have copied and pasted which likely caused the error.
Secondly, I would recommend you read Deep Learning for Computer Vision with Python so you can learn the fundamentals of deep learning. That book will help you understand how we preprocess images and better enable you to train your own CNNs.
Dear Sir,
This is a best literature I have come across internet for ML implementation.
It is the exact way for my assigned work.
Today morning 9am I have started and finished all by 8pm.
I have understood the concepts, and Implemented in Jupyter Notebook, and got the result after few changes.
CNN based model testing is pending, but I will do this from your other blog.
Such a nice way of explanation and detailed code needs lots of appreciation, so I am dropping this message.
Thanks a lot for your contribution for society and Human Race.
Thanks Chinmaya, I really appreciate the kind words 🙂 Congrats on training your own NNs and CNNs!
Hi dear adrian!
Can you help me to train it for two classes only.
See this comment thread.
Hi Adrian,
Can i use this code to train 1 class only?
I’m trying to identify a object in photo. If the object is there i will receive a “ok” and if it’s not i will receive a “nok”
Hi. how to download the animals dataset?
I couldn’t find it in the downloads section.
Thanks
Download the .zip of the file using the “Downloads” section of the tutorial. You’ll find the “animals” dataset there.
This was a very detailed tutorial. If I wanted to use Tensorflow 2.0 with the new keras interface, would I need to simply do something like: “import tensorflow.keras as keras” and the rest would work the same?
Thanks
You are absolutely correct! Since TensorFlow 2.0 is making big moves to use the “tensorflow.keras” package you can just import all Keras classes/functions directly from “tensorflow.keras”.
Hi Adrian, if I am adding another class “cow” for example, isn’t it necessary to change the epochs number?
Not necessarily. The epochs doesn’t impact the number of classes or vice versa. Try training using the same number of epochs. Additionally you should read Deep Learning for Computer Vision with Python to learn my best practices, tips, and suggestions when training your own deep learning models.
Hi Adrian,
I would like to know if there is an explanation for fixing the number of neurons in the first hidden layer as 1024 from the input shape as 3072 in Line 76 in train_simple_nn.py file. I understand in every hidden layer due to dimensionality reduction, the image size gets reduced to one half of the original image size. Hence from Hidden layer 1 -> Hidden Layer 2 the pixels get reduced to 512 from 1024. But How does it change from 3072 to 1024?
Thanks in Advance…..
Hi I got an error after the training and network evaluation finished. The error was in generating the plot:
Traceback (most recent call last):
File “train_simple_nn.py”, line 111, in
plt.plot(N, H.history[“acc”], label=”train_acc”)
KeyError: ‘acc’
Hi, I managed to get rid of the error by using metrics=[“acc”] in model.compile.
But after running training set, i notice that the accuracy is below 50%, that means it is performing worse than random chance. Infact I gave it a cat image to predict but it predicted it was a dog with 63% accuracy.
I don’t understand why its doing this?
In TensorFlow 2.0 the “acc” key was changed to “accuracy” and “val_accuracy”, respectively.
Hi Adrian,
If I would like to implement face recognition application based on your codes, What should I do except adding the face detection?
Thank you
You should follow my tutorials on face applications and face recognition.
Hi Adrain
Thanks for you post. Since i am using keras 2.3.1 and tensorflow 2.0.0. I read the previous comments and i changed the “acc” to accuracy and i got my plot as png. But still the other two model file and the pickle file is not loaded in the output folder. And also the pickle file is not loaded.
Thanks:)
Make sure you train your model first. Once the model is trained you can then make predictions using it.
Hi Adrian,
I created my own model with train_vgg.py and it works great. 🙂
With predict.py I can check individual images. However, I would like to check a live video with the created model.
That’s why I changed the code so that it checks the frames of the webcam – predictVideo.py. Alternatively, video files.
Unfortunately, the recognition (labeling) does not work well here, although I use the same model as the one
Checking individual images.
Example:
I extracted individual pictures from a video file and I check them with predict.py
Result: Everything is recognized correctly.
If I now check the video file with predictVideo.py, nothing is correctly recognized.
Is it because you cannot use the model for live or video file recognition?
Do I have to train the model differently?
Thanks a lot!
Anja
It’s hard to say what the issue is without seeing your code or video, but I would suggest you start with this tutorial to help you learn how to apply a Keras model to a video stream.
Secondly, double and triple-check that your preprocessing steps are the same for inference/prediction as they are for training. A common mistake I see beginners make is forgetting to preprocess their images in the same manner as training.
Hi how to insert my trained model since i don’t have any trained model in my disk?. it is required argument as per your code
You need to train your model before you serialize it to disk. From there you can use it to classify new input images.
Hi Adrian,
This is a great tutorial and made everything easy for me as always. I would like to know a robust way to predict when I have like around 50,000 images. I’m currently looping through the images with ” tensorflow.keras.backend.clear_session() ” line after the prediction line.
Is there any way of predict all the images at once and then loop through them and save?
You mean make predictions on all 50,000 images? Yes, absolutely, just use Keras’
predict_generatorfunction.
Hello Adrian sir,
Thank you very much for great tutorial .It’s very awesome and very easy to understand.
I have implemented it on my own data set of 3-classes of documents(Driving licences. I got good accuracy and I am getting good results on unseen images which belongs to the classes. But when I try to predict the image other than these 3-classes (ex. Dog or Cat) then also it showing match with one of the classes.. Why these is so? Please help.
You need to create a 4-th class called “ignore” that does not contain any of the documents, that way your model can predict one of the 3 document classes or the 4th “ignore” class.
What should we change if using a binary class dataframe?
using to_Categorical() would change some details in the code, what would be then?
Take a look at the comments on this post as I have addressed that question a few times. | https://www.pyimagesearch.com/2018/09/10/keras-tutorial-how-to-get-started-with-keras-deep-learning-and-python/ | CC-MAIN-2020-45 | refinedweb | 13,741 | 58.28 |
In FORTRAN, Perl, Python, and Ruby (and possibly many others1), ** is the exponentiation operator. A Perl example follows, because it's my language of choice.
perl -e 'print "2^$_ = ", 2**$_, "\n" for (0..9)'
OUTPUT:
2^0 = 1
2^1 = 2
2^2 = 4
2^3 = 8
2^4 = 16
2^5 = 32
2^6 = 64
2^7 = 128
2^8 = 256
2^9 = 512
In C and C++, the * is used both to declare and dereference pointers. It is orthogonal, so ** declares or dereferences a pointer to a pointer. Exponentiation in C and C++ is accomplished with the pow() function in the C math library. For C, use #include <math.h> and for C++, use #include <cmath>.
#include <math.h>
#include <cmath>
#include <stdio.h>
int main() {
int num = 10;
int *p1 = #
int **p2 = &p1;
printf("The number is %d\n", **p2);
return 0;
}
OUTPUT:
The number is 10
Thanks to OldMiner and ariels for pointing out that ** as exponentiation didn't first appear in perl and recommending that I show how C and C++ do exponentiation.Thanks to vruba for telling me ** is also used in Python and Ruby.1 - If you know of another language that uses ** as exponentiation, /msg me, and I'll add it.
Log in or register
to write something here or to contact authors. | http://everything2.com/title/%252A%252A | CC-MAIN-2013-48 | refinedweb | 223 | 72.76 |
Roland Cedo21,261 Points
Why use symbols instead of string keys in this case?
So Jason creates the class "Monster", initializes it with an instance variable called "actions" that is a hash with the key "scream" and value 0.
class Monster attr_reader :name, :actions def initialize(name) @name = name @actions = { scream: 0 } end def say_something(&block) block.call end def scream(&block) actions[:scream] += 1 print "#{name} screams!" yield() end end
Now, in the method "scream", he has to access the instance variable "scream" as a symbol so he can increment the instance variable's value:
def scream(&block) actions[:scream] += 1 print "#{name} screams!" yield() end
Can someone clarify why he chose to create "scream" as a symbol instead of a string key/value pairing like:
@actions = { "scream" => 0}
It is currently my understanding that you should use symbols when you want to have an immutable value in your object, correct? If so why use a symbol when we want to increment the value of scream when we call the method "scream"?
1 Answer
rowend rowend2,925 Points
Hi. He uses a symbol because it is more efficient in memory. Side note: when you use symbols inside of a hash you can change the values. | https://teamtreehouse.com/community/why-use-symbols-instead-of-string-keys-in-this-case | CC-MAIN-2020-24 | refinedweb | 206 | 68.6 |
Hey,
I’m trying to implement Programmer Sounds in addition to use mostly the BP integration, though I’m running into some massive issues.
Frankly I have no idea how to access the FMOD plugin via C++ code and how to additionally use the LowLevelAPI.
Is there a reasonably simple way to integrate Programmer Sounds into Unreal right now besides writing everything including the BP interface yourself?
I’m still using 1.07.02 and UE 4.9
Thanks for any help!
Edit: The inclusion of the plugin in C++ works. However I can’t seem to get the FMODSystem as described in the docs.
- Timo Müssig asked 3 years ago
- last edited 3 years ago
- You must login to post comments
Programmer Sounds, by their nature, require interfacing with the FMOD Studio API in C++. There is no way to do it via Blueprint alone.
The documentation describes how you can access the Studio API from UE4:
- Graeme Webb answered 3 years ago
I tried including it as described however I always get “‘IFMODStudioModule’ : is not a class or namespace name”. The rest includes and compiles just fine. However the way to get a system as described in the documentation doesn’t seem to work for me and I can’t find another way to get to it either.
Also is there a way to enable Visual Studios IntelliSense for FMOD specific stuff while working this way? (this is just a convenience thing. Not a huge deal if it doesn’t)
Sounds like you are missing an include file. Try this…
#include “FMODStudioModule.h”
#include “fmod_studio.hpp”
if (IFMODStudioModule::IsAvailable())
{
FMOD::Studio::System* StudioSystem = IFMODStudioModule::Get().GetStudioSystem(EFMODSystemContext::Runtime);
if (StudioSystem)
{
// Use it here
}
} | http://www.fmod.org/questions/question/using-programmer-sounds-in-addition-to-the-plugin/ | CC-MAIN-2018-39 | refinedweb | 285 | 66.44 |
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<tr><td>Select Group:
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If you enjoyed this post then why not add us on Google+? Add us to your Circles | http://www.roseindia.net/tutorialhelp/comment/48108 | CC-MAIN-2015-32 | refinedweb | 1,135 | 64.2 |
This patch adds support for emission of following DWARFv5 macro forms in debug_macro section.
Thank you @aprantl , for reviewing this.
Addressed minor review comment by @aprantl
Oh Sorry, that must've crept up/left while segregating the dwarf-dump and this patch. surprised this patch causes updates to the tests - what changes in the patch caused changes in these tests? (stringpool and dbg-stack-value-range.mir) - ah, because debug_str now needs to be emitted after debug_macro because the macro section might introduce new strings? OK. Could you separate that ordering change/test update out into a standalone patch. It'll make the rest of this more targeted when reviewing.
Build this with Dwarf.def rather than writing it out explicitly. Something like this:
return StringSwitch<unsigned>(MacroString)
#define HANDLE_DW_MACRO(ID, NAME)
.Case("DW_MACRO_" #NAME, ID)
#include "llvm/BinaryFormat/Dwarf.def"
.Default(DW_MACINFO_invalid);
This should probably be 4, not 3, since it's a bit field column. (if you tried to | in OPCODE_OPERANDS_TABLE of 3 into the table, you'd overwrite bits 1 and 2 (changing the value of offset_size and debug_line_offset, rather than specifying the value of opcode_operands))
This looks to be backwards - since OFFSET_SIZE_32 is zero, these two lines don't have any effect (& 32 bit is the default - if the bit is zero).
So it should /probably/ be:
if (offset byte size == 8)
Flags |= OFFSET_SIZE_32;
Seems this line offset is optional and the DWARF spec doesn't mention what it might be useful for. Do you have any specific use in mind? Otherwise I'd leave it out. (@aprantl @probinson )
I don't think this is a FIXME situation - LLVM has no extensions here, so there's no need for the opcode_operands_table.
Perhaps refactor this to only have "AddComment / EMitULEB128" written once, but parameterized on the enum, eg:
unsigned Type = M.getMacinfoType() == dwarf::DW_MACINFO_define ? dwarf::DW_MACRO_define_strp : dwarf::DW_MACRO_undef_strp;
Asm->OutStreamer->AddComment(dwarf::MacroString(Type));
Asm->EmitULEB128(Type);
Parsing constant strings back into constants is a bit suboptimal (both in terms of compile time performance, chance of mistakes (the string is checked at runtime whereas a reference to an enum would be checked at compile time)) & is curiously inverted compared to the line before - which uses an enum, then converts that to a string for the comment. There are a few other cases of this - in general, don't write string constants like this due to the lack of error/type checking, prefer using the enums & calling stringifying functions if needed.
It'd be nice to simplify this code a bit in general - the fact that this adds comments to the new debug_macro paths that are then missing from the debug_macinfo paths, etc, isn't ideal.
I'm wondering if it'd make sense to instead phrase this whole function parameterized on the type of enums, so it'd be implemented a bit like this:
if (UseMacro) {
emitMacroFileImpl(F, U, dwarf::DW_MACRO_start_file, dwarf::DW_MACRO_end_file, dwarf::MacroString);
} else {
emitMacroFileImpl(F, U, dwarf::DW_MACINFO_start_file, dwarf::DW_MACINFO_end_file, dwarf::MacinfoString);
}
So the implementation doesn't have conditionals in several places, keeps it consistent, etc.
This might be more legible using the conditional (?:) operator to pass the specific debug section - so it's obvious to the reader that that's the only difference (that they're not calling subtly differently named functions, etc - just calling the same function with a different argument), eg:
auto &ObjLower = Asm->getObjFileLowering();
emitDebugMacinfoImpl(getDwarfVersion() >= 5 ? ObjLower.getDwarfMacroSection() : ObjLower.getDwarfMacInfoSection());
In D72828#1824527, @dblaikie wrote: trying to get that patch ready. As for this, this patch doesn't have dependency on dwarfdump except that testing the section contents part. I've verified integrity of section content using objdump and lldb/gdb. My rationale behind this was this patch can get in, till we discuss and agree on dwarfdump extension to accommodate macro support.
Yes, that' s intentional. I've shifted the string emission to post macro emission to put macro content in string section. BTW are you suggesting here to do that change/patch commit separately ??
Thanks David for reviewing/sharing your thoughts on this.
Refactoring suggestion, I will address those in next revision.
I may be wrong here. Are you trying to suggest this ??
if (offset byte size == 8)
Flags |= OFFSET_SIZE_64;
I think we only need that in DWARF64 case, which this patch does not support.
So for consistency/readibility, I intentionally set OFFSET_byte_size_32 that even that has no effect.
Should we leave it as it is OR remove it and add comment that in default case DWARF32 Offset size will be 32.
Yes, One crucial thing I noticed while verifying section content is that, consumers objdump/lldb/gdb agrees on this representation and expect offset of debug_line section within macro section. So if we omit that, I'm afraid we might loose debuggability.
DWARF does not define symbols for the flag bits, but I'd still expect to see these in Dwarf.def where they could be shared with the dumper code.
Also, OPCODE_OPERANDS_TABLE should be 4 not 3; these are masks, not bit numbers.
If you're not supporting 64-bit offsets (which is entirely reasonable) you should have an assert() that the offset size is 4.
@dblaikie The reference to .debug_line is required for DW_MACRO_start_file, because that opcode has an operand that is a file number from the line-number program's file table. It's optional if that opcode is not used.
@SouraVX it is inconsistent to conditionalize setting the flag bit, and then unconditionally emit the debug_line_offset field. I have no problem with always emitting the field, but in that case you should unconditionally set the flag bit as well.
This captures the string offset into YYYY, but never uses the captured value. The old version of the test did verify the offset was used, presumably somewhere in the __debug_info section. So, this change has lost coverage.
Thanks @probinson for sharing thoughts.
Refactored code based on @dblaikie review
Addressed and implemented @probinson concerns
Thanks for sharing this, I've added forms in Dwarf.def and exapanded the enum here.
Will try to reuse this in corresponding dumping part.
Thanks for pointing this out.
Added corresponding debug info variable. Now we have back reference to info section from str section.
Since my emitMacroFileImpl causes the comments to be emitted in asm for both macinfo and macro section which is good. But this is sort of incomplete, since we're not emitting comments for macinfo type.
I'm planning to do a small factor on macinfo part also. To emit macro form comments for DW_MACINFO_define and others.
Making asm more readeable.
My comments have been addressed, but leaving final approval to @dblaikie.
Corresponding llvm-dwarfdump revision D73086
Gentle, friendly Ping! to all reviewers!
Child Revision - D73086
Gentle/Friendly Ping! @dblaikie @aprantl and all other reviewers!
lgtm if David is happy.
In D72828#1850038, @aprantl wrote:
lgtm if David is happy.
Thank You, @aprantl, for your acceptance. I agree, that part of macro implementation needs refactoring/In my opinion/. That was the reason, I was delaying and created separate patch for llvm-dwarfdump D73086. So that, even if we disagree/want changes, for a better implementation of dumping part.
We can still have emission part i.e this patch in LLVM {/tested/beneficial from consumer perspective GDB or LLDB/}
Ping!
Hi @dblaikie, Could you please share your thoughts/acceptance on this. All other reviewers had shared their acceptance.
This doesn't seem to be tested - the couple of test updates are to keep them passing after changing the ordering of sections - ideally that change (changing the ordering of sections, so strings can come after macros) should be committed separately (just change the order and update the few tests that need it) & explicit/full test coverage for this feature should be added and should use llvm-dwarfdump (so this patch should come after the one that adds functionality to llvm-dwarfdump for dumping this section).
Could this be Name + ' ' + Value? (perhaps it could be (Name + ' ' + Value).str() if it needs to be a string in the end - that would be a bit more efficient than the current code that stringifies the Name and Value separately)
Probably skip the "= + Value" part here (the same isn't done for the "Macro String"/name above - because the string itself is probably legible in the assembly? So the description is useful, but the value itself will be evident in the assembly without needing to be repeated in the comment)
Rename "Func" to a more informative name - "MacToString", perhaps?
Incorporated @dblaikie comments!
Committed string emission part separately.
Incorporated, other minor comments.
Ping this when the llvm-dwarfdump support for debug_macro is in and this patch has been updated with test coverage using that support.
Hi @dblaikie , it's already in pipeline. I mentioned in this revision. Corresponding dwarfdump emission D73086.
Remove OFFSET_SIZE_32, as this value does not define any real flag.
This should be just OFFSET_SIZE to correspond to the other flags.
The value for OPCODE_OPERANDS_TABLE should be 0x04. It looks like @dblaikie already said that for one of previous versions of the patch.
This crashes on a Debug build, probably because DwarfParams is not initialized.
Incorporated @ikudrin comments,
Removed a redundant check and a FIXME:Not emitting opcode_operands_table
Yes, theirs no particular flag in Spec. Spec says about "offset_size_flag" and how it's value is interpreted
0 - DWARF32 1 - DWARF64. I created these flags for readable/informative purpose.
Sorry for the trouble, I forgot to replace this with "0x03". Since, their was a discussion to keep this or not in first place because we are not emitting opcode_operands_table, So this flag is not used, at least right now.
Oh.., Yeah I also noticed this, even after initalizing dwarf::FormParams DwarfParams({5, 8, DWARF32}).
Still
assert(DwarfParams.getDwarfOffsetByteSize() == 4 && "DWARF64 not supported!"); not on release build.
this is failing, some how getDwarfOffsetByteSize() is not returning correctly.
Anyway I found this check to be a bit redundant in it's own way. So removed it.
This is false readability. You still have to remember that the value is not real and treat it accordingly. There is no distinct value for DWARF32 in the specs. The value of 0 means that the contribution has DWARF32 format AND does not have a debug_line_offset field AND does not have an opcode_operands_table. Moreover, you do not define pairs of values for the other flags, which makes all the definition inconsistent. So, please, remove that fictitious value and make the set of flags follow the documentation.
Revised and Addressed comments by @ikudrin.
Changes summary -
-No dependency on D73086, just the Macro flags defined in Dwarf.def are reused here while writing macro header flags field.
-Contents verification has been done using llvm-dwarfdump generated from D73086..
Flags = MACRO_FLAG_DEBUG_LINE_OFFSET;?
Addressed nits by @ikudrin
In D72828#1908583, @SouraVX wrote:?
That would be perfectly fine.
In my understanding, this should still depend on D73086 because this revision requires the dumper for the test(s).
Rebase!
@ikudrin this still depends on D73086, I've not removed parent-child relationship of revisions.
nit: Modified macro header comment emission. Previously we were emitting lineptr.
Based on @ikudrin comment on D73086 this is modified to debug_line_offset for consistency and correlation with v5 macro definition in spec.
Thanks for this!
Since most of this patch is reviewed already and this was blocking on D73086. Now D73086 is mostly ready to land so could you guys @dblaikie and @ikudrin can share some final comments on this one also.
Rather than duplicating the code here from DwarfCompileUnit::initStmtList, please refactor so that this value is computed once and shared from there. (perhaps DwarfCompileUnit can have a getLineTableStartSym function that can be used from here.
Addressed review comments by @dblaikie. Thanks for this!
-Refactored and rebased on trunk.
-Added a brief descriptive comment stating intention of the test case.
-Edited summary to remove previously stated objdump based testing statement.
Looks good to me - please wait for @ikudrin to circle back on this and approve it as well.
The test fails because this line lacks the RUN: prefix.
The function @main() and its dependencies are not required for the test. Please, shrink the test so that it includes only that is necessary.
Addressed comments by @ikudrin. Thanks for this!
-Reduced the test case to minimal.
Sorry, somehow the presence of line continuation(Previously inserted since the RUN line was long) was causing this test to be UnResolved.
Test has unterminated run lines (with '\')
Unresolved Tests (1):
LLVM :: DebugInfo/X86/debug-macro-v5.ll
Anyways removed the line continuation, Now this is passing.
LGTM. | https://reviews.llvm.org/D72828?id=238723 | CC-MAIN-2021-25 | refinedweb | 2,093 | 57.67 |
Behaviors is one of the extremely useful features in Xamarin.Forms that allows the user to add a new functionality in an already existing element in the view. Programmers just have to create a class that inherits from Behavior<T> where ‘T’ is an Element which is being extended. ListView is a control to store list of objects whose source might be static data from the web. But once in a while programmers need to get limited data time as a user scrolls (For example for news, a user might need to get 10 pieces of news at a time as news in the server may be in the thousands in number causing the app to crash). As Infinite scrolling is not a feature in ListView we have to insert a piece of code to get this functionality.
Create a new Xamarin.Forms App and select PCL(Portable Class Library),
Create a Folder named “Behaviors” and add a class InfiniteScroll inside it,
Inherit the class Behavior<ListView> which lies in namespace Xamarin.Forms and add the following codes,
The above code will create a ‘LoadMoreCommandProperty’ which is a type of command and will be invoked when the last item of list is diaplayed. We use OnAttachedTo and OnDetachingFrom methods to bind our context and invoke the command when ListView ItemAppearing event is triggered on last Item. Now that our bindable property is complete we need to create a listview in MainPage to get the functionality working.
But before that add a repository class which will return data page wise,
As we are using MVVM pattern we will create a new ViewModel which will contain a command and a List which contains the items of ListView. For this create a folder ViewModel and add class NewsViewModel. NewsViewModel will get data from the repository and notify when new data is loaded to listview.
Code in NewsViewModel
Now, Finally add a listview in MainPage,
Now set the BindingContext to new instance of NewsViewModel.
Now if you run the app you will get new data as you scroll and you can use rest service in place of repository in your application.
View All | http://www.c-sharpcorner.com/article/infinite-scrolling-listview-for-xamarin-forms-app-using-behaviors/ | CC-MAIN-2018-09 | refinedweb | 359 | 57.5 |
Hello,
It seems I cannot addChild a BitmapImage. It does allow me to do so with the Image component.
Is that bad practice?
Also, in the MXML code for views, should I preffer BitmapImage to Image?
Thank you.
BitmapImage is lighter weight than Image so if you don't need any features of the spark Image then BitmapImage is recommended.
BitmapImage is a lightweight GraphicElement that (typically) needs to be inside of a Group. If you add a Group to your renderer and put the BitmapImage inside of it that should be faster than just adding a spark Image (make sure to test to verify this in your case).
In the case of IconItemRenderer it has an extra optimization that allows it to handle a BitmapImage directly without requiring an extra Group. This is done by implementing the IGraphicElementContainer and ISharedDisplayObject interfaces.
Thank you, much clearer now.
I was aware that I can add it to a Group, but was worried Group+BitmapImage >> Image.
I studied the IconItemRenderer pretty good, and the only part that is still blurry, is the iconDisplay and all of its family of other auxiliary properties and namespace.
In anycase, I've decided to extend IconItemRenderer instead of LabelItemRender+own creation of decorator.
It seems to me that the IconItemRenderer is much faster and reliable for extending than the LabelItemRenderer (which is inherited by the IconItemRenderer).
The desktop ImageSkin has a few Groups in it which is why I suspect that a simple Group + BitmapImage would be faster. On mobile the ImageSkin is optimized so the difference might not be as obvious. I suspect that Group + BitmapImage is faster, but haven't verified that. As with any performance work you should probably test spark Image vs. Group + BitmapImage to know for sure.
Yup, thanks again. | https://forums.adobe.com/thread/884656 | CC-MAIN-2018-30 | refinedweb | 299 | 65.01 |
Coffeehouse Thread60 posts
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Interviewing programmers
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Pagination
What does the keyword virtual mean? When would you use it?
When would you use an abstract class over using an interface?
What can you do to ensure that your objects are properly disposed of by GC?
What happens when you call GC.Collect()? Why would you call it? What's the cost? What happens?
Implement ToString()
C
My approach
Start off by asking a few softball programming trivia questions that anyone with any experience should be able to answer. If they fail these simple questions, it's obviously time to say "Next!".
Then follow up by asking them to describe the project they're currently working on and some of the specific techniques they're using. Ask them specific, open ended, questions about it like, "Why did you use generic List rather than an array?" or "How did you decide that XML serialization was the best approach?" The idea is to get a taste of how they organize their thoughts on familiar ground.
The last part, if they've done well so far, is to present them with a sample problem that fits within your domain. For example, let's say you load a lot of oddly formatted raw data files into database tables. Ask them how they would approach the problem and have them pseudo-code out their solution. This will give you an idea of how they think when presented with something new.
You can also ask off-beat thinking questions like "Everybody knows why manhole covers are round but why are septic tank covers square?"
Mine does not have one
public class LittleguruFoo
{
public new bool ToString
{
get { throw new NotImplementedException("I don't have a ToString method!"); }
}
}
Hehe
Foo f = new Foo();
f.ToString(); // Compiler error.
object f2 = new Foo();
f2.ToString(); // Now I have one again. Holy cow, I can't escape.
And if that supports deterministic finalisation. Then ask about the Dispose pattern. (which is what i do, and did today)
How does new differ from override; best illustrated by a piece of sample code; where each class has a Message method printing the class name; then declare all 3 classes as the base type.
In the last 3 months only 1 person has gotten the final output right.
Well you haven't phrased your question properly. Write it out fully and I'll give it a stab.
Good points!
We use polymorphism when we are passing objects between the different tiers in our application. Any object that is exposed on the web tier and is passed back to the business tier MUST inherit off of an interface. The business tier and data access tier MUST use the same interface. In this case polymorphism is not used for code reuse but instead to keep our heads on straight. Especially since there are different programmers working in the different tiers.
I'll do it in the morning; if someone else hasn't done it.
Basically in BaseClass have a vitual method Message which prints "BaseClass". In SubClass1, derived from BaseClass override that method and print SubClass1, in SubClass2 new the method and print SubClass2. Now declare 3 variables of class BaseClass, one an instance of BaseClass, one an instance of SubClass1, one an instance of SubClass2. Call Message on each. What gets printed.
Pah, shift to late bound duck typed objects and remove that dependancy on a base object
I like questions that let the candidate and interviewer to run with them. It puts people at ease and it only gets as complicated as you want/need it to. So, in their basic form if the candidate can't even answer it to begin with then you do not have to go farther. But as they progress take them down a path and let the conversation kind of build on itself.
You could white board or on paper (which I hate personally) offer several items and start simple and ask to see them related programmatically. Just a half-dozen objects should be good. Just make sure they are different. So maybe some would be properties like type or color and some are obviously extended from other base classes to anyone who has actually written code. Make sure it's something simple and could go different directions:
1. Helicopter
2. Bird
3. Operator
4. Dump Truck
5. Seagull
6. Green
If they can't see a seagull and extending bird its over. Maybe they pose a question "Is an operator a person? Can they drive and fly?" Whatever. You should be looking intelligence and problem solving abilities. Posing the right questions and then constucting the answers in C#.
You could draw out a scenario all the way to building a small app on a white board. What methods would these objects have? How would they work? When?
I'm with Mr. Awesome here. I much prefer asking programmers questions around, "How would you design or program something" rather than really specific nit-pick topics.
There's so much an engineer has to know that it's impossible (for me at least) to keep it all in my head. I'd want to see creativity, how they approach the problem. Who cares what the enums for some specific API are, that's what MSDN is for.
Generally too I find that even just having a casual conversation about software and programming has been enough for me in the past to weed genuine candidates from BS'ers.
Ooh, good. Are you asking because of the use of ToString() here or because you think there's an inefficinet concat happening--because it's really not. C# 2 will use String.Concat(string,string,string) here. It's probably not any worse than using String.Format.
Riffing on Dispose:
a) Why would you implement IDispose?
b) What's a finalizer?
c) What should you clean up (or not) when Dispose is called?
d) What should you clean up (or not) when the finalizer is called?
e) What's the function that I always forget to call when I implement Dispose? (Interpret as "What's the function you should call when you implement Dispose?")
How many people do you suppose get c) and d) correct?
I too prefer this sort of direction when interviewing potential candidates.
Tell you what, as sad as it seems, I went to bed thinking about this thread last night. I was just about to shut the PC down for the night and thought I'd catch up on the evenings Coffeehouse postings and read this one. Do people really go this nasty and technical in interviews? I think I'd sooner be interigated by Jack Bauer than attend some peoples interviews in this thread
Actually, I'll go through those common question regarding OOP concepts. And then limit my question to those related to the job function.
Say that I'm hiring a Web Programmer knowing C#, it may not be so important to the interviewee whether he/she knows about IDispose/Finalization or not if our pages don't really touch them, however I'll want to make sure that know something about difference between Profile, Session and Viewstate, and of course, the events and their usage in Page Lifecycle.
If you're hiring Winform programmer for Database related programs, you'll probably want to ask them if they know anything about how to get things done in commonly used 3rd party tools like Crystal Report, as well as the ability to write SQL statements, or even stored procedures.
The ideas of best fit questions in interviews come from your currently working projects. Maybe pulling out helper functions that you think you'll able to finish in 5 minutes and ask them to implement in 15 minutes will be good enough.
I don't remember all the details for all the .NET framework object, and I don't expect candidates to either. The reason I ask 'nasty' questions is not so much for the answer the candidate gives, but for how they react and handle a question that they don't know.
If they just answer 'I don't know', or 'I'd have to Google that', then I take that as a positive. If they bluster and bullsh*t, then I take that as a negative. If they ask for the correct answer then that's a gold star.
I prefer not to ask simple answer questions, but questions that could lead to a brief discussion so I can gauge the intellect of the candidate.
We use sneaky non-technical questions too:
Recently we've been interviewing for a graduate tester position. We ask 'Where do you see yourself in three to five years time?'
If they say something like 'I don't plan that far ahead.' or 'I don't mind as long as I'm learning' then that's fine. If they say 'Running my own software firm' or (the classic) 'I plan to become a Developer' then that's a bad sign (we're going to train them as testers and they're just intending to use us as a leg up into a different career, thus wasting our efforts).
It's a bit of a game/battle : we are trying to sell our company to the top candidates because we want good employees while the candidates are trying to sell themselves to us because they want the job. The interview is where the interviewer and the candidates try and find the complete truth (Does the interviewer have any frustrations about the job? Does the candidate plan to stay for at least three years? How much overtime does the interviewer really do? Is the candidate really as smart as they appear in their CV?)
As an interviewer I try to be open, friendly, and honest, but you can't badmouth company culture/coworkers/bosses/customers/whatever in front of a candidate as it's not professional. At the same time you want the candidate to have a clear picture of what the job is like because there's no point in hiring them only to have them leave after a month when they realise the job is not what was outlined in the interview. So the interview (for me) becomes a subtle game of psychology to try and get/give the truth. Nasty technical questions are a part of that.
Herbie
Anyone has an opinion on multi-on-one vs. one-on-one interviews? Personally, I think being interviewed by many people is fun, but I hear it could be stressful, too. | https://channel9.msdn.com/Forums/Coffeehouse/257126-Interviewing-programmers?page=2 | CC-MAIN-2018-05 | refinedweb | 1,811 | 72.76 |
things easy, MS has a project template for Silverlight Navigation. This project provides basic infrastructure needed. Just check on that and you would get a direction to start on.
Not sure if this project was there with SL3 but it is there with SL4
OK I know the navigation template and without going into details I am not getting anywhere fast. The information supplied is confusing and examples on the web out dated. I cant find a basic example of page switching like my basic example above so that is why i am asking here.
HTH
Ashok
This CPTE Certified Penetration Testing Engineer course covers everything you need to know about becoming a Certified Penetration Testing Engineer. Career Path: Professional roles include Ethical Hackers, Security Consultants, System Administrators, and Chief Security Officers.
To do this in new Page Navigation, watch video at
HTH
Ashok
I am not sure if this is outdated or has errors.
re-create the navigation application by following steps.
It will work with VS 2008 and Silverlight 3.0.
HTH
Ashok
Open in new window
xmlns:navigation="clr-name
Open in new window
xmlns:local="clr-namespace
which gives an error. did you try my code in VS2008?
You are using <sdk:Frame where sdk refers to the namespace
""
whereas in the tutorial, <navigation:Frame is used and navigation refers to the namespace
"clr-namespace:System.Wind
Error 1 The type 'ResourceDictionary' is inside a ResourceDictionary and does not have a key. D:\silverlight\nav1\nav1\A
Open in new window
I AM buillding a small page.
In order to have a page switching ap I needed to add to app.xaml and i cant get around it as it is part of the solution. The error was in default code whci has nothong to do with what I typed in.
Why is it so hard get a simple page switching code in silverlight that switches actual pages and not frames. I dont know how to do this ! I just need a working framework.
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Ashok | https://www.experts-exchange.com/questions/25886406/silverlight-page-switch.html | CC-MAIN-2018-30 | refinedweb | 376 | 66.03 |
LOCK
Synopsis
LOCK:pc L:pc LOCK:pc +lockname#locktype:timeout,... L:pc +lockname#locktype:timeout,... LOCK:pc +(lockname#locktype,...):timeout,... L:pc +(lockname#llocktype,...):timeout,...
Arguments
Description
There are two basic forms of the LOCK command:
LOCK without Arguments
The argumentless LOCK releases (unlocks) all locks currently held by the process in all namespaces. This includes exclusive and shared locks, both local and global. It also includes all accumulated incremental locks. For example, if there are three incremental locks on a given lock name, InterSystems IRIS releases all three locks and removes the lock name entry from the lock table.
If you issue an argumentless LOCK during a transaction, InterSystems IRIS places all locks currently held by the process in a Delock state until the end of the transaction. When the transaction ends, InterSystems IRIS releases the locks and removes the corresponding lock name entries from the lock table.
The following example applies various locks during a transaction, then issues an argumentless LOCK to release all of these locks. The locks are placed in a Delock state until the end of the transaction. The HANG commands give you time to check the lock’s ModeCount in the Lock Table:
TSTART LOCK +^a(1) // ModeCount: Exclusive HANG 2 LOCK +^a(1)#"E" // ModeCount: Exclusive/1+1e HANG 2 LOCK +^a(1)#"S" // ModeCount: Exclusive/1+1e,Shared HANG 2 LOCK // ModeCount: Exclusive/1+1e->Delock,Shared->Delock HANG 10 TCOMMIT // ModeCount: locks removed from table
Argumentless LOCK releases all locks held by the process without applying any locks. Completion of a process also releases all locks held by that process.
LOCK with Arguments
LOCK with arguments specifies one or more lock names on which to perform locking and unlocking operations. What lock operation InterSystems IRIS performs depends on the lock operation indicator argument you use:
LOCK lockname unlocks all locks previously held by the process in all namespaces, then applies a lock on the specified lock name(s).
LOCK +lockname applies a lock on the specified lock name(s) without unlocking any previous locks. This allows you to accumulate different locks, and allows you to apply incremental locks to the same lock.
LOCK -lockname performs an unlock operation on the specified lock name(s). Unlocking decrements the lock count for the specified lock name; when this lock count decrements to zero, the lock is released.
A lock operation may immediately apply the lock, or it may place the lock request on a wait queue pending the release of a conflicting lock by another process. A waiting lock request may time out (if you specify a timeout) or may wait indefinitely (until the end of the process).
LOCK with Multiple Lock Names
You can specify multiple locks with a single LOCK command in either of two ways:
Without Parentheses: By specifying multiple lock arguments without parentheses as a comma-separated list, you can specify multiple independent lock operations, each of which can have its own timeout. (This is functionally identical to specifying a separate LOCK command for each lock argument.) Lock operations are performed in strict left-to-right order. For example:
LOCK var1(1):10,+var2(1):15Copy code to clipboard
Multiple lock arguments without parentheses each can have their own lock operation indicator and their own timeout argument. However, if you use multiple lock arguments, be aware that a lock operation without a plus sign lock operation indicator unlocks all prior locks, including locks applied by an earlier part of the same LOCK command. For example, the command LOCK ^b(1,1), ^c(1,2,3), ^d(1) would be parsed as three separate lock commands: the first releasing the processes’ previously held locks (if any) and locking ^b(1,1), the second immediately releasing ^b(1,1) and locking ^c(1,2,3), the third immediately releasing ^c(1,2,3) locking ^d(1). As a result, only ^d(1) would be locked.
With Parentheses: By enclosing a comma-separated list of lock names in parentheses, you can perform these locking operations on multiple locks as a single atomic operation. For example:
LOCK +(var1(1),var2(1)):10Copy code to clipboard
All lock operations in a parentheses-enclosed list are governed by a single lock operation indicator and a single timeout argument; either all of the locks are applied or none of them are applied. A parentheses-enclosed list without a plus sign lock operation indicator unlocks all prior locks then locks all of the listed lock names.
The maximum number of lock names in a single LOCK command is limited by several factors. One of them is the number of argument stacks available to a process: 512. Each lock reference requires 4 argument stacks, plus 1 additional argument stack for each subscript level. Therefore, if the lock references have no subscripts, the maximum number of lock names is 127. If the locks have one subscript level, the maximum number of lock names is 101. This should be taken as a rough guide; other factors may further limit the number of locks names in a single LOCK. There is no separate limit on number of locks for a remote system.
Arguments
pc
An optional postconditional expression that can make the command conditional. InterSystems IRIS executes the LOCK command if the postconditional expression is true (evaluates to a nonzero numeric value). InterSystems IRIS does not execute the command if the postconditional expression is false (evaluates to zero). You can specify a postconditional expression on an argumentless LOCK command or a LOCK command with arguments. For further details, refer to Command Postconditional Expressions in Using ObjectScript.
lock operation indicator
The lock operation indicator is used to apply (lock) or remove (unlock) a lock. It can be one of the following values:
If your LOCK command contains multiple comma-separated lock arguments, each lock argument can have its own lock operation indicator. InterSystems IRIS parses this as multiple independent LOCK commands.
lockname
A lockname is the name of a lock for a data resource; it is not the data resource itself. That is, your program can specify a lock named ^a(1) and a variable named ^a(1) without conflict. The relationship between the lock and the data resource is a programming convention; by convention, processes must acquire the lock before modifying the corresponding data resource.
Lock names are case-sensitive. Lock names follow the same naming conventions as the corresponding local variables and global variables. A lock name can be subscripted or unsubscripted. Lock subscripts have the same naming conventions and maximum length and number of levels as variable subscripts. In InterSystems IRIS, the following are all valid and unique lock names: a, a(1), A(1), ^a, ^a(1,2), ^A(1,1,1). For further details, see the Variables chapter of Using ObjectScript.
For performance reasons, it is recommended you specify lock names with subscripts whenever possible. For example, ^a(1) rather than ^a. Subscripted lock names are used in documentation examples.
Lock names can be local or global. A lock name such as A(1) is a local lock name. It applies only to that process, but does apply across namespaces. A lock name that begins with a caret (^) character is a global lock name; the mapping for this lock follows the same mapping as the corresponding global, and thus can apply across processes, controlling their access to the same resource. (See Global Structure in Using Globals.)
Process-private global names can not be used as lock names. Attempting to use a process-private global name as a lock name performs no operation and completes without issuing an error.
A lock name can represent a local or global variable, subscripted or unsubscripted. It can be an implicit global reference, or an extended reference to a global on another computer. (See Global Structure in Using Globals.)
The data resource corresponding to a lock name does not need to exist. For example, you may lock the lock name ^a(1,2,3) whether or not a global variable with the same name exists. Because the relationship between locks and data resources is an agreed-upon convention, a lock may be used to protect a data resource with an entirely different name.
locktype
A letter code specifying the type of lock to apply or remove. locktype is an optional argument; if you omit locktype, the lock type defaults to an exclusive non-escalating lock. If you omit locktype, you must omit the pound sign (#) prefix. If you specify locktype, the syntax for lock type is a mandatory pound sign (#), followed by quotation marks enclosing one or more lock type letter codes. Lock type letter codes can be specified in any order and are not case-sensitive. The following are the lock type letter codes:
S: Shared lock
Allows multiple processes to simultaneously hold nonconflicting locks on the same resource. For example, two (or more) processes may simultaneously hold shared locks on the same resource, but an exclusive lock limits the resource to one process. An existing shared lock prevents all other processes from applying an exclusive lock, and an existing exclusive lock prevents all other processes from applying a shared lock on that resource. However, a process can first apply a shared lock on a resource and then the same process can apply an exclusive lock on the resource, upgrading the lock from shared to exclusive. Shared and Exclusive lock counts are independent. Therefore, to release such a resource it is necessary to release both the exclusive lock and the shared lock. All locking and unlocking operations that are not specified as shared (“S”) default to exclusive.
A shared lock may be incremental; that is, a process may issue multiple shared locks on the same resource. You may specify a shared lock as escalating (“SE”) when locking and unlocking. When unlocking a shared lock, you may specify the unlock as immediate (“SI”) or deferred (“SD”). To view the current shared locks with their increment counts for escalating and non-escalating lock types, refer to the system-wide lock table, described in the “Lock Management” chapter of Using ObjectScript.
E: Escalating lock
Allows you to apply a large number of concurrent locks without overflowing the lock table. By default, locks are non-escalating. When applying a lock, you can use locktype “E” to designate that lock as escalating. When releasing an escalating lock, you must specify locktype “E” in the unlock statement. You can designate both exclusive locks and shared (“S”) locks as escalating.
Commonly, you would use escalating locks when applying a large number of concurrent locks at the same subscript level. For example LOCK +^mylock(1,1)#"E",+^mylock(1,2)#"E",+^mylock(1,3)#"E"....
The same lock can be concurrently applied as a non-escalating lock and as an escalating lock. For example, ^mylock(1,1) and ^mylock(1,1)#"E". InterSystems IRIS counts locks issued with locktype “E” separately in the lock table. For information on how escalating and non-escalating locks are represented in the lock table, refer to the “Lock Management” chapter of Using ObjectScript.
When the number of “E” locks at a subscript level reaches a threshold number, the next “E” lock requested for that subscript level automatically attempts to lock the parent node (the next higher subscript level). If it cannot, no escalation occurs. If it successfully locks the parent node, it establishes one parent node lock with a lock count corresponding to the number of locks at the lower subscript level, plus 1. The locks at the lower subscript level are released. Subsequent “E” lock requests to the lower subscript level further increment the lock count of this parent node lock. You must unlock all “E” locks that you have applied to decrement the parent node lock count to 0 and de-escalate to the lower subscript level. The default lock threshold is 1000 locks; lock escalation occurs when the 1001st lock is requested.
Note that once locking is escalated, lock operations preserve only the number of locks applied, not what specific resources were locked. Therefore, failing to unlock the same resources that you locked can cause “E” lock counts to get out of sync.
In the following example, lock escalation occurs when the program applies the lock threshold + 1 “E” lock. This example shows that lock escalation both applies a lock on the next-higher subscript level and releases the locks on the lower subscript level:
Main TSTART SET thold=$SYSTEM.SQL.Util.GetOption("LockThreshold") WRITE "lock escalation threshold is ",thold,! SET almost=thold-5 FOR i=1:1:thold+5 { LOCK +dummy(1,i)#"E" IF i>almost { IF ^$LOCK("dummy(1,"_i_")","OWNER") '= "" {WRITE "lower level lock applied at ",i,"th lock ",! } ELSEIF ^$LOCK("dummy(1)","OWNER") '= "" {WRITE "lock escalation",! WRITE "higher level lock applied at ",i,"th lock ",! QUIT } ELSE {WRITE "No locks applied",! } } } TCOMMITCopy code to clipboard
Note that only “E” locks are counted towards lock escalation. The following example applies both default (non-“E”) locks and “E” locks on the same variable. Lock escalation only occurs when the total number of “E” locks on the variable reaches the lock threshold:
Main TSTART SET thold=$SYSTEM.SQL.Util.GetOption("LockThreshold") WRITE "lock escalation threshold is ",thold,! SET noE=17 WRITE "setting ",noE," non-escalating locks",! FOR i=1:1:thold+noE { IF i < noE {LOCK +a(6,i)} ELSE {LOCK +a(6,i)#"E"} IF ^$LOCK("a(6)","OWNER") '= "" { WRITE "lock escalation on lock a(6,",i,")",! QUIT } } TCOMMITCopy code to clipboard
Unlocking “E” locks is the reverse of the above. When locking is escalated, unlocks at the child level decrement the lock count of the parent node lock until it reaches zero (and is unlocked); these unlocks decrementing a count, they are not matched to specific locks. When the parent node lock count reaches 0, the parent node lock is removed and “E” locking de-escalates to the lower subscript level. Any subsequent locks at the lower subscript level create specific locks at that level.
The “E” locktype can be combined with any other locktype. For example, “SE”, “ED”, “EI”, “SED”, “SEI”. When combined with the “I” locktype it permits unlocks of “E” locks to occur immediately when invoked, rather than at the end of the current transaction. This “EI” locktype can minimize situations where locking is escalated.
Commonly, “E” locks are automatically applied for SQL INSERT, UPDATE, and DELETE operations within a transaction. However, there are specific limitations on SQL data definition structures that support “E” locking. Refer to the specific SQL commands for details.
I: Immediate unlock
Immediately releases a lock, rather than waiting until the end of a transaction:
Specifying “I” when unlocking a non-incremented (lock count 1) lock immediately releases the lock. By default, an unlock does not immediately release a non-incremented lock. Instead, when you unlock a non-incremented lock InterSystems IRIS maintains that lock in a delock state until the end of the transaction. Specifying “I” overrides this default behavior.
Specifying “I” when unlocking an incremented lock (lock count > 1) immediately releases the incremental lock, decrementing the lock count by 1. This is the same behavior as a default unlock of an incremented lock.
The “I” locktype is used when performing an unlock during a transaction. It has the same effect on InterSystems IRIS unlock behavior whether the lock was applied within the transaction or outside of the transaction. The “I” locktype performs no operation if the unlock occurs outside of a transaction. Outside of a transaction, an unlock always immediately releases a specified lock.
“I” can only be specified for an unlock operation; it cannot be specified for a lock operation. “I” can be specified for an unlock of a shared lock (#"SI") or an exclusive lock (#"I"). Locktypes “I” and “D” are mutually exclusive. “IE” can be used to immediately unlock an escalating lock.
This immediate unlock is shown in the following example:
TSTART LOCK +^a(1) // apply lock ^a(1) LOCK -^a(1) // remove (unlock) ^a(1) // An unlock without a locktype defers the unlock // of a non-incremented lock to the end of the transaction. WRITE "Default unlock within a transaction.",!,"Go look at the Lock Table",! HANG 10 // This HANG allows you to view the current Lock Table LOCK +^a(1) // reapply lock ^a(1) LOCK -^a(1)#"I" // remove (unlock) lock ^a(1) immediately // this removes ^a(1) from the lock table immediately // without waiting for the end of the transaction WRITE "Immediate unlock within a transaction.",!,"Go look at the Lock Table",! HANG 10 // This HANG allows you to view the current Lock Table // while still in the transaction TCOMMITCopy code to clipboard
D: Deferred unlock
Controls when an unlocked lock is released during a transaction. The unlock state is deferred to the state of the previous unlock of that lock. Therefore, specifying locktype “D” when unlocking a lock may result in either an immediate unlock or a lock placed in delock state until the end of the transaction, depending on the history of the lock during that transaction. The behavior of a lock that has been locked/unlocked more than once differs from the behavior of a lock that has only been locked once during the current transaction.
The “D” unlock is only meaningful for an unlock that releases a lock (lock count 1), not an unlock that decrements a lock (lock count > 1). An unlock that decrements a lock is always immediately released.
“D” can only be specified for an unlock operation. “D” can be specified for a shared lock (#"SD") or an exclusive lock (#"D"). “D” can be specified for a escalating (“E”) lock, but, of course, the unlock must also be specified as escalating (“ED”). Lock types “D” and “I” are mutually exclusive.
This use of “D” unlock within a transaction is shown in the following examples. The HANG commands give you time to check the lock’s ModeCount in the Lock Table.
If the lock was only applied once during the current transaction, a “D” unlock immediately releases the lock. This is the same as “I” behavior. This is shown in the following example:
TSTART LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1)#"D" // Lock Table ModeCount: null (immediate unlock) HANG 10 TCOMMITCopy code to clipboard
If the lock was applied more than once during the current transaction, a “D” unlock reverts to the prior unlock state.
If the last unlock was a standard unlock, the “D” unlock reverts unlock behavior to that prior unlock’s behavior — to defer unlock until the end of the transaction. This is shown in the following examples:
TSTART LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1) // Lock Table ModeCount: Exclusive WRITE "1st unlock",! HANG 5 LOCK -^a(1)#"D" // Lock Table ModeCount: Exclusive->Delock WRITE "2nd unlock",! HANG 5 TCOMMITCopy code to clipboard
TSTART LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1) // Lock Table ModeCount: Exclusive->Delock WRITE "1st unlock",! HANG 5 LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1)#"D" // Lock Table ModeCount: Exclusive->Delock WRITE "2nd) // Lock Table ModeCount: Exclusive WRITE "2nd unlock",! HANG 5 LOCK -^a(1)#"D" // Lock Table ModeCount: Exclusive->Delock WRITE "3rd unlock",! HANG 5 TCOMMITCopy code to clipboard
If the last unlock was an “I” unlock, the “D” unlock reverts unlock behavior to that prior unlock’s behavior — to immediately unlock the lock. This is shown in the following examples:
TSTART LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1)#"I" // Lock Table ModeCount: null (immediate unlock) WRITE "1st unlock",! HANG 5 LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1)#"D" // Lock Table ModeCount: null (immediate unlock) WRITE "2nd unlock",! HANG 5 TCOMMITCopy code to clipboard
TSTART LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1)#"I" // Lock Table ModeCount: Exclusive WRITE "1st unlock",! HANG 5 LOCK -^a(1)#"D" // Lock Table ModeCount: null (immediate unlock) WRITE "2nd unlock",! HANG 5 TCOMMITCopy code to clipboard
If the last unlock was a “D” unlock, the “D” unlock follows the behavior of the last prior non-“D” lock:
TSTART LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1)#"D" // Lock Table ModeCount: Exclusive WRITE "1st unlock",! HANG 5 LOCK -^a(1)#"D" // Lock Table ModeCount: null (immediate unlock) WRITE "2nd unlock",! HANG 5 TCOMMITCopy code to clipboard
TSTART LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK +^a(1) // Lock Table ModeCount: Exclusive LOCK -^a(1) // Lock Table ModeCount: Exclusive/2 WRITE "1st unlock",! HANG 5 LOCK -^a(1)#"D" // Lock Table ModeCount: Exclusive WRITE "2nd unlock",! HANG 5 LOCK -^a(1)#"D" // Lock Table ModeCount: Exclusive->Delock WRITE "3rd)#"D" // Lock Table ModeCount: Exclusive WRITE "2nd unlock",! HANG 5 LOCK -^a(1)#"D" // Lock Table ModeCount: null (immediate unlock) WRITE "3rd unlock",! HANG 5 TCOMMITCopy code to clipboard
timeout
The number of seconds or fractions of a second to wait for a lock request to succeed before timing out. timeout is an optional argument. If omitted, the LOCK command waits indefinitely for a resource to be lockable; if the lock cannot be applied, the process will hang. The syntax for timeout is a mandatory colon (:), followed by an numeric value or an expression that evaluates to an numeric value.
Valid values are seconds with or without fractional tenths or hundredths of a second. Thus the following are all valid timeout values: :5, :5.5, :0.5, :.5, :0.05, :.05. Any value smaller than :0.01 is parsed as zero. A value of zero invokes one locking attempt before timing out. A negative number is equivalent to zero.
Commonly, a lock will wait if another process has a conflicting lock that prevents this lock request from acquiring (holding) the specified lock. The lock request waits until either a lock is released that resolves the conflict, or the lock request times out. Terminating the process also ends (deletes) pending lock requests. Lock conflict can result from many situations, not just one process requesting the same lock held by another process. A detailed explanation of lock conflict and lock request wait states is provided in the “Lock Management” chapter of Using ObjectScript.
If you use timeout and the lock is successful, InterSystems IRIS sets the $TEST special variable to 1 (TRUE). If the lock cannot be applied within the timeout period, InterSystems IRIS sets $TEST to 0 (FALSE). Issuing a lock request without a timeout has no effect on the current value of $TEST. Note that $TEST can also be set by the user, or by a JOB, OPEN, or READ timeout.
The following example applies a lock on lock name ^abc(1,1), and unlocks all prior locks held by the process:
LOCK ^abc(1,1)
This command requests an exclusive lock: no other process can simultaneously hold a lock on this resource. If another process already holds a lock on this resource (exclusive or shared), this example must wait for that lock to be released. It can wait indefinitely, hanging the process. To avoid this, specifying a timeout value is strongly recommended:
LOCK ^abc(1,1):10
If a LOCK specifies multiple lockname arguments in a comma-separated list, each lockname resource may have its own timeout (syntax without parentheses), or all of the specified lockname resources may share a single timeout (syntax with parentheses).
Without Parentheses: each lockname argument can have its own timeout. InterSystems IRIS parses this as multiple independent LOCK commands, so the timeout of one lock argument does not affect the other lock arguments. Lock arguments are parsed in strict left-to-right order, with each lock request either completing or timing out before the next lock request is attempted.
With Parentheses: all lockname arguments share a timeout. The LOCK must successfully apply all locks (or unlocks) within the timeout period. If the timeout period expires before all locks are successful, none of the lock operations specified in the LOCK command are performed, and control returns to the process.
InterSystems IRIS performs multiple operations in strict left-to-right order. Therefore, in LOCK syntax without parentheses, the $TEST value indicates the outcome of the last (rightmost) of multiple lockname lock requests.
In the following examples, the current process cannot lock ^a(1) because it is exclusively locked by another process. These examples use a timeout of 0, which means they make one attempt to apply the specified lock.
The first example locks ^x(1) and ^z(1). It sets $TEST=1 because ^z(1) succeeded before timing out:
LOCK +^x(1):0,+^a(1):0,+^z(1):0
The second example locks ^x(1) and ^z(1). It sets $TEST=0 because ^a(1) timed out. ^z(1) did not specify a timeout and therefore had no effect on $TEST:
LOCK +^x(1):0,+^a(1):0,+^z(1)
The third example applies no locks, because a list of locks in parentheses is an atomic (all-or-nothing) operation. It sets $TEST=0 because ^a(1) timed out:
LOCK +(^x(1),^a(1),^z(1)):0
Using the Lock Table to View and Delete Locks System-wide
InterSystems IRIS maintains a system-wide lock table that records all locks that are in effect and the processes that have applied them. The system manager can display the existing locks in the Lock Table or remove selected locks using the Management Portal interface or the ^LOCKTAB utility, as described in the “Lock Management” chapter of Using ObjectScript. You can also use the %SYS.LockQuery class to read lock table information. From the %SYS namespace you can use the SYS.Lock class to manage the lock table.
You can use the Management Portal to view held locks and pending lock requests system-wide. Go to the Management Portal, select System Operation, select Locks, then select View Locks. For further details on the View Locks table refer to the “Lock Management” chapter of Using ObjectScript.
You can use the Management Portal to remove (delete) locks currently held on the system. Go to the Management Portal, select System Operation, select Locks, then select Manage Locks. For the desired process (Owner) click either “Remove” or “Remove All Locks for Process”.
Removing a lock releases all forms of that lock: all increment levels of the lock, all exclusive, exclusive escalating, and shared versions of the lock. Removing a lock immediately causes the next lock waiting in that lock queue to be applied.
You can also remove locks using the SYS.Lock.DeleteOneLock() and SYS.Lock.DeleteAllLocks() methods.
Removing a lock requires WRITE permission. Lock removal is logged in the audit database (if enabled); it is not logged in messages.log.
Incremental Locking and Unlocking
Incremental locking permits you to apply the same lock multiple times: to increment the lock. An incremented lock has a lock count of > 1. Your process can subsequently increment and decrement this lock count. The lock is released when the lock count decrements to 0. No other process can acquire the lock until the lock count decrements to 0. The lock table maintains separate lock counts for exclusive locks and shared locks, and for escalating and non-escalating locks of each type. The maximum incremental lock count is 32,766. Attempting to exceed this maximum lock count results in a <MAX LOCKS> error.
You can increment a lock as follows:
Plus sign: Specify multiple lock operations on the same lock name with the plus sign lock operation indicator. For example: LOCK +^a(1) LOCK +^a(1) LOCK +^a(1) or LOCK +^a(1),+^a(1),+^a(1) or LOCK +(^a(1),^a(1),^a(1)). All of these would result in a lock table ModeCount of Exclusive/3. Using the plus sign is the recommended way to increment a lock.
No sign: It is possible to increment a lock without using the plus sign lock operation indicator by specifying an atomic operation performing multiple locks. For example, LOCK (^a(1),^a(1),^a(1)) unlocks all prior locks and incrementally locks ^a(1) three times. This too would result in a lock table ModeCount of Exclusive/3. While this syntax works, it is not recommended.
Unlocking an incremented lock when not in a transaction simply decrements the lock count. Unlocking an incremented lock while in a transaction has the following default behavior:
Decrementing Unlocks: each decrementing unlock immediately release the incremental unlock until the lock count is 1. By default, the final unlock puts the lock in delock state, deferring release of the lock to the end of the transaction. This is always the case when you delock with the minus sign lock operation indicator, whether or not the operation is atomic. For example: LOCK -^a(1) LOCK -^a(1) LOCK -^a(1) or LOCK -^a(1),-^a(1),-^a(1) or LOCK -(^a(1),^a(1),^a(1)). All of these begin with a lock table ModeCount of Exclusive/3 and end with Exclusive->Delock.
Unlocking Prior Resources: an operation that unlocks all prior resources immediately puts an incremented lock into a delock state until the end of the transaction. For example, either LOCK x(3) (lock with no lock operation indicator) or an argumentless LOCK would have the following effect: the incremented lock would begin with a lock table ModeCount of Exclusive/3 and end with Exclusive/3->Delock.
Note that separate lock counts are maintained for the same lock as an Exclusive lock, a Shared lock, a Exclusive escalating lock and a Shared escalating lock. In the following example, the first unlock decrements four separate lock counts for lock ^a(1) by 1. The second unlock must specify all four of the ^a(1) locks to remove them. The HANG commands give you time to check the lock’s ModeCount in the Lock Table.
LOCK +(^a(1),^a(1)#"E",^a(1)#"S",^a(1)#"SE") LOCK +(^a(1),^a(1)#"E",^a(1)#"S",^a(1)#"SE") HANG 10 LOCK -(^a(1),^a(1)#"E",^a(1)#"S",^a(1)#"SE") HANG 10 LOCK -(^a(1),^a(1)#"E",^a(1)#"S",^a(1)#"SE")
If you attempt to unlock a lock name that has no current locks applied, no operation is performed and no error is returned.
Automatic Unlock
When a process terminates, InterSystems IRIS performs an implicit argumentless LOCK to clear all locks that were applied by the process. It removes both held locks and lock wait requests.
Locks on Global Variables
Locking is typically used with global variables to synchronize the activities of multiple processes that may access these variables simultaneously. Global variables differ from local variables in that they reside on disk and are available to all processes. The potential exists, then, for two processes to write to the same global at the same time. In fact, InterSystems IRIS processes one update before the other, so that one update overwrites and, in effect, discards the other.
Global lock names begin with a caret (^) character.
To illustrate locking with global variables, consider the case in which two data entry clerks are concurrently running the same student admissions application to add records for newly enrolled students. The records are stored in a global array named ^student. To ensure a unique record for each student, the application increments the global variable ^index for each student added. The application includes the LOCK command to ensure that each student record is added at a unique location in the array, and that one student record does not overwrite another.
The relevant code in the application is shown below. In this case, the LOCK controls not the global array ^student but the global variable ^index. ^index is a scratch global that is shared by the two processes. Before a process can write a record to the array, it must lock ^index and update its current value (SET ^index=^index+1). If the other process is already in this section of the code, ^index will be locked and the process will have to wait until the other process releases the lock (with the argumentless LOCK command).
READ !,"Last name: ",!,lname QUIT:lname="" SET lname=lname_"," READ !,"First name: ",!,fname QUIT:fname="" SET fname=fname_"," READ !,"Middle initial: ",!,minit QUIT:minit="" SET minit=minit_":" READ !,"Student ID Number: ",!,sid QUIT:sid="" SET rec = lname_fname_minit_sid LOCK ^index SET ^index = ^index + 1 SET ^student(^index)=rec LOCK
The following example recasts the previous example to use locking on the node to be added to the ^student array. Only the affected portion of the code is shown. In this case, the ^index variable is updated after the new student record is added. The next process to add a record will use the updated index value to write to the correct array node.
LOCK ^student(^index) SET ^student(^index) = rec SET ^index = ^index + 1 LOCK /* release all locks */
Note that the lock location of an array node is where the top level global is mapped. InterSystems IRIS ignores subscripts when determining lock location. Therefore, ^student(name) is mapped to the namespace of ^student, regardless of where the data for ^student(name) is stored.
Locks in a Network
In a networked system, one or more servers may be responsible for resolving locks on global variables.
You can use the LOCK command with any number of servers, up to 255.
You can use ^$LOCK to list remote locks, but it cannot list the lock state of a remote lock.
Remote locks held by a client job on a remote server system are released when you call the ^RESJOB utility to remove the client job.
Local Variable Locks
The behavior is as follows:
Local (non-careted) locks acquired in the context of a specific namespace, either because the default namespace is an explicit namespace or through an explicit reference to a namespace, are taken out in the manager's dataset on the local machine. This occurs regardless of whether the default mapping for globals is a local or a remote dataset.
Local (non-careted) locks acquired in the context of an implied namespace or through an explicit reference to an implied namespace on the local machine, are taken out using the manager's dataset of the local machine. An implied namespace is a directory path preceded by two caret characters: "^^dir".
Referencing explicit and implied namespaces is further described in Global Structure in Using Globals.
See Also
^$LOCK structured system variable
Lock Management in Using ObjectScript
Using ObjectScript for Transaction Processing in Using ObjectScript
The Monitoring Locks section of the “Monitoring InterSystems IRIS Using the Management Portal” chapter in Monitoring Guide
The article Locking and Concurrency Control | https://docs.intersystems.com/irisforhealthlatest/csp/docbook/Doc.View.cls?KEY=RCOS_clock | CC-MAIN-2021-17 | refinedweb | 5,797 | 53.21 |
Home > Project Euler, python > Problem euler #46
Problem euler #46
dicembre 7, 2012 Lascia un commento Go to comments?
python:
import time ts = time.time() def is_prime(num): if num <= 1: return False elif num == 2: return True elif num % 2 == 0: return False else: d = 3 r = int(num**0.5) while d <= r: if num % d == 0: return False d += 2 return True def is_odd_goldbach(n): for prime in PRIMES: for m in xrange(1, 50): if n == prime + 2*m**2: return True return False def odds_generator(): n = 35 while True: if not is_prime(n): yield n n += 2 PRIMES = [i for i in xrange(3, 10000) if is_prime(i)] for n in odds_generator(): if not is_odd_goldbach(n): res = n break print "problem euler 41: {} \nelapsed time: {}sec".format(res, time.time() - ts)
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I absolutely love your blog.. Excellent colors &
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Hi, always i used to check web site posts here early in the daylight,
because i enjoy to learn more and more. | https://bancaldo.wordpress.com/2012/12/07/problem-euler-46/ | CC-MAIN-2017-26 | refinedweb | 283 | 76.35 |
limit what they can do. This trial mode limitation is completely up to you. You can allow them to play only a few levels of a game, limit them to adding 5 friends to some list, prevent them from saving an edited picture, whatever. The choice is yours.
With a PhoneGap application on Windows Phone, we can take advantage of the trial mode capability very easily.
First, take a look at this article for implementing trial mode in a Silverlight application (since that is what hosts a PhoneGap application). We’ll be using that as a basis for the code in this blog post.
Specifically, we’ll need to create an application level variable to store the value of the trial mode flag. We do this because checking the flag from the underlying marketplace API takes a little time to do, so for our app to be most responsive, we’ll cache that value in a variable. Also note in the article there are certain times when we ask the marketplace API for that value – when the application starts and when the application resumes. The reason we check it when it resumes is that the user can switch away from the running app, buy the app, then return immediately, and we want to be ready to expose all the features of our app in their full glory when the user comes back!
Open an existing PhoneGap project (or create a new PhoneGap project using the Visual Studio template as described here). Then, follow the section of the trial mode article above article entitled “Checking for a Trial License in Your Application”. That will enable us to cache the value of the trial mode flag. It also provides a way to test it, since when you’re developing, there’s no marketplace installation yet from which to pull the setting. This testing code is contained in a compiler directive #if DEBUG. When the application is published, you should change the value in the drop down at the top of the Visual Studio window from Debug to Release, and you won’t have to remove any of the code, it will just switch to using the other section in the #if directive.
Now that we have the trial mode value cached in our hosting Silverlight application, let’s access it from the code in our PhoneGap application. We’re going to use a Plugin as described in my previous post about SMS messages. The difference here is that when we used a Plugin to send an SMS message, it was fire and forget, and in this case the Plugin must now return that trial mode flag.
We’ll create the C# code first for the Plugin. Right click on the Plugins folder in your project in Solution Explorer, and create a new class called Marketplace.cs. In that class we’ll put the code that our Plugin is going to call. Replace all the code in that class with the following. Note the namespace is important, it ties this class to the PhoneGap Plugin plumbing.
using System;
using System.Net;
using System.Windows;
namespace WP7GapClassLib.PhoneGap.Commands
{
public class Marketplace : BaseCommand
{
public void checkLicense(string args)
{
PluginResult result = new PluginResult(PluginResult.Status.OK, (Application.Current as PGWP7_Trial.App).IsTrial);
this.DispatchCommandResult(result);
}
}
}
This Plugin references our IsTrial variable created in the above article on trial mode, so it’s important to realize it won’t work without that code.
Now that we have the function in the Plugin, we can invoke it from JavaScript inside our PhoneGap application. We’ll create a separate .js file to handle calling into the Plugin framework. Add a new text file in the www folder in the project, named marketplace.js.
function marketplace() {
this.resultCallback = null;
marketplace.prototype.checkLicense = function (callback) {
var args = {}
PhoneGap.exec(callback, null, "Marketplace", "checkLicense", args);
PhoneGap.addConstructor(function () {
if (!window.plugins) {
window.plugins = {};
window.plugins.marketplace = new marketplace();
);
This handles the call to the C# code above and makes the Plugin available to the rest of the code in the PhoneGap project.
Here’s a simple example to check the license. At the top of the index.html page, add a <script> tag referencing the markeplace.js file. Then use this code to check the license. Note that this pattern requires a callback, since that’s how the plugin model returns results. Passing the callback function name as a parameter each time it’s needed is an easy way to keep dependencies out of the marketplace.js file.
<script>
function checkLicense() {
window.plugins.marketplace.checkLicense(licenseCallback);
}
function licenseCallback(isTrial) {
if (isTrial) {
licenseDiv.innerHTML = 'Trial mode, please buy me!';
}
else {
licenseDiv.innerHTML = 'Thanks for buying!';
</script>
This bit of HTML will interact with that JavaScript.
<button onclick="checkLicense();">Check license</button>
<div id="licenseDiv"></div>
Any time you need to check the licensing for your app, just use that pattern. In my next post, we’ll expand the marketplace Plugin with some other features. So get those apps out with trial mode and hook in your users! | http://blogs.msdn.com/b/glengordon/archive/2012/03/02/phonegap-on-wp7-tip-6-trial-mode.aspx | CC-MAIN-2015-06 | refinedweb | 845 | 56.66 |
Felgo 3.5.0 adds support for WebAssembly (WASM). This allows you to use Felgo and Qt to build applications that also run in the browser. With this update you get access to a new target platform, with the same source code and skills you already used to develop mobile, desktop and embedded apps with Felgo and Qt.
Felgo for WebAssembly helps you to streamline your development process, and maintain a single universal code-base for all your deployment targets, including the web.
With Felgo for WebAssembly you can put production-ready Felgo and Qt apps to the web! The official Qt for WebAssembly port still suffers from several issues that we fixed for you, you can find more details further below.
What is WebAssembly?
WebAssembly is a new type of code that can be run in modern web browsers — it is a low-level assembly-like language with a compact binary format that runs with near-native performance and provides languages such as C++ the ability to run on the web. It is also designed to run alongside JavaScript, allowing both to work together.
WebAssembly support in browsers is evolving rapidly. It is being developed as a web standard via the W3C.
Qt for WebAssembly (WASM) is a platform plugin that allows execution of Qt apps on any compatible browser. The most common Qt and QML components are available and apps require little or no changes to the source code to be able to run in the browser.
With Felgo for WebAssembly, you get an improved version of the Qt WASM port, with several fixes and additional features. You can find a detailed list of the improvements later in this post. You can also use Felgo for WebAssembly with plain Qt applications, that do not include any Felgo components, to benefit from the improvements.
Use Cases for Web Apps using WebAssembly
Port Existing Applications to the Web
You can provide your existing Qt and Felgo applications also on the web, inside a browser, to reach a wider audience. With WebAssembly, this is possible without additional development effort. With Felgo you can share the same code-base for your mobile, desktop or embedded app as well. The UI/UX will automatically adapt to the platform.
Zero-Installation Experience
Getting people to install an app is actually a pretty significant obstacle to adoption. Now you can provide a zero-installation experience for your application, by serving it via the browser. Nothing is easier than just visiting a website with your browser.
Reuse Your Existing Skills
Now you can develop web applications with beautiful animated UIs, with your existing Felgo, Qt and QML knowledge.
Graphically Demanding or Computationally Heavy Applications
WebAssembly is also a perfect fit for applications that demand a lot of resources or performance. WASM is faster than JS for computationally or graphically demanding applications.
Integrate WASM Into Existing Websites
WebAssembly is rendered to a <canvas> HTML element. You can freely integrate it into any existing website or other web applications. WASM apps can also communicate with JS in both directions. Examples for this will follow soon.
Benefits of using WebAssembly to Develop Web Apps
Code Reuse & Portability
With the same code-base, you are now able to deploy your applications to mobile, desktop, embedded and the web. This can save tremendous amounts of time for developing and maintaining an additional platform.
Reduced Time to Market
There are several factors that lower the time to market using WebAssembly. Obviously reusing a universal code-base for all platforms is one of them. This also leads to heavily reduced testing times, as most bugs will be shared across all platforms and only need to be fixed once for all of them.
Compared to e.g. mobile applications, with store reviews taking several days and tight store guidelines that have to be met, a web app also allows shorter release cycles. You can quickly test and publish new features of your application.
Rights Protection
WebAssembly UI is rendered in a Canvas HTML element, users/extensions can not modify the content of the resulting UI, as well as protecting the assets and application logic.
Web crawlers/scrapers can not parse the UI rendered in the canvas, further protecting the information provided using WebAssembly.
Improvements of Felgo WASM compared to Qt WASM
Since Qt announced support for WebAssembly to enable Qt applications to run on the Web, we were closely following the progress. There are a couple of crucial fixes and additions that needed to be performed to use WebAssembly with Qt in production. Here is a quick overview of the most important improvements available with Felgo for WebAssembly:
Feature/Issue
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
Felgo for WebAssembly
QML LocalStorage and SQLite
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
Not Supported
Felgo for WebAssembly
Supported
Persistent File System Consistency (DBFS)
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
App execution is allowed during persistent FS sync, leading to missing files
Felgo for WebAssembly
FS is synchronized before application startup
C++ QNetworkAccessManager
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
Not supported
Felgo for WebAssembly
Supported
Click event bug QTBUG-74850
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
Some situations might cause missing events, and UI not responding to clicks
Felgo for WebAssembly
Fixed
QML rendering issues QTBUG-72231
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
Not fixed
Felgo for WebAssembly
Fixed
Nested event loops cause a browser JavaScript exception
Qt for WebAssembly
(tested with 5.14.* amd 5.15.0)
Not fixed
Felgo for WebAssembly
Fixed
Large QML projects won't start application stalls
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
Not fixed
Felgo for WebAssembly
Fixed
Qt location, positioning and sensors module stubs missing, causing runtime errors
Qt for WebAssembly
(tested with 5.14.* and 5.15.0)
Not fixed
Felgo for WebAssembly
Fixed
Test more WebAssembly Examples
You can check out a couple of Felgo examples using WebAssembly right in your browser.
How to Use Felgo for WebAssembly
Use QML Hot Reload with WebAssembly during Development
During development, you can use QML Hot Reloading also with WebAssembly. You can start the pre-built Web Live Client hosted by Felgo right from your Felgo Live Server.
The WASM Live Client will open in your browser and immediately connect to your Live Server using a localhost connection. Your source code will not leave your local network, not even your computer actually.
Build and Deploy your App with WebAssembly
You can find a detailed step-by-step guide on how you can build and deploy your application with Felgo for WebAssembly in the documentation.
Here are the most important steps as a quick overview.
1. Install the WebAssembly Package using the Maintenance Tool
Installing the necessary package for WebAssembly is as easy as for any other target platform. Just open the Maintenance Tool located in your installation directory, select “Add or remove components” and add the WASM package.
Please note you'll need a Qt commercial license to distribute your application with Qt for WASM. Contact us here to get access to the Felgo for WASM package.
2. Prepare and Build your Application using WebAssembly
Felgo for WebAssembly uses the Emscripten compiler to build C++ portable applications to target browsers with WebAssembly support.
All files of your project, including assets, need to be added to the Qt Resource System (qrc) to be available with WebAssembly. If you are not familiar with this, you can find more info here.
Since the Qt Creator plugin for WASM is still in an experimental phase, we recommend using the command line to perform the actual build. You can find all the necessary commands in the documentation: Felgo for WASM – Build your Project
3. Test your Application in the Browser
WASM modules can only be served using a web server. Simply opening the resulting .html file with your browser will not work. But it is easy to run it using a local web server for testing.
After you built your app, go to the build folder, enter the dist folder and run the following command to launch the application with the included local web server:
emrun --browser chrome index.html
You can find more info and alternative ways to launch your App here.
Use WebAssembly with Felgo Cloud Builds
Soon you will also be able to build your application using Felgo Cloud Builds, the CI/CD for Felgo and Qt projects. This allows you to easily build and distribute your application in the cloud, without installing the local toolchain for WebAssembly or any other target platform.
More Additions of Felgo 3.5.0
Update to Qt Creator 4.11.2
With Felgo 3.5.0, you get access to a newer Qt Creator version, with many improvements and better stability, for a better development experience.
Use Amplitude Analytics Plugin on Desktop & Embedded
This update adds support for the Amplitude analytics plugin on desktop and Embedded Linux platforms. You can now easily track sessions and events in your application like this:
import Felgo 3.0
Amplitude {
id: amplitude
// From Amplitude Settings
apiKey: "<amplitude-api-key>"
onPluginLoaded: {
amplitude.logEvent("App started");
}
}
Note that the Amplitude plugin will now also send events during development on desktop by default. If that is not desired, make sure to remove the apiKey during development, or e.g. check if system.publishBuild is set.
Spot Performance Issues with the FpsMeter
The new FpsMeter component allows you to quickly spot drops in the framerate of your app or game across all platforms or test devices. This serves as a quick mini-profiler to spot potential performance issues in your application.
import Felgo 3.0
import QtQuick 2.0
App {
id: app
Page {
// ... UI items go here ...
}
// Simply place the FpsMeter on top of other UI elements, no additional
// configuration is required as all properties are set to sensible defaults.
FpsMeter {
}
}
More Features, Improvements and Fixes
Felgo 3.5.0 includes many more features, for example:
- QML Hot Reloading now supports the QML on-syntax. You can add property value sources like PropertyAnimation on x and property value interceptors like Behavior on x at runtime using Hot Reloading.
- Several stability improvements for QML Hot Reload with Felgo Live.
- Fixes a potential crash on Android with the Soomla Plugin for in-app purchases.
- The new method NativeUtils::deviceManufacturer() provides information about the mobile device manufacturer._4<<
QML Hot Reload with Felgo Live for Qt
Release 3.4.0: QML Hot Reload with Felgo Live
Release 3.3.0: Update to Qt 5.13.2 and Qt Creator 4.10.2, Jira Tima App Demo
| https://blog.felgo.com/updates/release-3-5-0-run-qt-apps-in-browser-webassembly-wasm | CC-MAIN-2022-33 | refinedweb | 1,792 | 54.83 |
Feature #7121
Extending the use of `require'
Description
=begin
I was playing with Ruby tonight and thought up an interesting idea to make (({require})) a bit better, so you can load multiple files sequentially using one method call.
Currently, (({require})) supports one argument, and throws a (({TypeError})) if you pass an array:
irb(main):001:0> require %w(json yaml)
TypeError: can't convert Array into String
However, there's a way to patch Kernel that makes it respond to multiple objects passed in an (({Array})).
module Kernel
@@require = method :require
def require *args
args.flatten!
args.collect! do |a|
raise ArgumentError.new "arguments to `require' must be strings or symbols" unless a.is_a?(String) || a.is_a?(Symbol)
@@require.call a.to_s
end
args.length == 1 ? args.first : args
end
end
The new behavior doesn't actually require the modification of any code that calls (({require})) (pretty much anything, really), and new code can take advantage of the new functionality instantly.
irb> require %w(json yaml)
=> [true, false]
irb> require :pp
=> false
irb> require 'rails'
=> true
irb> require %w(json yaml), :pp, 'rails'
=> [true, false, false, true]
=end
Thanks for considering this.
History
#1
[ruby-core:48078]
Updated by Tom Wardrop about 4 years ago
I personally don't mind your suggestion. It makes sense to me. I can't think of any potential negative side effects. On that note, I think the return value should always be a boolean, instead of a boolean OR an array of booleans depending on the input. #require should return true if any of the listed files were loaded, or false if none of them were. If you need to determine the loaded state of each file (the lesser common use case I'd imagine), then you should resort to looping over multiple calls to #require.
#2
[ruby-core:49921]
Updated by Yusuke Endoh about 4 years ago
- Status changed from Open to Assigned
- Assignee set to Yukihiro Matsumoto
- Target version set to next minor
#3
[ruby-core:49994]
Updated by Thomas Sawyer about 4 years ago
It's ugly, as it makes code harder to read. Please no.
#4
[ruby-core:50051]
Updated by Ilya Vorontsov about 4 years ago
Just an alternative idea. What about using Regexp as an alternative to String?
require /.*_helper/
Also available in: Atom PDF | https://bugs.ruby-lang.org/issues/7121 | CC-MAIN-2017-04 | refinedweb | 387 | 59.94 |
Data Structures — Diving Into Data Structures (Part 1)
Data Structures are often our biggest blind spot.
This is a series of tutorials. We are going to:
When we have a programming problem, we dive into the algorithm, while ignoring the underlying data structure. And even worse, we think that using another data structure won’t make much of a difference, although we could vastly improve the performance of our code by picking an alternative data structure.
What Is A Data Structure
It doesn’t start without asking: What the heck data structure is?
It’s an intentional arrangement of a collection of data that we’ve built.
Intentional Arrangement
The intentional arrangement means the arrangement done on purpose to impose, to enforce, some kind of systematic organization on the data.
Because it’s useful, it makes our lives easier, and it’s easy to manage when you keep related information together.
Data Structures In our Life
We need data structures in our programs because we think this way as human beings.
A recipe is an actual data structure, as is a shopping list, a telephone directory, a dictionary, etc. They all have a structure, they have a format.
Data Structure and Object Oriented Programming
Now if you’re an object oriented programmer, you may be thinking, Well isn’t this what we do with classes and objects?.
I mean, we define these real-world objects in a program because we think this way as human being, or at least we’re supposed to.
And yes, absolutely. Objects are a type of data structure, and not the only one.
Five Fundamental Behaviors
How to access, insert, delete, find, & sort. These are the operations that you will most likely going to perform.
Not all of data structures have the five fundamental behaviors.
For example, many data structures don’t support any kind of searching behavior, It’s just a big collection, a big container of stuff, and If you need to find something, you just go through all of it yourself. And many don’t provide any kind of sorting behavior. Others are naturally sorted.
Each data structure has it’s own different way, or different algorithm for sorting, inserting, finding, …etc, Why? Because, due to the nature of the data structure, there are algorithms used with specific data structure, where some other can’t be used.
The more efficient & suitable the algorithm, the more you will have an optimized data structure. These algorithms might be built-in or implemented by developer to manage and run these data structures.
Always read the language documentation and check the performance of the algorithms used with the underlying data structure. Different algorithms might be used based on the data (it’s size, type, …) you have.
One-Dimensional Arrays
The array is the most fundamental, the most commonly used data structure across all programming languages. The support for one-dimensional arrays is generally built directly into the core language itself.
An array is an ordered collection of items, where each item inside the array has an index.
Indexes
The indexes are in order, they are zero-based index in most languages, but, that’s not the case with other few languages.
Size
The simplest arrays are fixed size, also called immutable, meaning unchangeable arrays. They can be created initially at any size. But once the array is created, you can’t add or remove elements from it.
Sometimes the ability to dynamically add or remove elements from it while the program is running is made available in the standard array in a language, and sometimes you have multiple different array types, depending on whether you need a fixed or resizable array.
Data Type
Simple arrays are typically restricted to a specific type of data. It’s an array of integers, or an array of booleans. But some languages allow you to create arrays of just generic objects, meaning you could put different data types.
array = [123, true, "string", [1,2,3], object]
Multidimensional Arrays
Taking the one dimensional array one step further, we can have arrays with two dimensions.
It’s basically an array of arrays, where each item in this array itself contains another array.
Therefore, any single array element is not accessed with just one index, but we need two numbers to get to it. Sometimes referred to as a matrix or a table because this is, effectively, rows and columns of information.
We can take the two-dimensional array further to three-dimensional arrays and even more.
Jagged Arrays
When we have a Multidimensional array, where each row, each item needs to have different number of items. It’s where Jagged arrays come into play.
It’s a Multidimensional array where each item can have different sizes.
When To Use Jagged Arrays
If you have a multidimensional array which records the number of sales every day. The first index is for the month, while the second is for the day.
sales = [[124,153,135, …], [135,545,342,678,], …]
You can notice that Jan has 31 days, while Feb 29, and so on. So, either leaving the irrelevant elements empty, or setting them to 0 or -99 or some other value is not always desirable. But, you shouldn’t have elements that represent impossibilities. Like In February, where days 30 & 31 don’t exist.
So, Using Jagged Arrays, we can get the average of sales in a month by grabbing all the sales in that month, add them all, and divide by the number of days in that month, without having to add logic to figure out the days we should be ignoring.
Resizable Arrays
Most languages provide some kind of resizeable array, or dynamic array, or mutable. In Java, the standard array is fixed-size and a fixed data type, but, you can also create a resizeable array using ArrayList.
Adding & Removing
The location where we add a new element or remove an existing one does matter, because adding or removing an element at the end is faster than at some where else.
So, elements will have to be shifted to the left or to the right, and re-indexed; re-ordered. Therefore, it does have a performance impact.
The way of shifting, differs from language to another, some will be shifting items in place, but, some other will just copy the entire contents of the old array into a new one with the item being added or removed.
Sorting Arrays
Sorting is always computationally intensive, you might need to do it but we want to minimize it. So, keeping aware about how much data we have and how often we’re asking to sort might lead us into choosing different data structures.
The Built-In Sorting Functionality
When we’re sorting arrays, there are things you need to understand the built-in sort functionality.
First, Is the built-in sort functionality will look at how big your array is?. Your language may automatically switch between different sorting algorithms based on the size of the array.
Second, Is the built-in sort functionality will attempt to sort an existing array in place or will create another copy?. Most languages will attempt to sort an existing array in place, while a few will create new copy of the original array to contain the sorted array.
Sorting Custom Objects
In object orientated languages, you often have arrays of your own custom objects, not just arrays of simple numeric or even string values.
When you then ask that array to sort those objects using the built in sort functionality in the language. It simply won’t know how to do it. Because you need to provide a little more information on which property to sort accordingly.
So, for example, sort the users by their id, name, or birth date. This defines the object’s property to sort accordingly.
Usually only needs a few lines and it’s typically called a comparator, or compare function, or compare method.
Searching Arrays
If we wanted to know if a specific value exists somewhere in an array or not, we could loop over array elements, and check the value at that current position, and see if it’s equal to goal or not.
The best case scenario is that the first element is the value we’re looking for. The worst case is that the value is at the end or does not appear anywhere in the array. This method is referred to as a linear search or a sequential search. This is an inelegant brute-force method.
While linear searches are simple to understand and they are easy to write and they will work, but, they’re slow. And the more elements you have, the slower they get.
Data Needs To Be Ordered
If there is no order, no predictable sequence to the values in the array, then, there may be no other options than check all the array elements.
But, if the data is ordered. If it has some kind of predictable sequence where the items are in strict ascending, or descending order. Then, there are much better options for searching than a linear search like binary search.
So, data must be ordered in a way so that we can use an algorithm other than linear search. Therefore, having some kind of order to those elements is more and more significant.
The Inherit Challenge of Data Structures
You may sometimes agree to use a slow search ability, because the only way of fixing that is to sort the array, which in turn will add a performance hit that it’s simply not worth it.
So, If you are going to search on an array once, It’s better to have a complexity of O(N) for linear search, than O(NLogN) for sorting + O(LogN) for searching. If, however, you are going to search a lot, then, you may first sort the array once at the beginning, and now, you can search with O(LogN) every time instead of linear search O(N).
You cannot have a data structure that is equally good in all situations. A naturally sorted data structure requires less time in searching for an element, and more time in inserting because it keeps the array sorted. While a basic array requires more time in searching, and less time in inserting elements to the end of the array.
Lists
Lists are pretty simple data structures. It’s structure keeps track of sequence of items.
It’s a collection of items (called nodes) ordered in a linear sequence.
These nodes don’t need to be allocated next to each other in the memory like an array is.
There is a general theoretical programming concept of a list, and there is the specific implementation of a list data structure, which may have taken this basic list idea and added a whole bunch of functionality. Lists are implemented either as linked lists (singly, doubly, circular, …) or as dynamic array.
An Array Vs A List
A list is a different kind of data structure from an array.
The biggest difference is in the idea of direct access Vs sequential access. Arrays allow both; direct and sequential access, while lists allow only sequential access. And this is because the way that these data structures are stored in memory.
The structure of the list doesn’t support numeric index like an array is.
Linked Lists
It’s a collection of nodes, where each node has a value and a link to the next node in the list.
The pointer of the last node points to NULL, or terminator, or a dummy node.
Because of the way it’s built, adding, and removing elements is much, much easier than with an array.
But, with arrays, it requires shifting to the left or to the right to keep its meaningful ordered structure. Even adding elements at the end of the array can still require reallocation of the entire array in order to store the array in a contiguous area of memory.
Doubly Linked List
What we have introduced is a linked list, But to be yet a little more specific, this is a called a “Singly Linked List”. We can also have a “Doubly Linked List”.
Instead of each node having a reference just to the next node, we add one more piece of data that it also has a reference to the previous node as well. So, it allows us to go forward and backward, to traverse the list in any direction.
Linked lists in most of the languages are typically implemented as doubly linked lists.
The Singly Vs Doubly Linked List
The doubly linked lists require more space per node because it maintains a pointer to the next and previous nodes.
Adding operation is clearly less work in a singly linked list, because doubly linked list requires changing more links than a singly linked list.
For singly linked list, we assume that we insert at the head or after some given node.
In case of adding before some given node, you need to know the node before that given node, which will require you to sequentially access all the nodes until you find the node you’re looking for.
Removing is simpler and potentially more efficient in doubly linked list, because in singly linked list, you need to know the node before the node to be deleted.
Circular Linked List
In a singly linked list, If the next pointer of the last node points back to the first node. Then, it’s “Circular Linked List”. And if the previous pointer of the first node points to the last node as well. Now this would be considered a “Circular Doubly Linked List”.
It’s not common, but it can be useful for certain problems. So, if we get to the end of the list and say next, we just start again at the beginning.
Stacks
Just like the arrays and lists, stacks and queues are also collection of items. They are just different ways we can hold multiple items. It’s last in, first out data structure, with no care about numeric indexes.
It’s a collection of items where we add and remove items to and from the top of the stack.
Stack Implementation
A stack can be easily implemented either using an array or a linked list
Usage of Stacks
Stack is not limited to only model the real world situations (same for queues). One of the best uses for a stack in programming is when parsing code or expressions, where you need to do something like validating the correct amount of opening and closing curly braces, square brackets or parenthesis.
The Basic Operations of Stacks
They are: push(), pop(), & peek(). push is for pushing a new element on the top of the stack, and pop will return (and remove) the element at the top, while peek will get the element at the top without removing it.
Stacks Vs Arrays Vs Linked Lists
Working with stack is simpler than working with arrays or linked lists, because there is less you can do with a stack.
This is an intentionally limited, an intentionally restricted data structure. All we do is push and pop and maybe peek. And if you’re trying to do anything else with this stack, you’re using the wrong data structure.
Queues
The key difference between a stack and a queue. Stacks are last in first out (LIFO), while queues are first in first out (FIFO). And as with stacks, we should not even be thinking about numeric indexes.
It’s a collection of items where we add items to the end and remove items from the front of the queue.
Queue Implementation
As with stacks, a queue can be implemented either using an array or a linked list.
Usage of Queues
Queues are very commonly used in concurrency situations to keep track of what tasks are waiting to be performed and making sure we take them in that order.
The Basic Operations of Queues
Just like a stack: add(), remove(), & peek().
Priority Queues
Some languages offer a version of a queue, called a priority queue. This allows you to arrange elements in the queue based on their priority.
It’s a queue, where items with higher priority step ahead of items with lower priority in the queue.
How Priority Queues Works
When you add items that have the same priority, they will queue as normal in a first in, first out order. If something comes along with a higher priority, then it will go ahead of them in the queue.
Defining The Priority
You can define based on what an element has higher, lower, or equal priority. This done by implementing a comparator or a compare function (as when sorting arrays), where you provide your own logic for comparing the priority between elements.
Deque
The deque, pronounced “DEK”, is used when we want to leverage the power of the queue and the stack, where you can add or remove from start or end.
It’s a queue and a stack at the same time.
Associative Arrays
They give the ability to use meaningful keys to work with elements in our data structures, rather than working with numeric indexes as keys. This gives a meaningful relationship between the key and the value.
It is a collection of key-value pairs.
var user = {
firstName: "Bob",
lastName: "Jones",
age: 26,
};
The implementation of associative arrays have different names. In Objective-C and Python, they’re called dictionaries.
The Order of Elements
Unlike a basic array, In an associative array the keys do not need to be in any specific order. Because order is not a concern in associative arrays.
Sure, you might find it useful to sort them by key. You might find it useful to sort them by value, or, you might not need to sort it at all.
Key Duplicates
The same way that you don’t get the same index number appearing twice in a basic array, there can be no duplicate keys, and keys must be unique in an associative array.
Keys & Values Data Types
You can usually use any data type as either the key or the value. It is common to use a string as a key.
Most associate arrays, whether they are called dictionaries or maps or hashes, are implemented using hash table data structure. So, we’ll start by hashing and then dive into hash tables.
Hashing
Hashing is a valuable concept in programming. It’s used, not just in data structures, but in security, cryptography, graphics, audio.
It’s a way to take our data and run it through a function, which will return a small, simplified reference generated from that original data.
The reference might just be an integer, or letters and numbers, …etc.
Why Using Hashing?
Because being able to take a complex object, and hash it down to a single integer representation. So, we can use that integer value to get to a certain location in the data structure.
Hashing Is Not Encryption
Hash functions are not reversible; They are one way. So, you cannot convert a hash value result back to the original data. Therefore, you lose information when hashing, that’s okay, that’s intentional.
Hashing Function Implementation
Say we have a person class defined, and we want a hash function defined on this class. The hash function should return a specific single reference (usually an an integer) for a specific person object. This single integer is generated using the data in a person object (firstname, lastname, birth date, …etc).
Hashing Rules
- If we take the exact same object, with this same data, and feed it into the hash function again, I would expect the same hash result.
- If you have two different objects that you consider equal, they should return the same hash value.
- While two equal objects should produce the same hash value, two equal hash values does not guarantee they came from equal objects, Why?Because two different objects might, under some circumstances, deliver the same result out of a hash function (See Hashing Collision).
Hashing Collision
It’s when we have different objects with different data, but giving the same hash value result.
It could be because the hashing function is simple hash function, but it’s also possible even with more complex hash functions. In most cases that’s okay, we can manage the hash collision.
Hash Tables
The idea of hashing was fundamental to understand the hash table data structure.
It’s a typical data structure to implement an associative arrays; mapping keys to values.
Hash Tables Vs Arrays Vs Lined List
The big benefit of hash tables over arrays and over linked lists is they’re very fast, both for looking at whether an item exists or finding a specific item in a hash table, and for inserting and deleting items.
How Hash Tables Work?
When a hash table is created, it’s really internally a very array-based data structure, and can usually be created with an initial capacity. The hash table consists of an array of slots, or buckets which contain the values.
When adding a key-value pair, It will take our key and it’ll run it through the hash function, getting a specific hash value out (usually an integer).
If this hash value is large, you might need to simplify it with respect to the current size of the hash table.
Then, it will assign the value to an array element with the index equals to the returned hash integer value.
// adding a key-value pair
hash_table.add(key, value)// what happen behind the scene
index = hash(key)
index = index % array_size
array[index] = value
Accessing a value given a key follows the same idea. It will take that key, run it through the exact same hash function, and it can then go directly to a specific location that contains the value we’re looking for.
There’s no linear search, no binary search, no traversing a list. We just go straight to the element we need.
Managing Collision
We can expect that a hash collision will arise; when we get the same hash value for different keys. But, how to manage it?
When we add a new key value pair, and collision happens, It’s going to put that value in the same location, even if there’s another existing value in that location.
Now, hash table implementations have different ways to automatically deal with this. These range from that each location contains a simple collection, like an array, or a linked list.
So, we would still be able to get to any location very fast, but once we get to the location with multiple values, the hash table will traverse that internal list to find what we’re looking for.
Each node in the linked list in turn will contain the value associated with a specific key. In addition, It will contain that key, or a reference to that key. Because in case of multiple values inside the same location, we need to know which key this value belongs to.
This is what is called the “Separate Chaining Technique” in hash tables. Now, there are other techniques for managing collisions inside hash tables, including open addressing, Cuckoo hashing, hop-scotch, and Robin Hood hashing.
Writing Hash Functions
When you want to store key-value pairs using hash table data structure, It’s probably most of objects already have hash function. The default behavior is usually returns an integer; calculated from the memory address of that object.
If you ever override the equality behavior in your class, you must override the hash behavior. Because hash codes are so tied to equality, And, if you have two objects that you consider equal, they should return the same hash value.
Again, If you change what it means for your objects to be equal, you should also change what it means to hash these objects.
String objects already overridden their own equality and hashing behavior. So if you have two separate string objects, they will still count as equal, and return the same hash, if they have the same value, even if they’re actually separate string objects allocated in different parts of memory.
Sets
When all what you need is a big container you can put a bunch of items into it, where you don’t care about the sequence.
There is no specific sequence as with a linked list, or a stack, or a queue. There is no key-value pairs as with a hash table.
It’s an unordered collection of items, with no repeated values.
By unordered, I mean there is no index like an array.
Set Implementation
Sets are actually use the same idea of hash tables data structure most of the time. But, instead of key-value pairs (hashing a key and store it’s value), when you’re using a set, the key is also considered as the value (or the value is assigned to a dummy or a default value).
So, to get any specific value, or any specific object in the set, you need to have the object itself. And the only reason to do this is to check for it’s existence. This is often referred to as “checking membership”.
Sets can be implemented using a self-balancing binary search tree for sorted sets, or a hash table for unsorted sets.
The Advantage of Sets
Unlike an array, or values in an associative array, or a linked list, sets do not allow duplicates. You cannot add the same object, the same value twice to the same set.
Sets are designed for very fast lookup, to very quickly be able to see if we already have a value contained in a collection.
You can also iterate through all the elements in a set, you just may not have any guaranteed order.
Trees
The idea of a tree data structure is that we have a collection of nodes, and the nodes have connections, they have links between each other.
This sounds similar to linked lists. But in a linked list, we always go from one node to a single specific next node. While in a tree, each node might link to one, or two, or more nodes.
It’s a collection of nodes, where each node might link to one, or two, or more nodes.
Tree Terminologies
There are some terminologies that come with the tree. You can find more about them here. They are essential to understand and work with trees.
Binary Trees
A binary tree is just a tree with maximum of two child nodes for any parent node. Binary trees are often used for implementing a wonderfully searchable structure called a “Binary Search Tree” or “BST”.
Binary Search Trees (BST)
It’s a specific type of binary tree, where the left child node is less than its parent, and a right child node is greater than its parent.
How Binary Search Trees Work?
The the rule is that the left child node must be less than its parents, and a right child node must be greater than its parents, and that rule follows all the way down in the tree.
And as we insert new nodes with values, the rule will always be followed to make sure that the tree stays sorted.
So, It is a data structure that naturally stays sorted and it’s sometimes called “A Sorted Tree” or “An Ordered Tree”.
Storing Nodes As Key-Value Pairs
A binary search trees are often used to store key value pairs, meaning, the nodes consists of a key, and an associated value. And it’s the key that would be used to sort the nodes accordingly in a binary search tree.
Duplicates
You can’t have duplicate keys, just as you don’t have duplicate keys in a hash table or even an array.
Adding & Accessing Nodes
Adding & Accessing nodes follows the same rule mentioned above. If the current node is less than, then go right, if greater than, go left.
Retrieve Nodes In Order
The other benefit is binary search trees are staying sorted. So, If we retrieve the items from a left to the right, bottom to top, we will get them all out in order.
Unbalanced Tree
It’s when the tree has more levels of nodes on the right hand side than on the left (or vice-versa).
Although it’s unusual for this kind of thing to happen, but,. And we would have to perform more checks to find or insert or delete any values on the right hand side than we would on the left (or vice-versa).
Binary Search Tree Implementations
What we have been talking about is the abstract idea of a binary search tree data structure. But, there are several implementations of this binary search tree idea that are self-balancing binary search trees.
The important idea with balancing a binary search tree is that the number of levels are roughly equal to each other. We don’t have three levels on the left and twenty on the right.
Examples of self-balancing trees could be: Red-Black, AVL or Adelson-Velskii and Landis’, Splay, Scapegoat trees, and more.
Binary Search Tree Vs Hash Table
Both are fast for insertion, fast for deletion, fast for accessing any element even at large sizes. But, because binary search trees stay sorted, they allow us to get all the items out of the tree in order, where the hash table doesn’t guarantee a specific order.
Heaps
Heaps are usually implemented using the idea of a binary tree, not a binary search tree but still, a binary tree. They’re a way of implementing other abstract data types like the priority queue.
It’s a specific type of binary tree, where we add nodes from top to bottom, left to right, and child nodes must be less (or greater) than or equal their parents.
Therefore, we completely fill out any level before moving on to the next. So we don’t have to worry about the tree becoming unbalanced like a binary search tree can.
Min Vs Max Heap
A min heap states that any child node must be greater than (or equal) its parent node, while a max heap states that any child node must be less than (or equal) its parent node. However, we don’t care if a node is less than or greater than it’s sibling.
How Heaps Work?
So, In case of Min Heap:
- We keep adding elements from top to bottom, left to right,
- Then, compare with the parent node; Is it less than its parent?
- If so, then swap the node with it’s parent,
- Keep doing steps from 2 through 3 until the node is greater than it’s parent (or it becomes the root node).
This little swapping of nodes is how a heap keeps itself organized.
Heap Is Not A Fully Sorted
Unlike a binary search tree, which does stay sorted, and where we can easily traverse the tree and retrieve everything out in order.
Because if you notice, that at any particular level past the root, the values do not have to be in any specific order, just as long as they’re all greater (or less) than their parent.
One of the benefits of this is a heap does not have to do as much reorganization of itself as may be necessary with a binary search tree.
The one thing we can be sure about, is that the parent node will always be less or greater than it’s child nodes, and hence the minimum or the maximum value will be always at the top.
And, therefore, heaps are most useful for the idea of a priority queue.
Graphs
The limitations of a tree are no longer exist here. A node can link to multiple other nodes, no specific sequence, no root node.
It’s a collection of nodes, where a node can link to multiple other nodes, no specific sequence, no root node.
Graph Theory In Mathematics
Because graphs in computer science are so closely linked to graph theory in mathematics. It is common to hear mathematical terms used. So, In graph theory, we call the nodes “vertices”, and the links between them are referred to as “edges”.
Graphs Usage
We could use a graph to model a social network with each node a person. Or, modeling the distances between cities. We could model a ethernet network in an office, or in an entire building, or a city.
Direct & Undirect Graphs
We can also say whether those edges should have a direction to them or not.
In some situations, it makes sense that any edge, any connection between two vertices, is only one-way; So, node A is connected to node B, while the reverse is not true; node B is NOT connect to node A.
In other situations, you might want to be able to follow that edge, that link, in either direction; So, node A is connected to node B, and also node B is connected to node A.
Weighted Graphs
You can also give every edge a weight; associating a number, with each of the edges.
You could do this to represent, say, the distances between cities, if you were trying to calculate the shortest route between multiple locations. Or, you could use a weight to indicate which edges take priority over other edges.
Abstract Data Types (ADTs)
Before diving into the abstract data types, what they are, and the difference between them and other concepts. Let’s define what’s meant by a data type.
Data Type
A variable’s data type determines the values it may contain, plus the operations that may be performed on it.
Data Types consists of: Primitive, Complex or Composite, and Abstract Data Types.
An Abstract Data Type (ADT)
It’s a data type, just like integers and booleans primitive data types. An ADT consist not only of operations, but also of values of the underlying data and of constraints on the operations.
A constrains for a stack would be that each pop always returns the most recently pushed item that has not been popped yet.
The actual implementation for an ADT is abstracted away, and we don’t have to care about. So, how a stack is actually implemented is not that important. A stack could be and often is implemented behind the scenes using a dynamic array, but it could be implemented with a linked list instead. It really doesn’t matter.
Lists, stacks, queues, and more are all abstract data types.
An Abstract Data Type & Data Structure
ADT is not an alternative to a data structure, they are different concepts.
When we say the stack data structure, we refer to how stacks are implemented and arrangement in the memory. But, when we say the stack ADT, we refer to the stack data type which has set of defined operations, the operations constrains, and the possible values.
We don’t care about the underlying implementation, same as when using integers, we are abstracted away from how integers are represented in the memory, we are only interested in the operations (add, subtract, …), and the possible values (…, −2, −1, 0, 1, 2, …).
Data structures can implement one or more particular abstract data types (ADT), which specify the operations that can be performed on a data structure.
An Abstract Data Type Is NOT An Abstract Class
Both have nothing to do with each other. An abstract class defines only the operations, sometimes with comments that describe the constraints, leaving the actual implementation to the inheriting classes.
Although ADTs are often implemented as Interfaces (abstract classes) as in Java. For example, The List interface in Java defines the operations of the List ADT, while the inheriting classes define the actual implementation (data structure).
But, this is not always the case. For example, Java has a stack class, It is a regular concrete class, but a stack is also an abstract data type, meaning, it represents the idea of having a last in, first out data structure. So, stack is a real concrete class and it’s also an abstract data type.
An Abstract Data Types Is A Theoretical Concept
An abstract data type (ADT) is a theoretical concept that’s irrelevant to programming keywords.
So, If we have a stack, we have a last in, first out data structure, that we can push and pop and peek. That’s what we expect a stack to be able to do. Whether a stack is implemented as a concrete class or whatever, It still have the idea of a last in, first out data structure.
Conclusion
Deciding on The Data Structure
There are some key questions you need to ask before deciding on the data structure
- How much data do you have?
- How often does it change?
- Do you need to sort it, do you need to search it? Faster to Access, Insert, or Delete?
If any place where you only have trivial amounts of data, it isn’t going to matter very much. Unless of course, those amounts of data change so frequently, or you have large amounts of data.
Immutable Data Structures
Now, a general principle that immutable or fixed size data structures tend to be faster and smaller in memory than mutable ones.
Why should we restrict the features of arrays? The reason is, that the more constraints you have (like fixed size, specific data type, …), the faster and smaller your data structure is able to be.
The pitfalls of having a data structure with many features (non-restricted) is the compiler cannot allocate the ideal amount of space, therefore, it must introduce overhead to support the flexibility of the data structure (like different data types, …).
Improve Your Code Performance
If you’re looking at existing code to see what to improve on, then see whatever holds the most data. There is no better way to really get the most out of these data structures than when you see some of the performance improvements you can get, just from simply changing from one structure to another.
Differences In Languages
The algorithms used with each data structure differs from one language to another, and the actual implementation of the data structure differs from one language to another. So, It’s worth to look closely at your language documentation. | https://medium.com/omarelgabrys-blog/diving-into-data-structures-6bc71b2e8f92?source=collection_home---1------2----------------------- | CC-MAIN-2019-43 | refinedweb | 6,431 | 61.06 |
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#include <libgen.h>
char *regcmp (string1 [, string2, . . . (char *)0) char *string1, *string2, . . .
char *regex (re, subject, [ ret0, . . . ]) char *re, *subject, *ret0, . . .
extern char *__loc1;
The regex routine executes a compiled pattern against the subject string. Additional arguments are passed to receive values back. regex returns NULL on failure or a pointer to the next unmatched character on success. A global character pointer __loc1 points to where the match began.
The regex and regcmp routines were borrowed from the editor, ed(C); however, the syntax and semantics have been changed slightly.
The following are the symbols understood by regex and regcmp, and their meanings.
By necessity, all the above defined symbols are special. They must, therefore, be escaped with a \ (backslash) to be used as themselves.
char *cursor, *newcursor, *ptr; ... newcursor = regex((ptr = regcmp("\n", (char *)0)), cursor); free(ptr);This example matches a leading new-line in the subject string pointed at by cursor.
Example 2:
char ret0[9]; char *newcursor, *name; ... name = regcmp("([A-Za-z][A-za-z0-9]{0,7})$0", (char *)0); newcursor = regex(name, "012Testing345", ret0);This example matches through the string ``Testing3'' and returns the address of the character after the last matched character (the ``4''). The string ``Testing3'' is copied to the character array ret0.
Example 3:
#include "file.i" char *string, *newcursor; ... newcursor = regex(name, string);This example applies a precompiled regular expression in file.i against string. See regcmp(CP).
Example 4:
char *ptr, *newcursor;It is assumed in this example that the current locale's collation rules specify the following sequence:
ptr = regcmp("[a-[=i=][:digit:]]*",(char*)0); newcursor = regex(ptr, "123CHICO321");
A,a,B,b,C,c,CH,Ch,ch,D,d,E,e,F,f,G,g,H,h,I,i.....The characters I and i are also both in the same ``primary'' collation group.
The following characters are all members of the digit ctype class:
0, 1, 2, 3, 4, 5, 6, 7, 8, 9This example matches through the string ``123CHIC'' and returns the address of the character ``O'' in the string. | http://osr507doc.xinuos.com/cgi-bin/man?mansearchword=regcmp&mansection=S&lang=en | CC-MAIN-2020-50 | refinedweb | 345 | 59.19 |
I am writing a Python client which connects with simple sockets in a server (also written in Python). I want to prevent client termination when the connection in server refused. In other words, I want to make client "search" for the server (if there is no connection) every 30 seconds.
Here is the code I wrote, but when the connection terminates from the server, the client returns an error for connection refused, and terminates itself.
Code:
#!/usr/bin/python
import socket
import time
while True:
sock = socket.socket()
host = socket.gethostname()
port = 4444
conn = sock.connect((host,port))
while(conn != None):
print 'Waiting for the server'
time.sleep(30)
sock = socket.socket()
host = socket.gethostname()
port = 4444
conn = sock.connect((host,port))
while True:
recv_buf = sock.recv(1024)
if (recv_buf == 'exit'):
break
print(recv_buf)
sock.send('hi server')
Traceback (most recent call last): File "s_client.py", line 12, in
conn = sock.connect((host,port)) File "C:\Program Files\python27\lib\socket.py", line 224, in meth
return getattr(self._sock,name)(*args) socket.error: [Errno 10061] ─ίΊ ▐ΪάΊ ϊΫΊάΪ▐ ύ ϊύΉώΎΫ±ή▀ά ≤²Ίϊί≤ύ≥,
Use
try-
except:
conn = None while(conn == None): sock = socket.socket() host = socket.gethostname() port = 4444 try: conn = sock.connect((host,port)) except: print 'Waiting for the server' time.sleep(30)
It's better to avoid the initial
connect call and perform the connect only through the
connect in the
while loop. I have made a few other changes too, like moving the
sleep call to the
except part. | https://codedump.io/share/na4GoRik1EsM/1/prevent-application-from-closing-due-to-a-39connection-refused39-error | CC-MAIN-2016-50 | refinedweb | 254 | 62.34 |
audio_engine_channels(9E)
audio_engine_playahead(9E)
- control a character device
#include <sys/cred.h> #include <sys/file.h> #include <sys/types.h> #include <sys/errno.h> #include <sys/ddi.h> #include <sys/sunddi.h> int prefixioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *cred_p, int *rval_p);
Architecture independent level 1 (DDI/DKI). This entry point is optional.
Device number.
Command argument the driver ioctl() routine interprets as the operation to be performed.
Passes parameters between a user program and the driver. When used with terminals, the argument is the address of a user program structure containing driver or hardware settings. Alternatively, the argument may be a value that has meaning only to the driver. The interpretation of the argument is driver dependent and usually depends on the command type; the kernel does not interpret the argument.
A bit field that contains:
Information set when the device was opened. The driver may use it to determine if the device was opened for reading or writing. The driver can make this determination by checking the FREAD or FWRITE flags. See the flag argument description of the open() routine for further values.
Information on whether the caller is a 32-bit or 64-bit thread.
In some circumstances address space information about the arg argument. See below.
Pointer to the user credential structure.
Pointer to return value for calling process. The driver may elect to set the value which is valid only if the ioctl() succeeds.
ioctl() provides character-access drivers with an alternate entry point that can be used for almost any operation other than a simple transfer of characters in and out of buffers. Most often, ioctl() is used to control device hardware parameters and establish the protocol used by the driver in processing data.
The kernel determines that this is a character device, and looks up the entry point routines in cb_ops(9S). The kernel then packages the user request and arguments as integers and passes them to the driver's ioctl() routine. The kernel itself does no processing of the passed command, so it is up to the user program and the driver to agree on what the arguments mean.
I/O control commands are used to implement the terminal settings passed from ttymon(1M) and stty(1), to format disk devices, to implement a trace driver for debugging, and to clean up character queues. Since the kernel does not interpret the command type that defines the operation, a driver is free to define its own commands.
Drivers that use an ioctl() routine typically have a command to ``read'' the current ioctl() settings, and at least one other that sets new settings. Drivers can use the mode argument to determine if the device unit was opened for reading or writing, if necessary, by checking the FREAD or FWRITE setting.
If the third argument, arg, is a pointer to a user buffer, the driver can call the copyin(9F) and copyout(9F) functions to transfer data between kernel and user space.
Other kernel subsystems may need to call into the drivers ioctl() routine. Drivers that intend to allow their ioctl() routine to be used in this way should publish the ddi-kernel-ioctl property on the associated devinfo node(s).
When the ddi-kernel-ioctl property is present, the mode argument is used to pass address space information about arg through to the driver. If the driver expects arg to contain a buffer address, and the FKIOCTL flag is set in mode, then the driver should assume that it is being handed a kernel buffer address. Otherwise, arg may be the address of a buffer from a user program. The driver can use ddi_copyin(9F) and ddi_copyout(9F) perform the correct type of copy operation for either kernel or user address spaces. See the example on ddi_copyout(9F).
Drivers have to interact with 32-bit and 64-bit applications. If a device driver shares data structures with the application (for example, through exported kernel memory) and the driver gets recompiled for a 64-bit kernel but the application remains 32-bit, binary layout of any data structures will be incompatible if they contain longs or pointers. The driver needs to know whether there is a model mismatch between the current thread and the kernel and take necessary action. The mode argument has additional bits set to determine the C Language Type Model which the current thread expects. mode has FILP32 set if the current thread expects 32-bit ( ILP32) semantics, or FLP64 if the current thread expects 64-bit ( LP64) semantics. mode is used in combination with ddi_model_convert_from(9F) and the FMODELS mask to determine whether there is a data model mismatch between the current thread and the device driver (see the example below). The device driver might have to adjust the shape of data structures before exporting them to a user thread which supports a different data model.
To implement I/O control commands for a driver the following two steps are required:
Define the I/O control command names and the associated value in the driver's header and comment the commands.
Code the ioctl() routine in the driver that defines the functionality for each I/O control command name that is in the header.
The ioctl() routine is coded with instructions on the proper action to take for each command. It is commonly a switch statement, with each case definition corresponding to an ioctl() name to identify the action that should be taken. However, the command passed to the driver by the user process is an integer value associated with the command name in the header.
ioctl() should return 0 on success, or the appropriate error number. The driver may also set the value returned to the calling process through rval_p.
Example 1 ioctl() entry point
The following is an example of the ioctl() entry point and how to support 32-bit and 64-bit applications with the same device driver.
struct passargs32 { int len; caddr32_t addr; }; struct passargs { int len; caddr_t addr; }; xxioctl(dev_t dev, int cmd, intptr_t arg, int mode, cred_t *credp, int *rvalp) { struct passargs pa; #ifdef _MULTI_DATAMODEL switch (ddi_model_convert_from(mode & FMODELS)) { case DDI_MODEL_ILP32: { struct passargs32 pa32; ddi_copyin(arg, &pa32, sizeof (struct passargs32),\ mode); pa.len = pa32.len; pa.address = pa32.address; break; } case DDI_MODEL_NONE: ddi_copyin(arg, &pa, sizeof (struct passargs),\ mode); break; } #else /* _MULTI_DATAMODEL */ ddi_copyin(arg, &pa, sizeof (struct passargs), mode); #endif /* _MULTI_DATAMODEL */ do_ioctl(&pa); . . . . }
stty(1), ttymon(1M), dkio(7I), fbio(7I), termio(7I), open(9E), put(9E), srv(9E), copyin(9F), copyout(9F), ddi_copyin(9F), ddi_copyout(9F), ddi_model_convert_from(9F), cb_ops(9S)
Non-STREAMS driver ioctl() routines must make sure that user data is copied into or out of the kernel address space explicitly using copyin(9F), copyout(9F), ddi_copyin(9F), or ddi_copyout(9F), as appropriate.
It is a severe error to simply dereference pointers to the user address space, even when in user context.
Failure to use the appropriate copying routines can result in panics under load on some platforms, and reproducible panics on others.
STREAMS drivers do not have ioctl() routines. The stream head converts I/O control commands to M_IOCTL messages, which are handled by the driver's put(9E) or srv(9E) routine. | http://docs.oracle.com/cd/E23824_01/html/821-1476/ioctl-9e.html | CC-MAIN-2017-04 | refinedweb | 1,205 | 52.8 |
In this article, you will learn about Python tuples, including what they are, how to create them, when to use them, the operations you can perform on them, and the various functions you should be familiar with.
Tuples, like Python lists, are a standard data type that allows you to store values in a sequence. They could be helpful when you want to share data with someone but not allow them to manipulate it.
Tuples are a type of variable that allows you to store several elements in a single variable.
The tuple is one of Python’s four built-in data types for storing data collections; the other three are List, Set, and Dictionary, all of which have different properties and applications. In addition, a tuple is a collection of items that is both ordered and immutable. Further, round brackets are used to write tuples.
They can use the data values, but no change is reflected in the original shared data.
Data structures are essential components of any programming language. Therefore, to build robust and high-performing products, one must be well-versed in data structures.
This post will look at a crucial data structure in the Python programming language: the tuple. A tuple is a group of values separated by commas and enclosed in parenthesis. Tuples, unlike lists, are immutable.
The immutability of tuples can be regarded as a distinguishing feature.
In this tutorial, you will learn about Python tuples in-depth:
You will discover how to initialize tuples. You will also see how immutable tuples are and how a tuple differs from a Python list. Then you’ll see tuple operations like slicing, multiplying, concatenating, and so on;
Some built-in tuple functions are helpful, and you’ll examine some of the most significant ones in this section.
Finally, you’ll see that tuples can have several values assigned to them at the same time. In addition, we’ll use examples to explain the characteristics of tuples and operations on them.
Tuples in Python
As previously stated, you may use this Python data structure to store an immutable (or unchangeable) and ordered series of things.
Tuples are started with () brackets instead of [] brackets like lists. That implies all you have to do to make one is perform the following:
define_tuple = ('n','e','w','t','u','p','l','e') print(type(define_tuple))
Keep in mind that type() is a built-in function that can determine the data type.
Both homogeneous and heterogeneous values can be stored in a tuple. However, keep in mind that once you’ve defined your values, you won’t be able to edit them:
define_mixed_type = ('t',9,2,'u','P','l','e',8,3,'f') for i in define_mixed_type: print(i,":",type(define_mixed_type)) define_mixed_type[1] = 'P'
Because you can’t alter the values within a tuple, you receive this last error notice.
Another technique to make a tuple is as follows:
define_numbers_tuple = 4,5,6,7,8 print(type(define_numbers_tuple ))
Tuple Operations Commonly in Python
You can modify tuples in Python in a variety of ways. Let’s take a look at a few of the essential ones, along with some examples.
Making tuples
Tuples are made up of values enclosed in parenthesis and separated by a comma.
define_tuple= (9, 8) print(type(define_tuple))
Tuples can store values of various data types as well as duplicate values.
define_tuple = (9, 9, 'x', [7,8]) print(define_tuple) print(type(define_tuple))
We can also make tuples without the use of parenthesis. A tuple is formed by a series of values separated by commas.
define_tuple = 6, 7, 8, 9 print(type(define_tuple))
Making a tuple with either 0 or 1 element
A tuple with zero elements is simply an empty one, and it is formed as follows:
define_tuple = () print(type(define_tuple))
There is, however, a simple trick for creating a tuple with only one element. After the element, a comma is required. Otherwise, you will create a variable of the value’s type.
define_tuple = (6) print(type(define_tuple)) define_tuple_two = ([4,5]) print(type(define_tuple_two))
Let’s try it again, but this time with a comma after the values:
define_tuple = (6,) print(type(define_tuple)) define_tuple_two = ([4,5],) print(type(define_tuple_two))
Tuples can be iterated
You can iterate over a tuple in the same way that you can iterate over a list.
define_tuple = (1, 2, 3) for tup in define_tuple: print(tup**2)
Slicing and indexing
Tuples are indexed and sliced in the same way as lists are.
define_tuple = (6, 8, 'x', 8) print(f'The first element of tuple define_tuple is {define_tuple[0]}') print(f'The last element of tuple define_tuple is {define_tuple[-1]}')
Slicing examples
define_tuple = (4, 5, 8, 9, 10) print(define_tuple [-2:]) print(define_tuple [:3])
Tuples are immutable, although their elements can be changed
Tuples’ immutability may be their most distinguishing trait. A tuple’s items cannot be assigned.
define_tuple = (6, 8, 'x', 8) define_tuple[0] = 7 #error
Tuples, on the other hand, can contain mutable items like lists.
define_tuple = ([4,5], ['x', 'y']) define_tuple[0][0] = 68 define_tuple[1][0] = 't' print(define_tuple)
Sort vs. sorted
We can’t order tuples using sort because they’re immutable:
define_tuple = (6, 0, 5) define_tuple.sort() #error
On the other hand, the sorted function can accept a tuple as an input and return a sorted list of the tuple’s values. It is essential to notice that this method does not produce a sorted tuple. The return variable’s type is the list.
define_tuple_one = (3, 5, 8, 2) define_tuple_two = sorted(define_tuple_one) print(define_tuple_two) print(type(define_tuple_two))
A tuple’s length
To find the length of a tuple, use the len function.
define_tuple = (3, 0, 2) len(define_tuple)
Counting and indexing techniques
Tuples have techniques for counting and indexing. The count method returns the number of times a value appears in a tuple.
define_tuple = (4, 'x', 4, 4, 'x') print(define_tuple.count('x')) print(define_tuple.count(4))
The index method returns the tuple’s value’s index.
define_tuple = (4, 'x', 6, 8, 'x') print(define_tuple.index('x')) print(define_tuple.index(4))
If a value appears in a tuple numerous times, the index method returns the index of the first occurrence.
Concatenating tuples
To add tuples together, use the ‘+’ operator.
define_tuple_one = (1, 2) define_tuple_two = ('x', 'y') define_tuple_three = define_tuple_one + define_tuple_two print(define_tuple_three )
Functions that return multiple values
Functions that return several values are one of the most popular uses of tuples. The total and count of items in an array are returned using the following procedure.
def count_sum(arr): count_val = len(arr) sum_val = arr.sum() return count_val, sum_val
This function returns a tuple with two elements:
import numpy as np ran_array = np.random.randint(6, size=9) define_tuple = count_sum(ran_array) print(define_tuple) print(type(define_tuple))
Other Tuple Operations
Multiplication of multiples
The tuple is repeated after the multiplication operation.
define_tuple = (4,5,6,7) z = define_tuple*2 print(z)
Functions in Tuples
Tuples, unlike Python lists, lack methods like append(), remove(), extend(), insert(), and pop() due to their immutability. There are, however, a slew of other built-in tuple methods:
Index()
tuple.index(el)
The index method returns the index of the element’s first occurrence in a tuple.
define_tuple = (1, 44, 65, 74, 8, 54, 44) print(define_tuple.index(1))
This method can also be used to return the index of the element’s last occurrence.
define_tuple = (1, 44, 65, 74, 8, 54, 44) print(define_tuple.index(24, -1))
It’s also possible to search inside a specific range, as shown below.
define_tuple = (1, 44, 65, 74, 8, 54, 44) print(define_tuple.index(44, 4, 7))
count() and len()
count() returns the number of times a given item appears in a tuple.
define_tuple = [4,5,6,7,8,8] define_tuple.count(8)
You can get the length of a tuple using the len() function:
define_tuple = (4,5,6,7,8) print(len(define_tuple))
Any()
It can be used to determine whether or not any element of a tuple is iterable. If this is the case, you’ll get true; otherwise, you’ll get False.
define_tuple = (1,) print(any(define_tuple))
Take note of the comma in the tuple declaration above. When you don’t include a comma when initializing a single item in a tuple, Python guesses you added an extra pair of brackets by accident (which is fine), but the data type is no longer a tuple. So when declaring a single item in a tuple, remember to include a comma.
Returning to the any() method now: The value of an item is unimportant in a boolean context. Therefore, any tuple with at least one item is valid, while an empty tuple is false.
define_empty_tuple = () print(any(define_empty_tuple))
If you’re calling a tuple anywhere in your application and want to make sure it’s populated, this function can come in handy.
tuple()
To convert a data type to a tuple, use tuple(). For instance, you are converting a given list into a tuple. You can see an example of this in the code section below.
define_a_list = [3,5,6,7,8] define_tuple = tuple(define_a_list) print(type(define_tuple))
min() and max()
While max() delivers the tuple’s most significant element, you can use min() to get the tuple’s smallest element. Consider the following illustration:
print(max(a)) print(min(a))
It also works with tuples that include the string data type.
The string ‘Apple’ is automatically converted into a sequence of characters.
a = ('Apple') print(max(a))
sum()
This function returns the total sum of the components in a tuple. It is only applicable to numerical numbers.
sum(a)
sorted()
Use sorted() to return a tuple with elements in sorted order, as shown in the following example:
define_tuple = (6,7,4,2,1,5,3) sorted(define_tuple)
It’s important to note that the return type is a list rather than a tuple. The data type of ‘a’ remains a tuple, and the sequence in the original tuple ‘a’ is not modified.
cmp()
The cmp() tuple method in Python compares the elements of two tuples.
Syntax
The syntax for the cmp() method is as follows:
cmp (define_tuple1, define_tuple2)
Parameters
define_tuple1- This is the first tuple to be compared.
define_tuple2- This is the second tuple to be compared.
Return value
Perform the comparison and return the result if the items are of the same type. Check to see if the elements are numbers if they are of different types.
If there are numbers, use numeric coercion if necessary before comparing.
If one of the elements is a number, the other is “bigger” (numbers are “smallest”).
Types are arranged alphabetically by name otherwise.
If we get to the end of one of the tuples, the longer one is “larger.” If both tuples are exhausted and contain the same data, the result is a tie and 0 returns.
Example
The cmp() method is demonstrated in the following example.
define_tuple1, define_tuple2 = (312, 'xyz'), (645, 'abc') print(cmp(define_tuple1, define_tuple2)) print(cmp(define_tuple2, define_tuple1)) define_tuple3 = define_tuple2 + (678,); print (cmp(define_tuple2, define_tuple3))
Assigning Multiple Values
Tuples may be used to assign several values at the same time, which is an excellent feature. Take a look at this:
define_tuple = (1,2,3) (first,second,third) = define_tuple print(second)
The (first, second, third) is a tuple of three variables and a tuple having three elements. When you assign (first, second, third) to a tuple, it gives the values to variables one, two, and three in that sequence. It is useful when you need to assign a range of values to a series in a tuple.
Example:
def cmp(tuple_one, tuple_two): return bool( tuple_one > tuple_two) - bool( tuple_one < tuple_two) tuple_one = (100, 200) tuple_two = (300, 400) print(cmp(tuple_one, tuple_two)) print(cmp(tuple_two, tuple_one)) tuple_one = (100, 200) tuple_two = (100, 200) print(cmp(tuple_two, tuple_one)) tuple_one = (100, 300) tuple_two = (200, 100) print(cmp(tuple_two, tuple_one))
Additional Information
Lists and tuples are both collections of values. Immutability is the most fundamental distinction.
Copying tuples and lists differ due to their immutability. Because lists are mutable, we must be more cautious while duplicating them. In addition, we can replicate a list and assign it to a new variable in one of three ways:
define_list = [4, 5, 6] y = define_list z = define_list[:] t = define_list.copy()
The values in the lists y, z, and t are the same as define_list. On the other hand, Y points to the values of define_list, whereas z and t are entirely different lists.
As a result, any change in define_list will result in a change in y.
define_list.append(4) print(y) print(t)
When copying lists, we must exercise extreme caution. Tuples, on the other hand, should not raise the same concerns because they are immutable.
When you copy a tuple and assign it to a new variable, the values in memory are all the same.
define_tuple = (1, 2, 3) b = define_tuple c = a[:]
Test for Multiple Membership
Using the keyword in, we can determine whether or not an item exists in a tuple.
#testing for Membership in a tuple define_tuple = ('a', 'p', 'p', 'l', 'e',) # using 'In' operation print('l' in define_tuple) print('b' in define_tuple) # using 'not in' operation print('g' not in define_tuple) print('e' not in define_tuple)
Lists versus Tuples
Tuples are similar to lists, as you may have noticed. They are immutable lists, which implies that once a tuple is generated, the values of the elements stored in it cannot be deleted or changed. You can’t change any of the values.
define_tuple = (1,2,3,4,5) define_list = [1,2,3,4,5] # Append a number to the tuple define_tuple.append(6)
Because you can’t remove or append to a tuple, but you can with a list, this results in an error.
# Append numbers to the list define_list.append(9) define_list.append(10) define_list.append(11) # Remove a number from the list define_list.remove(9 ) print(define_list)
But, if tuples are immutable, why would you utilize them?
They are not only faster than lists, but they also provide “read-only” access to the data values. Take a look at the following lines of code:
import timeit timeit.timeit('x=(1,2,3,4,5,6,7,8,9)', number=100000) timeit.timeit('x=[1,2,3,4,5,6,7,8,9]', number=100000)
What does immutable mean in the context of tuples?
Immutable is defined as “an object having a fixed value” in the official Python manual, although “value” is a somewhat ambiguous term; the correct time for tuples is “id.” The identity of the position of an object in memory is referred to as ‘id.’
Let’s take a closer look at this:
# Tuple 'define_a_tuple' with a list as one of its items. define_a_tuple = (1, 1, [3,4]) #Items with same value have the same id. id(define_a_tuple[0]) == id(define_a_tuple[1]) #Items with different value have different id. id(define_a_tuple[0]) == id(define_a_tuple[2]) id(define_a_tuple[0]) id(define_a_tuple[2]) define_a_tuple.append(11)
We can’t append an item to a tuple, which is why you’re getting an error like this. It is for this reason why a tuple is referred to as immutable. However, you can always perform the following:
define_a_tuple[2].append(5) define_a_tuple
As a result, you’ll be able to alter the original tuple. So how is it that the tuple is still referred to as immutable?
Even though you added 11, the id of the list within the tuple remains the same.
id(define_a_tuple[2])
Value access in Tuples
Use the square brackets for slicing along with the index or indices to get the value accessible at that index in a tuple.
define_tup_1 = ('first', 'second', 200, 400); define_tup_2 = (3, 5, 6, 7, 8, 9, 10 ); print(define_tup_1[0]) print(define_tup_2[1:5])
For instance, when the above code is run, the following is the result:
Negative Indexing
Python sequences support negative indexing. For instance, the index of -1 denotes the last item, the index of -2 the second last item, and so on.
# Negative indexing while accessing elements in a tuple define_tuple = ('p', 'e', 'r', 'm', 'i', 't') # how to output: 't' print(define_tuple[-1]) # how to output: 'p' print(define_tuple[-6])
Value update in Tuples
Tuple elements are immutable, which means you can’t update or change their values. However, as seen in the following example, you can use parts of existing tuples to generate new ones.
define_tup_1 = (12, 34.56) define_tup_2 = ('abc', 'xyz') # Following action is not valid for tuples # define_tup_1[0] = 100 # So let's create a new tuple as follows define_tup_3 = define_tup_1 + define_tup_2 print(define_tup_3)
Removing Tuple Elements
Individual tuple elements cannot be removed. But, of course, there’s nothing wrong with putting together another tuple without the unwanted components.
Use the del statement to precisely remove a whole tuple. For instance,
define_tup_1 = ('first', 'second', 200, 400) print(define_tup_1) del define_tup_1 print("After deleting define_tup_1 : ") print(define_tup_1)
As a result, you’ll get the following outcome. There is an error triggered because the tuple does not exist after del define_tup_1.
There are no enclosing delimiters
Any comma-separated group of numerous objects written without distinguishing symbols, such as brackets for lists, parentheses for tuples, and so on, defaults to tuples, as seen in these short examples.
print( 'abc', -4.24e93, 18+6.6j, 'xyz') x, y = 1, 2 print ("Value of x , y : ", x,y)
When the above code is run, the following result is obtained:
Tuple has several advantages over a list
- Because tuples and lists are so similar, they’re utilized in similar scenarios. However, there are some advantages to using a tuple rather than a list. The following are some of the most significant benefits:
- We use tuples for heterogeneous (different) data types, while we use lists for homogeneous (similar) data types.
- Iterating over a tuple is faster than iterating through a list because tuples are immutable. As a result, there is a minor performance boost.
- Tuples containing immutable elements can be used as a dictionary’s key. It is not feasible with lists.
If you have non-changing data, implementing it as a tuple will ensure that it remains write-protected.
Example of Using cmp()
# program illusrating how to use # cmp() define_tuple1 = ('python', 'codeunderscored') define_tuple2 = ('coder', 1) if (cmp(define_tuple1, define_tuple2) != 0): # cmp() returns 0 if matched, 1 when not tuple1 # is longer and -1 when tuple1 is shoter print('Not the same') else: print('Same')
Applications of Tuples
Tuples are frequently employed as a kind of modification resistance. Tuples can be used to write-protect data because they are immutable.
When it comes to iterating over a tuple, we see a significant performance boost compared to lists. It is more noticeable when the tuple size is large. We can observe that iterating tuples is significantly faster than iterating lists using Python’s timeit function.
An immutable key exists in the dictionary data structure. As a result, tuples can be utilized as a dictionary key.
Tuples can be used to organize data that is related. An entry in a database table, for example, can be joined together and stored in a tuple.
Conclusion
You’ve completed this tuple tutorial! You learned more about Python tuples, how to initialize them, the most frequent operations you can do on them to modify them, and the most popular ways you can use to get more information from these Python data structures along the way. You also learned that you could assign multiple values to tuples.
Some tuples (those containing only immutable objects such as strings, etc.) are immutable, while others (those containing one or more mutable objects such as lists, etc.) are mutable. It is a more detailed article on the subject. However, this is a contentious topic among Pythonistas, and you will need more background knowledge to comprehend it fully. So, for the time being, let us state that tuples are immutable in general.
Because tuples are immutable, you can’t add elements to them. Tuples have no append() or extend() methods, and you can’t remove elements from them due to their immutability. Tuples don’t have remove() or pop() methods, but you can discover features in them because they don’t affect the tuple.
You may also use the in operator to see if a tuple element exists.
Use a tuple instead of a list if you’re defining a constant set of values that you’re just going to cycle through. It will be faster and safer than working with lists because tuples contain “write-protected” data.
Thank you for taking the time to read this. Would you mind letting us know if you have any suggestions? | https://www.codeunderscored.com/tuples-in-python/ | CC-MAIN-2022-21 | refinedweb | 3,444 | 54.12 |
Created on 2019-09-10 13:32 by pierreglaser, last changed 2020-01-28 10:36 by steve.dower. This issue is now closed.
If I am not mistaken, when creating a new process on Python3.7 and later on Windows, if using a virtualenv, Python now uses a launcher. The launcher is being notified that it must create a virtual-environment Python (and not a system Python) program using the __PYVENV_LAUNCHER__ environment variable, passed as part of the environment of launcher process created using in _winapi.CreateProcess
(see)
However, if I am not mistaken `env` is not passed at the right position (). These lines were part of a bugfix patch (see), solving an issue for multiprocessing-based packages. We ended trying to backport to loky (, a multiprocessing-based package) but the bug was not fixed. Passing 'env' correctly fixed the bug.
Two things:
- It is hard to provide a reproducer for this issue as it requires patching the CPython source code.
- I don't understand why env being not passed correctly does not manifest itself in the test-suite. What is even more troubling is that even with this bug, the virtualenv launcher seems to get that a virtualenv is used when creating processes in multiprocessing (at least, sys.path includes the path/to/venv/lib/python3.x/site-packages). However, I am not familiar with the virtualenv launcher for python3.7+ and windows.
Yeah, very strange that. I can only assume that it's launching the venv redirector directly, rather than the real sys.executable, and we aren't ever calling set_executable() with the real one anymore.
Dropping this into Lib/multiprocessing/spawn.py should cause a repro:
if WINSERVICE:
_python_exe = os.path.join(sys.exec_prefix, 'python.exe')
else:
_python_exe = getattr(sys, '_base_executable', sys.executable)
And as you point out, fixing the CreateProcess call should provide a fix.
Could you try that? And maybe submit a PR with the fix?
> Dropping this into Lib/multiprocessing/spawn.py should cause a repro:
if WINSERVICE:
_python_exe = os.path.join(sys.exec_prefix, 'python.exe')
else:
_python_exe = getattr(sys, '_base_executable', sys.executable)
In this case, spawn.get_executable() will return (sys._base_executable), and `env` will be set to None anyways no? (see these lines:)
We need to trigger the if clause of these lines instead, which happens by default in a virtual env -- this is why it is so troubling: even though a very simple case (launching a new process from within a virtualenv) should trigger a bug, it does not.
> And maybe submit a PR with the fix?
Will do.
The difference is that launching sys._base_executable *without* __PYVENV_LAUNCHER__ set (because env is not being passed) should lose you access to anything installed into the venv. You may also need to import something from the venv in order to see the issue.
Launching sys.executable will hit the launcher that sets the environment variable. Setting the environment correctly and launching sys._base_executable will also load correctly. The latter is theoretically required for correct handle sharing, but that may depend on which Windows version you're running.
I'd like to see both changes in the PR. Just setting the environment variable doesn't really improve the situation at all.
I posted a second PR with the rest of the change, as it'd be good to get this in before the next 3.8 release.
New changeset f2b7556ef851ac85e7cbf189d1b29fdeb9539b88 by Miss Islington (bot) (Steve Dower) in branch 'master':
bpo-38092: Reduce overhead when using multiprocessing in a Windows virtual environment (GH-16098)
Thanks for the report and partial patch!
New changeset 436b429ade87b10879b3f944e99a515478e86e5e by Miss Islington (bot) in branch '3.8':
bpo-38092: Reduce overhead when using multiprocessing in a Windows virtual environment (GH-16098)
This should revert to setting `_python_exe = sys.executable` in Lib/multiprocessing/spawn.py. Then the code in Lib/multiprocessing/popen_spawn_win32.py will set __PYVENV_LAUNCHER__ in the spawned process to the virtual environment's sys.executable. Otherwise the worker process has no connection to the virtual environment, other than how sys.path gets manually copied from the parent process. In particular, without setting __PYVENV_LAUNCHER__, sys.executable is not the virtual-environment executable and sys.prefix is not the virtual-environment directory.
Also, the fix for the parameters that are passed to _winapi.CreateProcess needs to be backported to 3.7. Else __PYVENV_LAUNCHER__ won't actually be set in the child.
You're right, the logic to actually launch _base_executable is in there twice now, and the second one (that never gets used) is more important.
New changeset 6990d1b6131873c7f0913908162e4c723d00ea19 by Steve Dower (Adam Meily) in branch '3.7':
bpo-38092: Reduce overhead when using multiprocessing in a Windows virtual environment (GH-16098)
Fixed via issue39439 | https://bugs.python.org/issue38092 | CC-MAIN-2021-21 | refinedweb | 784 | 59.4 |
If you’ve been learning about Kubernetes, chances are you’re familiar with the concept of pods. Pods are an essential component in Kubernetes. That’s why the “Pod of Minerva” (an interactive guide used in this Certified Kubernetes Administrator course), is standing for the guide to the pod.
The Pod
Pods are scheduled to machines or VMs, in which the scheduler (the control plane component) attempts to fit the pod on a VM, given it has enough CPU and memory to sustain the needs of the pod. For those of us who want to utilize all of the resources of our VMs, you may be asking “How can I tell Kubernetes to fit pods on my VM so that it’s utilizing all the resources it has?” After all, most of us don’t have the ability to create an infinite amount of VMs for our pods to live on and utilizing every square inch of the resources that we’ve paid for is not only cost-effective, but allows us to ensure our pods are receiving adequate resources to run, in turn, allowing our app to perform better.
In this short tutorial, you’ll learn how to use requests and limits for your pods in order to better organize how your pods are scheduled across your cluster. I aim to convince you that adding this to every pod definition is a great idea that offers you peace of mind that will add value to your application running on Kubernetes.
Requests and Limits
When creating a pod, you can specify the amount of CPU and memory a container needs, called the requests. You can also set a limit on the amount of CPU and memory a container should use, which is called limits. Setting the requests and limits becomes very important when considering the JVM heap size for Java applications. Most likely, if not set correctly, the JVM process will be killed by the systems OOM killer.
Let’s go ahead and create a pod with just requests and I’ll explain what this is doing for the pod. First, create the following pod YAML that will specify the image to use and the request amounts. If you don’t have access to your own cluster, get started with Linux Academy’s free community edition (for limited access).
apiVersion: v1 kind: Pod metadata: name: pod1 spec: containers: - image: busybox command: ["dd", "if=/dev/zero", "of=/dev/null"] name: pod1 resources: requests: cpu: 800m memory: 20Mi
Go ahead and run the following command to create the pod:
kubectl create -f pod.yaml
To see this pod and which node it’s running on, enter the following command:
kubectl get pods -o wide
To get more information about the node and its utilized resources, enter the following command:
kubectl describe node [node_name]
Note: If you don’t know the node name, type the following to get it:
kubectl get nodes
At the bottom of the output from the
kubectl describe node command, you will notice the requests and limits, similar to this:
You might notice from the screenshot above, there is more than just one pod running on this node. That’s because flannel and kube-proxy will be running in the cluster as well, in the kube-system namespace. And that’s where the total amount of requests comes from. From the screenshot above, the flannel pod is requesting 100m of CPU and the pod we just scheduled is requesting 800m of CPU. That gives us our total of 900m (90%) listed at the bottom.
The Node CPU Resource
You’d think that because each of these pods has requested an amount, they will only use the requested amount and that’s it. That is not true. Actually, both pods will most likely use all the remaining CPU if required. But, they don’t just split it evenly. The remaining CPU is split in a 1 to 5 ratio. The first pod will get one-sixth of the CPU time and the other will get the remaining five-sixths.
To explicitly state the maximum amount of CPU and memory a pod can use, we can set limits in the pod YAML as well. Here’s the same YAML from the first pod, but we’ve added limits:
apiVersion: v1 kind: Pod metadata: name: pod1 spec: containers: - image: busybox command: ["dd", "if=/dev/zero", "of=/dev/null"] name: pod1 resources: requests: cpu: 800m memory: 20Mi limits: cpu: 800m memory: 20Mi
To apply these changes, you’ll have to delete the existing pod and re-create it using the modified YAML. Use the following command to delete the pod:
kubectl delete pods pod1
Then, you can create the pod with the new YAML using the following command:
kubectl create -f pod.yaml
We can check if the pod is running by entering the following command:
kubectl get pods -o wide
Now that our pod is running, it has requested 800m CPU and 20Mi of memory, and because we set the limit of the same, it will use the requested amount and nothing more.
More on Pod CPU and Memory
This has been a short tutorial on setting CPU and memory requests and limits in Kubernetes. If you’d like to know more about scheduling pods in Kubernetes, check out the Cloud Native Certified Kubernetes Administrator (CKA) course on Linux Academy or check out these free resources below to learn more about Kubernetes:
- Managing Storage in Kubernetes
- Deploying Services in Kubernetes
- Kubernetes Cheat Sheet
- Building a Three-Node Kubernetes Cluster | Quick Guide
- Getting Started with Kubernetes Using Minikube
- Running Prometheus on Kubernetes | https://linuxacademy.com/blog/kubernetes/throttling-pods-in-kubernetes/ | CC-MAIN-2020-16 | refinedweb | 939 | 60.69 |
xTurtle is built as a small and easy-to-use visual programming language that makes use of Java.
The drawing area of xTurtle includes a twenty-by-twenty square in which the turtle can move and draw.
This square has horizontal coordinates from -10 on the left to 10 on the right, and it has vertical coordinates from -10 at the bottom to 10 at the top.
Because the drawing area is unlikely to be exactly square, the coordinates for the entire drawing area probably extend beyond the range -10 to 10 in either the horizontal or vertical direction.
The turtle starts out in the center of the screen — at the point (0,0) — facing to the right. It can obey commands such as “forward(5),” which tells it to move forward five units, and “turn(120),” which tells it to rotate in place through an angle of 120 degrees.
The turtle can draw a line as it moves. You can think of it as dragging a pen that draws as the turtle moves.
The command “PenUp” tells the turtle to “raise the pen.” While the pen is raised, the turtle will move without drawing anything. The command “PenDown” tells the turtle to lower the pen again.
XTurtle Crack + Free License Key Free Download [Mac/Win] [Updated] 2022
You can use this package to test the program by running a sample program named xTurtle. A sample program is provided with the archive.
You can view the package contents by unpacking the archive and then viewing the contents of the subdirectory named xTurtle. A number of the java files in the xTurtle package are smaller than 4K. A.jar file named xTurtle.jar is created to wrap the xTurtle package contents.
This package contains several classes and other files.
For a list of the classes contained in this package, refer to the file xTurtle.java.
The source file (already converted to use tabs and to replace with newlines) is xTurtle.java. It can be viewed by using a text editor, such as EditPad Pro or Notepad.
The main classes in the package are Turtle and Screen.
The class Turtle has functions to move the turtle around. It also has functions to draw lines and arcs.
The class Screen has functions to draw xTurtle graphics on the screen.
A class named Screen may be used to draw graphics in various ways on the screen.
It is used here to draw the path that the turtle draws as it moves.
A Screen object may be used to create a window to use xTurtle graphics.
You can use a Screen object to draw graphics in a window. You may use this object to draw graphics on your desktop.
Here, the xTurtle graphics are drawn on a black background.
You can set the appearance of the window by setting the value of Screen.setColor() and Screen.setBackground().
You can draw a shape by using Screen.fillRect() or Screen.strokeRect().
The package also contains some supporting classes.
A file named ModifyTurtle.java is the source file for a sample of the ModifyTurtle class. It is also included in this archive.
The ModifyTurtle class has some utility functions.
The ModifyTurtle class may be used to move the turtle around and to draw shapes and lines.
It is used here to draw a shape named “square,” that is, a rectangle that is 10 pixels wide and 10 pixels high.
A sample program xCircle.java is included in this archive. The program is a turtle graphics sample that creates a turtle and then draws a circle.
It
XTurtle Crack+
An easy-to-use visual programming language that makes use of Java.
xTurtle Download With Full Crack Code:
// xTurtle Cracked Accounts – a visual: Cracked xTurtle With Keygen.java *
//* Author: Jonathan Allen *
//* Date: 15 Sep 2000 *
//*
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public void drawSegment(int x1, int y1, int x2, int y2):
Q:
Windows 7’s Mail not sending out until after Windows is logged in
I’ve been trying to send an email from Windows 7’s mail program (with Office 2007). After doing so, the program locks itself to the mail screen for 5-10 seconds before opening. After that, it works fine.
I’ve tried uninstalling and reinstalling the program multiple times, as well as disabling and re-enabling windows firewall. It still happens.
Does anyone have any ideas?
I’m running Office 2007 on Windows 7 Professional.
A:
I had the same problem. In my case I had to go to the “account settings” of the email account and mark the option to “skip new email checks” (which is the opposite of what people are saying in the comments here).
Q:
Can not handle-error callback in promisify()
I’m trying to make a promise wrapper for HTTP response (3xx) errors. This is the code I use:
let wrapper = (data, status, err, res, resolve
What’s New In?
% xTurtle.java
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/**
* A very simple visual programming language.
*
* @author Eric Paumier
*/
public class xTurtle extends JPanel
implements ActionListener
{
// Maximum length of a line the turtle can draw.
// If a line is too long to fit in the current
// drawing area, the turtle will doodle in the
// area until it is finished.
private static final int MAX_LINE_LENGTH = 20;
// Drawing area.
private static final int X_BORDER = -10;
private static final int Y_BORDER = -10;
// Image of the turtle.
private static final BufferedImage TURTLE_IMAGE = new BufferedImage(80, 80, BufferedImage.TYPE_3BYTE_BGR);
// Draw a line as the turtle moves.
private static final int LINE_DRAWING_SPEED = 5;
// Coordinates for the current position of the turtle.
private static final int TURTLE_POSITION[] = new int[2];
// Display the xTurtle on the current screen.
private static JComponent fComponent = new JComponent()
{
@Override public Dimension getMaximumSize()
{
return new Dimension(300, 300);
}
@Override public void paint(Graphics g)
{
// Draw the turtle at the current x, y location.
g.drawImage(TURTLE_IMAGE, 0, 0, null);
}
};
// Constructor.
public xTurtle()
{
addMouseListener(new MouseAdapter()
{
public void mouseClicked(MouseEvent me)
{
System Requirements:
Minimum:
OS: Windows XP (SP3) or later, Vista (SP1) or later. (32-bit & 64-bit supported)
Processor: Intel Core 2 Duo or AMD Athlon 64 X2 Dual Core
Memory: 2 GB RAM (8 GB recommended)
Graphics: Intel HD Graphics 2000 or AMD HD Radeon 4000 or better, or GeForce 9500 or higher
Hard Drive: 2 GB available space
Input devices: Keyboard, Mouse
Sound: DirectX 9.0 compatible sound | https://setewindowblinds.com/xturtle-for-windows-april-2022/ | CC-MAIN-2022-40 | refinedweb | 1,071 | 65.73 |
I want to learn SFML and I've tried loads of different tutorials but I just get errors with everything I put into it, whether I copy it and type it or if I paste it.
My code:
#include <SFML/Window.hpp> int main() { sf::Window window; window.create(sf::VideoMode(640,480), "Window"); while(window.isOpen()) { sf:Event event; while(window.pollEvent(event)) { if(event.type = sf::Event::Closed) window.close(); } } return 0; }
Errors:
g++ -c main.cpp main.cpp: In function ‘int main()’: main.cpp:6:9: error: ‘class sf::Window’ has no member named ‘create’ window.create(sf::VideoMode(640,480), "Window"); ^ main.cpp:7:15: error: ‘class sf::Window’ has no member named ‘isOpen’ while(window.isOpen()) ^ main.cpp:9:6: error: ‘Event’ was not declared in this scope sf:Event event; ^ main.cpp:9:6: note: suggested alternative: In file included from /usr/include/SFML/Window.hpp:34:0, from main.cpp:1: /usr/include/SFML/Window/Event.hpp:197:7: note: ‘sf::Event’ class Event ^ main.cpp:9:12: error: expected ‘;’ before ‘event’ sf:Event event; ^ main.cpp:10:16: error: ‘class sf::Window’ has no member named ‘pollEvent’ while(window.pollEvent(event)) ^ main.cpp:10:26: error: ‘event’ was not declared in this scope while(window.pollEvent(event)) ^ main.cpp:13:11: error: ‘class sf::Window’ has no member named ‘close’ window.close(); ^
Have I installed it wrong or am I missing something? | http://www.gamedev.net/topic/653550-sfml-cant-even-compile-tutorial-code/ | CC-MAIN-2014-41 | refinedweb | 240 | 55 |
Developing using Docker has many benefits, like ensuring your builds always build in the same way and ensuring a consistent way of installation. Although the development environment of our developers may be different, the use of Docker ensures that the build works on every machine, every time. No more libsass incompatibilities for us.
With edi, as we call our solution, we provide a set of scripts and Docker images for developing EmberJS apps. Cloning and starting an existing repository could look like:
# clone the project git clone git@git.pintafish.be:fish-tracker cd fish-tracker # install the dependencies edi npm install edi bower install # launch the development browser (ember serve) eds
Installation
In order to install edi, we have to install the edi and eds commands, and ensure Docker creates files under our own namespace.
Docker traditionally runs as the root user on your local machine. The side-effect is that the files which edi ember generate creates, are owned by root. With user-namespaces, it is possible to run Docker under your own user, and thus creating files under your own namespace.
The installation shown here should run on modern Linux distributions.
Using docker namespaces
User-namespaces essentially provide an offset to the regular user identifiers. This means we can map the root’s user-id to your own user-id. This also means that when the root user in the container creates a file, the UID will be the root UID in the container, but it will be our UID outside of the container.
In order to make this work we have to supply the mapping. Edit the /etc/subuid and /etc/subgid files with the following commands:
MY_USER_UID=`grep my-user /etc/passwd | awk -F':' '{ print $3 }'` MY_USER_GUID=`grep my-user /etc/passwd | awk -F':' '{ print $4 }'` echo "ns1:$MY_USER_UID:65536"| sudo tee -a /etc/subuid echo "ns1:$MY_USER_GUID:65536"| sudo tee -a /etc/subgid
Next, we have to tell the Docker daemon to use this new namespace. The configuration script may be in various locations, depending on your Linux distribution. systemctl provides a utility to find and edit the right file.
systemctl edit docker.service
Once the editor opens, ensure the following contents are present:
ExecStart= ExecStart=/usr/bin/dockerd --userns-remap=ns1
Note the ExecStart= line, it is necessary to indicate that we intend to override the original ExecStart command. Without it, our new command will be ignored.
Installing the scripts
The scripts are contained in the madnificent/docker-ember repository and we will add them to our PATH.
Open a terminal in a folder where you have access rights to, and in which you’d like to permanently store the reference to the ember-docker. Then execute the following commands:
git clone echo "export PATH=\$PATH:`pwd`/docker-ember/bin" >> ~/.bashrc source ~/.bashrc
Our first new app using Docker
All commands, except for ember serve which deserves special attention, can be ran through the edi command.
Let’s create a new project:
edi ember new my-edi-app
This will generate a new application. Once all dependencies have been installed, we can move into the application folder, and start the ember server:
cd my-edi-app eds
You will see the application running. Moving your browser to, you will see the ember-welcome-page. Yay! It works \o/
Let’s remove the welcome-page. As instructed, we’ll remove the {{welcome-page}} component from the build. Open your favorite editor, and update the contents of application.hbs to contain the following instead.
<h1>My first edi app</h1> {{outlet}}
We can generate new routes with the ember application still running. Open a new terminal and open the my-edi-app folder. Then generate the route:
edi ember generate route hello-link
edit the app/templates/hello-link.hbs template so it contains the following
<p>Hello! This is some nested content from my first page. {{link-to 'Go back' 'index'}}</p>
and add a link to app/templates/application.hbs
<h1>My first edi app</h1> <p>{{link-to 'Hello' 'hello-link'}}</p> {{outlet}}
Boom, we have generated files which we can edit. Lastly, we’ll install the ember-cli-sass addon as an example.
edi ember install ember-cli-sass
Now restart eds to ensure the ember server picks up the newly installed addon, remove the old app/styles/app.css and add a background-color to app/styles/app.scss
body { background-color: green; }
Caveats
There are some caveats with the use of edi. First is configuring the ember version. You can switch versions easily by editing a single file. Next is configuring the backend to run against.
Configuring the ember version
You may want to have more than one ember version installed when generating new applications. When breaking changes occur to ember-cli, or if you want to be sure to generate older applications. Perhaps you simple don’t want to download all the versions of ember-cli. Whatever your motives are, you can set the version in ~/.config/edi/settings
If the file or folder does not exist, create it. You can write the following content to the file to change the version:
VERSION="2.11.0"
Supported versions are the tags available at.
Linking to a backend
Each Docker Container is a mini virtual machine. In this virtual machine, the name localhost indicates that little virtual machine. We have defined the name host to link to the machine serving the application. In case you’d setup a mu.semte.ch architecture backend, published on port 80 of your localhost, you could connect your development frontend to it as such:
eds --proxy
It is a common oversight to try to connect to localhost from the container instead.
Way ahead
Our EmberJS development has become a lot more consistent and maintainable with the use of edi. We have used it extensively, and have been able to reproduce builds easily in the past year.
Over time we have extended edi with support for developing addons. Stay tuned to read more about this. | https://mu.semte.ch/2017/03/09/developing-emberjs-with-docker/ | CC-MAIN-2017-30 | refinedweb | 1,011 | 56.25 |
In August 2017 a typosquatting attack was discovered:
@kentcdodds Hi Kent, it looks like this npm package is stealing env variables on install, using your cross-env package as bait: pic.twitter.com/REsRG8Exsx— Oscar Bolmsten (@o_cee) August 1, 2017
The npm package
crossenv was found to contain malicious code that exfiltrated environment variables upon installation.
The attack was executed by the npm user
hacktask who authored 40 packages with names similar to common packages.
Examples of package names (and the ones they imitate) in the attack were:
- crossenv (cross-env)
- mongose (mongoose)
- cross-env.js (cross-env)
- node-fabric (fabric)
The attacker tried to use human error and common npm naming conventions to trick users into installing the malicious packages.
A reply to the initial tweet suggested a way to mitigate similar attacks in the future:
would be super useful if @npmjs would deny publishing a package if another one with a #levenshtein distance <3 is already published !!!— Andrei Neculau (@andreineculau) August 1, 2017
This suggested to create a package name validation based on the Levenshtein distance and reject publication of a new package if the name has a distance of less than 3 to an existing one. This would have identified and blocked the creation of the
crossenv package which has a distance of 1 with the name
cross-env, and may mitigate most spelling mistakes.
I wanted to investigate whether:
- a Levenshtein distance based validation was a viable solution and see if I could use the npmjs.com infrastructure to find other active typosquatting attacks
- I could use other properties of the attack and package metadata to find other active attacks
Search - Levenshtein distance
The Levenshtein distance is a metric for measuring the similarities of two strings. The distance is an integer which describes the number of single character edits required to transform one string into the other.
We can search the npm repository to find pairings of package names with low Levenshtein distances as these may be cases of typosquatting. If we find low distance combinations of package names and aggregate by author it should be possible to identify authors such as
hacktask who have multiple packages with similar names to existing ones.
data
The data required for our search is package name and author, npmjs.com stores package data in a CouchDB database which can be accessed at.
CouchDB is a JSON document store with a REST API for data access/editing. It is built with replication as a first class concept which makes it very easy to make copies of databases.
After installing CouchDB we can locally replicate the npm database with:
# create the database curl -X PUT # npmjs has two databases, 'fullfatdb' which contains the metadata and attachments and # 'skimdb' which only contains the metadata, we only need to replicate the 'skimdb' server curl -d '{"source":"", "target":"registry"}' \ -H "Content-Type: application/json" \ -X POST
The
registry database uses the package name as the key and the value is a JSON document containing information on the package versions.
The data for the package
d3fc can be found at and a reduced representation of the document is:
{ "_id": "d3fc", "name": "d3fc", "time": { "modified": "2017-10-16T16:20:51.718Z", "created": "2015-06-19T15:46:55.951Z", "13.1.1": "2017-10-16T16:20:51.718Z" }, "maintainers": [ { "name": "chrisprice" }, { "name": "colineberhardt" } ], "dist-tags": { "latest": "13.1.1" }, "versions": { "13.1.1": { "version": "13.1.1", "description": "A collection of components that make it easy to build interactive charts with D3", "main": "build/d3fc.js", "_npmUser": { "name": "colineberhardt" }, "maintainers": [ { "name": "chrisprice" }, { "name": "colineberhardt" } ], "dependencies": { "d3": "^3.5.4" } } } }
From this data we want to extract the name of the package
d3fc and the authors
chrisprice and
colineberhardt. Querying data from a CouchDB database requires a View which is written in JavaScript and is similar in concept to a map-reduce query. Views contain a
map function and optionally contain a
reduce function, these are executed on each document and the results aggregated and returned as a JSON object.
We only need to write a
map function to take in the
doc as a parameter and call the
emit function with the package name and an array of distinct values for the author(s):
function (doc) { var getNameOrEmailOrNull = function (data) { if (!data) { return null; } if ("name" in data) { return data.name; } if ("email" in data) { return data.email; } return null; } var getSafe = function (p, o) { return p.reduce(function (xs, x) { return (xs && xs[x]) ? xs[x] : null }, o) } var namesSet = Object.create(null); var addToNamesIfExists = function (path) { var authorOrNull = getSafe(path, doc); var valueOrNull = getNameOrEmailOrNull(authorOrNull); if (valueOrNull && (valueOrNull in namesSet === false)) { namesSet[valueOrNull] = true; } }; var searchThroughUsers = function (prefixProps) { addToNamesIfExists(prefixProps.concat(["_npmUser"])); addToNamesIfExists(prefixProps.concat(["maintainers", 0])); addToNamesIfExists(prefixProps.concat(["maintainers", 1])); addToNamesIfExists(prefixProps.concat(["maintainers", 2])); addToNamesIfExists(prefixProps.concat(["contributors", 0])); addToNamesIfExists(prefixProps.concat(["contributors", 1])); addToNamesIfExists(prefixProps.concat(["contributors", 2])); } // doc._npmUser, doc.maintainers[0], doc.contributors[0] etc searchThroughUsers([]); // the npm procedure when a malicious package is found is to change the author to npm // searching for the '0.0.1-security' version of the package finds the original author searchThroughUsers(["versions", "0.0.1-security"]); var latest = getSafe(["dist-tags", "latest"], doc); if (latest) { searchThroughUsers(["versions", latest]); } emit(doc._id, Object.keys(namesSet)); }
After saving the view as
getAuthors in the app
repoHunt, we can see the results of the view at.
To test the view we can append
?key=%22d3fc%22 which gives us the results of the view run against just the
d3fc data and shows the two expected authors:
{ "rows": [ { "id": "d3fc", "key": "d3fc", "value": [ "chrisprice", "colineberhardt" ] } ] }
processing
There are currently over 580,000 package names in the npm repository and applying the algorithm to this many combinations (~1.7E11) presents a challenge. Since we know the set of names to be compared against we can use a Trie and distance upper limit to minimise the search space and then parallelise the computation for each word.
The processing results in a list of name pairings and their Levenshtein distance, we can join this with the authors data and group by author. This should show
hacktask and other authors with many packages with similar names to other packages.
The Levenshtein distance between two words can be deceptively small, which may result in a lot of false positive results. To try and reduce noise we can scrape the popular packages from the npm website and join with this data, as attackers are only likely to imitate popular packages.
We can guess the practicality of using a Levenshtein distance based validation on new package names, it will only be practical if new names aren’t rejected a large percentage of the time. We can find the percentage of names with another name of a certain Levenshtein distance to give a rough idea of a new name being rejected.
results
46% of npm package names have another name within a Levenshtein distance of 2 or less (64% for a distance of 3 or less and 26% for 1), this is a high percentage and suggests that the distance name validation may be impractical for new packages unless name choice behaviours change.
We can plot the number of packages and the percentage of names of distance away from another name, against name length:
This graph shows that 100% of names with 1 character are of distance 1 away from a name in npm (logically this is true since the names with two chars include each letter of the alphabet) and that 56% of names with 14 characters are a distance of 3 or less away from another name. The longer the package name, the less likely a package will have a low distance to another name. This is consistent with intuition and supports npm’s recent suggestion to add scopes to package names as part of their new package moniker rules.
The test for this analysis and approach is whether it would catch the
hacktask user’s attack. We can aggregate package combinations of distance 1 to popular packages by author name.
The user
hacktask has 4 packages with names close to popular packages and is seen after the 475 users with the same number or more.
hacktask doesn’t stand out because of the sheer number of prolific authors in the npm repository (there are 419 users with over a 100 packages and 6 with over 1000). The number of packages, combined with the npm preference for short package names provide a lot of noise to drown out the signal of the low Levenshtein distance.
Searching for low Levenshtein distance pairings has discovered a few authors who are typosquatting but either don’t appear to be doing so with malicious intent or are not engaged in attacks. The authors and packages that look suspicious have been reported to npm.
A disadvantage of the above approach is that aggregating by author name will not catch authors which only have a single, or low numbers of malicious packages. If an attacker wanted to evade this type of analysis they could easily just create an account for every malicious package they published. We can try to look for other traits of the
crossenv package for further search inspiration.
Search - package metadata
The similar package name was only one characteristic of the
crossenv attack.
There were some other interesting features:
- package used a dependency with a very similar name to it (
cross-env)
- package made a call to
nodein one of the script events called on installation.
- package versioning does not start at
0.or
1..
We can write views to look for all of these characteristics, any packages which fulfil one or more of these criteria might be suspicious.
View - similar named dependency
The
crossenv package was essentially a wrapper around the
cross-env package that ran malicious code on installation.
crossenv needed to have a dependency on the actual
cross-env package to function and avoid detection.
We can write a view to find similar packages by running the Levenshtein distance algorithm against a package’s dependencies:
function (doc) { var getLevDistance = function ]; }; var maxDistance = 3; var latestVersion = doc['dist-tags'] && doc['dist-tags'].latest latestVersion = latestVersion && doc.versions && doc.versions[latestVersion] if (!latestVersion) return if ("dependencies" in latestVersion === false) { return; } var results = []; var dependencies = latestVersion["dependencies"]; for (var property in dependencies) { if (property !== doc.name) { if (dependencies.hasOwnProperty(property)) { var distance = getLevDistance(doc.name, property); if (distance <= maxDistance) { results.push(property); } } } } if (results.length > 0) { emit(doc._id, results); } }
View - node script
The malicious code in the
crossenv package was executed on the
postinstall event. The event executed
node package-setup.js, where
package-setup.js was the malicious script.
We can create a view to search the
scripts node of the
latest version of the package and return any calls out to
node.
function (doc) { var latestVersion = doc['dist-tags'] && doc['dist-tags'].latest latestVersion = latestVersion && doc.versions && doc.versions[latestVersion] if (!latestVersion) return if ("scripts" in latestVersion === false) { return; } var scripts = latestVersion["scripts"]; var npmInstallEvents = [ "preinstall", "install", "postinstall", "prepublish", "prepare", "prepack"] for (var i in npmInstallEvents) { var eventName = npmInstallEvents[i]; var script = scripts[eventName]; if (script) { var scriptContainsNode = script.toLowerCase().indexOf("node ") !== -1 if (scriptContainsNode) { emit(doc._id, script) } } } }
View - major version
The first released version of the
crossenv package was
5.0.0-beta.0, this is inconsistent with semantic versioning which typically suggests that package versioning initially starts with
0. or
1..
We can write a view to detect if a package is uploaded with the initial package version being greater than
1.:
function (doc) { if (!String.prototype.startsWith) { String.prototype.startsWith = function (search, pos) { return this.substr(!pos || pos < 0 ? 0 : +pos, search.length) === search; }; } // detect jumps from nothing to a non 1 major version. var docTime = doc.time; for (var name in docTime) { if (docTime.hasOwnProperty(name)) { if (name !== "created" && name !== "modified" && name.indexOf("security") === -1) { var firstVersion = name; if ((firstVersion.startsWith("0.") === false) && (firstVersion.startsWith("1.") === false)) { emit(doc._id, firstVersion); } return; } } } }
results
The package features that these views expose can arise from valid use cases, but when packages adhere to more than one then they become a candidate for inspection.
There are a few packages which meet all of the criteria in the Views but do not appear to be suspicious, an example of these is the package edge-js. This package is a fork of the Edge.js package which explains the initial version number of
6.5.7, has the dependency
edge-cs which is a distance of 1 away from it’s name and on
install, makes a call to
node tools/install.js which appears benign when viewed on Runkit.
Search conclusion
The Levenshtein distance check was not particularly effective due to the nature of the problem and the sheer number of packages in the npm repository. Malicious typosquatting is very hard to detect because behaviour that could be considered as typosquatting is so prevalent.
Examples of this are:
- a package is similar in concept to another package, e.g.
preactand
react.
- a package extends a library towards a specific purpose, e.g.
d3fcand
d3.
- a package bridges two technologies and use the a combination of the words in the new package name, e.g.
bochaand
mocha.
- someone decides that a package deserves a better name, e.g.
class-namesand
classnames.
- a package which parodies another one,
blodashand
lodash.
These behaviours aren’t malicious typosquatting, but produce false positives with an analysis based on Levenshtein distance.
The
crossenv attack went unnoticed for 2 weeks and isn’t considered to have been very effective due to the low numbers of package downloads. My analysis didn’t uncover any active typosquatting attacks in the npm repository and in this type of investigation, no news is good news. The absence of active attacks leads me to believe that npm must already implement checks similar to those described above and/or attackers don’t consider it to be an effective method. All of the code used in this analysis can be found on github. | https://blog.scottlogic.com/2018/02/27/hunting-typosquatters-on-npm.html | CC-MAIN-2021-21 | refinedweb | 2,348 | 53.51 |
Hi
I have used a bit of TextMate in the past. And one of the things that that I really liked in it in the past (and something that I've missed in other editors) is autocompletion of symbols.
Say for example, I have a piece of Rails code:
class CommentsController < ApplicationController
def create
@post = Post.find(params:post_id])
# The exclamation raises an error rather than returning false
@comment = @post.comments.new(params:comment])
@comment
if @comment.save
redirect_to @post
else
#render :partial => "/posts/comment_failed", :object => @comment
flash:error] = "Unable to add your comments... Make sure you fill in your name, email and some comment."
redirect_to @post
end
end
end
So, if I wanted to use the @comment symbol, I could simple type @c and press ESC key to cycle through all symbols/words that start with @c in file.
Does Sublime have similar functionality? I know finding words through (Command-p-#) and use autocompletion (ctrl-spacebar/option-ESC) for snippets is possible.
Is there a way for me to emulate the Textmate functionality of typing in the first few letters of a symbol/word, and then hitting a particular key repeatedly to autocomplete the word?
Thanks. | https://forum.sublimetext.com/t/autocomplete-words-symbols/1415/2 | CC-MAIN-2017-43 | refinedweb | 197 | 54.83 |
, ...
qvist manual (as described in the SEE ALSO section of
this manpage).
DESCRIPTION
C mas-
ter every detail to do useful work with cvs; in fact, five
commands are sufficient to use (and contribute to) the
source repository.
cvs checkout modules...
A necessary preliminary for most cvs work: creates
your private copy of the source for modules (named
collections of source; you can also use a path.
-Q Causes the command to be really quiet; the command
will generate output only for serious problems.
-q Causes the command to be somewhat quiet; informa-
tional-
name of the master source repository. Overrides
the setting of the CVSROOT environment variable.
This value should be specified as an absolute path-
name.
-e editor
Use editor to enter revision log information.
Overrides the setting of the CVSEDITOR and the EDI-
TOR environment variables.
-f Do not read the cvs startup file (~/.cvsrc).
-l Do not log the cvs_command in the command history
(but execute it anyway). See the description of
the history command for information on command his-
tory.
unfa-
miliar command.
-r Makes new working files read-only. Same effect as
if the CVSREAD environment variable is set.
-v [ --version ]
Displays version and copyright information for cvs.
-w Makes new working files read-write (default).
Overrides the setting of the CVSREAD environment
3
CVS(1) CVS(1)
variable.
-x Encrypt all communication between the client and
the server. As of this writing, this is only
implemented when using a Kerberos connection.
-z compression-level
When transferring files across the network use gzip
with compression level compression-level to com-
press. How-
ever, many options are available across several commands.
You can display a usage summary for each command by speci-
fying argu-
ments, executions hierarchies of sources under cvs
control. (Does not directly affect repository;
changes working directory.)
admin Execute control functions on the source repository.
(Changes repository directly; uses working direc-
tory without changing it.)
4
CVS(1) CVS(1); creates directory reposi-
tory.).)
5
CVS(1) CVS(1)
status Show current status of files: latest version,
This section describes the command_options that are, supported, in particular ISO
("1972-09-24 20:05") or Internet ("24 Sep 1972
20:05").; see the
description of the update command). -D is avail-
able with the checkout, diff, history, export,
rdiff, rtag, and update commands. Examples of
valid date specifications include:
1 month ago
2 hours ago
400000 seconds ago
last year
6
CVS(1) CVS(1)
last Monday
yesterday
a fortnight ago
3/31/92 10:00:07 PST
January 23, 1987 10:05pm
22:00 GMT
:
-H Help; describe the options available for this com-
mand. This is the only option supported for all
cvs commands.
-k kflag
Alter the default processing of keywords. The -k
option is available with the add, checkout, diff,
export, rdiff, and update commands. Your kflag
specification is ``sticky'' when you use it to cre-
ate, rtag, status,
tag, and update. Warning: this is not the same as
the overall `cvs -l' option, which you can specify
to the left of a cvs command!
-n Do not run any checkout/commit/tag/update program.
(A program can be specified to run on each of these
activities,
7
CVS(1) CVS(1).
-r tag Use the revision specified by the tag argument
instead of the default ``head'' revision. As well
as arbitrary tags defined with the tag or rtag com-
mand, two special tags are always available: `HEAD'
refers to the most recent version available in the
repository, and `BASE' refers to the revision you
last checked out into the current working direc-
tory.
summary line.
Working Directory, or Repository?
Some cvs commands require a working directory to
operate; some require a repository. Also, some
commands change the repository, some change the
8
CVS(1) CVS direc-
tory in the source repository. The files or direc-
tories specified with add must already exist in the
current directory (which must have been created
with the checkout command). To add a whole new
directory hierarchy to the source repository (for
example, files received from a third-party vendor),
use the `cvs import' command instead.
If the argument to `cvs add' refers to an immediate
sub-directory, the directory is created at the cor-
rect place in the source repository, and the neces-
sary
example% mkdir new_directory
example% cvs add new_directory
example% cvs update new_directory
An alternate approach using `cvs update' might be:
example% cvs update -d new_directory
(To add any available new directories to your work-
ing directory, it's probably simpler to use `cvs
9
CVS(1) CVS(1)
make the new file permanent. If you'd like to have
another logging message associated with just cre-
ation of the file (for example, to describe the
file's purpose), you can specify it with the `-m
message' option to the add command.
The `-k kflag' option specifies the default way
that this file will be checked out. The `kflag'
argument is stored in the RCS file and can be
changed with `cvs admin'. Specifying `-ko'.
Requires: repository.
Changes: working directory.
Synonyms: co, get
Make a working directory containing copies of the
source files specified by modules. You must exe-
cute `cvs checkout' before using most of the other
cvs commands, since most of them operate on your
working directory.
modules are either symbolic names (themselves
defined as the module `modules' in the source
repository; see cvs(5)) for some collection of
source directories and files, or paths to directo-
ries or files in the repository. reposi-
tory; or commit your work as a permanent change to
the repository.
Note that checkout is used to create directories.
The top-level directory created is always added to
the directory where checkout is invoked, and usu-
ally has the same name as the specified module. In
the case of a module alias, the created sub-direc-
tory may have a different name, but you can be sure
that it will be a sub-directory, and that checkout
10
CVS(1) CVS(1)
will show the relative path leading to each file as
it is extracted into your private work area (unless
you specify the -Q global option).
Running `cvs checkout' on a directory that was
already built by a prior checkout is also permit-
ted,
corresponding work-
ing file.
In addition, each -j option can contain on optional
date specification which, when used with branches,
can limit the chosen revision to one within a spe-
cific. (Nor-
mally, cvs shortens paths as much as possible when
you specify an explicit target directory.)
Use the -c option to copy the module file, sorted,
to the standard output, instead of creating or mod-
ifying any files or directories in your working
11
CVS(1) CVS(1)
directory.
Use the -d dir option to create a directory called
dir for the working files, instead of using the
module name. Unless you also use -N, the paths
created under dir will be as short as possible.
Use the -s option to display per-module status
information stored with the -s option within the
modules file.
commit [-lnR] [-m 'log_message' | -f file] [-r
revision] [files...]
Requires: working directory, repository.
Changes: repository.
Synonym: ci
Use `cvs commit' when you want to incorporate
changes from your working source files into the
general cur-
rent source
repository file. You can instead specify the log
message on the command line with the -m option,
thus suppressing the editor invocation, or use the
-F option to specify that the argument file con-
tains the log message.
The -r option can be used to commit to a particular
symbolic or numeric revision. For example, to
bring all your files up to the revision ``3.0''
12
CVS(1) CVS(1)
(including those that haven't changed), you might
do:
example% cvs commit -r3.0
cvs will only allow you to commit to a revision
that is on the main trunk (a revision with a single
dot). However, you can also commit to a branch
revision (one that has an even number of dots) with
the -r option. To create a branch revision, one
typically use the -b option of the rtag or tag com-
mands. Then, either checkout or update can be used
to base your sources on the newly created branch.
From that point on experimen-
tal change.
diff [-kl] [rcsdiff_options] [[-r rev1 | -D date1] [-r
rev2 | -D date2]] [files...]
Requires: working directory, repository.
Changes: nothing.
You can compare your working files with revisions
in the source repository, with the `cvs diff' com-
mand. If you don't specify a particular revision,
your files are compared with the revisions they
13
CVS(1) CVS(1)
were based on. You can also use the standard cvs
command option -r to specify a particular revision
to compare your files with. Finally, if you use -r
twice, you can see differences between two revi-
sions
differences for all those files in the current
directory (and its subdirectories, unless you use
the standard option -l) that differ from the corre-
sponding with-
out the cvs administrative directories. For exam-
ple, module paths). These have the same mean-
ings as the same options in `cvs checkout'.
The -kv option is useful when export is used. This
causes any keywords to be expanded such that an
import done at some other site will not lose the
keyword
14
CVS(1) CVS(1)
COMMON COMMAND OPTIONS.
Several options (shown above as -report) control
what kind of report is generated:
-c Report on each time commit was used (i.e., each
time the repository was modified).
-m module
Report on a particular module. (You can min-
utes.
15
CVS(1) CVS(1)
.
import [-options] repository vendortag releasetag...
Requires: Repository, source distribution direc-
tory.
Changes: repository.
Use `cvs import' to incorporate an entire source
distribution from an outside source (e.g., a source
vendor) into your source repository directory. You
can use this command both for initial creation of a
repository,
16
CVS(1) CVS(1)
prior import), it will notify you of any files that
conflict in the two branches of development; use
`cvs checkout -j' to reconcile the differences, as
import instructs you to do.
By default, certain file names are ignored during
`cvs import': names associated with CVS administra-
tion, cre-
ated each time you execute `cvs import'.
One of the standard cvs command options is avail-
able: -m message. If you do not specify a logging
message with -m, your editor is invoked (as with
commit) to allow you to enter one.
There are three additional special options.
Use `-d' to specify that each file's time of last
modification should be used for the checkin date
and time.
Use `-b branch' to specify a first-level branch
17
CVS(1) CVS(1)
(including tag definitions, but omitting most of
the full log); -r to select logs on particular
revisions or ranges of revisions; and -d to select
particular dates or date ranges. See rlog(1) for
full explanations. This command is recursive reposi-
tory, con-
tained in more than one directory, then it may be
necessary to specify the -p option to the patch
command when patching the old sources, so that
patch is able to find the files that are located in
other directories.
The standard option flags -f, and -l are available
with this command. There are also several special
options flags:
If you use the -s option, no patch output is pro-
duced. Instead, a summary of the changed or added
files between the two releases is sent to the stan-
dard output device. This is useful for finding
out, for example, which files have changed between
two dates or revisions.
If you use the -t option, a diff of the top two
revisions
18
CVS(1) CVS(1) direc-
tory, if you like; but you risk losing changes you
may have forgotten, and you leave no trace in the
cvs history file that you've abandoned your check-
out.
Use `cvs release' to avoid these problems. This
command checks that no un-committed changes are
present; that you are executing it from immediately
above, or inside,.
You can use the -d flag to request that your work-
ing copies of the source files be deleted if the
release succeeds.
remove [-lR] [files...]
Requires: Working directory.
Changes: Working directory.
Synonyms: rm, delete
Use this command to declare that you wish to remove
files from the source repository. Like most cvs
commands, `cvs remove' works on files in your work-
ing.
19
CVS(1) CVS(1)
rtag [-falnRQq] [-b] [-d] [-r tag | -D date]directories of modules you specify in the argu-
ment. You can restrict its operation to top-level
directories with the standard -l option; or you can
explicitly request recursion with -R.
The modules database can specify a program to exe-
cute
20
CVS(1) CVS
potential.
tag [-lQqR] [-F] [-b] [-d] [-r tag | -D date] [-f] sym-
bolic_tag [files...] creat-
ing a software
21
CVS(1) CVS(1) explicitly.
If you use `cvs tag -d symbolic_tag...', the sym-
bolic tag you specify is deleted instead of being
added. Warning: Be very certain of your ground
before you delete a tag; doing this effectively
discards some historicaldi-
rectories; you can prevent this by using the stan-
dard rec-
oncile your work with any revisions applied to the
source repository since your last checkout or
update.
update keeps you informed of its progress by
22
CVS(1) CVS `cvs commit' on the
file. This is a reminder to you that the file
needs to be committed.
R file The file has been removed from your private copy
of the sources, and will be removed from theifi-
cations to the same file in the repository, so
that your file remains as you last saw it; or
there were modifications in the repository as
well as in your copy, but they were merged suc-
cessfully, without conflict, in your working
directory.
C file A conflict was detected while trying to merge
your changes to file with changes from the
source repository. file (the copy in your work-
ing directory) is now the result of merging the
two versions; an unmodified copy of your file is
also in your working directory, with the name
`.#file.version', where
23
CVS(1) CVS spe-
cific directo-
ries
specify several files to ignore. By default, update
ignores files whose names match certain patterns; for
an up to date list of ignored file names, see the
Cederqvist manual (as described in the SEE ALSO sec-
tion of this manpage).
24
CVS(1) CVS(1)
repository.
variable is not set. A warning message will be
issued when the contents of this file and the CVS-
ROOT
25
CVS(1) CVS(1)
specify -r or -D to the checkout or update)
#cvs.lock
A lock directory created by cvs when doing sensi-
tive changes to the invoca-
tion, you can supply it on the command line: `cvs
-d cvsroot cvs_command...' You may not need to set
CVSROOT if your cvs binary has the right path com-
piled pro-
grams, such as co(1) and ci(1) (CVS 1.9 and older).
CVSEDITOR
Specifies the program to use for recording log mes-
sages during commit. If not set, the EDITOR envi-
ronment variable is used instead. If EDITOR is not
set either, the default is /usr/ucb/vi.
CVS_IGNORE_REMOTE_ROOT
If this variable is set then cvs will ignore all
references
27
CVS(1) CVS(1)
the name of the cvs server command. If this vari-
able is not set then `cvs' is used.
CVSWRAPPERS
This variable is used by the `cvswrappers' script
to determine the name of the wrapper file, in addi-
tion to the wrappers defaults contained in the
repository (CVSROOT/cvswrappers) and the user's
home directory (~/.cvswrappers).
AUTHORS').).
28 | http://www.rocketaware.com/man/man1/cvs.1.htm | crawl-002 | refinedweb | 2,649 | 62.07 |
01 March 2010 12:10 [Source: ICIS news]
SINGAPORE (ICIS news)--China’s imports of adipic acid in December fell by 61% year on year as domestic production was sufficient to cover demand, industry sources said on Monday.
?xml:namespace>
However, the country's imports of adipic acid in December increased by 46% from November due to good downstream production of polyurethane, market observers said.
Adipic acid is primarily used in the production of nylon 6,6, as well as in the manufacturing of polyurethanes, which is used in shoe soles and polyester resins. Nylon 6,6, is used in the manufacturing of tyre cord.
Major adipic producers | http://www.icis.com/Articles/2010/03/01/9338557/chinas-december-adipic-acid-imports-fall-61-year-on-year.html | CC-MAIN-2013-48 | refinedweb | 108 | 59.43 |
I have posted this problem once for build 1050 - now I have to repost it as build 1074 is not working as well with my configuration (it could be I am configuring wrong, though - but I am quite sure I should be right...) am kind of devastated here ... I would love to have the thing running with just the jar, as the web-application resolves the tags perfectly!
my directory structure:
/web (= web root with a /)
/WEB-INF
web.xml
/lib
myfaces.jar (with tld's in it)
/classes
*.jsp
is there something incorrect with that structure?
Best regards,
Martin
I have posted this problem once for build 1050 - now I have to repost it as build 1074 is not working as well with my configuration (it could be I am configuring wrong, though - but I am quite sure I should be right...)
Yeah, taglibs are broken in 1074 for me again. Moving back to 1071.
I just got taglibs working again in 1074. Seems that my settings kept getting reset, my webapp dir setting lost, the Distributable checkmarks, and a few other things. I finally got the settings to save somehow (maybe by modifying my web.xml path again).
Ian Zabel wrote:
You must have tried to work with a previously created project/module.
New ones created in 1074 from scratch work just fine.
Glad you found it.
R
I'm using 1074 and created a webmodule from scratch. My TLDs also do not work, but there is one interesting thing:
A TLD in a file, that is referenced via web.xml is found. TLDs in the META-INF of a library are not found.
There seems to be a serious bug with children modules and the "distributable" flag (BTW, what's it for?): After applying changes, closing window and open it again, the settings are unchanged or scrambled (some children modules on, some are off).
Perhaps this bug has something to do with TLD problems?
Manfred Geiler wrote:
Not only that if you try it again the library will show up twice, then
try it one more time and the libs are fixed and the settings are
changed. This is already fixed in 1076 I believe.
R
I have this problem also in 1080 -- a TLD referenced in the web.xml (using version 2.4 with xsd) works ok -- hooray! But one referenced in a library (in this case, JSTL using the Apache implementation consisting of jstl.jar and standard.jar) does not resolve properly.
If anyone has a magic incantation to make this happen I'm highly interested.
Chris Winters wrote:
Just curious is that library part of the libraries pane for the module,
and is it checked off as a child in the Web Module tab of the web module
(boy that's confusing)
R
Yes and yes (relative path: '/WEB-INF/lib')-- and both jstl.jar and standard.jar are part of the 'JSTL' library.
I'm not sure if TLDs inside jar files are supported, I never saw an official statement from JetBrains about that yet. I also tried to use Apache's JSTL and had no success, unless I extracted the TLDs from the jar files and stored them explicitely.
TLDs inside jar files WERE supported in idea 3.0.x !
So, IMHO, there is no need for an official statement.
Ok, I wasn't aware of that since I never used it yet. But of course you're right. If it was supported in 3.0.x then it should definitively work in Aurora. Is there already a bug report for it?
Martin Fuhrer wrote:
Well I tried this yesterday, and was not sure what was going on. I have
the c.tld outside the jar too, and can't get it to resolve.
it was a long day, so I gave up and will try again today, but there is
something funky there.
R
Well - a little update:
it seems that some tld's just do not resolve, whether you have them out of a jar, in a jar or whereever....
(that might be additionally to a problem with tld's in jars)
I have filed a bug for that and included several tld's to help debugging... Maybe someone of you can check if the tld's do not resolve with him, too...
Attachment(s):
myfaces_core.tld
myfaces_ext.tld
myfaces_html.tld
Martin Fuhrer wrote:
We support TLDs inside jar files. But for this you have to include them
in deployment (Settings | Paths | Web Module). On the current build it
works fine if addressing via URIs (we checked this on struts). But if
you address tag libs via their jars it fails. This was a bug and it's
fixed now.
IK
--
Igor Kuralenok
Developer
JetBrains Inc.
"Develop with pleasure!"
I tried this in 1089 and got the same result. (TLDs found in JARs cannot be referenced via the URI in the 'taglib' JSP declaration.) The JARs are in the Web Module and marked for inclusion under 'Settings | Paths | Web Module'. I even tried splitting out the 'jstl.jar' and 'standard.jar' into separate libraries (e.g., 'JSTL' and 'JSTL Apache'). No good.
I shouldn't need to re-create the module, should I?
I far as I know we've changed format for web modules config in one of
recent builds so please try to reconfigure. Also we had a number of
requests on TLD resolve caused by incorrect namespace inside of taglib
descriptor check this too.
IK
Chris Winters wrote:
--
Igor Kuralenok
Developer
JetBrains Inc.
"Develop with pleasure!"
As far as I know these files does not define a taglib because of incorrect namespace. The only namespace which was announced by Sun is one for JSP 2.0 other versions had DTD definitions only. To relax this condition IDEA accept DTD urls as correct namespaces but no other.
IK
Using 1094 I've just tried re-creating the web module in my project and get the same results -- a TLD declared in the web.xml is properly found and parsed, one referenced by a URI found in a library JAR (included in webapp) is not found.
I'm referencing the taglib in my JSP (in the directory marked as the web root) like this:
]]>
And the 'standard.jar' in my library has:
JSTL 1.1 core library JSTL core 1.1 c ... ]]>
Let me know if I can provide additional information to help out.
We've just included new namespace (2.0 one) to supported list so please wait for 1095+ build.
Thanks,
IK
Thanks! | https://intellij-support.jetbrains.com/hc/en-us/community/posts/206356089-Once-again-TLD-s-are-not-resolved?page=1 | CC-MAIN-2020-10 | refinedweb | 1,096 | 84.27 |
#include <mucroomhandler.h>
Describes a participant in a MUC room.
Definition at line 32 of file mucroomhandler.h.
If the presence change is the result of an action of a room member, a pointer to the actor's JID is stored here, if the actor chose to disclose his or her identity. Examples: Kicking and banning. 0 if the identity is not disclosed.
Definition at line 54 of file mucroomhandler.h.
The participant's affiliation with the room.
Definition at line 40 of file mucroomhandler.h.
If
flags contains UserRoomDestroyed, and if the user who destroyed the room specified an alternate room, this member holds a pointer to the alternate room's JID, else it is 0.
Definition at line 71 of file mucroomhandler.h.
ORed MUCUserFlag values. Indicate conditions like: user has been kicked or banned from the room. Also may indicate that this struct refers to this instance's user. (MUC servers send presence to all room occupants, including the originator of the presence.)
Definition at line 46 of file mucroomhandler.h.
Pointer to the occupant's full JID in a non-anonymous room or in a semi-anonymous room if the user (of gloox) has a role of moderator. 0 if the MUC service doesn't provide the JID.
Definition at line 42 of file mucroomhandler.h.
In case of a nickname change, this holds the new nick, while the nick member holds the old room nick (in JID form).
newNick is only set if
flags contains UserNickChanged. If
flags contains UserSelf as well, a foregoing nick change request (using MUCRoom::setNick()) can be considered acknowledged. In any case the user's presence sent with the nick change acknowledgement is of type
unavailable. Another presence of type
available (or whatever the user's presence was at the time of the nick change request) will follow (not necessarily immediately) coming from the user's new nickname. Empty if there is no nick change in progress.
Definition at line 59 of file mucroomhandler.h.
Pointer to a JID holding the participant's full JID in the form
room@service/nick.
Definition at line 34 of file mucroomhandler.h.
If the presence change is the result of an action where the actor can provide a reason for the action, this reason is stored here. Examples: Kicking, banning, leaving the room.
Definition at line 51 of file mucroomhandler.h.
The participant's role with the room.
Definition at line 41 of file mucroomhandler.h.
If the presence packet contained a status message, it is stored here.
Definition at line 69 of file mucroomhandler.h. | https://camaya.net/api/gloox-0.9.9.12/structgloox_1_1MUCRoomParticipant.html | CC-MAIN-2019-18 | refinedweb | 433 | 67.86 |
Build Your Own ASP.NET Website Using C# and VB.NET. Pt. 4.
Build Your Own ASP.NET Website Using C# and VB.NET. Pt. 4.
Reproduced from "Build Your Own ASP.NET Website Using C# & VB.NET" by permission of SitePoint. ISBN 0-9579218-6-1 , copyright 2004. All rights reserved. See for more information.
Table of Contents
- Working with HTML Controls
- HtmlAnchor
- HtmlButton
- HtmlForm
- HtmlImage
- HtmlGenericControl
- HtmlInputButton
- HtmlInputCheckBox
- HtmlInputFile
- HtmlInputHidden
- HtmlInputImage
- HtmlInputRadioButton
- HtmlInputText
- HtmlSelect
- HtmlTable, HtmlTableRow and HtmlTableCell
- HtmlTextArea
- Processing a Simple Form
- Introduction to Web Forms
- Introduction to Web Controls
- Basic Web Controls
- Handling Page Navigation
- Using The HyperLink Control
- Navigation Objects And Their Methods
- Postback
- Formatting Controls with CSS
- Types of Styles and Style Sheets
- Style Properties
- The CssClass Property
- A Navigation Menu and Web Form for the Intranet Application
- Introducing the Dorknozzle Intranet Application
- Building the Navigation Menu
- Create the Corporate Style Sheet
- Design the Web Form for the Helpdesk Application
- Summary. In this chapter I’ll introduce you to the following concepts:
HTML controls
Web Forms
Web controls
Handling page navigation
Formatting controls with CSS
Toward the end of the chapter, you’ll put all of these concepts to work into a real world application! I’ll introduce the Dorknozzle Intranet Application that you’ll be building throughout this book, and see how what you learned in this chapter can be applied to some of the pages for the project.
HTML controls are outwardly identical to plain old HTML 4.0 tags, but employ the runat="server" attribute. For each of HTML’s most common tags, a corresponding server-side HTML control exists, although Microsoft has added a few tags and some extra properties for each. Creating HTML controls is easy—we simply stick a runat="server" attribute on the end of a normal HTML tag to create the HTML control version of that tag. The complete list of current HTML control classes and their associated tags is given in Table 4.1.
These HTML control classes are all contained within the System.Web.UI.HtmlControls namespace.
Because HTML controls are processed on the server side by the ASP.NET runtime, we can easily access their properties through code elsewhere in the page. If you’re familiar with JavaScript, HTML, and CSS, then you’ll know that manipulating text within HTML tags, or even manipulating inline styles within an HTML tag, can be cumbersome and error-prone. HTML controls aim to solve this by allowing you to manipulate the page easily with your choice of .NET language, for instance, using VB.NET or C#. We’ll start by looking at the HTML controls library, then we’ll explore in more detail the properties exposed by the controls when we process a simple form containing HTML controls and code.
The HtmlAnchor control creates a server-side HTML <a href="…"> tag.
<a href="somepage.aspx" runat="server">Click Here</a>
This line would create a new hyperlink with the text “Click Here.” Once the link is clicked, the user would be redirected to somepage.aspx as given by the href attribute.
The HtmlButton control creates a server-side HTML <button> tag.
<button id="myButton" OnServerClick="Click" runat="server">Click Here</button>
Notice that we’re using events here. On HTML controls, we need to use OnServerClick to specify the ASP.NET handler for clicks on the button, because onclick is reserved for handling clicks with JavaScript on the client side. In this example, the handler subroutine is called Click, and would be declared in a script block with the same form as the Click handlers we looked at for <asp:Button> tags previously:
<script runat="server" language="VB"> Sub Click(s As Object, e As EventArgs) Response.Write(myButton.ID) End Sub </script>
<script runat="server" language="C#"> void Click(Object s, EventArgs e) { Response.Write(myButton.ID); } </script>
In this case, when the user clicks the button, the ServerClick event is raised, the Click() subroutine is called to handle it, and the ID of the HtmlButton control is written onto the screen with Response.Write() (the Write() method of the Response object).
Created: March 27, 2003
Revised: July 12, 2004
URL:
Information Technology Manager (MN)
Next Step Systems
US-MN-Minneapolis
SR UI DEVELOPER - JSF - Ajax - ICE Faces - Rich Faces
Next Step Systems
US-IL-Chicago
Technical Specialist – Pre-sales (MA)
Next Step Systems
US-MA-Littleton | http://www.webreference.com/programming/asp_net4/index.html | CC-MAIN-2014-15 | refinedweb | 732 | 54.12 |
Handling database write conflicts.
Overview
This tutorial is intended to help you better understand how to handle conflicts that occur when two or more clients write to the same database record in a Windows Store app. Two or more clients may write changes to the same item, at the same time, in some scenarios. Without any conflict detection, the last write would overwrite any previous updates even if this was not the desired result. Azure can occur when updating the TodoItem database.
Prerequisites
This tutorial requires the following
- Microsoft Visual Studio 2013 or later.
- This tutorial is based on the Mobile Services quickstart. Before you start this tutorial, you must first complete Get started with Mobile Services.
- Azure Account.
Update the application to allow updates.
- In Visual Studio, open the TodoList project you downloaded in the Get started with Mobile Services tutorial.
In the Visual Studio Solution Explorer, open MainPage.xaml and replace the
ListViewdefinition with the
ListViewshown below and save the change.
<ListView Name="ListItems" Margin="62,10,0,0" Grid. <ListView.ItemTemplate> <DataTemplate> <StackPanel Orientation="Horizontal"> <CheckBox Name="CheckBoxComplete" IsChecked="{Binding Complete, Mode=TwoWay}" Checked="CheckBoxComplete_Checked" Margin="10,5" VerticalAlignment="Center"/> <TextBox x: </StackPanel> </DataTemplate> </ListView.ItemTemplate> </ListView>
In the Visual Studio Solution Explorer, open MainPage.cs in the shared project. Add the event handler to the MainPage for the TextBox
LostFocusevent.cs for the shared project, add the definition for the MainPage
UpdateToDoItem()method referenced in the event handler as shown below.
private async Task UpdateToDoItem(TodoItem item) { Exception exception = null; try { //update at the remote table await todoTable.UpdateAsync(item); } catch (Exception ex) { exception = ex; } if (exception != null) { await new MessageDialog(exception.Message, "Update Failed").ShowAsync(); } }
The application now writes the text changes to each item back to the database when the TextBox loses focus.
Enable Conflict Detection in your application.
TodoItemclass definition with the following code to include the
__versionsystem property enabling support for write conflict detection.
public class TodoItem { public string Id { get; set; } [JsonProperty(PropertyName = "text")] public string Text { get; set; } [JsonProperty(PropertyName = "complete")] public bool Complete { get; set; } [JsonProperty(PropertyName = "__version")] public string Version { set; get; } }
By adding the
Versionproperty to the
TodoItemclass, the application will be notified with a
MobileServicePreconditionFailedExceptionexception during an update if the record has changed since the last query. This exception includes the latest version of the item from the server. In MainPage.cs for the shared project, add the following code to handle the exception in the
UpdateToDoItem()method.) { //Conflict detected, the item has changed since the last query //Resolve the conflict between the local and server item await ResolveConflict(item, ((MobileServicePreconditionFailedException<TodoItem>) exception).Item); } else { await new MessageDialog(exception.Message, "Update Failed").ShowAsync(); } } }
In MainPage await UpdateToDoItem(localItem); }; ServerBtn.Invoked = async (IUICommand command) => { RefreshTodoItems(); }; await msgDialog.ShowAsync(); }
Test database write conflicts in the application
In this section you will build a Windows Store app package to install the app on a second machine or virtual machine. Then you will run the app on both machines generating a write conflict to test the code. Both instances of the app will attempt to update the same item's
text property requiring the user to resolve the conflict.
Create a Windows Store app package to install on second machine or virtual machine. To do this, click Project->Store->Create App Packages in Visual Studio.
On the Create Your Packages screen, click No as this package will not be uploaded to the Windows Store. Then click Next.
On the Select and Configure Packages screen, accept the defaults and click Create.
On the Package Creation Completed screen, click the Output location link to open the package location.
Copy the package folder, "todolist_1.0.0.0_AnyCPU_Debug_Test", to the second machine. On that machine, open the package folder and right click on the Add-AppDevPackage.ps1 PowerShell script and click Run with PowerShell as shown below. Follow the prompts to install the app.
Run instance 1 of the app in Visual Studio by clicking Debug->Start Debugging. On the Start screen of the second machine, click the down arrow to see "Apps by name". Then click the todolist app to run instance 2 of the app.
App Instance 1
App Instance 2
In instance 1 of the app, update the text of the last item to Test Write 1, then click another text box so that the
LostFocusevent handler updates the database. The screenshot below shows an example.
App Instance 1
App Instance 2
At this point the corresponding item in instance 2 of the app has an old version of the item. In that instance of the app, enter Test Write 2 for the
textproperty. Then click another text box so the
LostFocusevent handler attempts to update the database with the old
_versionproperty.
App Instance 1
App Instance 2
Since the
__versionvalue used with the update attempt didn't match the server
__versionvalue, the Mobile Services SDK throws a
MobileServicePreconditionFailedExceptionallowing the app to resolve this conflict. To resolve the conflict, you can click Commit Local Text to commit the values from instance 2. Alternatively, click Leave Server Text to discard the values in instance 2, leaving the values from instance 1 of the app committed.
App Instance 1
App Instance 2
Automatically handling conflict resolution in server scripts:
- If the TodoItem's
completefield is set to true, then it is considered completed and
textcan no longer be changed.
- If the TodoItem's
completefield is still false, then attempts to update
textwill be comitted.
The following steps walk you through adding the server update script and testing it.
Log into the Azure classic.'); } } }); }
Run the todolist app on both machines. Change the TodoItem
textfor the last item in instance 2. Then click another text box so the
LostFocusevent handler updates the database.
App Instance 1
App Instance 2
In instance 1 of the app, enter a different value for the last text property. Then click another text box so the
LostFocusevent handler attempts to update the database with an incorrect
__versionproperty.
App Instance 1
App Instance 2
Notice that no exception was encountered in the app since the server script resolved the conflict allowing the update since the item is not marked complete. To see that the update was truly successful, click Refresh in instance 2 to re-query the database.
App Instance 1
App Instance 2
In instance 1, click the check box to complete the last Todo item.
App Instance 1
App Instance 2
In instance 2, try to update the last TodoItem's text and trigger the
LostFocusevent. In response to the conflict, the script resolved it by refusing the update because the item was already completed.
App Instance 1
App Instance 2
Next steps
This tutorial demonstrated how to enable a Windows Store app to handle write conflicts when working with data in Mobile Services. Next, consider completing one of the following Windows Store tutorials:
Add authentication to your app
Learn how to authenticate users of your app.
Add push notifications to your app
Learn how to send a very basic push notification to your app with Mobile Services. | https://azure.microsoft.com/en-us/documentation/articles/mobile-services-windows-store-dotnet-handle-database-conflicts/ | CC-MAIN-2016-40 | refinedweb | 1,180 | 56.25 |
Subject: Re: [linux-audio-dev] MidiShare Linux
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: Thu Jul 20 2000 - 14:26:36 EEST
>Actually i don't really understand the way your fifo (with ringbuffer) works.
>How can you garantee that the write operations works correctly in a
>multi-thread context?
>Can you explain the design ?
as the "designer" of the thread safe version, i'll push my way in here :)
you have an array, with two indexes: the read ptr and the write ptr.
only readers adjust the read ptr and only writers adjust the write
ptr. to figure out the date/space available for reading or writing,
you do a fairly simple subtraction:
size_t write_space () {
size_t w, r;
w = write_ptr;
r = read_ptr;
if (w > r) {
return ((r - w + size) & size_mask) - 1;
} else if (w < r) {
return (r - w) - 1;
} else {
return size - 1;
}
}
size_t read_space () {
size_t w, r;
w = write_ptr;
r = read_ptr;
if (w > r) {
return w - r;
} else {
return (w - r + size) & size_mask;
}
}
Now, access to read_ptr and write_ptr are not atomic with respect to
the operations of the other thread in the sense that they may change
during this computation. But the key things to notice are:
1) only the writer ever computes write_space(), so only the read_ptr
can move during this time.
2) only the reader ever computes read_space(), so only the write_ptr
can move during this time.
3) if the read_ptr moves during the computation of write_space(), it
means only that we under-estimate the amount of space available
to write into the ringbuffer.
4) if the write_ptr moves during the computation of read_space(), it
means only that we under-estimate the amount of data available
to read from the ringbuffer.
The net result is that these computations are always thread safe if
there is just one reader and one writer. The only detail is that its
possible to underestimate the data or space available, and thats
nearly always completely OK.
Note that I have a more efficient implementation of a lock-free FIFO
for use where the characteristics of a ringbuffer are not desired
(i.e. you really are always just pushing and popping elements from the
FIFO). The ringbuffer implementation allows it to be used to store
streaming data efficiently, but is not so quick for simple push/pop
operations.
--p
This archive was generated by hypermail 2b28 : Thu Jul 20 2000 - 15:00:21 EEST | http://lalists.stanford.edu/lad/2000/Jul/0284.html | CC-MAIN-2013-20 | refinedweb | 403 | 56.89 |
How to fix ‘items.map is not define’ error in Reactjs
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I'm just new developer about reactjs
I'm try to map data.I am following reactjs tutorial and this is my result, but i trying and trying again is it not working. How can i solve is ??
class App extends Component { constructor(props) { super(props); this.state = { error: null, isLoaded: false, items: [] }; } componentDidMount() { // API from reqres fetch("") .then(res => res.json()) .then( (result) => { console.log(result.data); this.setState({ isLoaded: true, items: result.data }); }, (error) => { this.setState({ isLoaded: true, error }); } ) } render() { const { error, isLoaded, items } = this.state; if (error) { return <div>Error: {error.message}</div>; } else if (!isLoaded) { return <div>Loading...</div>; } else { return ( <div> //this is the problem {items.map(item=> { return <div> <p>{item.id}</p> </div> })} </div> ); } } } export default App;
Please help me, I just want to view my data :(
After I change fetch to Axios i have the same problem ??
Axios({ method:"GET", url:"" }).then(res => { this.setState({ isLoaded:true, items: res.data }) console.log(res.data) }).catch(err => { console.log(err) })
Fetch data from
"" and use that data, becouse /users returns array of users,and /users/2 returns user object for userId=2.
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You can fix this by giving items a default value:
const { error, isLoaded, items = [] } = this.state;
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This is the response data from server
{ "data": { "id": 2, "first_name": "Janet", "last_name": "Weaver", "avatar": "" } }
If you can change the server, change data result to array. It's gonna works well.
{ "data": [{ "id": 2, "first_name": "Janet", "last_name": "Weaver", "avatar": "" }] }
But you can't change the response data, you can't use with
.map
render() { const { error, isLoaded, items } = this.state; if (error) { return <div>Error: {error.message}</div>; } else if (!isLoaded) { return <div>Loading...</div>; } else { return ( <div> //just use for one(object) <div> <p>{item.id}</p> </div> </div> ); } }
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- Can you log what items is within the render function and tell us the result?
- Return data from reqres.in/api/users/2 is not array.
datais object. The map method is for Array.
- thank kkangil, but what is for my api ??
- I see my problem then, tks ivica.moke a lot :))
- Glad I could help :) | https://thetopsites.net/article/55489416.shtml | CC-MAIN-2021-25 | refinedweb | 735 | 68.36 |
S
- If you
@importthe same file multiple times, it can slow down compilation, cause override conflicts, and generate duplicate output.
- Everything is in the global namespace, including third-party packages – so my
color()function might override your existing
color()function, or vice versa.
- When you use a function like
color(). it’s impossible to know exactly where it was defined. Which
@importdoes it come from?
Sass package authors (like me) have tried to work around the namespace issues by manually prefixing our variables and functions — but Sass modules are a much more powerful solution. In brief,
@import is being replaced with more explicit
@use and
@forward rules. Over the next few years Sass
@import will be deprecated, and then removed. You can still use CSS imports, but they won’t be compiled by Sass. Don’t worry, there’s a migration tool to help you upgrade!
Import files with @useImport files with @use
@use 'buttons';
The new
@use is similar to
@import. but has some notable differences:
- The file is only imported once, no matter how many times you
@useit in a project.
- Variables, mixins, and functions (what Sass calls “members”) that start with an underscore (
_) or hyphen (
-) are considered private, and not imported.
- Members from the used file (
buttons.scssin this case) are only made available locally, but not passed along to future imports.
- Similarly,
@extendswill only apply up the chain; extending selectors in imported files, but not extending files that import this one.
- All imported members are namespaced by default.
When we
@use a file, Sass automatically generates a namespace based on the file name:
@use 'buttons'; // creates a `buttons` namespace @use 'forms'; // creates a `forms` namespace
We now have access to members from both
buttons.scss and
forms.scss — but that access is not transferred between the imports:
forms.scss still has no access to the variables defined in
buttons.scss. Because the imported features are namespaced, we have to use a new period-divided syntax to access them:
// variables: <namespace>.$variable $btn-color: buttons.$color; $form-border: forms.$input-border; // functions: <namespace>.function() $btn-background: buttons.background(); $form-border: forms.border(); // mixins: @include <namespace>.mixin() @include buttons.submit(); @include forms.input();
We can change or remove the default namespace by adding
as <name> to the import:
@use 'buttons' as *; // the star removes any namespace @use 'forms' as f; $btn-color: $color; // buttons.$color without a namespace $form-border: f.$input-border; // forms.$input-border with a custom namespace
Using
as * adds a module to the root namespace, so no prefix is required, but those members are still locally scoped to the current document.
Import built-in Sass modulesImport built-in Sass modules
Internal Sass features have also moved into the module system, so we have complete control over the global namespace. There are several built-in modules —
math,
color,
string,
list,
map,
selector, and
meta — which have to be imported explicitly in a file before they are used:
@use 'sass:math'; $half: math.percentage(1/2);
Sass modules can also be imported to the global namespace:
@use 'sass:math' as *; $half: percentage(1/2);
Internal functions that already had prefixed names, like
map-get or
str-index. can be used without duplicating that prefix:
@use 'sass:map'; @use 'sass:string'; $map-get: map.get(('key': 'value'), 'key'); $str-index: string.index('string', 'i');
You can find a full list of built-in modules, functions, and name changes in the Sass module specification.
New and changed core featuresNew and changed core features
As a side benefit, this means that Sass can safely add new internal mixins and functions without causing name conflicts. The most exciting example in this release is a
sass:meta mixin called
load-css(). This works similar to
@use but it only returns generated CSS output, and it can be used dynamically anywhere in our code:
@use 'sass:meta'; $theme-name: 'dark'; [data-theme='#{$theme-name}'] { @include meta.load-css($theme-name); }
The first argument is a module URL (like
@use) but it can be dynamically changed by variables, and even include interpolation, like
theme-#{$name}. The second (optional) argument accepts a map of configuration values:
// Configure the $base-color variable in 'theme/dark' before loading @include meta.load-css( 'theme/dark', $with: ('base-color': rebeccapurple) );
The
$with argument accepts configuration keys and values for any variable in the loaded module, if it is both:
- A global variable that doesn’t start with
_or
-(now used to signify privacy)
- Marked as a
!defaultvalue, to be configured
// theme/_dark.scss $base-color: black !default; // available for configuration $_private: true !default; // not available because private $config: false; // not available because not marked as a !default
Note that the
'base-color' key will set the
$base-color variable.
There are two more
sass:meta functions that are new:
module-variables() and
module-functions(). Each returns a map of member names and values from an already-imported module. These accept a single argument matching the module namespace:
@use 'forms'; $form-vars: module-variables('forms'); // ( // button-color: blue, // input-border: thin, // ) $form-functions: module-functions('forms'); // ( // background: get-function('background'), // border: get-function('border'), // )
Several other
sass:meta functions —
global-variable-exists(),
function-exists(),
mixin-exists(), and
get-function() — will get additional
$module arguments, allowing us to inspect each namespace explicitly.
Adjusting and scaling colorsAdjusting and scaling colors
The
sass:color module also has some interesting caveats, as we try to move away from some legacy issues. Many of the legacy shortcuts like
lighten(). or
adjust-hue() are deprecated for now in favor of explicit
color.adjust() and
color.scale() functions:
// previously lighten(red, 20%) $light-red: color.adjust(red, $lightness: 20%); // previously adjust-hue(red, 180deg) $complement: color.adjust(red, $hue: 180deg);
Some of those old functions (like
adjust-hue) are redundant and unnecessary. Others — like
lighten.
darken.
saturate. and so on — need to be re-built with better internal logic. The original functions were based on
adjust(). which uses linear math: adding
20% to the current lightness of
red in our example above. In most cases, we actually want to
scale() the lightness by a percentage, relative to the current value:
// 20% of the distance to white, rather than current-lightness + 20 $light-red: color.scale(red, $lightness: 20%);
Once fully deprecated and removed, these shortcut functions will eventually re-appear in
sass:color with new behavior based on
color.scale() rather than
color.adjust(). This is happening in stages to avoid sudden backwards-breaking changes. In the meantime, I recommend manually checking your code to see where
color.scale() might work better for you.
Configure imported librariesConfigure imported libraries
Third-party or re-usable libraries will often come with default global configuration variables for you to override. We used to do that with variables before an import:
// _buttons.scss $color: blue !default; // old.scss $color: red; @import 'buttons';
Since used modules no longer have access to local variables, we need a new way to set those defaults. We can do that by adding a configuration map to
@use:
@use 'buttons' with ( $color: red, $style: 'flat', );
This is similar to the
$with argument in
load-css(). but rather than using variable-names as keys, we use the variable itself, starting with
$.
I love how explicit this makes configuration, but there’s one rule that has tripped me up several times: a module can only be configured once, the first time it is used. Import order has always been important for Sass, even with
@import. but those issues always failed silently. Now we get an explicit error, which is both good and sometimes surprising. Make sure to
@use and configure libraries first thing in any “entrypoint” file (the central document that imports all partials), so that those configurations compile before other
@use of the libraries.
It’s (currently) impossible to “chain” configurations together while keeping them editable, but you can wrap a configured module along with extensions, and pass that along as a new module.
Pass along files with @forwardPass along files with @forward
We don’t always need to use a file, and access its members. Sometimes we just want to pass it along to future imports. Let’s say we have multiple form-related partials, and we want to import all of them together as one namespace. We can do that with
@forward:
// forms/_index.scss @forward 'input'; @forward 'textarea'; @forward 'select'; @forward 'buttons';
Members of the forwarded files are not available in the current document and no namespace is created, but those variables, functions, and mixins will be available when another file wants to
@use or
@forward the entire collection. If the forwarded partials contain actual CSS, that will also be passed along without generating output until the package is used. At that point it will all be treated as a single module with a single namespace:
// styles.scss @use 'forms'; // imports all of the forwarded members in the `forms` namespace
Note: if you ask Sass to import a directory, it will look for a file named
index or
_index)
By default, all public members will forward with a module. But we can be more selective by adding
show or
hide clauses, and naming specific members to include or exclude:
// forward only the 'input' border() mixin, and $border-color variable @forward 'input' show border, $border-color; // forward all 'buttons' members *except* the gradient() function @forward 'buttons' hide gradient;
Note: when functions and mixins share a name, they are shown and hidden together.
In order to clarify source, or avoid naming conflicts between forwarded modules, we can use
as to prefix members of a partial as we forward:
// forms/_index.scss // @forward "<url>" as <prefix>-*; // assume both modules include a background() mixin @forward 'input' as input-*; @forward 'buttons' as btn-*; // style.scss @use 'forms'; @include forms.input-background(); @include forms.btn-background();
And, if we need, we can always
@use and
@forward the same module by adding both rules:
@forward 'forms'; @use 'forms';
That’s particularly useful if you want to wrap a library with configuration or any additional tools, before passing it along to your other files. It can even help simplify import paths:
// _tools.scss // only use the library once, with configuration @use 'accoutrement/sass/tools' with ( $font-path: '../fonts/', ); // forward the configured library with this partial @forward 'accoutrement/sass/tools'; // add any extensions here... // _anywhere-else.scss // import the wrapped-and-extended library, already configured @use 'tools';
Both
@use and
@forward must be declared at the root of the document (not nested), and at the start of the file. Only
@charset and simple variable definitions can appear before the import commands.
Moving to modulesMoving to modules
In order to test the new syntax, I built a new open source Sass library (Cascading Color Systems) and a new website for my band — both still under construction. I wanted to understand modules as both a library and website author. Let’s start with the “end user” experience of writing site styles with the module syntax…
Maintaining and writing stylesMaintaining and writing styles
Using modules on the website was a pleasure. The new syntax encourages a code architecture that I already use. All my global configuration and tool imports live in a single directory (I call it
config), with an index file that forwards everything I need:
// config/_index.scss @forward 'tools'; @forward 'fonts'; @forward 'scale'; @forward 'colors';
As I build out other aspects of the site, I can import those tools and configurations wherever I need them:
// layout/_banner.scss @use '../config'; .page-title { @include config.font-family('header'); }
This even works with my existing Sass libraries, like Accoutrement and Herman, that still use the old
@import syntax. Since the
@import rule will not be replaced everywhere overnight, Sass has built in a transition period. Modules are available now, but
@import will not be deprecated for another year or two — and only removed from the language a year after that. In the meantime, the two systems will work together in either direction:
- If we
@importa file that contains the new
@use/
@forwardsyntax, only the public members are imported, without namespace.
- If we
@useor
@forwarda file that contains legacy
@importsyntax, we get access to all the nested imports as a single namespace.
That means you can start using the new module syntax right away, without waiting for a new release of your favorite libraries: and I can take some time to update all my libraries!
Migration toolMigration tool
Upgrading shouldn’t take long if we use the Migration Tool built by Jennifer Thakar. It can be installed with Node, Chocolatey, or Homebrew:
npm install -g sass-migrator choco install sass-migrator brew install sass/sass/migrator
This is not a single-use tool for migrating to modules. Now that Sass is back in active development (see below), the migration tool will also get regular updates to help migrate each new feature. It’s a good idea to install this globally, and keep it around for future use.
The migrator can be run from the command line, and will hopefully be added to third-party applications like CodeKit and Scout as well. Point it at a single Sass file, like
style.scss. and tell it what migration(s) to apply. At this point there’s only one migration called
module:
# sass-migrator <migration> <entrypoint.scss...> sass-migrator module style.scss
By default, the migrator will only update a single file, but in most cases we’ll want to update the main file and all its dependencies: any partials that are imported, forwarded, or used. We can do that by mentioning each file individually, or by adding the
--migrate-deps flag:
sass-migrator --migrate-deps module style.scss
For a test-run, we can add
--dry-run --verbose (or
-nv for short), and see the results without changing any files. There are a number of other options that we can use to customize the migration — even one specifically for helping library authors remove old manual namespaces — but I won’t cover all of them here. The migration tool is fully documented on the Sass website.
Updating published librariesUpdating published libraries
I ran into a few issues on the library side, specifically trying to make user-configurations available across multiple files, and working around the missing chained-configurations. The ordering errors can be difficult to debug, but the results are worth the effort, and I think we’ll see some additional patches coming soon. I still have to experiment with the migration tool on complex packages, and possibly write a follow-up post for library authors.
The important thing to know right now is that Sass has us covered during the transition period. Not only can imports and modules work together, but we can create “import-only” files to provide a better experience for legacy users still
@importing our libraries. In most cases, this will be an alternative version of the main package file, and you’ll want them side-by-side:
<name>.scss for module users, and
<name>.import.scss for legacy users. Any time a user calls
@import <name>, it will load the
.import version of the file:
// load _forms.scss @use 'forms'; // load _forms.input.scss @import 'forms';
This is particularly useful for adding prefixes for non-module users:
// _forms.import.scss // Forward the main module, while adding a prefix @forward "forms" as forms-*;
Upgrading SassUpgrading Sass
You may remember that Sass had a feature-freeze a few years back, to get various implementations (LibSass, Node Sass, Dart Sass) all caught up, and eventually retired the original Ruby implementation. That freeze ended last year, with several new features and active discussions and development on GitHub – but not much fanfare. If you missed those releases, you can get caught up on the Sass Blog:
- CSS Imports and CSS Compatibility (Dart Sass v1.11)
- Content Arguments and Color Functions (Dart Sass v1.15)
Dart Sass is now the canonical implementation, and will generally be the first to implement new features. If you want the latest, I recommend making the switch. You can install Dart Sass with Node, Chocolatey, or Homebrew. It also works great with existing gulp-sass build steps.
Much like CSS (since CSS3), there is no longer a single unified version-number for new releases. All Sass implementations are working from the same specification, but each one has a unique release schedule and numbering, reflected with support information in the beautiful new documentation designed by Jina.
Sass Modules are available as of October 1st, 2019 in Dart Sass 1.23.0.
Damn, I’m going to have a lot of projects to migrate! At least they’re giving us a couple of years, one to deprecate and another to remove.
Perfect! I just started a new project and this update came at a very opportune time.
Will implement all these new features on my new project. Thank God i found this article now.
I think when you alias a namespace, you need to omit quotes around the alias.
So this:
@use 'forms' as 'f';
Should be this:
@use 'forms' as f;
Thanks for the article! I’m refactoring my current project now and having fun with the update!
Some very exciting features in store. Looking forward for them to be implemented in node-sass
Am I the only one, who is surprised about the silence in the community for this big new feature? Only 5 comments so far. No discussion on StackOverflow or Reddit (that I’m aware of). No mentioning in the frontend newsletters I subscribed to…
I will need a day of experimenting to get a grasp on the implications. I’ve no idea about the practical implications for big projects. While I get the positive feeling of improving scoping and avoiding bleeding of module stuff into a global scope, I’m still undecided, if this “JS thinking” is really relevant for SCSS/CSS.
On the top of that, are some edge topics like Shadow DOM, STYLE[scoped] and custom properties, which makes the whole scenario even more complex.
With more and more browsers/operating systems getting dark mode, will theming getting more relevant? Theming could be a top application for the new module system – but in 19 years of working with frontend, I got not a single client who wanted me to make multiple themes for his site.
So while I recognize the thinking behind module system, I will need more time and practice to judge the need and the way of implementation into projects.
I do think it’s big news and deserves more attention, but I wouldn’t really call it JS thinking or relate it to Shadow DOM and scoped styles. This is more based on python/nunjucks modules, and only relates to Sass-specific elements like variables, functions, and mixins. It has no direct impact on the output CSS – only on how we combine partials and share libraries in Sass. It is not an attempt to manage DOM scope, themes, or other “modular CSS” concerns. This is very much as Sass language feature, and not a new way of approaching CSS itself. That may be why it’s flown under the radar.
The more I use SCSS the more I like LessJS.
Maybe this is good, but its irritating nonetheless, since implementing a project isn’t as easy as you imply, and we’re back to trying the 100 permutations of uses, forwards, folder structures etc, trying to get our projects to somehow work.
Sigh…
Ok, so I just forget about it and use @import instead – that still works at least.
Maybe it will all become clearer later.
Sheesh, its tough being outside the industry and trying to keep up :(
This is a change for the better.
Interesting development – Like others have said this looks to be like a broadly good idea, but I do have initial concerns about how straight-forwardly the transition will go. Like others have said, I’m also surprised how little I’ve heard about this, as it sounds like a significant development.
I notice that this post doesn’t state the deprecation timeline for @import and the current global functions. From the Sass release post:
It seems that some thought has gone into the deprecation plan, but the timings do seem a little short given the wide variety of projects and libraries relying on Sass.
Seems SASS modules (use of @use, @forward etc.,) is not yet supported in Angular 8.x or higher even though dart-sass is being used.
It is frustrating to note that no where is this issue mentioned in angular site or even in github regarding this. I woke up to this bitter surprise after completing sass folder structure with all the variables and mixins.
I’m new to SCSS
I have this file
// Theme.scss
$palette-primary-dark: #007daa;
and than import into another
// global.scss
@use “./Theme.scss” // omitting .scss like you do results in error
.error {
color: theme.$palette-error; // theme.$palette-error errors with does not exist
}
I can’t reproduce your error with
@use 'Theme'. That should work fine without any need for
./or
.scss, unless there are other factors in your setup that aren’t clear here. The other issues I see:
The variables
$palette-primary-darkand
$palette-errordon’t match, but I assume that’s a copy/paste error
Namespaces are case-sensitive, so you’ll need
Theme.$palette-errorrather than
theme.$palette-error
Having issues with importing compiled css font files using @use. Seems it can’t resolve the file paths, which I think is to do with the @font-face rule being used in these files? Has anyone came across this yet? Or know of a way to import the @font-face blocks in using the @use method?
Font-face shouldn’t cause any issues. If the path is failing to resolve, I would expect there is either an issue with how Sass import paths are configured – or there’s another build tool (webpack?) involved that is changing how paths are resolved. | https://css-tricks.com/introducing-sass-modules/ | CC-MAIN-2022-27 | refinedweb | 3,673 | 54.73 |
09 February 2007 21:26 [Source: ICIS news]
HOUSTON (ICIS news)--US base oils giant ExxonMobil lowered posted prices by 5-10 cents/gal ($15-30/tonne) across-the-board, effective on Friday, due to lower operating costs and heightened competitive spot activity, market sources said.
This drop brings list numbers to a spread of $2.82-$3.50/gal FOB (free on board) US Gulf coast, and $3.03-3.71/gal FOB ?xml:namespace>
Large consumers said another reason for the downward adjustment was to realign various accounts by eliminating steep discounts and incentive programmes that had previously been used in concluding contractual business.
Sunoco was the only other major Group I producers that announced a similar reduction of 5-10 cents/gal, effective on Monday. Citgo, Valero,
Major Group II producers, including Motiva, Chevron and Flint Hills, have not announced plans to amend posted prices. They have not followed the last two price drops initiated by Group I producers.
One key buyer did not expect Group II producers to make a move either as they had issued decreases several months ago.
Some participants said they were surprised by the timing of the ExxonMobil adjustment as this was the start of the spring buying season and crude oil prices had increased in recent weeks. NYMEX light sweet crude values were over the $60/bbl mark | http://www.icis.com/Articles/2007/02/09/9005764/exxonmobil-lowers-base-oils-5-10-centsgal.html | CC-MAIN-2015-06 | refinedweb | 227 | 50.46 |
Pandas are mostly used Python Packages for Data Manipulation. You can read, write. convert manipulate CSV and data frames easily. Some more tasks it can do are handling of missing values, merging and joining of the two CSV files, time series analysis e.t.c. But one question that is most interesting is how to insert pandas dataframe into Mongodb and this tutorial is entirely on it. You will learn to insert entire data from URL and put it into the MongoDB database through steps.
Before moving to the demonstration part make sure that you have installed Pandas in Pycharm. In this entire tutorial, I am using pycharm for coding. That why I will recommend you to use it only.
Step 1: Import the necessary libraries
I am using the Pandas libraries for data manipulation, Quandl for downloading Sensex index data (You can choose any data), Pymongo for doing data manipulation.
import quandl import pandas as pd import pymongo from pymongo import MongoClient
Step 2: Connect the MongoDB
Make a connection to the database using the MongoDB.
# Making a Connection with MongoClient client = MongoClient("mongodb://localhost:27018/") # database db = client["stocks_database"] # collection company= db["Company"]
Here I am first connecting the MongoDb Server locally on the port 27018 and then creating a database with the name stocks_database. MongoDB has a collection that is a table and thus creating it as a Company.
Step 3: Get the Stocks Data from Quandl
Quandl has large collection of the financial dataset and I am getting Sensex stock data from there. Please note that Quandl requires an API key for access, therefore you have to first signup there and get your own API key. Here I am leaving a blank for security reasons. You have to put your own key. The argument start_date is the date from when you want the records.
You can also use your own dataset server. I have chosen Stocks data for demonstration purposes only.
data = quandl.get("BSE/SENSEX", authtoken="",start_date = "2019-01-01")
Step 4: Insert the Data into Database
Now you have got the data now you can insert it into the MongoDB database. But before it, you have to do convert the data frame into a dictionary (MongoDB uses JSON format data ) and then insert it into the database. The other thing you should note is that the Date column is set as Index of the Dataframe, therefore you have to reset the index before inserting it. Use the following code.
data.reset_index(inplace=True) data_dict = data.to_dict("records") company.insert_one({"index":"Sensex","data":data_dict})
You have successfully inserted the data into the database.
How to Load data from MongoDB to pandas dataframe?
In the above steps, you have successfully dumbed the data into the database. Now you can also directly get that stored data from the database and load into the dataframe. Just use the code below.
data_from_db = company.find_one({"index":"Sensex"}) df = pd.DataFrame(data_from_db["data"]) df.set_index("Date",inplace=True) print(df)
You can see in the above code I am first receiving the data from MongoDB using the find_one() and then converting the data into Dataframe using pandas. After that, I set the “Date” as the index and display it on the screen. You can see the output below.
Export data to CSV from MongoDB using python
You can also export the data you have read from MongoDB. To do you have to use the pandas.to_csv() method. Using the same above code you have to just add one line of code. It will export data to CSV after reading from MongoDB.
data_from_db = company.find_one({"index":"Sensex"}) df = pd.DataFrame(data_from_db["data"]) df.set_index("Date",inplace=True) df.to_csv("Sensex.csv")
Here Sensex.csv is the filename for the CSV file you want to export. Please note that the file will be exported on the same working directory until you specifically define the path.
Export data to JSON from MongoDB
You can also fetch data from the MongoDB database and then convert it to JSON using dataframe.to_json() function. Just put the fetched dataframe inside the to_json() method. and it will convert it to JSON. Now you can send the JSON data through endpoints.
I hope you have understood how to Insert Pandas Dataframe into MongoDB as well as reading it and converting it into Data Frame. If you have any query then contact us for more information. To know more about pandas learn from the Offical Pandas Documentation.
Join our list
Subscribe to our mailing list and get interesting stuff and updates to your email inbox. | https://www.datasciencelearner.com/insert-pandas-dataframe-into-mongodb/ | CC-MAIN-2021-39 | refinedweb | 765 | 65.42 |
The cutest secure JavaScript authenticated encryption container
Nermal makes securing your JavaScript application's data much easier.
Nermal does private-key authenticated encryption with a trusted algorithm (AES-256/GCM) implemented by a trusted library (SJCL) with the best existent key-derivation system (scrypt). It keeps track of salts for its keys, and automatically generates random nonces. It also pads the data with a random number of random bytes, which makes it harder to determine what sort of operations are being performed on the data.
Authenticated encryption basically means that when you decrypt the data, you can be confident that it's something which you encrypted, in the format that you encrypted it in. Nermal also authenticates and stores a namespace string, so that there is a nice place for you to store version numbers so that you can reorganize your data format later.
Nermal boxes are newline-separated ASCII strings[note 1], so you can save them to disk or transmit them as JSON or whatever you want, interoperably.
Nermal was written to be interoperable with Node.js, but also to work client-side in the browser. To use with node:
npm install nermal
To use with the browser, you will need to load the files for SJCL and
scrypt in your HTML file first, then include
nermal.js with a
script tag -- it will initialize
scrypt for you. I may eventually release a
packed version which contains all of the source for the browser.
Nermal has a minimalist API. A nermal box is ultimately just a JavaScript
string and can be transmitted or stored easily as as such. Nermal
only encrypts JavaScript strings and Uint8Arrays, leaving questions of
how your data is serialized to you. Other than putting data into/out of the box
with
encrypt and
decrypt, nermal provides
newKey and
getKey for
applications which want to manage keys (so that you don't have to wait for
scrypt twice), and some developer functions are exposed with leading
underscores.
Full docs are available in
nermal/API.md. The types and argument orders of the
most common functions are:
encrypt: (ns: string, data: $bin, key: string | $key, nonce: $bin?) -> $nermal_box! decrypt: (box: $nermal_box, key: string | $key, raw: boolean?) -> $bin newKey: (pass: string) -> $key! getKey: (box: $nermal_box, pass: string) -> $key version: string
JSON.stringify(ns).slice(1, -1)so that you don't have to worry about, say, control characters in the resulting string. | https://www.npmjs.com/package/nermal | CC-MAIN-2015-48 | refinedweb | 405 | 62.17 |
The QObject class is the base class of all Qt objects. More...
#include <qobject.h>
Inherits Qt.
Inherited by QWidget, QWSInputMethod, MmsComms, QSocket, QAction, AudioDevice, ID3Tag, MediaPlayerState, QServerSocket, Categories, Ir, QStyle, QApplication, StorageInfo, Accessory, DeviceButtonManager, QProcess, QDLLink, QDLHeartBeat, QDLClient, SerialDeviceBase, PhoneLine, QTimer, PhoneBook, PhoneServer, PhoneSignal, PhoneSocket, PhoneVendorAt, SerialProxy, SimToolkit, SMSRequest, PhoneStatus, AddressBookAccess, DateBookAccess, TodoAccess, TransferReceipt, QUrlOperator, DialerControl, PhoneManager, QLayout, QAccel, QDataPump, QClipboard, QCopChannel, QDns, QDragObject, QFileIconProvider, QNetworkProtocol, QWSKeyboardHandler, QNetworkOperation, QSessionManager, QSignalMapper, QSocketNotifier, QSound, QStyleSheet, QToolTipGroup, QTranslator, QValidator, and QWSMouseHandler.
List of all member functions.
QObject is the heart of the Qt object model. The central feature in this model is a very powerful mechanism for seamless object commuinication dubbed signals and slots. With connect(), you can connect a signal to a slot and destroy the connection again, it will automatically do an insertChild() on the parent and thus show up in the parent's children() list. The parent receives object ownership, implement signals, slots or properties. You also need to run the moc program (Meta Object Compiler) on the source file. We strongly recommend to use the macro in all subclasses of QObject regardless whether they actually use signals, slots and properties or not. Otherwise certain functions can show undefined behaviour.
All Qt widgets inherit QObject. The convenience function isWidgetType() returns whether an object is actually a widget. It is much faster than inherits( "QWidget" ).
See also
The parent of an object may be viewed as the object's owner. For instance, a dialog box is the parent of the "ok" and "cancel" buttons inside it.
The destructor of a parent object destroys all child objects.
Setting parent to 0 constructs an object with no parent. If the object is a widget, it will become a top-level window.
The object name is a text that can be used to identify this QObject. It's particularly useful in conjunction with the Qt Designer. You can find an object by name (and type) using child(), and more than one using queryList().
See also parent(), name(), child(), and queryList().
All signals to and from the object are automatically disconnected.
Warning: All child objects are deleted. If any of these objects are on the stack or global, your program will sooner or later crash. We do not recommend holding pointers to child objects from outside the parent. If you still do, the QObject::destroyed() signal gives you an opportunity to detect when an object is destroyed.
Emitted signals disappear into hyperspace if signals are blocked.
If there isn't any such object, this function returns null.
If there is more than one, one of them is returned; use queryList() if you need all of them.
Child events are sent to objects when children are inserted or removed.
Note that events with QEvent::type() QEvent::ChildInserted are posted (with QApplication::postEvent()), to make sure that the child's construction is completed before this function is called.
Note that if a child is removed immediately after it is inserted, the ChildInserted event may be suppressed, but the ChildRemoved event will always be sent. In this case.
The QObjectList class is defined in the qobjectlist.h header file.
The latest child added is the first object in the list and the first child added is the last object in the list.().
This function is generated by the Meta Object Compiler.
Warning: This function will return an invalid name if the class definition lacks the Q_OBJECT macro.
See also name(), inherits(), isA(), and isWidgetType().
You must use the SIGNAL() and SLOT() macros when specifying the signal and the member.
Example:
QLabel *label = new QLabel; QScrollBar *scroll = new QScrollBar; QObject::connect( scroll, SIGNAL(valueChanged(int)), label, SLOT(setNum(int)) );
This example connects the scroll bar's valueChanged() signal to the label's setNum() slot. It makes the label always display the current scroll bar value.
A signal can even be connected to another signal, i.e. member is a SIGNAL().
class MyWidget : public QWidget { public: MyWidget(); ... signals: void aSignal(); ... private: ... QPushButton *aButton; }; MyWidget::MyWidget() { aButton = new QPushButton( this ); connect( aButton, SIGNAL(clicked()), SIGNAL(aSignal()) ); }
In its constructor, MyWidget creates a private button and connects the clicked() signal to relay clicked() to the outside world. You can achieve the same effect by connecting the clicked() signal to a private slot and emitting aSignal() in this slot, but that takes a few lines of extra code and is not quite as clear, of course.
A signal can be connected to many slots/signals. Many signals can be connected to one slot.
If a signal is connected to several slots, the slots are activated in arbitrary order when the signal is emitted.
The function returns TRUE if it successfully connects the signal to the slot. It will return FALSE when it cannot connect the signal to the slot.
See also disconnect().
Connects signal from the sender object to member in this object.().
All the objects's children are destroyed immediately after this signal is emitted.
A signal-slot connection is removed when either of the objects involved are destroyed.
disconnect() is typically used in three ways, as the following examples show. member of receiver.. This function does nothing if the library has been compiled in release mode (i.e without debugging information).
This function is useful for debugging. This function.
The reimplementation of this virtual function must return TRUE if the event should be stopped, or FALSE if the event should be dispatched normally.
Warning: If you delete the receiver object in this function, be sure to return TRUE. If you return FALSE, Qt sends the event to the deleted object and the program will crash.
See also installEventFilter().
Reimplemented in QScrollView, QSpinBox, QLayout, QAccel, QFontDialog, and QSGIStyle.
High priority objects are placed first * s = new QScrollBar; // inherits QWidget and QRangeControl s->inherits( "QWidget" ); // returns TRUE s->inherits( "QRangeControl" ); // returns FALSE
See also isA() and metaObject().
See also metaObject().
Warning: This function cannot be used to make a widget a child widget of another. Child widgets can be created only by setting the parent widget in the constructor or by calling QWidget::reparent().
See also removeChild() and QWidget::reparent().
An event filter is an object that receives all events that are sent to this object. The filter can either stop the event or forward it to this object. The event filter obj receives events via its eventFilter() function. The eventFilter() function must return TRUE if the event should be stopped, or FALSE if the event should be dispatched normally.
If multiple event filters are installed for a single object, the filter that was installed last is activated first.
Example:
#include <qwidget.h> class MyWidget : public QWidget { public: MyWidget::MyWidget( QWidget *parent=0, const char *name=0 ); protected: bool eventFilter( QObject *, QEvent * ); }; MyWidget::MyWidget( QWidget *parent, const char *name ) : QWidget( parent, name ) { if ( parent ) // has a parent widget parent->installEventFilter( this ); // then install filter } bool MyWidget::eventFilter( QObject *o, QEvent *e ) { if ( e->type() == QEvent::KeyPress ) { // key press QKeyEvent *k = (QKeyEvent*)e; qDebug( "Ate key press %d", k->key() ); return TRUE; // eat event } return QWidget::eventFilter( o, e ); // standard event processing }
The QAccel class, for example, uses this technique.().
Calling this function is equivalent to calling inherits("QWidget"), except that it is much faster.
The timer identifier is returned by startTimer() when a timer event is started.
See also timerEvent(), startTimer(), and killTimers().
Note that using this function can cause hard-to-find bugs: It kills timers started by sub- and superclasses as well as those started by you, which is often not what you want. Therefore, we recommend using a QTimer, or perhaps killTimer().
See also timerEvent(), startTimer(), and killTimer().
A meta object contains information about a class that inherits QObject: class name, super class. If the object does not have a name, it will return "unnamed", so that printf() (used in qDebug()) will not be asked to output a null pointer. If you want a null pointer to be returned for unnamed objects, you can call name( 0 ).
qDebug( "MyClass::setPrecision(): (%s) unable to set precision to %f", name(), newPrecision );
The object name is set by the constructor or by the setName() function. The object name is not very useful in the current version of Qt, but will become increasingly important in the future.
You can find an object by name (and type) using child(), and more than one using queryList().
See also setName(), className(), child(), and queryList().
The QObjectList class is defined in the qobjectlist.h header file.
The latest root object created is the first object in the list and the first root object added is the last object in the list.
See also children(), parent(), insertChild(), and removeChild().
See also children().
If no such property exists, the returned variant is invalid.
Information about all available properties are provided through the metaObject().
See also setProperty(), QVariant::isValid(), metaObject(), QMetaObject::propertyNames(), and QMetaObject::property().
If regexpMatch is TRUE (the default), objName is a regexp that the objects's names must match. If regexpMatch is FALSE, objName is a string and object names must match it exactly.
Note that iner function child()
Warning: Delete the list away as soon you have finished using it. The list contains pointers that may become invalid at almost any time without notice - as soon as the user closes a window you may have dangling pointers, for example.
See also child(), children(), parent(), inherits(), name(), and QRegExp.
This function is for internal use.().
Returns a pointer to the object that sent the signal, if called in a slot before any function call or signal emission. Returns an undefined value in all other cases. practical when many signals are connected to a single slot. The sender is undefined if the slot is called as a normal C++ function.
You can find an object by name (and type) using child(), and more than one using queryList().
See also name(), className(), queryList(), and child().
Returne TRUE is the operation was successful, FALSE otherwise.
Information about all available properties are provided through the metaObject().
See also property(), metaObject(), QMetaObject::propertyNames(), and QMetaObject::property().). The accuracy depends on the underlying operating system. Windows 95 has 55 millisecond (18.2 times per second) accuracy; other systems that we have tested (UNIX X11, Windows NT and OS/2) can handle 1 millisecond intervals.
The QTimer class provides a high-level programming interface with one-shot timers and timer signals instead of events.
See also timerEvent(), killTimer(), and killTimers().
This function is misleadingly named, and cannot be implemented in a way that fulfills its name. someQWidget->superClasses() should have returned QPaintDevice and QObject, obviously. And it never can, so let us kill the function. It will be removed in Qt-3.0
Oh, and the return type was wrong, too. QStringList not QStrList.
QTimer provides a higher-level interface to the timer functionality, and also more general information about timers.
See also startTimer(), killTimer(), killTimers(), and event().
See also QApplication::translate().
Returns a translated version of text in context QObject and with no comment, or text if there is no appropriate translated version. All QObject subclasses which use the Q_OBJECT macro have a reimplementation of this function which uses the relevant class name as context.
See also QApplication::translate().
Returns a pointer to the child named name of QObject parent which inherits type type.
Returns 0 if there is no such child.
QListBox * c = (QListBox *)::qt_find_obj_child(myWidget,QListBox, "listboxname"); if ( c ) c->insertItem( "another string" );
This file is part of the Qtopia platform, copyright © 1995-2005 Trolltech, all rights reserved. | http://doc.trolltech.com/qtopia2.2/html/qobject.html | crawl-001 | refinedweb | 1,917 | 57.77 |
On Sun, 17 Jun 2007 19:25:29 -0400, Dav Clark <dav at securme.net> wrote: >I'm slowly beginning to wrap my head around Nevow. For one, while it's not >explicit anywhere, it seems really clear that the intention is simply to >add the Nevow root directory to your python path. The Nevow install process is more or less the same as the install process for any other Python package. Yep, the package directories need to be in sys.path somehow, either by having their parents added to PYTHONPATH or by being copied to a directory which is in the default search path. >In my case, I'm using >the easy_install develop workaround: > >python -c "import setuptools; execfile('setup.py')" develop > >from the .../Nevow path. This means I can svn update, and that version is >working without any more reinstalls. > This may indeed work, although setuptools isn't really supported (meaning there is no automated test coverage for setuptools working, and further none of the primary Nevow developers use setuptools, so if it is working now, we might break it unintentionally and unknowingly at some future time). I use Combinator to manage my Python import path. If you're tracking svn trunk at HEAD, you might want to consider it too. Or you can just edit your shell's startup script to add the checkout directory to PYTHONPATH. . > Oops, that sounds like some unfortunately misleading documentation. Do you think you could correct the wiki page in question to make this explicit? ). Aha. Yes, please do fix this. :) > . setup.py is basically fully supported. If you find bugs in it, we will do our best to fix them. easy_install isn't really supported at all; please don't suggest it or anything related to setuptools. > ')).? > . The plugin system uses some advanced features of the Python package system. Normally Python packages wouldn't let you have multiple packages or modules with the same name (and even here it doesn't really - the nevow/plugins and nevow directories you create to add plugins are just directories, rather than packages, although nevow/plugins/ does _contribute_ to "the" nevow.plugins package). There is necessarily the potential for a name conflict here, since multiple authors are contributing to the same namespace. This is the same as the problem of top-level Python packages, since two authors might choose to name their package the same thing. However, unlike that case, it is trivially resolved, since the names of things in nevow/plugins/ are essentially irrelevant. At packaging or installation time, the name can be changed to resolve a conflict without breaking the plugins (this might be a problem for unit tests, though, if they try to import from the plugins package in order to test functionality it provides - they will be broken by the name change, probably). > ? > >4) Perhaps have a page describing Divmod wiki etiquette... answering the >question of this e-mail, which is "How liberal should I be in editing the >Wiki(s)?" > >5) Why do all examples have twistd -noy, when -y implies -o? > Historic reasons. The people writing these wiki pages probably still have finger memory from before -y implied -o. :) Feel free to fix. > Thanks for digging into this and collecting your experiences in this email! Jean-Paul | http://twistedmatrix.com/pipermail/twisted-web/2007-June/003419.html | CC-MAIN-2014-10 | refinedweb | 548 | 62.78 |
20 January 2011 09:09 [Source: ICIS news]
SINGAPORE (ICIS)--?xml:namespace>
The plant would remain off line for around 10 days, the official added.
The date was brought forward from 1 February as the company had sold out its inventory earlier than expected, the source said.
“We thought we will start around late January to build up stocks in anticipation of the demand after Lunar New Year holidays,” he said.
Slackwax is crude wax produced as a by-product of refining Group I base oils, and the type IRPC produces is less than 10% oil content. It is a raw material for paraffin waxes.
Slackwax prices were assessed steady at $830-870/tonne (€614-644/tonne) FOB (free on board)
( | http://www.icis.com/Articles/2011/01/20/9427673/thailands-irpc-shuts-slackwax-facility-in-rayong-for-10.html | CC-MAIN-2013-48 | refinedweb | 121 | 72.05 |
AbHhGD - the Arduino Based Hand-held Gaming Device
Introduction: AbHhGD - the Arduino Based Hand-held Gaming Device
This is a write-up on my Arduino based hand-held gaming device. I realize it’s a somewhat poshy statement but hey, it is Arduino based, it’s hand-held and it’s a device that plays games!
Step 1: A Hand-held Gaming Device...
The device sports a couple of games and a menu system consisting of a letter indicating the current selection. The menu options may be selected by turning the dial and the corresponding game is started pressing either one of the push buttons. When the game is finished playing it returns to the menu system allowing the user to immerse herself in yet another one of the many exciting gaming experiences the AbHhGD has to offer!
Step 2: The Parts
To build this little hack requires just a few parts:
- Arduino Nano/Uno.
- Max7219 LED matrix.
- Mini bread board.
- Two push-buttons.
- 50K Potentiometer.
- And of course, some jumper wires.
Step 3: The Wiring
The LED matrix already contains a Max7219 LED driver chip so wiring it is very easy. Five wires is all it takes and each of them go to the Arduino. The attached sketch expects the following pins:
- VCC - 5V
- GND - GND
- DIN - D12
- CS - D10
- CLK - D11
Step 4: The Controller
Then the controller stuff: the potentiometer is wired to 5v, ground and analog port #1. The buttons are wired to ground and respectively D4 and D5. I used the Arduino’s internal pull-up resistors to pull the in-ports high. Since the game loop runs rather slow there’s no need to bother with debouncing so I didn’t bother using any capacitors, although a 10uF capacitor between the potentiometer’s middle pin and ground might take care of some occasional jerkiness in the dial’s readings.
Step 5: The Games, the Code
The games, six of ‘m as of yet:
1. Good ol’ Pong, the well-known infinite loop [Bounce the ball with the paddle. Wait for the ball to return. Repeat]. I’ve put in a very rudimentary level-up strategy, mainly to keep me from going insane while testing during development: everytime the ball hits the paddle a level-up-counter goes up by one, every ten level-ups the game runs a little bit faster. After two times going a bit faster two bumpers appear in the playing field. If the player even survives that ordeal for ten hits in a row the paddle shrinks by one dot. This repeats until the paddle has shrunk to no paddle at all.
2. Tedshow. A regular feature in a rather moronic quiz show called “De Ted Show” which was aired during the early eighties in the Netherlands would require the winner of the quiz catching some sticks falling randomly out of the ceiling to determine the prizes he or she would win. The game is as brain dead as the quiz show I’m afraid.
3. Space Invaders. This true classic features some of the most effective A.I. in gaming history: [Keep moving left, until hit wall. Move down. Keep moving right, until hit wall. Move down. Repeat]. Due to scarce real-estate however, I modified it a bit in having the invaders bounce to and fro a couple of times before moving down. The player is allowed to fire a single bullet at the time, as are the invaders. Starting with two rows of invaders, each level-up adds another row. Again, scarce real-estate forced me to refrain from adding a fourth level. Guess I should have put in a boss-level..
4. Snake. Turn left and right using the push buttons. Eat apple, snake grows and moves faster. Don’t bite yourself!
5. Break-out, or Pong with obstacles.
6. And of course, no gaming device is complete without a racing game!
The sketch contains a number of different units. Some of those units in turn consist of both a .h (header) file and a .ino file. The should be rather self-explanatory and is full of comments to clarify.
Step 6: The Casing
Finally, a nice container would add to the portability of the handheld gaming device :-)
I started out with a little plastic container. The lid would fit the LED matrix and the buttons and dial. I made a square hole in it and hot-glued the LED matrix fixed. I swapped the Arduino Uno with a Nano and had to bend the Nano’s pins to make it fit the container. I used a lot of hot glue to prevent the pins from shortening with any metal parts inside the container. The buttons are hot-glued to the case as well and the potentiometer would fit nicely through an M6 drilled hole.
It is somewhat bulky, especially with the 9v battery container hot-glued to the back, but certainly a handheld gaming device now it is!
Hi
I was wondering how to download all the libraries for the code because when i try to download them into the libraries file the Arduino I.D.E it says this...
Arduino: 1.8.1 (Windows 10), Board: "Arduino/Genuino Uno"
C:\Users\MRYntema\AppData\Local\Temp\Temp2_FAYTMGRILJSEUQ1.zip\ABHHGD\ABHHGD.ino:13:19: fatal error: types.h: No such file or directory
#include "types.h"
^
compilation terminated.
exit status 1
Error compiling for board Arduino/Genuino Uno.
This report would have more information with
"Show verbose output during compilation"
option enabled in File -> Preferences.
Thanks
Has anyone been able to build this with Arduino IDE 1.6.XX ? I have 1.6.11 and one of many errors I get is:
'Controller' has not been declared
Looking at the .ino files, none of them includes any header files - does the IDE do this magically somehow?
Thanks!
Great project! I made it with the joystick shield, and I noticed that you can plug the display right into the aruidno! One issue though, the screen is the wrong way around. What would be the easiest way to rotate the display 180 degrees?
This project was a lot of fun to make, and even more fun to play with!
Hey! I'm about to make your project, but I have absolutely no idea how to upload the code sense it's all separate. Could you help me with that? Thanks!
Hi there,
If unzip the file into a folder named ABHHGD and open the ABHHGD.ino file in the Arduino IDE it should build.
Just don't forget to also install the libs:
LedControl:
LinkedList:
Thank you so much! It worked! Now all I have to do is wait for my LED matrix to come in :/
This is really an amazing project! Thanks for sharing!
In the AbHhGD arduino folder it has...
#include <LinkedList.h>
#include "LedControl.h"
when they both don't exist... Help?
Ah yes, I'm sorry, should have added that to the write-up. The sketch uses 2 libraries, one of them being the LedControl lib and the other is a LionkedList object:
LedControl:
LinkedList:
Just install them as any Arduino library.
I wonder how hard it would be to port it to the digipixel.
Flappybird works great on 64 leds btw.
Incredible. I probably couldn't even.
Great project! Thanks for sharing, I plan to make a rainbowduino version when I get a chance.
Nice documentation! Thanks for sharing your project and welcome!
hi there and thanks! | http://www.instructables.com/id/AbHhGD-the-Arduino-Based-Hand-held-Gaming-Device/ | CC-MAIN-2017-34 | refinedweb | 1,254 | 73.88 |
they saw President Barack Obama as the president of promise and reformation? During President Obama's administration, unemployment and national debt is the HIGHEST it has been. More and more civil liberties are being eroded. Despite Obama's dismal and horrific record, Americans voted for him TWICE! What are people "thinking"? America as we know it has been HAD and totally BAMBOOZLED!
The choices in both elections falls clearly on the GOP as they offered even candidates most Republicans felt queasy about against a consummate politician. With McCain and then Romney the GOP offered candidates who clearly did not understand the constituency and lost as a result. Was America fooled by an incredibly gifted orator and political strategist? Probably. Did the GOP offer a clearly better choice? The results are in the proof of the pudding. The real question to ask is what are they going to do about Hillary? Benghazi? Whitewater? Vince Foster? And ignore the issues as a result. They will get more of the same unless they wise up.
The only reason any liberal can get elected in America, is because of the decay of christian morals and a profound ignorance of history and the Constitution. The real truth is that a good man is not easy to con but a con man can be conned because of his vices. Why was a man with no experience in governing elected when America was and is in a great crisis? Well Obama is very charismatic, intelligent and well spoken. And also the novelty of electing the first black president was more than a lot of people could resist.
Interesting question and I had a curious hair rise up and looked about with recent Calif activity with politics.
Data from Info Please sourced to New York Times
2008 Election
Popular Vote
Obama - 66,882,230
McCain - 58,343,671
Total 125,225,901
2012 Election
Obama - 62,611,250
Romney - 59,134,475
Total 121,745,725
Difference 3,480,176 less total votes. Where did they go? Were there that many deaths? Did they vote another party? How many simply abstained?
Difference by %
Democrat @ 6% Less votes between 2008 & 2012
Republican @ 1% Increase in votes between 2008 & 2012
Overall difference 3% less votes Total
Yes, old news . . . but who elected who?
Electoral College
Democrats increased from 332 (2008) to 365 (2012)
Republicans decreased from 206 (2008) to 173 (2012)
Difference is 33 vote gain by Obama or +6%
(Calif = 55 = Democratic)
The 'What if' is Romney 62,614,651 if those 'did not votes were his'. That would mean he would have the the popular vote by 3,401. "Of Course" that is a big 'What if'!
I see it as a minority of voters changed destiny with the popular vote. The minority being those who did not vote along a party line. The question is would that have changed the 'Electoral College' voting? That said the vote that changed destiny could be said was the vote of the states and their destiny(s) were overwhelmingly greater than the populous. Or, what statement was made regarding the state of affairs of individual states contrasting the US?
So, that brings up the issue of dividing California (55 Electoral votes, 2 senators, and 53 representatives) into 6 separate states. Initiative #13-0063 on the November 2014 ballot is at issue for California as the petitions have been pressed and flying strong.
How would that affect the next presidential election and strengths in congress. There would still be near the same representatives, yet party affiliation may change by district. There would be 12 senators or the addition of 10. And, the electoral college would change too.
I think during the first election, those that voted for Obama saw him as young, unspoiled by wealth, impassioned toward doing the right thing and a fresh alternative to the Bush royal house. During the second election, I think those that tapped the winning votes for him were too busy enjoying the afterlife to care who had pilfered the info off their voter registration cards.
I remember several years back when people were saying this was going to happen, and everyone thought they were just being racist, hateful, or crazy. None of us can just believe what we are told anymore, not by just anyone.
The scary part about it is that people are not using critical thinking in much of anything anymore. So the "ear tickling" stuff is very appealing. People want what they want to be true so often over what actually is. It is hurting all of us as a country and not helping the world either.
We were thinking, "Okay, he's not great and I kinda don't want to vote for him. What's the Republican party offering--OH SH*T NOPE NOPE NOPE NOPE NOPE NOPE NOPE *vote Obama*"
Uh huh, understand, so Obama was the lesser of the two evils, so let's vote for him to see how it will go. Oops, Obama did not do so well,oops, there it IS!
So Zelkiiro, what was it that got your vote? Was it the record debt? The persistently high unemployment over the length of his first term? High gas prices? 47 million people on food stamps? The lowest labor force participation since the great depression? The billions of taxpayer dollars lost to his "green investments"? The shovel ready jobs that weren't or the recovery summer that wasn't?
Seriously, what really earned your vote for Obama? I mean with that list of achievements I know it might be hard to pick just one, but try ok?
And you can't choose Obamacare because the election was before that glorious and successful piece of work really rolled out.
The fact that Mitt "I'd sell my mother to a whorehouse for $5 and a ham sandwich" Romney was his opponent.
Cogent reasoning as always. I wonder how much he would have received for the sale of the XL Pipeline, Barrack only got $100 million from billionaire phony and hypocritical, BIGOIL polluter Tom Steyer. Such a deep and reasonable argument you have there. Since Barack's mother is dead we will never know how much Tom Steyer might have paid for her
Why because Romney is a business man, is that what makes him evil? That's a bunch of liberal non sense. All Obama ever did for a living is rabble rouse and run for office, Romney actually ran a business and governed a state.
Nope. He was a businessman who frequently flip-flopped about his policies just to try to appeal to the masses, instead of relying on his actual policies (whatever they might have been, we'll never know) to win people over.
Same thing happened in 2004 with legendary flip-flopper John Kerry, and everyone gave him sh!t for that. Why so surprised that Mitt Romney receives it, too?
1) Closing Guantanamo - 5 years ago
2)End military tribunals - 5 years ago
3)End Rendition
4)Limited Presidential Power - to conduct an unauthorized war(Libya)
5) - to conduct surveillance(NSA)
6) - to issue signing statements(NDAA)
7) - to hold Americans as unlawful combatants( or kill them)
8) -to ignore human rights treaties ( … 963f4.html)
9) - to ignore Habeas Corpus
()
10) - to do all the things covered by the Patriot Act
( … 67851.html)
ALL from one interview - … A/ObamaQA/
11) Put anti-missile systems in Poland and Czech Republic - 5 years ago … Delivered/
12) Hold Sudan accountable for Darfur Genocide - 10 years ago … -in-sudan/
13) Support national sovereignty in Europe - 5 years ago
.”" … lip-flops/
14) Restore America's global standing -
15) Reinvigorate NASA - … 02810.html
Obama has been a lying disaster. I wonder what Romney flip-flop compares to any one of Obama's?
Hindsight is always 20/20. What makes you think Romney would have handled any of it differently? The GOP was so adamant about backing Bush's policies that who could believe anything they were saying. Is Obama any good? Who knows with the partisan bickering and failed policies due to it but you can't know that Romney and his cronies would have been any better. The funny thing is that these arguments always revolve around what power the president has to effect changes while congress is always in the mix to help really screw it up. They are politicians with a totally separate agenda that does not include us!
You mean like the legislature in Massachusetts that added its own little flare to Romneycare? Of course Romney would have been different. For one thing there would have been much less name calling and pouting.
"For one thing there would have been much less name calling and pouting." and less transparency and special interest and etc......... Don't you understand that they are all cut from the same cloth now. Where are the Lincoln's, Adams's and Washington's anymore? They are dead and gone as the billion dollar campaigns are run and rewarding those that donate. Romney was just another tool of the GOP as was Obama of the Liberal Democrats. Until the money is out of the election process we will encounter more of the same elite candidates bankrolled by the very rich who have their own agendas.
Do you think Romney would have had the White House windows bricked over because that is the only way there could be less transparency than the current administration.
Being better than Obama is a pretty low bar don't you think?
By any possible metric the man is a failure as president, that he had not one whit of experience as an executive or a leader should have been more than a clue, especially after the whole nation being witness to his first term.
+
I am not convinced that he is such a great speaker or all that bright and considering his callous disregard for his own aunt, all that compassionate.
I don't know if what you say is entirely accurate as a leader but he did address the economic disaster with the exact opposite that Romney was spouting. Hoover was in charge and said let the markets control the destiny of the economy and did nothing to prevent it. One of Romney's main proposals was to rescind the Dodd-Frank Act that regulated investment banking in: "plain vanilla" products as well as strengthened investor protection;
4.Tools for financial crises,";
5.Various measures aimed at increasing international standards and cooperation including proposals related to improved accounting and tightened regulation of credit rating agencies.
The repeal of this would send us immediately back on a track towards the depression the Glass-Steagal act was created to protect us from another depression. That was repealed in 1999 which paved the way for the banks to become too big to fail.
Romney wanted to repeat the past with the economy and that was a shame as I thought he had some good ideas beyond this.
He may be a failure as a leader but as a politician he rates among the best. Besides we got what was presented by the elite who bankrolled him, a great strategist and politician. The proof is that he got elected twice and won some and bamboozled others.
hmmmm . . . seems to be a great observation. The puppet string theory could be introduced. We all know with our own lives we consult and seek advisement for major decisions and minor too. The idea was to get a democrat in office. Simple enough. The best choice to fill that was made. The task was done. Success.
While I voted for Obama I did not like the choices presented me. Obama was at least not as immersed in executive politics as Romney but possessed the savvy and knowhow to assemble a good group of advisors and run a successful campaign. On the other hand Romney held no clout with the constituency with regards to relating on the masses level. Romney also had a cloud of oligarchic backing with his ties to Bain Capital that was murky in its definitions of who was in charge and what decisions were whose. Bain Capital that oversaw many a takeover and debt loaded sell off of many companies was what concerned many and therefore labeled him as a corporate sell out in many liberal and independents minds. … in-romney/
Here's how great Obamacare is:
My family and I have health insurance. I pay for it through my work. We were just given notice that our insurance premium will increase quite substantially, as it has four of the last five years. I decided to shop around to see if I could get a better deal. That seems reasonable, right?
Because of Obamacare, I'm not permitted to change insurance plans now. If you have existing insurance, you're not allowed to change until the next Obamacare open enrollment, starting next November. This is America? Since when can't I shop for insurance? Now, I have to find a way to pay for insurance I can't really afford. There's something wrong with a system that makes you keep insurance that is overpriced and won't let you comparison shop until you're given permission by the federal government. My other option is to drop existing insurance coverage for my family and pay the tax penalty for having no insurance. I HATE Obama"care."
Two points here.... first, you said yourself that your premiums had increased substantially in four of the last five years - so you can't blame the ACA for the increase, as it was likely to happen anyway. Second, all health insurance policies have a period of open enrollment, and they have for years. The only time you have ever been able to get new insurance in the middle of the year is when you get a new job (or become eligible in your present job). And if you ever wanted to change or upgrade your employer-provided insurance plan, you probably had to do so before the new year. So you can't blame the ACA for that, either.
Not as much has changed as you think.
". . . so you can't blame the ACA for the increase,"
I didn't say Obamacare is responsible for all of those increases. However, health insurance has increased directly because of Obamacare. That is a fact. Somebody has to pay extra to make sure that some pay less. Insurance companies aren't going to just cut their premiums, because it's the right thing to do. Somebody has to pay, healthy people and the middle class.
"The only time you have ever been able to get new insurance in the middle of the year is when you get a new job."
According to six different insurance agents and several articles, that is entirely false. Yes, you could get insurance, at any time of the year, prior to Obamacare and not just when you were fired, had a baby, or found a new job. Obamacare changed that and made it more difficult for people to get insurance. Here's an article that addresses the issue. If you don't like this article, I can provide other sources. Better yet, call an insurance agent. You'll find that you could get insurance at any time of the year prior to Obamacare.
." … ear-round/
Obamacare makes insurance more expensive for millions of people; young, healthy people and the middle class will now pay more than their fair share. Obamacare makes it more difficult for some to get insurance. It's okay though, because I can keep my doctor, right?
The market place for health insurance has been severely regulated for years. Medicare and Medicaid had already distorted the cost and availability of medical care. There hasn't been a government distortion free market place in either health insurance or health care since the 1960's - or even as far back as the 1940's when employers started offering any number of perquisites to retain employees because the Federal Government froze wages while the supply of labor contracted. When the government insinuates itself into economic decisions it distorts those decisions.
One need only look at other complex medical care that is not covered by insurance or government regulation - outside of safety - to see that the market works when left to do so. Vision correction and cosmetic procedures are far less controlled and typically not paid for by insurance, government or private, yet the availability increases and the cost declines for both types of medical care. Why?
Demand is up, as is supply, as the population ages and doctors flee the restrictive and burdensome government controlled market.
Are you referring only to Employer offered plans vs. Individual plan purchase? I agree regarding employer plan qualifiers. I disagree with individual application and plan purchase having been regulated in the past.
It's been a while since I had to buy insurance a la carte, as I have been fortunate enough to have had employer-subsidized insurance policies (and college-subsidized policies, too), but in my experience, I had to wait for months (while I paid premiums) before actual coverage would kick in. The exception was at the very end of the year, when there was "open enrollment," and the waiting period was waived.
My other experience is through clients (I'm a divorce attorney), who always have had trouble getting health insurance if and when they lost access to their spouse's plan. In my experience, it is not possible to simply buy a health insurance policy and be immediately covered, as when you buy auto insurance. Maybe the recent changes in the laws have improved things, I don't know.
I am not sure, so a IMHO. When acquiring work having a disability I shopped and do not remember a waiting period told to me. Cost was prohibitive. Recently I elected Cobra because of market policies being cost prohibitive. That was expensive too as the former employer paid 50%. A quick hike in allocated personal budget. Yet, I needed it with a disability, medications, and a recommended operations, of which were approved and very expensive.
Also, now on disability (state) in Calif with no income indicated with earnings it kicks the applicant to Medical - state program, while declaring an option for private is kinda' not allowed. There website does not allow shopping to occur. It prevents that unless you change the income to near $20K or about. Savings would last until a new job for a private carrier. But, medical will not provide the quality health care I have received in the past.
From your source:
>." <<
It is not the ACA preventing insurance companies from selling you insurance. They are just afraid of losing money, as always. Before legislation forced them to cover everybody, insurance companies wouldn't cover you if you were sick or had preexisting conditions (or, they just made it prohibitively expensive). It has never been cheap or easy for an individual to buy health insurance in this country.
You are looking back as if we moved away from the good ol' days, the Golden Age of healthcare insurance. You have a short memory, because healthcare insurance was a huge mess (and getting worse every year). Employers were paying higher premiums, too. The percentage of people covered by employer-subsidized insurance was going down, and insurance was unaffordable for individuals.
As for your contention that "somebody has to pay more so that others can pay less," that is actually not true. The Feds can pay for this (and they are paying for much of it) with deficit spending. And no, nobody has to "pay that back."
You have very little to complain about. Your costs always went up anyway. Look around and appreciate that the less fortunate people around you, the ones that ring you up at the store or cook your lunch, can now get affordable, subsidized health insurance for the first time in their lives.
One of the insurance agents I talked to was pretty depressed. She said that her livelihood has been largely destroyed, because now she can't sell insurance until the next Obamacare open enrollment. Her job is now going to be a feast-or-famine kind of job. She needs a good laugh. I think I'll call her and read your post.
Please, I urge you to call an insurance agent, any insurance agent. You'll find that Obamacare has increased insurance premiums, and you'll find that it has also made it much more difficult for people to change insurance plans.
I have a lot to complain about. My insurance DOES cost more because of Obamacare, and yes, Obamacare has made it more difficult for me to change insurance.
You said, "The Feds can pay for this (and they are paying for much of it) with deficit spending. And no, nobody has to 'pay that back.'" That's part of the problem with the Left..'"
What's worse than that is the fact that we're paying low interest rates right now. What happens when global interest rates." … -stacks-up
Now I took that "no payback" to mean the govt. can simply print the money it needs, an extra trillion a year or whatever, and mail it out in payments to doctors, nurses, hospitals, etc.
This is a very smart move, as it will cause very high inflation, meaning more taxes taken in and more ability to pay our debt. That it also causes hunger, despair and poverty is irrelevant; govt. can simply print more money to give out more food stamps, free housing, etc. and thus lock more people into perpetual poverty. And what could be better than locking people into dependence on the party of entitlements? It keeps them in power, and produces perpetual power and income to it's politicians.
After all, it worked in 1920's Germany, didn't it? Ending up with Hitler and WWII?
"Look around and appreciate that the less fortunate people around you, the ones that ring you up at the store or cook your lunch, can now get affordable, subsidized health insurance for the first time in their lives."
And now, in order to help pay for less fortunate people, I may be working right next to them. After working 10 hours in my regular job, I may have to go work for a few more hours in a second job, so I can afford insurance under Obamacare.
It seems that, now, I will be the less fortunate person. Thank you Obamacare!
Don't bother - that "affordable, subsidized health insurance" is just that - insurance. It is not health care and will not provide for any, either.
I know - I'm one of those getting 100% subsidized insurance, but with a deductible so high it will bankrupt me before the insurance ever pays a dime. As far as I'm concerned, then, it is worth exactly the same as not having insurance at all - either way I can afford a few thousand but will be bankrupted with any major bill.
EA and Wilderness - I have some articles about the deficit that you could both learn from. In a nutshell, governments that print money get the benefit of spending that money into the economy. Call it seigniorage, if you like (it's a bit different). It does not lead to inflation. And Germany didn't go broke printing money, they printed money in response to going broke. They owed war reparations, in gold. Next topic...
Interest rates on govt. bonds do not go up and down with "global interest rates" (which do not exist). The Fed sets the rate by participating in the bond auctions. Not that it would matter, because it costs the govt. nothing to create the dollars to pay the interest. Next....
Sorry you guys have such crappy health insurance situations, but I doubt they would be any better than they were pre-ACA. Wilderness, if you are getting 100% subsidized insurance, what did you have before this? Nothing?
Finally, while I never like to hear about anybody (the insurance agent) hitting hard times, I'm not nearly as concerned with keeping insurance companies rich as I am with making healthcare available to everyone that needs it. The old system wasn't coming close. I personally would have preferred single-payer, but Republicans killed that dream long ago. (Probably at the behest of the insurance companies.)
***********
It strikes me that a lot of this complaining revolves around money - higher costs, higher taxes, and higher govt. spending. The solution to all of this is, brace yourselves, higher government spending. You both think it's a bad thing, that the govt. is like a household, and when they print dollars, it's like you or I using a credit card. That is not even close to being correct. That kind of thinking, though, has dominated for the past 40-50 years, and a lot of it can be blamed on Milton Friedman - a smart guy, but wrong about the economy - he thought it was all about the number of dollars. Look at the past 35 years, since Reagan really started to deficit spend heavily - we don't have high inflation; we don't have high interest rates; the economy is doing pretty well (except for providing jobs); and basically everything that those Friedmanite economists have been afraid of has turned out to be wrong. Yet an irrational fear of deficit spending still drives policy, because it's still what most people believe, and they vote accordingly.
You are both in favor of cutting government spending, which obviously hurts a lot of people. But why? None of your fears have been borne out, after 35+ years. It's time to re-examine your beliefs about the economy. This self-imposed austerity just isn't necessary.
Sorry, Germany had raging hyperinflation before it paid the first dollar of war debt. Yes, they were broke, even more so that the US is, but it was only made worse by printing extra money. As it would be here - any economist worth anything could (and would) tell you that indiscriminate of money printing is a road to disaster.
Insurance - I had none that would help me pay any health care bill. Which is what I have now - after going bankrupt before meeting the deductible I will no longer own any money, so anything paid by the insurance company won't help me at all. The Affordable Care Act produced affordable (free) insurance in my case, but no affordable care at all. And, after examining the insurance plans in my state, I very highly doubt that any of them are any different; it will take a rich person indeed to cover the costs of any major care.
And yes, govt. spending badly needs cut because the money isn't there to be spent. Despite what you claim, the govt. cannot continue to borrow money without paying interest AND principle back, neither of which it has. And neither of which can be simply indiscriminately printed or created by some other magic.
Now if you could magically erase all govt. debt - it would certainly be time to simply eliminate all medical insurance and make all care bills paid by government. We would then have the money to do that.
Your policy is to let the good times roll, to print, borrow, grow government, and pretend that none of this matters? Are you from Greece?
Actually, we're spending more, per person, than Greece was. How did that turn out for Greece?
My insurance poor, and I pay a lot for it. You don't want to acknowledge that insurance premiums have increased under the debacle we call Obamacare. Fine. Let's talk about whether or not the insurance has improved. The answer is a resounding. . . NO.
Obamacare is a total failure.
Is that a serious question, Beth?
EA and Wilderness, it is obvious that neither one of you has put any sustained effort into understanding economics. Both of you are just repeating the same old stuff we hear from journalists (who know nothing about the subject). This is understandable - not many people are interested enough to want to do the work to learn. But this is also the tragic part of it, because America's collective inability to understand economics is why we keep electing the idiots we elect. Economically, we are voting ourselves a starvation diet, when there is plenty of food to be had.
EA - Greece cannot print their own money. They use the euro, which they have to borrow from the ECB. You see, there is much to learn about this stuff.
Wilderness - what makes you think that the U.S. is broke? The fact that there are a lot of federal bonds outstanding? Do you think that equals debt in the same sense that you or I can be in debt? Do you think that China can demand anything but more paper for their bonds?
It is amusing to hear an advocate of increased government spending criticize others for failing to understand economics. Government has no money. It takes, inflates or borrows money, all three of which have an adverse impact on the direction and flow of money through the economy. Although China may be unlikely to "call its note," the interest paid to the Chinese on the debt they hold is sufficient to bankroll the expansion of their military. Though Greece may not be able to print its own money and must borrow from the European Central Bank, the United States government merely distorts the value of the aggregate dollars in the economy to finance spending driven by policy rather than the billions of decisions made by those who produced those dollars in the first place.
Concentrating economic decision making in the hands of 536 people who make a few, grand policy decisions each year that are driven by political agendas and the desire for perpetual re-election is irrational when the alternative is billions of small economic decisions made everyday by millions of individuals, as well as every conceivable size business, based solely in the desire to maximize the efficient and effective use of those dollars. How does a central economic authority gather a sufficient amount of economic information to effectively and efficiently spend money in such a way that it is superior to the micro-economic decisions of millions of consumers?
Centrally directed economies are rubbish and concentrating vast sums in the hands of the federal government is a recipe for disaster. You might understand that if you knew more about economics than what Paul Krugman, that phony hack, spouts.
"It is amusing to hear an advocate of increased government spending criticize others for failing to understand economics. "
Good point.
That's nice.
Read this.
[b]:
"[b." … s_it_needs
Greece can and does print euros. How did that work out for them?
"You see, there is much to learn about this stuff."
Retief - you are wrong. If governments do not create money, who does? The bills in my wallet don't say "Citibank" on them.
China cannot "call its note" on U.S. bonds. Nobody can. Bonds have a designated time at which they mature, and when they do, we simply exchange the mature bond for dollars. The exchange costs our government nothing. They exchange dollars for bonds and bonds for dollars every day. And they produce both dollars and bonds out of thin air. The idea that China loans us dollars demonstrates a complete lack of understanding of how bond sales work.
Finally, your faith in the decision-making of the masses is misplaced. People, including people as a whole, make terrible decisions all the time. The whole idea is just more Austrian garbage that has zero basis in reality. And calling all government spending a "centrally-directed economy" is ridiculous on its face. Every government in the world spends money. I suppose you think that every country now has a centrally-directed economy, too.
What is your take on why government collects taxes instead of just printing another few trillion?.
This is all one need read to dismiss everything else you have written.
I couldn't agree more.
So you have no answer then.
Retief said: "Government has no money. It takes, inflates or borrows money, all three of which have an adverse impact on the direction and flow of money through the economy."
How, then, does the number of dollars increase? Does China print them? Do the banks? Where do you think dollars come from in the first place?
The problem with your thinking is that you are starting with a political slant ("the government is bad"), and then you attempt to make the facts fit your political slant, instead of the other way around. You would be better off learning how things actually operate, then base your political views on that (new) knowledge.
The government isn't bad when it isn't bloated and irresponsible. Of course, I don't know when that last was.
paper chits are not money
Go to the grocery store with some "paper chits", a credit card, and some gold bullion. See which two methods of payment will allow you to buy groceries, then get back to me.
Oh, now relying on the micro-economic. What next a reliance on aggregate consumer decision making? I am not China and that was your point. You have a problem understanding money. It is okay, one cannot expect too much from lefties.
EA - that article is talking about an illegal act, basically printing counterfeit money. (It even said so.) It is not relevant to the discussion. Greece (as long as it does not go rogue and start counterfeiting euros) does indeed borrow euros. All Eurozone countries do. They do not get the benefit of seigniorage - they can only spend what they can tax away or borrow. This is a huge disadvantage, as it basically eliminates govt. deficit spending as a fiscal policy tool.
It's totally relevant if Greece did it. Greece did it, and its economy still tanked.
The Krugman solution of minting a trillion dollar coin, printing money to pay for debt, was the laugh of the decade. His notoriety plummeted, among both economists and the untrained, when he came up with that "winner." You're advocating the same thing, print and spend. With all due respect, it's not a deep thought, and it doesn't show some kind of greater analysis.
The theory is that countries that print their own money can not default on their debt. Tell that to Russia, Jamaica, Ecuador, Argentina, Brazil, and so many other countries that print their own currency.
To all 3 of you - I have never understood the sheer hostility to new or different ideas when people discuss economics. It's like discussing religion, except that there is some available data and evidence to go on.
After listening to politicians and pundits blather on incorrectly for 35+ years about all of the horrible things that are just about to happen if we don't stop deficit spending, why are so few people unwilling to even question the validity of these dire predictions? Interest rates haven't gone up, inflation has remained low, the economy is still the largest on Planet Earth, yet you guys still believe the same old stuff. That is the very definition of insanity. Or religious faith, take your pick.
But...there is nothing new about government creating false value by printing $$ or borrowing more than we can ever pay back. It is been the liberal dream for decades!
Printing money to cover debts isn't new.
What does religion have to do with this? Was it just a way to work it into the discussion?
Wilderness - first of all, if we can print it (and we can), why on Earth would we borrow it, too? Think it through. We haven't "borrowed" dollars since we were on the gold standard, and new dollars cost something (we had to procure the gold) to create. Second, what is "false value"? A dollar is a dollar. If you believe that the value of dollars can be somehow "diluted," you need to realize that there is not a fixed quantity of goods that are being produced. The more dollars that are spent, the more demand there is, and the more goods that are produced. Prices don't go up unless companies are no longer able to increase production to meet demand.
Odd - I was sure we sold bonds ("borrowed") every year.
A dollar is a piece of paper. It represents a certain value, which is not a piece of paper, and that value can indeed be diluted. It has happened very nearly every year for the past 100 or so.
If you think prices don't go up until maximum production is reached you obviously did not live through the double digit inflation of the 70's. Prices rose even as factories closed because no one was buying.
EA - you didn't even read your own article. Greece did NOT do it. They did not go rogue and start counterfeiting euros. If that's your argument, you lose.
Also - it was never Krugman's idea to mint the coin. And his good reputation remains intact, btw. You simply do not understand the mechanics of the coin - yet that does not seem to stop you from denigrating the idea. That's typical of people who don't want to bother learning.
Finally (and it's not a theory, it's fact), countries that print their own fiat money AND HAVE NO FOREIGN-DENOMINATED DEBTS can not be forced to default on debts DENOMINATED IN THEIR OWN CURRENCY. All of those countries you mentioned (and others) had foreign debt, which you pay off with, guess what, foreign currencies.
Are you kidding? I don't want to learn from Krugman when he starts talking about printing trillion dollar coins. His reputation is not secure. Let's see a list of economists who didn't laugh at his idea and actually got on board with printing trillion dollar coins. GOOD LUCK creating the list. … ollar-coin
This is what the article you are referencing says:
"Greece is already estimated to have created up to 96 billion euros to help its banks using the ELA."
Here's another source:
"The new arrangement allows Greece to print T-bills and then sell them to its own banks who then pledge them to the Bank of Greece as collateral for euros. In this way, Greece has already printed 5 billion euros into existence."
The end result is free euros. How did the free euros work out for Greece? What about Russia? They don't use the euro. How about Argentina?
I compared your faith(s) in economic schools of thought to religion because the analogy is fitting. You are defending the legitimacy of something that you don't understand, you have no firsthand knowledge of, and have no solid proof of. That "something" being what you all believe will happen if we continue deficit spending. Like scientists who carbon-dated dinosaur bones and provided solid evidence that the Bible's timeline was impossible, I tried to explain how we don't really borrow dollars and pointed out that inflation and interest rates did not actually behave as you would expect them to. Yet, against the weight of the evidence (and with none of your own), your belief in monetarism persists. So my analogy stands.
Wilderness - please read my article on the gold standard. It explains the very real difference between bond sales in gold-convertible and fiat economies.
As to the dilution thing - if your business produces 100 loaves of bread/day (to meet demand), but is capable of producing 120 loaves/day, what happens when demand goes up? Do you increase your prices, or do you just bake and sell more loaves? Because if you raise your prices, the bakery down the street will undercut you every time.
I was only a teenager during the 70's, but even so I understand that our inflation was caused by oil prices. There was even an embargo, remember? It certainly wasn't caused by printing too much money, because we didn't start heavy deficit spending until Reagan's presidency.
Inflation (devaluing of our money) in the 70's was driven by excessive union power as much as oil prices. Unions demanded, and got, higher wages for no additional production, requiring raising prices. Which caused others to also demand raises, putting them back on par with the unionized employee. Who then wanted, and got, another raise to once more (temporarily) earning more than his neighbors. And round and round and round.
And yes, when demand goes up so does price. Because the bakery down the street will see you raise yours but instead of picking up more sales by undercutting your price (and increasing production via more workers and equipment) will raise theirs as well. Free profits for the taking, and not requiring any more company infrastructure or investment.
Don't ever open up a bakery. You'll be out of business in a month.
I have NEVER heard the theory that unions caused inflation. And I don't think I ever will again, to be honest.
Union sympathizers never think that raising costs will result in rising prices. It is always assumed that the companies will simply take it out of profits (even when those profits won't cover the raises) but somehow it never works that way. Prices rise, causing another round of wage demands, causing another round of price increases. It's pretty simple, really.
I take it you are a union sympathizer, assuming that prices won't rise when labor costs go up?
Good evening, John. Happy to run into you here.
Perhaps, when it comes to economics and the many causes of inflation, you may not have read all there is to read and, hence, you may not know all there is know. I know near to nothing about economics, but I do know that Wilderness did not fabricate the notion that unions in the '70s caused inflation.
In a paper by Robert L. Hetzet, “Arthur Burns and Inflation”, the author explores the unusual inflation of the ’70 while Arthur Burns was Chairman of the Federal Open Market Committee (FOMC) of the Federal Reserve System (the Fed) from February 1970 until December 1977. When discussing Mr. Burns' inflation views as chairman, Mr. Hetzet says, .” {1}
"Burns drew the conclusion that the contemporaneous inflation arose primarily from a rise in wages due to the exercise of monopoly power by labor unions...
The Nixon Administration designed the wage and price controls program that began August 15, 1971, on the assumption that the monopoly power of labor unions was producing a cost-push inflation." {2}
You heard it from Wilderness. You heard it again from me with a link to a verifiable source. Finally, if you follow the link and read the source, you will have heard it for a third time from the Federal Reserve Bank of Richmond Economic Quarterly.
I think NEVER is NEVER as far off as we think and I think Wilderness would do quite well in the bakery business.
Your posts are interesting, John. I enjoyed reading them.
{1} … hetzel.pdf P.23
{2} Ibid. p.35-36
I have no problem with unions. They don't have much power when the demand for labor is low (like today). We are generally better off as an economy when the demand for labor is higher and more of the economy's profits go to workers. Unfortunately, I think those days are over.
Here is a chart of historical oil prices. Between 1972 and 1979, the nominal price went up almost 7x. Since the price of oil affects the price of just about everything else, I think it more than explains the inflation we had in 1970. … _Table.asp
I'm aware of what oil prices did then; I worked in a gas station during the period when gas became scarce and prices rocketed.
I'm also aware of what labor costs did, nearly always beginning with a large, strong union somewhere. One local town near me nearly became a ghost town when the union demanded a raise the leading employer there could not afford to pay and they closed their doors. As a union employee myself (prior to the gas crunch) we struck each year, gaining a raise big enough to make up for lost wages from striking, spread over the next year - a fine example of the value of indiscriminate union demands.
Wilderness - sorry, I missed one of your earlier posts.
"What is your take on why government collects taxes instead of just printing another few trillion?"
First of all, most in government are still in the same monetarist rut that you guys are in. Even Democrats think there is a need to keep the deficit low.
Taxes still have a useful purpose - they still drive the demand to earn dollars (as opposed to bitcoins or some other form of currency). They are still useful for pushing people in certain directions (home ownership, etc.). And theoretically, taxes carve out a portion of our economy's production for the government's use. I'm sure you have heard the axiom that production = consumption, right? If we produce $100 worth of widgets, we will earn $100, which can then be spent on the next round of production, etc. Now this is a terribly oversimplified scenario, because it doesn't allow for savings or trade imbalances, etc., but anyway, the theory goes that if you consume all that you can produce and don't save, any new dollars the govt. introduces as demand will drive up prices, assuming the economy is already at max production. So they would tax away some of your dollars to spend and not introduce new demand. In reality, there is LOTS of unused productive capacity, and our economy is capable of producing quite a bit more than it does presently, so new demand will not drive up prices. >> That, btw, is the problem with the idea that ANY new demand will drive up prices. There aren't many businesses around that are turning away customers these days, are there?
"..."
Why don't we play this game with realistic numbers? Remember when Dubya sent out those tax rebate checks, and everybody got about $800 in the mail? That didn't cause inflation, even though there was a rash of spending. (Also, our government didn't have any trouble at all covering those checks.)
What you need to understand about government spending is that (except for some welfare and SS checks), the government gets something for their dollars, either services (from, say, paying govt. empoyees) or goods. (Even welfare and SS checks are quickly spent into the economy.) New dollars aren't just sprinkled over the populace - they are spent. And if you want some of them, you have to earn them. That is production - production that would not have existed without government spending.
EA said: (from an article) "Greece is already estimated to have created up to 96 billion euros to help its banks using the ELA."
Using the ELA is still borrowing from the ECB. In each case, most of the collateral is still that country's bonds. The main differences are a higher interest rate, lower collateral requirements (i.e., lower rated bonds), and the liability sits on the books of the country's central bank instead of directly on the ECB's books. (Though each country's central bank is just an arm of the ECB anyway.)
It is not "free money." It is not under the sole control of the Greek government or the Greek central bank, either - the ECB has to approve use of the system and they can pull the plug on ELA lending with two-thirds of the countries' say-so. In each case, most of the collateral is still that country's bonds.
Lots of Eurozone countries have used ELA loans - Ireland, Belgium, Cyprus, etc.
So, basically you're saying that borrowing too much money can result in a debt default? Go figure.
Were you able to come up with a lot of economists who agreed with Krugman's trillion-dollar coin idea?
Greece borrows euros from the ECB, and does not have the authority to print euros as they see fit. That is a true debt situation, and they can certainly default.
The U.S., like Canada, Japan, the U.K., Australia, et al, does not actually borrow their own currency. Bond sales are unnecessary in fiat currency economies. They are relics of the gold standard days. The fact that the number of dollars in existence keeps going up should clue you in to the reality that the same dollars do not get recycled over and over.
There is still a ton of monetarist thinking dominating the world, and a lot of people who should know better are still convinced that bonds are what keeps inflation in check. But, as I tried to point out earlier, there is no evidence to back up this thinking.
Quilligrapher - welcome to the discussion.
Interesting article, thank you for the link. From that article:
.”
I do agree that labor costs can contribute to inflation, but I disagree with Burns when he blamed inflation primarily on labor unions. With or without labor unions, the price of labor should rise and fall depending upon the demand for labor. In times of high demand, when labor unions are strong, they can flex their muscle. But in times of low demand, like today, unions lose much of their power, and labor costs are relatively low. I know that there are some exceptions, and other factors can have an effect, but I think the general rule holds pretty well.
My take is that inflation is caused by leverage. Competition keeps prices low, unless somebody somewhere has leverage over the situation. OPEC had the leverage in the 70's, and they still have quite a bit today. Unions used to have a lot of leverage; today, they have little. If you have a brand that has no generic equal (Apple, for instance), a professional sports team that you can hold over the head of a city, if you hold a commodity that is in truly short supply, you can push prices up, regardless of your costs. If, on the other hand, you are the producer of no-name Android tablets, loaves of bread, or some other commodity-type product, keeping your prices down is everything.
Now I'm going to take the opportunity to blather on about "monetizing the debt," a phrase which has a lot of people, some economists included, absolutely terrified. Monetizing the debt would basically be exchanging dollars for bonds - so instead of $17 trillion in outstanding bonds and $1 trillion in dollars, there would be $18 trillion in dollars floating around out there. Monetarists believe this would lead to instantaneous inflation. I don't agree, and here is why...
Bonds are already very liquid instruments. If you have $1 million worth of U.S. bonds, you can change that into dollars in minutes. So if there was something the bondholder would like to spend that money on, including an investment with a higher return (and more risk), there is nothing preventing him from doing so. And the paltry interest we are presently paying on bonds can't be the incentive to sit on those dollars, because it probably doesn't even keep up with inflation. There is simply a desire to sit on savings. People have always done it. If we ever exchanged dollars for bonds, I think the vast majority of those dollars would be moved to vaults; not other investments, and certainly not goods or services.
"Were you able to come up with a lot of economists who agreed with Krugman's trillion-dollar coin idea?"
Again - it wasn't Krugman's idea. I don't know why you insist on repeating that.
The idea has been around for a while, but the recent (within the last few years) interest in the idea came from an economics poster with the screen name Beowulf, who posts on MMT forums. (The whole story is on Wikipedia.) And you will get the best commentary on the coin from MMT economists - Mosler, Kelton, Wray, etc. It's not a compicated idea - if you have an open mind, I explain it in my hub on the gold standard:
"Since the Treasury can mint coins as needed without backing, the idea of minting a few trillion-dollar platinum coins and depositing them into Treasury's account has been considered. This would satisfy the requirement to keep Treasury's account in the black without issuing more bonds (and increasing the national debt), while allowing the government to spend dollars. If nothing else, this should serve to illustrate that fiat dollars are not backed by anything, since the true value of the metal in the coin is minimal. By the same token, bonds are merely promises to deliver paper dollars at a later date - so bonds and dollars are basically equivalent instruments."
There is general agreement out there that this would satisfy the legal requirement that Treasury keeps its Fed account in the black while it spends money. The monetarists are worried that it will cause inflation, but they, of course, can offer no proof or evidence of this.
BTW, did you ever come up with any evidence that deficits cause inflation/high interest rates/an inability to sell bonds?
"BTW, did you ever come up with any evidence that deficits cause inflation/high interest rates/an inability to sell bonds?"
When did I say any of this?
Yes, the idea of print and spend has been around for a long time. Paul Krugman didn't invent the idea, but he took it to a new level. You said that Krugman did not diminish his reputation. I would like to see proof. Were any economists in agreement with the whole coin idea? Please provide a list of economists who were on board, perhaps some quotes.
Greetings JohnfrmCleveland,
Can I pull up a chair?
You seem to b e both knowledgeable and a proponent of MMT.
I did not know what it was until I stumbled across your comments.
(but I have been trying to understand it more in the last few days through available materials)
You sparked an interest that has put me in a quandary. So as the instigator of my interest, I hold you responsible for my "quandary."
My perception is this:
As an explanation, or theory, MMT seems logical in its accounting perceptions. If the premise of MMT is correct, then even the "trillion dollar coin" solution doesn't seem too illogical.
But in all the accounting jazz, I keep stumbling over my thought that money - any of the various kinds the explainers of MMT describe, is more than an accounting entity.
Of course I have only grazed the surface of the theory, (so far), but I think money has a "perceived value component. Whether it was physical gold in the ol' days, or the confidence of the market, (users), my gut tells me that money has to have that component.
For instance; if I have one bar of gold, and you asked for it, I probably would not give it too you. But if I had a million bars of gold - that one bar would probably have a lesser perceived value to me and I would probably generously hand one over to you.
Maybe that is a poor example, and illustrates my misunderstanding of what you are trying to explain. But, I don't feel too lonely, as several sources I read offered similar thoughts.
One writer used the phrase "accounting is not economics," and another remarked comparing it to socialism - in that as a theory it sounded good and seemed to make sense, but it just doesn't, (or hasn't so far), work in the real world of humans..
Today I think that perceived-value component is the users opinion of the issuers fiscal responsibility.
Your responsibility, should you decide to accept it, is to point out the primary mistake in my thinking. And perhaps explain why a theory first introduced in the 1890s, and further studied, tweaked, refined and propounded by some apparently smart and savvy guys over the last hundred years or so, is still looked at as a system that "just isn't right."
ps. I did read several of your hubs on the topic. It all sounds logical if the world worked as an accountant's ledger does - but that isn't the reality of human behavior.
pss. you do present a very understandable explanation of MMT and why it should work - interesting reads
GA
"When did I say any of this?"
Right here.
."
Then, you went on to quote Erskine Bowles, who couldn't be more wrong about economics.
I gave you a list of economists in my last post - Mosler, Kelton, Wray, and MMT economists in general, in addition to Krugman. The discussion of the platinum coin option SHOULD serve to illustrate that bonds and the national debt are not a problem; the fact that a coin with no metallic value can take the place of a trillion dollars' worth of bonds should clue you in to the fact that those bonds do not represent actual debt. The coin is a political tool, an option to circumvent the idiots in Congress who are trying to use the debt ceiling as leverage. These economists understand that bonds are not a problem when you control your own currency. A simple search will give you a wealth of information on the subject.
You said, ". . .deficits cause inflation/high interest rates/an inability to sell bonds?"."
I didn't mention inflation. I didn't mention the inability to sell bonds. I didn't mention high interest rates; I mentioned paying interest. The interest rate and the interest paid are not the same thing, and we both know it.?
I appreciate that you've listed some people who you claim agree with the TDC, but I'd like to see some quotes by these people, quotes that truly show that they believe in the TDC
Still, I'd like to thank you on raising the bar a bit. This is a fine debate, and I appreciate the level of discussion.
GA - welcome to the discussion. I'm not completely sure I'm understanding what you want here, so please stick with me and help me understand your concerns, if I don't get them right.
."
In the world of finance, there is no problem with confidence in the U.S. government. Bond traders understand that governments sovereign in their own currencies can always meet obligations in their own currencies (they can always redeem their bonds). The risk is (almost) zero - the small bit of risk is the chance that Congress will refuse to allow an increase in the debt ceiling, and no emergency measures would be used to allow Treasury to pay the bills. So bonds from the U.S., Japan, Canada, U.K., Australia, etc., are all considered zero-risk places to park money, and the (low) yields reflect this confidence.
Consumer confidence is more an issue of whether or not people feel secure in their jobs. For most people, what they believe about the U.S. economy doesn't really affect their spending. You have to pay the rent and buy the groceries, no matter what you think about the dollar.
If you are referring to the possibility of hyperinflation, that is not caused by money printing (although that could do it, in theory). Every instance of hyperinflation that I can think of has been the result of a large dropoff in production, excessive foreign debts, or some sort of social upheaval (like war, or Yugoslavia splitting up), or some combination of those factors. Printing money in an attempt to match inflation comes as a response. Hyperinflation normally goes hand in hand with a lack of stuff on the shelves to buy, especially food. America is a long, long way from running out of stuff on the shelves to buy, and we have the capacity to produce far more than we are presently producing. All demand is being met, and the economy isn't breaking a sweat. More demand isn't going to push us over the edge.
Many people (and economists) will say that deficit spending will somehow "dilute" the value of the dollar, because there will be more dollars chasing the same amount of production. But money enters the economy by spending, and that spending induces new production, so that reasoning is clearly incorrect. New demand should not lead to serious demand-pull inflation until there is a shortage of some component of production - energy, labor, raw materials, etc. The goal of MMT is to spend for the purpose of reaching 100% employment. The theoretical limit on spending would be (serious) demand-pull inflation.
That was kind of scattershot - did any of that answer your question(s)?
It was an honestly valiant attempt to explain, but I just can't get passed my instinctive reaction to the importance and impact of the currency users perceived-value component.
From what little I understand at this point, MMT just doesn't see that as important. Nor did your explanation imply that it was. as in...
"...the small bit of risk is the chance that Congress will refuse to allow an increase in the debt ceiling, and no emergency measures would be used to allow Treasury to pay the bills. ..."
This has been shown to not be an improbable event.
"...Consumer confidence is more an issue of whether or not people feel secure in their jobs. For most people, what they believe about the U.S. economy doesn't really affect their spending...."?
Thanks for the effort though, and I will continue to look into MMT. However, I am not optimistic about a conversion - I think I am going to continue to run into the apparent common sense vs. theory roadblock.
GA
"I didn't mention inflation. I didn't mention the inability to sell bonds. I didn't mention high interest rates; I mentioned paying interest. The interest rate and the interest paid are not the same thing, and we both know it."
Sorry. These are the standard arguments that go along with the fear of deficits. When you went on to quote Bowles and what he had to say on the possibility of interest rates rising, I assumed you went along with that thinking, since you did quote it.
.""
This is incorrect, because there is not a finite number of dollars. Paying interest does not remove dollars from a finite pile from which we pay for other things. Also, "paying back the debt" is a misnomer. There is no extinguishing sovereign debt in the same way you or I extinguish a bank loan when we finish payments. The government exchanges bonds for dollars - this is commonly called "debt." When the government completes its bond obligation, it returns the dollars, plus a few more, in exchange for the bond. But their liability has not changed - dollars are accounting liabilities, too, same as bonds. On the government's ledger, there is no difference between the two. And fiat dollars are not true liabilities, like convertible dollars were - they are just out there, and the government has no further obligation on them. The only thing the government does with dollars is replace them from time to time when they get too ragged.
?"
Greenspan (like any Fed chair) understood the mechanics of dollar creation - the govenrment can produce dollars at will, they can buy their own bonds without limit, and they can control the interest rate. But he was also a monetarist who believed that, somehow, you controlled inflation by controlling the number of dollars in play. That includes interest payments, even though interest payments are overwhelmingly rolled over into more bonds, and never spent.
"I appreciate that you've listed some people who you claim agree with the TDC, but I'd like to see some quotes by these people, quotes that truly show that they believe in the TDC."
You aren't going to find a lot of quotes out there. You would have to dig through the comments sections of blogs, and (sometimes) know who was behind the screen names. The coin idea was a product of discussion forums, not research papers. I know this, because it came from the discussion forums and blogs that MMTers (including myself) participate in. There is an understandable reluctance for big name economists to officially endorse something like the coin, because there is so much immediate blowback (like on this thread, for instance ), and it's hard enough to get people to give heterodox ideas a fair chance without tossing an easy talking point like a trillion-dollar coin out there for reactionists to jump on before they even hear the details. (If you doubt that, just look at the crap a Nobel laureate like Krugman got from a bunch of nobodies for even discussing the subject.)
"These are the standard arguments that go along with the fear of deficits." I understand that, but they weren't my arguments. I specifically strayed away from making those arguments.
Your answer, regarding economists' quotes, was plausible. I'll drop that point..
GA wrote: ?"
Are you implying that prices are determined by what we think they should be? As in, "one dollar should buy a loaf of bread"? Or are you saying something like "I perceive prices to be going up, so I should be ready/willing to pay $1.25 for a loaf of bread"?
Prices are what prices are. They don't go up or down based on perceptions. Now, if you are doing well and have a pocketful of money, you might be less inclined to fret about getting the best deal, but that works in the other direction as well.
I don't think that gold-convertible currency had any anchoring effect on our money, either. Prices fluctuated back then, too. But very few people ever bothered converting their bills to gold, and I doubt that they checked the spot price of gold before they shopped. Besides, what determines the price of gold? It's just another commodity, one of many.
***
"Thanks for the effort though, and I will continue to look into MMT. However, I am not optimistic about a conversion - I think I am going to continue to run into the apparent common sense vs. theory roadblock."
In a sense, you are already a convert - we all are - because most of MMT is simply a description of how our economy works right now. That's why it is so heavy on the accounting - it is meant to demonstrate what happens to dollars, where they come from, why they don't cost anything for the government to produce, etc. The only "theory" is in the policy prescriptions that stem from the understanding that fiat currencies are not borrowed or financed. Those policies are obviously not in place, but the mechanics of dollar creation, bond sales, reserve banking, and interest rate control are all accurate descriptions of how today's economy actually operates. Even the Austrians agree that MMT has the mechanics right.
No John, I don't think I am a convert. Mainly because it seems that, of the reading I have done so far, most proponents of MMT, while saying it is a description, are also saying if the prescriptions deduced from accepting the premise of MMT were actual policies - everything could be honky-dory .
To me, the mechanics of MMT's description of a fiat currency economy were easily understood and very educational. Your own writings were as good as any I found elsewhere. (I did read all of them)
But... and this is where my initial "gut instinct" kicked in, while excelling as a description of the accounting process - it appears totally lacking in understanding the human involvement factor.
As one writer said, "Accounting is not economics."
MMT excels at accounting but fails at economics, at least in my weakly informed mind..
My understanding of MMT so far, and as you have stated, is that supply shortages are the only probable factor that could influence the value of any fiat currency - I disagree. I still believe "perceived value" by its users, (the market), can also affect its value.
What would happen if the market's big players, (Wall Street, other nations, etc.), decided to shift to another currency because they lost faith in the government behind the fiat currency?
Another writer, an MMT criticizer, uses an example of U.S. big market players using other currencies for their transactions, (Francs, Yen, whatever), and only converting to dollars at the moment of need for a dollar required transaction.
While agreeing with MMT's description of money as just another name for debt for use in accounting practices and descriptions - in reality, money and debt are not the same. Money is a medium of exchange, not just an accounting notation, and that medium must be trusted by both sides of any transaction to be viable.
Anyway, I probably got the specifics of what I said above wrong, but the point it all leads to is that I don't think MMT understands real world, human involved economics.
Finally, I must both curse you and thank you. The "damn you" curse is for showing me another rabbit hole to chase something down, (my quest to understand MMT), and the thank you is for providing the prompt that caused me to learn something.
Any day I learn something new is a great day!
GA
?"
Well, how do you think a government would even go about "dumping" a bunch of money into the economy? This is a real sticking point, because it is easy to look at the increase in base money and just assume that all of these dollars are out and about, getting spent.
Lots of people think that QE pushed a lot of dollars into the broad economy, but it didn't. During QE, a lot of dollars were created, but they were only used to pump up bank reserves, exchanging dollars for bonds or other assets (often, MBSs and other troublesome assets). The thinking was that this would drive banks to make more loans, thereby stimulating the economy. The problem with that thinking is that banks were always able to make loans - there just weren't many creditworthy borrowers out there to create loans for. The amount of reserves that banks have has no bearing on their ability (or even willingness) to create loans, because they don't actually loan out reserves; reserves (for the most part) remain in their accounts at the Fed. The only reserves that ever leak into the broad economy come from vault cash - vault cash counts as reserves, and that's where you get your ATM money from. So the amount of cash in circulation is determined by the public's demand, largely through cash withdrawls and deposits. But even in times of high demand for cash (like Christmas), that is just a trickle. And since the Fed has never failed to provide banks with any reserves they wish to borrow, there is no "supply" factor when it comes to dollars - it is determined solely by demand. So QE never made a difference in the demand for cash or the demand for loans.
Dollars generally enter the economy through government spending. So for our government to "dump" a bunch of dollars into the economy, they would either have to spend it in, or give it to somebody that would presumably spend it as well. The only other ways I can think of to push money into an economy are to give money to banks, or to give money to people. As was true in QE, banks would still have no extra incentive to spread that money out to borrowers unless they expected more dollars back in return. Giving money to people, though, is a viable alternative, assuming you don't give them so much that their demand would overwhelm the economy's ability to meet that demand. This is actually being considered in Switzerland - giving people an annual stipend.
Some economists have tried to track what governments have done in times of hyperinflation, but the records of these events are amazingly lacking. I was reading about the Yugoslavian hyperinflation of the 90's, which started when the country split apart, trade slowed, and production dropped way down. Apparently the government tried to anticipate how much inflation was going to go up over the short term and increased their payments accordingly - to me, that sounds like an inflation driver right there. It always seems to be a big dropoff in production that gets the inflation started.
."
No, it wasn't a Democratic idea at all. It was purely a topic of discussion in the MMT blogosphere, until some mainstream news outlets (and mainstream economists) picked up on it. It had been out there for a couple of years before the Dems kicked the idea around.
It could have been a temporary workaround, or it could have simply replaced bonds altogether. Bond issuance is not operationally necessary - a government can simply issue currency directly and be done with it. But we are required by law to keep Treasury's balance at the Fed in the black, and this is normally done through bond sales (even if we buy our own bonds). The coin, deposited in that same account, would take the place of $1 trillion worth of bonds.
There is a school of thought out there that believes we need to keep the number of loose dollars in play down, and this is done by exchanging bonds for dollars. There is another school of thought that says there is no evidence or logic behind the other school of thought, and bonds - which are very liquid and yield little interest - aren't what keep bondholders from spending that money at all. (This is where I stand.) If so, we are paying interest for no reason at all, and while it doesn't cost our government anything, it does put even more dollars in the hands of the already rich, which affords them more political power. Anyway, it's an arguable point, and nobody in the MMT crowd is adamant about eliminating bond sales, because they do serve to control interest rates, and they do little (or no) harm. But the whole debt ceiling debate drives us crazy, because we generally believe that the government should be deficit spending more than they do now.
EA said: "A fiat system has no physical backing, just the faith of the public."
The anchor I think you are looking for is taxation. The government that creates the fiat currency also demands taxes paid in that currency. (Some people also think this helps to set the value.) So, faith or not, people are forced to use the country's currency.
I haven't responded, because I'm doing extensive reading on the subject.
I'm not trying to totally diminish the value of MMT, but I would like to point out that it is theory, theory that flies in the face of a lot of traditionally fundamental concepts in economics. Further, there are a lot of economists who are not supporters of the theory.
I'll get back to you once I feel better versed in the concept.
Best wishes.
I'm happy to hear that you're trying! I had to unlearn a lot of stuff before I got over the hump. Almost all MMTers do, because most of us had the same Econ 101 experience, we read the same news stories, and we hear the same political posturing about the deficit. There is a tremendous amount of noise to tune out.
Keep in mind that other economists usually have a lot at stake, and they are slow to admit that they have been wrong. Paul Krugman, for instance, is doing very well being Paul Krugman, and he's not about to stand up and say, "This other guy is correct." He agrees with about 95% of MMT, though, and he admits that we have the mechanics right. He just won't completely abandon his concern over deficits.
I'm no Krugman fan, but I want to learn about the theory.
I like that Warren Mosler believes in minimal taxes. However, IF taxes are not necessary to fund government, why do we need taxes at all? Wouldn't a tax-free society be a massive stimulus to the economy?
Taxes are necessary, at some level, to make ensure that people use the currency. If you have to pay taxes in dollars, then you need to get your hands on some dollars, and not bitcoins or bank script, etc. On a more theoretical level, if your economy is at full employment/full production, and your populace is spending all of its earnings on that production, any deficit spending would cause demand-pull inflation, because there would be no idle resources to meet the new demand. So government would need to tax away some of the populace's demand for its own use.
Plus, in the real world, you can't go around saying you want to eliminate all taxes, because you won't be taken seriously. And being taken seriously is the hurdle we are facing now. We can win the debates with other economic schools of thought, but average people simple are not ready to accept that we don't (presently) need taxes, the "national debt" is not really a debt, China is not going to foreclose on us, etc.
An electronic transfer is necessary? People will use the currency regardless of whether or not there are taxes. . . .unless somebody is worried about the devaluation of the currency should there be massive hyperinflation..
I believe the media has led people by their noses for the most part.
On one side you have Fox news fueling this conservative indignation with the radical right.
But vast majority of the media lean left, many lean heavily left. If anyone thinks the liberal media is being any more honest than Fox news, they themselves are deluded by left-wing media. The liberal media wasn't reporting facts and they essentially were campaigning for the Democrats. And there are simply more liberal media outlets than there are conservative.
To further the problem, people don't do their own responsible research. They parrot the rah-rah-rah extremist websites that tell them what they want to hear. They think shows like the Colbert Report is news, and they can't tell the difference between news reporting and news commentary.
It became an us-against-them game of schoolyard dodge ball. People were loyal to their "team" so they would fail to point out their side's flaws, and go overboard in nit-picking on the other side. People stopped listening to people with different views-- the rivalry between the teams became too intense and people had a knee-jerk reaction the minute they found someone disagreed with them. Minds shut down, confirmation bias kicked in.
They "villanized" each other, and the media fueled it giving people all the ammo they could find (even if it was intellectually dishonest, it didn't seem to matter).
President Obama has exacerbated the division between the parties like no president before him has ever done. He's all but stamped his foot on the floor in a huff when pointing to the Republican side of the isle in blaming every problem in the country on Republicans. And unfortunately, the majority of the media being left wing, have supported this and hailed it as some kind of heroic action when it was really just bad leadership. And even more unfortunately, most monkeys just follow along, hooting and hollering that it's another point for their team.
EA said: "An electronic transfer is necessary?"
What do you mean?
"People will use the currency regardless of whether or not there are taxes. . . .unless somebody is worried about the devaluation of the currency should there be massive hyperinflation."
This is the theoretical basis. I agree that once a currency is established, it will get used at least as long as it holds its value. The dollar is so stable that it is difficult to imagine people looking for alternatives, but there are a lot of currencies out there that might make their users worry. The Fed, for all of the complaints people come up with, has very stablizing policies. But there are a lot of other currencies (or bonds) that I wouldn't want to hold long-term.
?"
Currencies retain value when there is stuff on the shelves to buy. If an economy is producing, money will be moving around and product will be bought and sold. But look at countries where there has been some form of upheaval. When Yugoslavia split apart, trade between the new territories stopped, then production went way down. Food gets scarce, so prices go up. When food is scarce, all currencies lose value. If you can't buy potatoes with dinar, you probably can't buy them with American dollars any easier.
."
No, the first point was the same one I made in my last post. IF your economy is at full production (a big "if"), then the government will need to tax away some money (demand) in order to spend for the government's benefit without causing demand-pull inflation. If you are at full production and the government adds more money (demand) to the mix by deficit spending, then there will be more dollars chasing the same amount of goods, and you would get inflation. And that is really the only point on the curve where the conventional "more dollars = inflation" idea has any merit - when an economy is stretched to the limit and cannot accomodate any more demand.
A state of "full production" is a bit of a fantasy at this point, because productivity is so high, plus there is a lot of automation, plus you have cheap foreign labor. But look back 100 years ago, when most people still worked in agriculture, because you needed that many farmers to produce enough food for the nation. (Today, 2% of our labor force produces a large surplus of food.) So when industry needed labor, they had to offer higher wages to pull workers from the farms. Shortage of labor = higher wages = one cause of inflation. Not that inflation is always bad - I'd rather have a growing economy and a high demand for labor with some accompanying inflation than the opposite. So the goal is 100% employment - if you are ever going to run short of some material necessary for production, it should be labor. But I don't think we could consume all that we would produce if all of our unemployed were producing goods for the private sector - this is why MMT advocates for a guaranteed government job; those workers would not be competing with the private sector, which already meets all demand..
EA said: ."
No, that is not what MMT holds at all. Those are two very separate issues.
A country - ANY country - that a) creates its own fiat currency and b) has no foreign-denominated debts can always meet its obligations that are denominated in its own currency. That says nothing at all about inflation. It just states that, if all I owe you are pieces of paper with my signature on them, I will be able to pay that obligation. And this is true of fiat currency economies, because there is no real cost (like gold) to creating those pieces of paper.
Inflation can be caused by a lot of things, but they generally involve production, not the number of dollars in play. Some of these are out of our control - the price of oil; droughts that affect food production; things like hurricanes, that can lead to temporary shortages of building materials; etc. But if the economy can meet the demand (and competition is present), then there is no reason that prices should go up, unless/until there is a shortage of some component of production (labor, energy, raw materials, etc.). If government spending does not add so much demand that there is a shortage of goods on the shelves, then prices should stay the same. But if government spending increases demand to the point where the economy cannot meet demand, of course you will get inflation.
And again - belief has nothing to do with it. You don't pay more for a loaf of bread just because you somehow perceive that the dollar should be losing value - you pay the going price, just like everybody else.
EA said: ."
Where are you getting these ideas of what MMT is about? It sounds like you are getting them from somebody trying to disprove MMT - somebody who really doesn't understand it well enough to do so. There are plenty of those sites around. This "billion dollars into everybody's accounts" is the same junk that I hear from every naysayer. MMT doesn't advocate anything of the sort. And the government can only purchase what its economy is capable of producing. This isn't magic.
The government is ABLE to create all the fiat currency it wants. That does not mean that MMT advocates it, or says it's a good idea.
One of the insights from MMT is that you don't get inflation simply from putting more dollars in play. The obvious policy prescription from this insight is that the government can help the economy by creating and spending some amount of new money (deficit spending over and above replacing saved dollars), and there is no big downside from deficits or debt. The confusion (or disbelief) often comes when discussing how to go about putting that new government money into the economy. There are 3 main ways - the government can spend in an attempt to boost private sector demand enough to get everybody a private sector job; the government can guarantee everybody a minimum-wage public sector job; or the government can simply give everybody a Basic Income Guarantee (BIG), some amount that still gives people an incentive to work, and also does not flood the economy with too much demand. And of those who advocate for a BIG, there are exactly zero who think we should give everybody a billion dollars.
" And of those who advocate for a BIG, there are exactly zero who think we should give everybody a billion dollars."
Why not? If the use of a fiat currency, utilizing MMT, really has no downside, why wouldn't you distribute massive quantities of currency?
Because you would outstrip your economy's ability to meet the new demand. I think I already explained that.
Allow me to frame this argument in different terms:
JfC: Aspirin is an effective anti-inflammatory that can ease pain.
EA: Why don't we just give everybody a billion aspirin tablets a day?
Do you see the problem here? Nobody is proposing that we give anybody a billion aspirin tablets a day, because that is not the effective dose. And saying that a billion aspirin tablets a day would kill you isn't a very good argument against the use of aspirin in normal quantities, is it?
That's exactly my point. If that's not the effective dose, what would the outcome be, inflation? Inflation can occur when money is dumped in the market. Dumping 17-18 trillion dollars, our debt, would cause inflation, because it's not the "effective dose."
How, exactly, is $17 trillion going to be "dumped" into our economy?
IF a large number of dollars were ever spent in short order, enough to outstrip our economy's ability to produce and meet demand, then yes, of course there would be inflation. But where is this giant heap of cash going to come from? What, exactly, are you worried about?
It would have to be electronic in nature.
The point is that inflation could be a concern. You don't see many MMT supporters admit that it's even a possibility, do you?
Inflation is always a concern - just about the only concern - and yes, it is an integral part of MMT. If you are reading the main MMT sites, I'm surprised you haven't come across this yet.
Again, inflation happens when demand outstrips an economy's ability to meet that demand, or when there is an instance of leverage (OPEC, hot name brands, a monopoly, etc.). MMT certainly recognizes the possibility of this happening, but we also recognize the reality of today's economy, in that our economy is nowhere near its capacity to produce. So it is not a front-burner concern of ours. Right now, we are far more concerned with a) squashing the idea that the U.S. govt. is in debt, and b) spending in order to reach 100% employment.
GA wrote: "As one writer said, "Accounting is not economics.""
But if your economics don't square up with the accounting, your economics are wrong, not the accounting.
."
First of all, to the best of my knowledge, we have never defaulted on our debt. Second, the legitimacy of MMT does not hinge upon us not defaulting. The point was always that we can never be forced into a default by our "creditors" (bondholders). To this day, there are trained economists - with degrees in the field - that think China has us by the short hairs because they hold a pile of our bonds. We are also not dependent on outside entities buying our bonds.
"My understanding of MMT so far, and as you have stated, is that supply shortages are the only probable factor that could influence the value of any fiat currency - I disagree. I still believe "perceived value" by its users, (the market), can also affect its value."
OK. How? What is your mechanism?
"What would happen if the market's big players, (Wall Street, other nations, etc.), decided to shift to another currency because they lost faith in the government behind the fiat currency?"
I don't know. Why, exactly, do you think they would make this shift? Why would they lose faith, and why would that matter? Again - what is your mechanism? I could make the claim that the sky might turn green tomorrow if everybody lost faith in blue, but it's an untestable hypothesis, especially if I have no basis for believing it.
"Another writer, an MMT criticizer, uses an example of U.S. big market players using other currencies for their transactions, (Francs, Yen, whatever), and only converting to dollars at the moment of need for a dollar required transaction."
What was HIS mechanism? And what was HIS reasoning? I can hardly defend MMT against something when I have no idea what made the writer think that this scenario could happen.
I'm more than happy to stay here and explain everything I know about MMT, but I need something solid to go up against. I haven't come across a critic yet that has produced a good argument against MMT mechanics, or even MMT policies. People are "uncomfortable" with the new ideas, but nobody has ever been able to convince me that I should be uncomfortable with them as well.
"Finally, I must both curse you and thank you. The "damn you" curse is for showing me another rabbit hole to chase something down, (my quest to understand MMT), and the thank you is for providing the prompt that caused me to learn something."
I'm happy to have led you there.
I understand what you mean about the rabbit hole. I was introduced to MMT on a debate site that I frequent. The thread started at the end of 2010 and lasted for almost two years. I have been obsessed with the idea for over three years now. But getting other people to listen long enough to understand has been like pulling teeth. That's my curse.
Thanks for the reply John, I started a new thread, (to avoid the continued hijacking of this one), to answer you. I hope you find it.
GA
We really should move this discussion over to GA's forum question, because it has gone way off topic.
Can we move this over to GA's forum question, please? We are completely off the subject of this thread.
Yes, this is a worthy debate, one that I am enjoying and learning about at the same time. Let's move to the proper forum.
Best wishes.
by Ralph Deeds4 years ago
Private equity fund operator Steven Rattner provides a fair assessment of Romney's record at Bain here: … ef=opinion. | http://hubpages.com/politics/forum/121437/to-all-conservatives-and-moderates--what-were-on-peoples-minds-when- | CC-MAIN-2017-17 | refinedweb | 15,585 | 71.55 |
🔔 This article was originally posted on my site, MihaiBojin.com. 🔔
This is an introductory post about Search Engine Optimization with Gatsby.
It covers a few basics that are easy to implement but will help with your SEO ranking in the long run.
Google Search Console
One piece of low-hanging fruit is to verify your domain with Google's Search Console.
Take 5 minutes to do it; you will get helpful information, for example:
Canonical links
Every page should define a canonical link. These are useful because they help search engines such as Google figure out the original content, routing all the 'juice' to that one page.
Consider the following URLs:
- - -
The same content can be access at multiple URLs. However, Google wouldn't know what page holds the original content, so it would most likely split the ranking between a few of these pages and mark most of them as duplicates. This is highly unpredictable and undesirable. A better approach is to define a canonical link, helping search engines rank a single URL, the one you choose.
You can define a canonical link by including the following tag in the site's head:
<link rel="canonical" href=""/>
(where
href is the URL you choose to represent your original content.)
This approach is highly effective when you syndicate your content on other sites. For example, if you did so on Medium, Google would most likely rank it as the original due to the site's higher overall ranking, leading to poor SEO impact on your domain.
There's an effortless way to add canonical links in Gatsby: using the gatsby-plugin-react-helmet-canonical-urls plugin.
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gatsby-config.js:
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Google will gradually discover and index your site's pages over time. You can define a sitemap to help Google (and other search engines) find all your pages. This process does not ensure faster indexing, and in the early days of your site, it also doesn't make much of a difference, but it will matter more as your site grows!
First, install the gatsby-plugin-sitemap plugin.
npm install gatsby-plugin-sitemap
Then you will need to add some custom configuration in
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If you're wondering why we're loading a
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Check your sitemap locally by running
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Robots
Robots.txt is an old concept; the
robots.txt file tells search engines what URLs are okay to access (and subsequently index) on your site.
If you're looking for an automated way to generate this file, gatsby-plugin-robots-txt is your friend!
Install the plugin by running
npm install --save gatsby-plugin-robots-txt and add the following to your
gatsby-config.js:
module.exports = { plugins: [ { resolve: 'gatsby-plugin-robots-txt', options: { host: process.env.SITE_URL, sitemap: process.env.SITE_URL + '/sitemap/sitemap-index.xml', policy: [ { userAgent: '*', allow: '/', disallow: ['/404'], }, ], }, }, ], };
Setting up the plugin as above will generate a
/robots.txt file that specifies the options listed above.
If, however, you're looking for a simpler approach, skip all of the above and create
/static/robots.txt, with the same contents.
User-agent: * Allow: / Disallow: /404 Sitemap: https://[SITE_URL]/sitemap/sitemap-index.xml Host: https://[SITE_URL] Make sure to replace SITE_URL with the appropriate value!
There is one disadvantage of the latter, in that you will have to remember to update the SITE_URL in this file. This is unlikely to be a problem in practice, but still... using the plugin and relying on a globally defined
SITE_URL is less hassle in the long run.
Note: In Gatsby, any file created in the
/static directory will be copied to and included as a static file on your site.
You may have noticed the
Sitemap directive. That allows letting crawlers know where they can find your sitemap index. Earlier in this article, we accomplished that using the Google Search Console, which is the better approach. However, there are other search engines except for Google and having this directive means they can all find and process your sitemap.
SEO with Gatsby
We're finally at the end - albeit this is the trickiest part since it requires an understanding of how Gatsby does SEO.
If you have no experience with that, I recommended reading the Gatsby Search Engine Optimization page (don't worry about Social Cards for now).
This article won't go into advanced SEO tactics (mostly because I'm no SEO expert).
In time, as I write more content and I learn new search engine optimization tips and tricks, I will update this page.
There is, however, a minimal set of configurations any site owner should do, the bare minimum, if you will:
title, description, and keywords meta tags that represent your content
and a canonical link (explained above)
If you search the Gatsby Starters library, you will find many implementations and slightly different ways of achieving this goal.
Here's how I implemented it. I don't claim this is better or provides any advantages - it simply does the job!
import * as React from "react"; import PropTypes from "prop-types"; import { Helmet } from "react-helmet"; import { useSiteMetadata } from "../hooks/use-site-metadata"; function Seo({ title, description, tags, canonicalURL, lang }) { const { siteMetadata } = useSiteMetadata(); const pageDescription = description || siteMetadata.description; const meta = []; const links = []; if (tags) { // define META tags meta.push({ name: "keywords", content: tags.join(","), }); } if (canonicalURL) { links.push({ rel: "canonical", href: canonicalURL, }); } return ( <Helmet htmlAttributes={{ lang, }} // define META title title={title} titleTemplate={siteMetadata?.title ? `%s | ${siteMetadata.title}` : `%s`} link={links} meta={[ // define META description { name: `description`, content: pageDescription, }, ].concat(meta)} /> ); } Seo.defaultProps = { lang: `en`, tags: [], }; Seo.propTypes = { title: PropTypes.string.isRequired, description: PropTypes.string.isRequired, tags: PropTypes.arrayOf(PropTypes.string), canonicalURL: PropTypes.string, lang: PropTypes.string, }; export default Seo;
This code uses
react-helmet to define the specified tags.
You might have noticed that it uses a react hook,
useSiteMetadata. I learned this trick from Scott Spence.
My code looks like so:
import { useStaticQuery, graphql } from 'gatsby'; export const useSiteMetadata = () => { const { site } = useStaticQuery( graphql` query SiteMetaData { site { siteMetadata { title description author { name summary href } siteUrl } } } `, ); return { siteMetadata: site.siteMetadata }; };
Don't forget to define the required metadata in
gatsby-config.js:
module.exports = { siteMetadata: { title: `Mihai Bojin's Digital Garden`, description: `A space for sharing important lessons I've learned from over 15 years in the tech industry.`, author: { name: `Mihai Bojin`, summary: `a passionate technical leader with expertise in designing and developing highly resilient backend systems for global companies.`, href: `/about`, }, siteUrl: process.env.SITE_URL, } };
And that's it - you will now have basic SEO for your GatsbyJS site, by including this component into every article page, e.g.:
<Seo title={} description={} tags={} canonicalURL={} />
Typically, these values would be populated manually for static pages, or passed via frontmatter for blog posts.
For example, to populate canonical links I use a function to generate the appropriate value: frontmatter for blog posts or the page's path as a default.
function renderCanonicalLink(frontmatter, siteUrl, location) { return frontmatter?.canonical || (siteUrl + location.pathname); }
This concludes my introductory post about Search Engine Optimization in GatsbyJS.
If you'd like to learn more about this topic, please add a comment on Twitter to let me know! 📢
Thank you!
If you liked this article and want to read more like it, please subscribe to my newsletter; I send one out every few weeks!
Top comments (0) | https://practicaldev-herokuapp-com.global.ssl.fastly.net/mihaibojin/search-engine-optimization-with-gatsbyjs-4406 | CC-MAIN-2022-40 | refinedweb | 1,363 | 56.96 |
Things used in this project
Story
Introduction & Motivation.
In the future, voice user interfaces and vision recognition will be combined to provide very useful products:
- Smart histology assistant. In the biomedical area, imagine how a pathologist works today. They are provided with a stained tissue sample on a slide and examine multiple fields of view under a microscope. After analyzing the characteristics they see, they formulate a list of differential diagnoses. What if the pathologist could now talk to the microscope, telling it to move from place to place and use a vision recognition model to give an opinion? Maybe, "Hey Bones, what cell type is this?" Instead of "Hey Mycroft, ..."
- "Hey Mycroft, What the heck is this?" In this type of application, you walk into the hardware store (good luck finding a helpful person), show the item of interest and Mycroft tells you not only what it is, but more importantly where to find it.
- Voice controlled robot vision. Imagine using your Raspberry Pi 3 as a the brain for your next mobile robot project with Picroft installed. Not only will you be able to tell it where to go and what to do, it could take a look at things and let you know what it sees!
The skill I have created is a far cry from the ideas above, but it does show how two great AI platforms can be combined. In fact, it really needs a lot more work to really be a skill, but it does serves as a prototype for the ideas above and it certainly is a great and fun way to experiment with clarifai.
As you may be able to tell from the video examples, it is very interesting and fun to hear what clarifai and Mycroft will respond with! I see this more of an example of how to get two platforms to work together rather than a mature or developed skill.
Mycroft.ai & clarifai
Mycroft.ai is an open source voice assistant software package, written predominantly in Python. It comes in 3 different varieties:
- A Raspberry Pi version called Picroft. This is version I have chosen to use.,
- Mycroft Mark 1 a very cool looking prototype physical enclosure based around raspberry pi than can be purchased from Mycroft.ai
- An Ubuntu 16.04 Desktop version
Like Alexa, Siri or Google Assistant, Mycroft responds to voice commands to enact skills. These skills are written in Python and as I explore more, it seems that if you can write it in Python, you can have it work as a Mycroft skill.
What is clarifai? There is no better explanation than their own from their Developer Guide:
The.
What this means to me is that I can use a python API to quickly and easily send image files to a clarfai "model" or even one of my own. In return, clarifai will send me back a list of tags or concepts it finds in the image.
In this simple test case "skill" we simply have Mycroft report back the tags or concepts associated with an image at or over a certain confidence threshold with clarifai's general model.
We could, however, create a custom model for the detection of neoplastic (cancerous) characteristics of cell types for our histology assistant. We could train up a model on our catalog of store items. We could also make a custom model of the inside of a nuclear reactor facility before it gets hit by and earthquake, tsunami and partial melt-down to aid in autonomous of semi-autonomous exploration of it afterwards.
So I hope that this "skill" helps you dream up and develop interesting combinations of voice and vision! And also gives a sense of some of the challenges you may encounter getting several platforms to work together.
Installing the clarifai Python API
To use clarifai you'll have to setup your account and get API keys. The free level of clarifai allows for:
Search and predict, 5,000 free operations per month, 10,000 free inputs and Train your own model 10 free custom concepts.
I recommend reading the developer docs prior to starting your adventures in clarifai.
In order to use clarifai with Mycroft, we need to install the clarifai Python API. I started the python interpreter on picroft and determined that picroft is running Python 2.7.9 and luckily the clarifai API works with Python2.
After,
sudo pip install clarifai
You aren't done! When the install process gave some error messages, I carefully read these messages, I saw that clarifai required the python Pillow library.
But it is not sufficient to just:
sudo pip install Pillow
You will also have to:
sudo apt-get install python-dev python-setuptools
This should allow you to install Pillow and then use the clarifai Python api.
However, I want to say that I recreated this string on instructions from memory and some sketchy notes! So my advice for you is that you should do as I did, carefully read the error messages and brave the somewhat treacherous waters of google searches and stackoverflow.com.
Actually the reverse order of these instructions should get it going for you! But the description above is closer to the way it happened for me. Good grief Charlie Brown! If I got this all to work, you can too!
Skill Creation Strategy
The best way to learn how to create skill from Mycroft is to read the documentation on skill creation, Creating a skill, and then try your hand at writing one! The Geeked Out Solutions YouTube channel has some excellent videos specifically devoted to Mycroft. I highly recommend looking at both prior to creating your own skill.
The Mycroft.ai commuity forum is an active and friendly place to learn more about mycorft and skill creation.
A skill resides in its own folder with a appropriate name under the /opt/mycroft/skills/ directory. The bulk of the activity of the skill takes place in a file called __init__.py I have found it a bit challenging to debug my python code in this file by editing the code in the template skill first.
So what I did in developing this skill, in writing my prior one, is to create a python script file that has the essential functionality of the skill. By running this under Python on the CLI, I can debug in a more comfortable way prior adding in the extra layers of complexity that come with interacting with Mycroft. I was happy to see that,btotharye, who is a professional programmer adopt a similar strategy is his video tutorial, Mycroft - Creating First Skill TSA Wait Times.
This skill has 2 components or intents. With the first, you can ask Mycroft to send an image file to clarifai. The image must be located in the /TestImages directory folder of the the skill and must end with a .jpg file extension. He will respond with the concept tags generated by clarifai's general model with 98% confidence. The following phrases, from the LocalImageKeyword.voc file allow this:
look at let's take a look at what do you see in could you look at
It's really that simple. To understand how to connect these phrases with a file name to to send to clarifai, see the section on RegularExpressions below.
The second intent in this skill will take a picture using the pi camera, send the image to clarifai, which will then send the concepts found at 90% confidence.
look at this take a look at this what do you see
Perhaps we should add some phrases that are associated with taking pictures, such as "smile" or "say cheese" however this skill is more about analyzing an image than about just taking a picture.
Regular Expressions
In my first Mycroft project I did not take advantage of regex, but I specifically wanted to try this feature out and this project gave me the opportunity to do so.
Regular expressions(regex) are a method of text pattern matching. Regular-expressions.info defines them this way: site is also a great place for learning about regex.
In the context of Mycroft, regex allow for adding a feeling of responsiveness, flexibility and customization to your voice interface experience. Regex allow us to provide variable data to our intents. For this project, we can have Mycroft take a look at any image in the /TestImages directory by a name we specify.
This is accomplished in the skill-smart-eye/regex/en-us/imagefile.rx file:
(take a look at|what is in|look at|look at this|could you look at) (?P<FileName>.*)
The pipe,'|', operator, acts as an OR statement and will seek a match to what you tell Mycroft when this skill is activated.
The (?P<FIleName.*> ) captures the word following one of these phrases and assigns it the variable name of FileName. In this case it allows Mycroft to select out the name of the file from your utterance. The asterix, '*', captures any possible matches to whatever is spokenafter the phrase. This is about as simple as a Regex can get. You can imagine that much more powerful Regex combinations can be made to further enhance the responsiveness, flexibility and customization to your voice interface experience.
You can see here how my intent uses the FileName variable in the __init__.py file:
def handle_local_image_intent(self, message): fileName = message.data.get("FileName") general_model = self.clarifai_app.models.get("general-v1.3") image_file = '/opt/mycroft/skills/skill-smart-eye/TestImages/' + fileName + '.jpg'
You must ensure that the variable is the exact same as it has been specified in the imagefile.fx folder. It's that easy to share the get the information from the utterance into the site of action, __init__.py!
Experimenting with my design, however, I feel that saying:
Hey Mycroft, look at cat
or
Hey Mycroft, could you look at butterfly
is a bit clunky and unnatural. I really what to say something like, "Hey Mycroft, could you look at the file named cat.jpg in the TestImages folder". While this is verbose, it feels more natural than the stutter step command above. But my intention in writing this part of the skill was to debug the connection between Mycroft and clarifai, not to fully form the interface.
The second intent of this skill is to look at images captured by the picamera and then sends the resulting image to clarifai and report back any tags or concepts detected with greater than 90% confidence.
Parsing the concepts returned caused me a bit of an issue. My first attempts to look at the returned JSON seemed to returned a single large value for 1 key. After a lot of trial and error and a bit of looking about sample code, I came up with the following:
response = general_model.predict_by_filename(image_location,min_value=0.90) j_dump = json.dumps(response['outputs'][0],separators=(',',': '),indent=3)
We grab the JSON response from the clarifai general model in a variable called response. You can see these are the concepts returned at minimum of 90% confidence. The clarfiai API is that easy to use, it almost read like a sentence in a natural language!
We take the JSON and grab the 0 index value from the outputs key. This is the large set of concepts returned. We then convert this dump into a load and iterate deep, ['data']['concepts'][index]['name'], into the JSON tree of key:value concept names by an index number.
j_load = json.loads(j_dump) index = 0 results = "" for each in j_load['data']['concepts']: results = results + j_load['data']['concepts'][index]['name'] + " " index = index + 1
The for each statement above, allows for a simple and elegant approach to handling our inability to know how many concepts, at any confidence level, will be returned. We could specify a maximum with the clarfiai API or limit our replies, but in this stage that would not be helpful. In future development, this might be useful due to the cognitive overload hearing many concepts would cause.
Picamera Use Issues
The python test script to access the picamera worked well from the start. When I integrated the picamera functionality into the skill's __init__.py file, at first it didn't work,then after some tweaking it did work, but only once!
The file /var/log/mycroft-speech-client.log and /var/log/mycroft-skill.log are very useful files to look at if your skill is not working. After some looking, I found an error dealing with a "vchiq instance".
Having learned my lesson from past experience, I did a google search, and found that in order the access the camera, the user executing the Python program or Mycroft skill in this case needed to have a file permission to do this. In Linux most everything is a file, even a device. To access the picamera, a user needs access to a file called /dev/vchiq. So the user executing the python test script had access, but the user, called pi, executing the __init__.py did not. Hence the failure to take the picture at all. Following the directions from Raspberry Pi – failed to open vchiq instance [Solved] demonstrates how to change the user permissions for this file to allow access to the device. I've placed a pdf of this post in my github repository for this project in case the link goes stale.
The next problem followed as I was only able to take one picture, then I was not able to use the camera again. This was due to an error I made in the instantiation of the camera instance. Initially I was executing this statement
self.camera = picamera.PiCamera()
every time the intent handler was called. However, this object was being preserved in between called, causing a conflict upon "reinstantiating" it(I wonder if I can use this persistence to useful effect with future skills?). By moving the above statement to the __init__ function:
def __init__(self): super(SmartEyeSkill, self).__init__(name="SmartEyeSkill") self.clarifai_app = ClarifaiApp(api_key='***Your API Key Here') self.camera = picamera.PiCamera() ...
I was able to solve this issue and able to call the picamera over multiple times successfully.
The main lesson here is that is good to have a decent handle of the Linux command line and always be ready to work through error messages and understand the nature of the Mycroft "enclosure".
Experimenting
Why 90% for the picamera intent and why the black background?
In my initial experimentation with clarifai, the tags or concepts returned from the test images were excellent. When I initially placed some of the objects you see below in front of the picamera with a white background, the results were purely awful. Looking at the test images, I saw that many of them had dark backgrounds. So I added a black background and the results were better, but not great. Lowering the confidence level to 90% greatly improved things in most cases as you can see in the examples below.
I think some work is needed on the quality of the images I am sending and in working with the models available on clarifai. What I find most interesting is not the specific "noun" tags returned, but the more conceptual tags returned. Such as "cute" for our cat, which is of course very true.
Comparing Apples and Oranges:
Conclusions
Once completed to this stage, I realized what I had created was easy to use platform for experimenting with voice and vision. The project allowed me to explore the use of regular expressions to provide some "generality" to the voice user interface. The project also allowed me to explore.
Combining voice and vision into a useful skill will clearly take some more work and perhaps a bit more focus on a specific voice controlled vision recognition task.
If you are interested in pursuing this, I encourage you to muscle through the Python module dependency issues and linux issues to get this working and please share your efforts here on Hackster.io! I can't wait to see what you do with the image concepts returned by clarifai!
Schematics
Code
skill-smart-eye
Credits
Gregory O. Voronin
Replications
Did you replicate this project? Share it!I made one
Love this project? Think it could be improved? Tell us what you think! | https://www.hackster.io/gov/smart-eye-for-your-pi-b3f5bf | CC-MAIN-2018-09 | refinedweb | 2,726 | 62.68 |
Not to sound crazy or trolly, but actually learning machine language or Assembly is definitely more favoring to programmers in the long run. Sure,
#include <iostream> using namespace std; int main(){cout << "Hello, boring old high-level language!"; cin.get();}is definitely easier, but it's just so gloomy and dull after you realize how far you are from direct hardware access and control.
It's like ... here's an example... I want to go see a basketball game. C++ is like sitting on the 18th row about 200 feet away from the court. Assembly is like sitting on the first row only 15 feet from the center of the court. The court itself is the processor...
Understand?
I feel that more programmers should dig deeper into what they're "really doing" rather than just tire themselves out with high-level lack of control, confusion on "APIs work", which is only 100 feet away from the game.
It's a long walk, but for what? You can't actually see the game clearly, can you? And even with all of these "tools", nothing beats sitting right in front of the players and witnessing it up close and direct.
It just, to me, seems like a big mess of disorder and tirade attempts for people to torture themselves learning these APIs, high-level languages, etc., when low-level is more right on to things and there's no memorizing/references of thousands of things that you don't even really know what they do 100%.
...I came to see a basketball game with binoculars on the last row. I can see it, but the people in the front are really witnessing the feel of it and getting more excitement, thrill and just full brain-eye accomplishment.
I'm sorry if this comes off in a bad way, it's just an opinion. | https://www.gamedev.net/topic/602297-i-think-all-programmers-should-know-machine-code/ | CC-MAIN-2017-17 | refinedweb | 311 | 70.94 |
Quick sort is a sorting algorithm that uses recursion and nested loops to sort items. Here is an implementation in Python
def split_list(unsorted, low, high): # Set our temp item at the low end item = unsorted[low] # Variables for tracking left and right # side of the list left = low right = high # loop until our left side is less than right side while left < right: # Move left to the right while it's less than item while unsorted[left] <= item and left item: right -= 1 # Check if we need to swap elements if left low: # Split unsorted into two lists index = split_list(unsorted, low, high) # Sort the left hand of the list using recursion quick_sort(unsorted, low, index - 1) # Sort the right hand of the list using recursion quick_sort(unsorted, index + 1, high) if __name__ == '__main__': items = ['Bob Belcher', 'Linda Belcher', 'Tina Belcher', 'Gene Belcher', 'Louise Belcher'] print(items, '\n') print('Sorting...') quick_sort(items, 0, len(items) - 1) print(items)
When run, this code will produce the following output
['Bob Belcher', 'Linda Belcher', 'Tina Belcher', 'Gene Belcher', 'Louise Belcher'] Sorting... ['Bob Belcher', 'Gene Belcher', 'Linda Belcher', 'Louise Belcher', 'Tina Belcher']
The key in this algorithm is that we split our list into two halfs and then use recursion to sort each half. The work of swapping elements takes place in the split_list function. However, the quick_sort function is responsible for calling split_list until all items are sorted. | https://stonesoupprogramming.com/2017/05/08/quick-sort-python/ | CC-MAIN-2021-31 | refinedweb | 236 | 50.54 |
In this tutorial we will learn how to detect the client connection event when using the Bluetooth Serial library of the Arduino core. The tests were performed using a DFRobot’s ESP32 module integrated in a ESP32 development board.
Introduction
In this tutorial we will learn how to detect the client connection event when using the Bluetooth Serial library of the Arduino core.
As covered here, this library allows to establish a serial connection over Bluetooth, leveraging the Serial Port Profile (SPP).
This library offers a class called BluetoothSerial that behaves very similarly to the Serial object we use on wired serial communication. This means that we also have methods such as the available, to check if the client sent data, or the read, to read data.
So, a very simple way of implementing the serial communication is polling for incoming data with the available method and then reading the content when it’s available. Nonetheless, polling is not a very optimized approach, since it wastes CPU cycles that, in many cases, could have been used for other useful computation.
Another important thing to take in consideration is that the BluetoothSerial.h library is implemented on top of the IDF Bluetooth APIs, which are event based. An event based approach can lead to a more efficient implementation of our programs.
So, an option could be using these IDF APIs directly on the Arduino core, since we can access them on our programs. Nonetheless, they are much lower level and harder to use, which means we would loose the simplicity of the BluetoothSerial.h library, which makes it really easy to use Bluetooth Classic.
So, we can leverage a new method from the BluetoothSerial class that allows to register a callback function that is triggered when a SPP event occurs. Note that, at the time of writing, this method was recently added, so you should pull the latest changes of the Arduino core Git repository, if you haven’t yet done it.
Note that, in the implementation of the BluetoothSerial.h library, there’s already an internal callback function handling these SPP events. When an event occurs (ex: new client connected, data received, etc..) this function is responsible for handling it. Nonetheless, this function is internal and not exposed to the user of the BluetoothSerial.h API.
So, in the current implementation, at the end of this internal handling function and after the received event is processed, if there’s a user callback function registered, it is called, receiving as arguments the event type and a data structure with some additional parameters for that event. You can check here the implementation file for the BluetoothSerial.h.
This user defined callback function is naturally our responsibility to implement, which gives great flexibility to what we can do.
Note however that both the event type and the mentioned data structure that are passed to our callback are lower level constructs from IDF’s Bluetooth APIs. But, although this makes us looking a little bit to the lower level, it offers a lot of flexibility by allowing us to receive the lower level events without having to do polling, while keeping the rest of the very simple and easy to use BluetoothSerial.h interface.
In our case, one of the events we will look for is the client connection, although there are others that we can leverage, as shown here.
The tests were performed using a DFRobot’s ESP32 module integrated in a ESP32 development board.
The code
We will start our code by including the BluetoothSerial.h library, which exposes the functionality we will need to establish the serial connection over Bluetooth.
#include "BluetoothSerial.h"
Then we will need an object of class BluetoothSerial. We will interact with this object to initialize the Bluetooth interface and to configure the callback function that will listen to the client connection event.
BluetoothSerial SerialBT;
Moving on to the Arduino setup, we will open a regular (wired) serial connection, to later print some messages from our program.
Serial.begin(115200);
After that, we will call the register_callback method on our BluetoothSerial object, in order to register a callback for the Bluetooth related SPP events. Note that we can do this before initializing the Bluetooth interface.
As input, this method receives the callback function that will be executed when a Bluetooth SPP event occurs. This function needs to have the signature defined by the esp_spp_cb_t type, which can be found here.
We will define the callback function below and, for now, we will assume it will be called callback, as shown below.
SerialBT.register_callback(callback);
Next we will initialize the Bluetooth interface by calling the begin method on the BluetoothSerial object. This method receives as input a string with the name we want to assign to the ESP32. This name will be seen by other Bluetooth enabled devices when performing the discovery procedure.
Since this method call returns as output a Boolean value indicating if the initialization was successful, we will use that value for error checking.
if(!SerialBT.begin("ESP32")){ Serial.println("An error occurred initializing Bluetooth"); }else{ Serial.println("Bluetooth initialized"); }
The full setup function can be seen below.
void setup() { Serial.begin(115200); SerialBT.register_callback(callback); if(!SerialBT.begin("ESP32")){ Serial.println("An error occurred initializing Bluetooth"); }else{ Serial.println("Bluetooth initialized"); } }
To finalize, we need to declare our callback handling function which, as already mentioned, needs to follow the signature specified by the esp_spp_cb_t type.
So, this function should return void, receive as first parameter a variable of type esp_spp_cb_event_t and as second parameter a variable of type esp_spp_cb_param_t *.
The first parameter corresponds to an enumerated value that indicates the type of SPP event that has occurred. The second argument, which we will not use on this tutorial, is a pointer to a data structure that contains additional parameters regarding the event that occurred.
void callback(esp_spp_cb_event_t event, esp_spp_cb_param_t *param){ // Callback function implementation }
Note that this function will be called for all the SPP related events. So, it’s our responsibility to choose which events we want to handle and which events we want to ignore. The simplest way of doing it is with IF conditions.
So, since we are going to print a message when detecting the client connection, we need to look for the corresponding SPP event. The list of existing events can be seen here.
In our case, we are going to check for the ESP_SPP_SRV_OPEN_EVT event, which is triggered when a new client connects. When we receive this event, we will simply print a message indicating the client has connected.
if(event == ESP_SPP_SRV_OPEN_EVT){ Serial.println("Client Connected"); }
The full callback function can be seen below. Since we are not interested in any other event type, we don’t any other IF condition.
void callback(esp_spp_cb_event_t event, esp_spp_cb_param_t *param){ if(event == ESP_SPP_SRV_OPEN_EVT){ Serial.println("Client Connected"); } }
The final complete code is shown below.
#include "BluetoothSerial.h" BluetoothSerial SerialBT; void callback(esp_spp_cb_event_t event, esp_spp_cb_param_t *param){ if(event == ESP_SPP_SRV_OPEN_EVT){ Serial.println("Client Connected"); } } void setup() { Serial.begin(115200); SerialBT.register_callback(callback); if(!SerialBT.begin("ESP32")){ Serial.println("An error occurred initializing Bluetooth"); }else{ Serial.println("Bluetooth initialized"); } } void loop() {}
Testing the code
To test the code, simply compile it and upload it to your ESP32 using the Arduino IDE. When the procedure finishes, open the serial monitor using the wired connection serial port and wait for the “Bluetooth initialized” message to be printed.
After this, the ESP32 should become discoverable for other Bluetooth enabled devices. So, pair with the device from a Bluetooth enabled computer.
Once the pairing procedure finishes, a new COM port should be available for connection. On Windows, you can use the device manager to check which COM ports are operating over Bluetooth, as explained in more detail at the end of this post.
Note that for programs that can establish serial connections, such as the Arduino IDE, this serial port should appear as any other regular wired serial port, so you can connect to it like you would do for a wired connection.
So, use a serial program of your choice to connect to the Bluetooth COM port. Note that you should leave the wired serial connection with the ESP32 opened to see the results from the program.
This means that, if you want to use the Arduino serial monitor to also establish the connection with the Bluetooth COM port, you need to open another instance of the IDE and connect from there. Alternatively, you can use other tool such as Putty, which is detailed at the end of this post.
After the Serial over Bluetooth connection is established, go back to the wired connection opened first. You should see a result similar to figure 1, which shows the message corresponding to the detection of the client connection event.
Figure 1 – Detection of the client connection event.
2 Replies to “ESP32 Arduino Serial over Bluetooth: Client connection event” | https://techtutorialsx.com/2018/12/09/esp32-arduino-serial-over-bluetooth-client-connection-event/ | CC-MAIN-2019-04 | refinedweb | 1,489 | 53.41 |
unity.scopes.QueryBase
Abstract server-side base interface for a query that is executed inside a scope. More...
#include <unity/scopes/QueryBase.h>
Inheritance diagram for unity::scopes::QueryBase:
Detailed Description
Abstract server-side base interface for a query that is executed inside a scope.
Member Function Documentation
Called by the scopes runtime.)
Implemented in unity::scopes::qt::QPreviewQueryBaseAPI, unity::scopes::qt::QSearchQueryBaseAPI, and unity::scopes::ActivationQueryBase.
Returns a dictionary with the scope's current settings.
Instead of storing the return value, it is preferable to call settings() each time your implementation requires a settings value. This ensures that, if a user changes settings while the scope is running, the new settings take effect with the next query, preview, and so on.
- Note
- The settings are available only after this QueryBase is instantiated; do not call this method from the constructor!
- Returns
- The scope's current settings.
Check whether this query is still valid.
valid() returns false if this query is finished or was cancelled earlier. Note that it is possible that the runtime may call SearchQueryBase::run(), ActivationQueryBase::activate(), or PreviewQueryBase::run() after cancelled() was called. Your implementation of these methods should check whether the query is still valid and, if not, do nothing.
This method is provided mainly for convenience: it can be used in your s
run() or
activate() implementation to avoid doing a lot of work setting up a query that was cancelled earlier. Note that, because cancellation can happen at any time during query execution, your implementation should always test the return value of
push(). If
push() returns
false, the query was either cancelled or exceeded its cardinality limit. Either way, there is no point in continuing to push more results because, once
push() returns
false, the scopes runtime discards all subsequent results for the query. | https://phone.docs.ubuntu.com/en/scopes/api-cpp-current/unity.scopes.QueryBase | CC-MAIN-2021-04 | refinedweb | 301 | 54.83 |
Thanks for your feedback.
We are routing this issue to the appropriate group within the Visual Studio Product Team for triage and resolution. These specialized experts will follow-up with your issue.
This applies to c++ Inside a sizeof statemen, when there's a template mebmer function, and another function outside the class with the same name, the compiler sometimes wrongly chooses the outside one. More specifcally, it always chooses the function from a namespace matching it's argument, even if the member function is explicitely specified as shown in the example code. If the outside function doesn't have the correct signature for the parameter, then a compiler error is generated.
Please wait...
Just checking that the problem is actually fixed, instead of just being automatically closed because of no activity, or not being able to repeat. | https://connect.microsoft.com/VisualStudio/feedback/details/634966 | CC-MAIN-2017-17 | refinedweb | 138 | 52.09 |
Slashdot Log In
Celebrate the XML Decade
Posted by CowboyNeal on Thu Nov 16, 2006 09:49 PM
from the happy-birthday dept.
from the happy-birthday dept.
IdaAshley writes "IBM Systems Journal recently published an issue dedicated to XML's 10th anniversary. Take a look at XML application techniques, and general discussion of the technical, economic and even cultural effects of XML. Learn why XML has been successful, and what it would take for XML to continue its success."
This discussion has been archived. No new comments can be posted.
Celebrate the XML Decade | Log In/Create an Account | Top | 177 comments | Search Discussion
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
Re:Celebrate the XML Decade (Score:5, Funny)
( | Last Journal: Tuesday October 16, @03:26PM)
I started this morning by talking to everyone in XML.
I hope the black eye my coworker gave me heals before my presentation to the CTO tomorrow morning
Re:Celebrate the XML Decade (Score:5, Funny)
We all needed to leave the first post in this to the guy with
the sig
"XML is like violence, if it doenst fix the problem, you arent using enough"
Or words to that effect.
Re:Celebrate the XML Decade (Score:4, Insightful)
My conspiracy theory is that XML was secretly invented by Intel in order to require 3GHz processors for the simplest of tasks.
Re:Celebrate the XML Decade (Score:5, Funny)
( | Last Journal: Wednesday April 11 2007, @09:55AM)
<greeting type="friendly">Hello, fellow coworker type dude!</greeting>
<response type="violent">Have a black eye!</response>
</conversation>
Re:Celebrate the XML Decade (Score:4, Funny)
Re:Celebrate the XML Decade (Score:5, Funny)
I took the liberty of revising the format a little, is this better?
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
o n"
<conversation
xmlns="
xmlns:
<participants>
<participant>
<short-name>OP</short-name>
<full-name>Original poster</full-name>
</participant>
<participant>
<short-name>CW</short-name>
<full-name>Unwitting coworker</full-name>
</participant>
</participants>
<relationships>
<two-way-relationship
<person>OP</person>
<person>CW</person>
</two-way-relationship>
</relationships>
<greeting time="2006-11-17T10:12:10Z" speaker="OP" targets="CW">
<type>
<demeanour>friendly</demeanour>
</type>
<speech>
<text type="text/plain">
Hello, fellow coworker type dude!
</text>
</speech>
</greeting>
<response time="2006-11-17T10:12:34Z" speaker="CW" targets="OP">
<type>
<demeanour>angry</demeanour>
<context>
<divorce type="messy"/>
<custody-battle
</context>
</type>
<speech>
<text type="application/xhtml+xml">
Have a <html:em>black eye</html:em>!
</text>
</speech>
<action>
<punch>
<recipient>OP</recipient>
<aim>eye</aim>
</punch>
</action>
</response>
</conversation>
I'm sort of disappointed that I only got to use two namespaces. Can't get indentation to work either, unfortunately.
Half-Life 7? (Score:1, Offtopic)
()
Why XML was successful (Score:4, Insightful)
Marketing to PHBs, mostly.
However here on earth a lot of people still hand-code the stuff. IMO a C-like syntax using nested {}s would've been better.
Re:Why XML was successful (Score:5, Informative)
( | Last Journal: Friday August 29 2003, @07:54PM)
JSON [wikipedia.org]?
Re:Why XML was successful (Score:5, Interesting)
()
When we designed XML, we had over a decade of solid experience with interoperability in the world of SGML, and we also knew about the kinds of problems that different sorts of users had with different sorts of syntax.
The primary users of SGML-based documentation systems were not programmers. They were people who were often not likely to know about a bracket-matching option in an editor or about code indenting, for example. But they were still legitimate users.
You can't easily test the markup in a declarative system: if in an HTML document I used H3 instead of P in a document it might not look right, but it would still parse OK. If I muddle up Author and Title in a bibliography, same thing.
So, the redundancy of end tags in XML is there because, in practice, if you didn't have it, we had learned that our users had problems correcting their documents, and we knew that, in general, it was only rarely possible for software to give the users much help. There were some experiments early on with </>, allowed by SGML (with various options set) to end any element; it soon became obvious that this caused more problems than it was worth, and even Microsoft disabled the troublesome feature in their XML parser.
It's true that today XML is used in lots of situations we didn't predict. We were amazed that by the time we got XML published as a Recommendation there were over 200 users. So no, we didn't predict the future percfectly. But the popularity of XML shows we can't have done all that badly, really
Liam
(Liam Quin, currently W3C XML Activity Lead)
Re:Why XML was successful (Score:4, Informative)
()
One case where it helps most is when an incorrect start tag was applied; with the empty end tag this could not be detected, and it turned out to be more comman than one might expect. You're right that the error messages often aren't good, but did you ever try debugging a large SGML document with OMITTAG and SHORTREF in use? The error message was almost always "characters found after end of document" because the required strategy by SGML (in one of the most common error situations) was to close elements until you got a match, so the parser typically closed elements all the way up the tree to the document element, and then gave up.
We were bound, at the time, to strict SGML compatibility; perhaps if we had known XML would succeed we could have made more changes, but then we would have strayed further from the well-trodden path of implementation experience.
As to comments for attributes, I agree with you; we lost them, though because we needed a language simple enough it could be processed e.g. with Perl. We didn't dare dream that Perl would support XML natively!
I agree with you that structured tools should generally be used. The redundancy and simplicity help computer-generated XML, and help to detect, say, missing portions of documents. If xml-rpc is scary, s-expr rpc is even scarier!
Liam
Re:Why XML was successful (Score:5, Insightful)
Re:Why XML was successful (Score:5, Insightful)
Unfortunately I'm a Java developer... (Score:5, Funny)
Re:Unfortunately I'm a Java developer... (Score:5, Interesting)
Pro
Eventually we settled on gzipped xml. It required a little more code, but everyone seemed happy. Oh, and we stored images as separate
I think my experience is pretty common, though. And from experience, libxml2 + libz is still very, very fast, and there's not a (whole lot) of wasted space.
I'd like to hear other people's success stories, if anyone wants to reply... I liked reading the article, too.
Re:Unfortunately I'm a Java developer... (Score:5, Interesting)
Arguably the single biggest problem with XML that causes slow processing is that software can predict almost nothing about an XML stream and therefore has to allow for anything. The opening bracket tells you very little about what to expect, and creates few implicit failure or non-conformance tests that allows one to terminate processing because there is no definition of "unreasonable". If I want to embed a terabyte of data between XML tags, there is no built-in basic mechanism to inform the software of how much data I should expect to see before a closing tag and no basic mechanism to cue the software as to the type of data to expect. (Yes, you can sort of do it with lots of other layers strapped on, but it isn't core and strapping it on adds complexity.) This is the primary reason it gives miserable performance as a wire protocol format -- the software cannot make decisions about the data without slurping most or all of it, with no way to predict what "most" or "all" actually is. In well engineered standards such as ASN.1, they use the good old tag-length-value (TLV) format. The "tag" tells you what to expect, the length tells you how many bytes to expect, and the value is the actual data. In short, the encoding tells the software exactly what it is about to do before it does it in enough detail that the software can make smart and performant handling decisions.
The only real advantage XML has is that it is (sort of) human readable. Raw TLV formatted documents are a bit opaque, but they can be trivially converted into an XML-like format with no loss (and back) without giving software parsers headaches. There is buckets of irony that the deficiencies of XML are being fixed by essentially converting it to ASN.1 style formats so that machines can parse them with maximum efficiency. Yet another case of computer science history repeating itself. XML is not useful for much more than a presentation layer, and the fact that it is often treated as far more is ridiculous.
Just in time for the festive season (Score:5, Funny)
()
Then with every following year, I'll be sending a stylesheet card which they can apply to the original XML.
And if they need to locate their names on the card, they can use
No mention of XML's creators? (Score:3, Informative)
Re:No mention of XML's creators? (Score:5, Informative)
( | Last Journal: Sunday June 06 2004, @02:21AM)
I have to do this once per year or so, here's the 2006 iteration: I am not XML's inventor. There were 150 people in the debating society and 11 people in the voting cabal and 3 co-editors of the spec. Of the core group, I (a) was the loudest mouth, (b) was independent so I didn't have to get PR clearance to talk, and (c) don't mind marketing work.
-Tim
Don't feel too bad, Tim (Score:5, Funny)
A decade of bloat. (Score:1, Informative)
S-expressions, of the sort used in Common Lisp and Scheme, would have been a good alternative. They're simple, use a minimal number of characters, and are very easy to parse. Hell, most Comp Sci grads have written at least once such parser during their education.
The worst use has perhaps been with AJAX. Had AJAX been based around data passed as sexprs rather than as XML, it would consume much less bandwidth, and could be handled far quicker on the server side. Unfortunately, a poor technical decision was made to use XML. And so we get to hear all about the performance problems people experience with AJAX systems.
Re:JSON itself is still quite bloated. (Score:4, Insightful)
The formatting strings in Janus controls come to mind.
I have heard that the new Office format (XML) was pretty unreadable.
And what is with modding everything in this thread to zero.
news flash (Score:2, Insightful)
()
Cultural Effects? This is a spec for structuring data, not a Picasso.
XML Decade? (Score:5, Funny)
MCMXC was 1990...
MDCCCLX was 1860...
I give up! Which decade was XML?
- RG>
So where is this old chestnut? (Score:1)
XML is what it is (Score:1)
XML has a purpose, combined with expat, it is a convenient, if inefficient, method by which programs can exchange data relatively easily.
I am not an XML fan, by any means, but if absolute efficiency is not important, XML provides a common format for data exchange.
Stuck (Score:2, Insightful)
()
Yay! Lets party!
XML is for data interchange, nothing else. Unfortunately, it's being used for everything but.
Longevity (Score:1)
just plain wrong (Score:2)
a decade of ... (Score:3, Insightful)
Obligatory link (Score:1, Redundant)
notice too late (Score:2)
()
Bah, it's too late to tell us to celebrate during the decade of XML because that decade is now over!
Yeah, should have done that; celebrating.
Significant technical victory (Score:1)
Ten years of XML ... (Score:2)
L
XML: the CSV of Y2K (Score:1)
()
Can someone explain why I should care? (Score:2)
( | Last Journal: Friday November 01 2002, @06:19PM)
I see XML as a glorified CSV file. Instead of being a two-dimensional representation of a data structure, you can use an N-dimensional representation.
If that's all it was, I wouldn't mind. But it gets so much hype. Why?
Celebrate? (Score:1)
()
XML is a nescessary evil... (Score:2)
()
XML is a nescessary evil. Even though it's slow and inefficent, it's a good system for quickly developing a parser for varied file types without having to design an editor.
Acedemicly-pure XML is just needless overkill, IMO.
Re:XML's Existing (Score:3, Interesting)
<content name="Shameless Self Promotion">
Good point, though there's a better way to edit binary files.
For example, I make a product called FileCarver which allows you to create a file format definition (in XML! heh), that describes the format of a binary file, and the program will automatically provide you with a GUI to edit it. Check it out at http:/fizzysoft.net/filecarver/
</content>
Re:XML "Sucks" (Score:4, Funny)
(Last Journal: Saturday October 14 2006, @08:12AM)
Re:XML "Sucks" (Score:5, Funny)
Re:XML -- The answer to a problem that didn't exis (Score:2)
()
You are trolling, right? Your rant basically consists of few obvious misunderstandings or statements that are factually wrong.
Seems like a knee-jerk reaction from someone who doesn't understand what XML is and its intended purpose. Seeing the HTML remark was rather amusing though. Way to go to show your ignorance on the subject.
BTW: XML is not designed to or intended to be a SQL replacement. Only morons would think that, claim that or use it as such.
Re:XML "Sucks" (Score:1) | http://it.slashdot.org/it/06/11/17/002223.shtml | crawl-002 | refinedweb | 2,342 | 62.38 |
Eclipse Community Forums - RDF feed Eclipse Community Forums JPA and historic sessions, HistoryPolicy, etc. <![CDATA[I have a requirement to keep historical data and found that Eclipselink "Classic" has built-in support for this kind of stuff with HistoryPolicy, historical sessions and queries with an AsOfClause, etc. My question is how can I use all that when I approach Eclipselink through the JPA interfaces, not the classic API? Thanks, Frank Sauer]]> Frank Sauer 2009-05-13T13:15:54-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[You should still be able to configure your descriptor with a HistoryPolicy in JPA using a DescriptorCustomizer. To use a historical query you can use the EclipseLink JpaEntityManager interface to create a JPA Query using a EclipseLink DatabaseQuery (ReadAllQuery, etc.). For a HistoricalSession you would need to access the EclipseLink Session from the JpaEntityManager and acquire a HistoricalSession from this using the native EclipseLink API. Please log an enhancement request to have JPA support added for historical sessions. --- James]]> James Sutherland 2009-05-13T14:19:41-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[I believe we have a few already Please vote for or express your interest in these ERs Doug]]> Doug Clarke 2009-05-13T21:42:09-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[Hi, I would also like to use History Policy, however I cannot find an example of how to use that. So, as an example of eclipse link project, I followed ml Let's say I want to configure Person in the example to use HistoryPolicy, what do I have to do? It'd be great if someone can give me a pointer as I cant seem to find any on the eclipse link's wiki. Many thanks, Anna]]> Anna 2010-03-22T19:11:21-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[I started an effort to publish an example of using HistoryPolicy with JPA under bug 294499 but never published any of my work. I still have the code and just need to add some comments explaining what the various pieces are doing. I configure history for an entity using a customer as: /** * Descriptor customizer that will configure a HistoryPolicy on the descriptor * using a common pattern for the version column names and the audit table. * * @author dclarke * @since EclipseLink 1.2.0 */ public class HistoryDescriptorCustomizer implements DescriptorCustomizer { public static final String START_FIELD_SUFFIX = "AUDIT_START"; public static final String END_FIELD_SUFFIX = "AUDIT_END"; public static final String AUDIT_TABLE_SUFFIX = "_AUDIT"; public void customize(ClassDescriptor descriptor) throws Exception { String primaryTable = descriptor.getTableName(); HistoryPolicy policy = new HistoryPolicy(); policy.addStartFieldName(primaryTable + "." + START_FIELD_SUFFIX); policy.addEndFieldName(primaryTable + "." + END_FIELD_SUFFIX); for (DatabaseTable table : descriptor.getTables()) { policy.addHistoryTableName(table.getName(), table.getName() + AUDIT_TABLE_SUFFIX); } descriptor.setHistoryPolicy(policy); if (Auditable.class.isAssignableFrom(descriptor.getJavaClass()) ) { descriptor.getEventManager().addListener(new AuditInfoListener(descriptor)); } } } This customizer is configured using a the persistence unit property: sistence/config/PersistenceUnitProperties.html#DESCRIPTOR_CU STOMIZER_ I will see if I can get my example at least attached the bug if not published soon. Doug]]> Doug Clarke 2010-03-23T21:35:29-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[FYI For some (most?) databases is it possible to put the history tables in a separate database as long as it is running on the same DB instance. In Informix I created such a database "history" and named the tables "history:" + table.getName() This keeps the schema's clean. Tom]]> Tom Eugelink 2010-03-24T07:27:25-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[> Have I > been searching with the wrong key word or is there an obvious solution I > have missed? Or is everyone just implementing history data storage with > triggers or something obvious? I can't tell you that. I found that Informix' audit features were terrible (the whole UI is for that matter, it seems to be stuck somewhere in the 80's, but that is even more off topic). I expected keeping track an audit trail to be something that would be fairly common and supported by databases themselves. But that seems not to be the case. So no; I do not thing you were searching wrong. After considering trigger and not wanting to go there, I was trying to figure out how to bolt this onto my business model, when I the very supportive Eclipselink people pointed me to this solution; and it works like a charm. The drawback is that I now need to do every change via a Java program (instead of SQL) since otherwise I'm breaking my audit trail. And you have to be very aware of trivial changes to entities. For example I have a "who done it" field that gets set on a every change, so I can see who made a certain change. But I ended up filling my history table with records that only had a changed "who done it" field. For example: an entity was added to a detail-collection, thus the collection-owning entity was considered "modified" and I updated its who-done-it (and a last-modified timestamp)... But a master-detail is stored in the database using a FK from the detail to the master, so the master record (in database perspective) was not changed at all. But since I'd set its who-done-it/last-modified, it did change and got written to the DB and history. Tom]]> Tom Eugelink 2010-03-24T11:00:08-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[I am hoping eclipse link can automagically manage the history data for me - such that my application focus on inserting the current data (without worrying about the start and end date) into a employee_current table, and by setting a property and customiser within EclipseLink, the historic data is managed by EclipseLink, for example, insert a row to employee_history table with start and end date. @Doug, thanks. If I put in a history descriptor customiser class, how do I make use of it? or is that currently blocked due to bugs? @Tom, thanks, I think a clean schema always sounds good! (I'll probablty use different tables if not different databases). This maybe unrelated to this forum (sorry!) but I am very curious about the information around history/temporal data on the internet. Most of the searched results (papers and frameworks) I found seem to have started at the end of 1990s, since then, there seem to be very few updated discussion/framework around it (apart from EclipseLink). Have I been searching with the wrong key word or is there an obvious solution I have missed? Or is everyone just implementing history data storage with triggers or something obvious? Anna]]> Anna 2010-03-24T15:03:58-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[Ok, I got HistoryPolicy working - thanks Doug. There seems to be a bug whereby the writes to the history table are being done with the ClassDescriptor of the main table. My JPA entity/table has an IDENTITY primary key: @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private long id; This causes the HistoryPolicy writes to expect that inserts on the history table will return an @@IDENTITY despite the fact that it is clearly inserting the id explicitly. I have tested two workarounds: (1) adding a new synthetic IDENTITY PK on the history table so @@IDENTITY returns something or (2) proxying ClassDescriptor to always return false from usesSequenceNumbers(). Neither sound like the right thing. Is this a bug or am I using it wrongly?]]> Anna 2010-03-25T10:26:20-00:00 Re: JPA and historic sessions, HistoryPolicy, etc. <![CDATA[Sounds like a bug with history and identity sequencing, please log this issue. You should be able to use TABLE or SEQUENCE sequencing instead. These are normally preferable to IDENTITY anyway. ]]> James Sutherland 2010-03-25T18:23:45-00:00 | http://www.eclipse.org/forums/feed.php?mode=m&th=126287&basic=1 | CC-MAIN-2015-40 | refinedweb | 1,309 | 54.32 |
View demo Download source we’ll show you one way of building the ripple effect specifically outlined under Radial Action of the Google Material Design specification by combining it with the powers of SVG and GreenSock.
Responsive Action
Google defines Responsive Interaction using Radial Action as follows:
Radial action is the visual ripple of ink spreading outward from the point of input.
The connection between an input event and on-screen action should be visually represented to tie them together. For touch or mouse, this occurs at the point of contact. A touch ripple indicates where and when a touch occurs and acknowledges that the touch input was received.
Transitions, or actions triggered by input events, should visually connect to input events. Ripple reactions near the epicenter occur sooner than reactions further away.
Google makes it very clear that input feedback should take place from it’s origin and spread outwards. For example, if a user clicks a button directly in the center, this ripple will expand outward from that point of initial contact. This is how we indicate where and when a touch occurs in order to acknowledge to the user that input was received.
Radial Action In SVG
The ripple technique has been authored by many developers using primarily CSS techniques such as
@keyframes,
transitions,
transforms pseudo trickery,
border-radius and even extra markup such as a
span or
div. Instead of using CSS, let’s take a look at how SVG can be used to create this radial action using GreenSock’s TweenMax library for the motion.
Creating The SVG
Believe it or not you don’t need a fancy application like Adobe Illustrator or even Sketch to author this effect. The markup for the SVG can be written using a few XML tags that might already be familiar and in use with your own work.
<svg version="1.1" xmlns="" xmlns: <symbol viewBox="0 0 100 100"></symbol> </svg>
For those using SVG sprites for icons, you’ll notice the use of
<symbol>. The
symbol element allows authors to match the correlating XML within individual
symbol instances and subsequently instantiate them—or in other words—use them across an application like a stamp. Each instance stamped is identical to it’s sole creator; the symbol it resides within.
Symbol elements accept attributes such as
viewBox and
preserveAspectRatio that provide a
symbol the scale-to-fit ability within a rectangular viewport defined by the referencing
use element. Sara Soueidan wrote a wonderful article and built an interactive tool to help understand the
viewBox coordinate system once and for all. Simply put, we’re defining the initial x and y coordinate values (0,0) and finally defining a width and height (100,100) of the SVG canvas.
The next piece to this XML puzzle is adding a shape we intend to animate as the ripple. This is where the
circle element comes in.
<svg version="1.1" xmlns="" xmlns: <symbol viewBox="0 0 100 100"> <circle /> </symbol> </svg>
The
circle will need a bit more information then what it posseses in order to display correctly within the SVG’s
viewBox.
<circle cx="1" cy="1" r="1"/>
The attributes
cx and
cy are coordinate positions relative to the
viewBox of the SVG;
symbol in our case. In order to make the click feel natural, we’ll need to make sure the trigger point rests directly underneath the user’s finger tip when input is received.
The attributes for the middle example of this diagram create a 2px x 2px circle with a radius of 1px. This will ensure our circle doesn’t crop like we see in the bottom example of the diagram.
<div style="height: 0; width: 0; position: absolute; visibility: hidden;" aria- <svg version="1.1" xmlns="" xmlns: <symbol id="ripply-scott" viewBox="0 0 100 100"> <circle id="ripple-shape" cx="1" cy="1" r="1"/> </symbol> </svg> </div>
For the final touches, we’ll wrap it with a
div containing inline CSS for brevity to hide the sprite. This prevents it from taking up space in the page when rendered.
As of this writing, an SVG sprite containing symbol blocks that reference it’s own gradient definition—as you’ll see in the demos— by ID cannot find the gradient and render it properly; the reason for the
visibility property used in place of
display: none as the entire gradient fails on Firefox and most other browsers.
The use of
focusable="false" is required for all IE’s up to 11; with the exception of Edge as it has yet to be tested. It was a proposal from the SVG 1.2 specification describing how keyboard focus control should work. IE implemented this, but no one else did. For consistency with HTML, and also for greater control, SVG 2 is adopting
tabindex instead. HT to Amelia Bellamy-Royds for the schooling on this tip.
Making Markup
Writing solid markup is the reason we all get up in the morning so let’s write a semantic
button element to use as our object that will reveal this ripple.
<button>Click for Ripple</button>
The markup structure for the
button that most are familiar with is straight forward including some filler text.
<button> Click for Ripple <svg> <use xlink:</use> </svg> </button>
To take advantage of the
symbol element created earlier, we’ll need a way to reference it by utilizing the
use element inside the button’s SVG referencing the symbol’s ID attribute value.
<button id="js-ripple-btn" class="button styl-material"> Click for Ripple <svg class="ripple-obj" id="js-ripple"> <use width="100" height="100" xlink:</use> </svg> </button>
The final markup possesses additional attributes for CSS and JavaScript hooks. Attribute values beginning with “js-” denote values only present in JavaScript and thereby removing them would hinder interaction, but not affect styling. This helps differentiate CSS selectors from JavaScript hooks in order to avoid one another from causing confusion when removal or updating is required in the future.
The
use element must have a width and height defined otherwise it will not be visible to the viewer. You could also define this in CSS if you decided against having it directly on the element itself.
Styling The Joint
When it comes time for authoring the CSS, very little is required to achieve the desired result.
.ripple-obj { height: 100%; pointer-events: none; position: absolute; top: 0; left: 0; width: 100%; z-index: 0; fill: #0c7cd5; } .ripple-obj use { opacity: 0; }
Here’s what remains when removing the declarations used for general styling. The use of
pointer-events eliminates the SVG ripple from becoming the target of mouse events as we only need the parent object to react; the
button element.
The ripple must be invisible initially hence the
opacity value set to zero. We’re also positioning the ripple object in the top left of the
button. We could center the ripple shape, but since this event occurs based on user interaction it’s meaningless to fret over position.
Giving It Life
Breathing life into this interaction is what it’s all about and exactly what Material Design guidelines document as one of the most crucial parts of their visual language.
<script src=""></script> <script src="js/ripple.js"></script>
To animate the ripple we’ll be using GreenSock’s TweenMax library because it’s one of the best libraries out there to animate objects using JavaScript; especially when it comes to the headaches involved with animating SVG cross-browser.
var ripplyScott = (function() {} return { init: function() {} }; })();
The pattern we’re going to be using is what’s called a module pattern as it helps to conceal and protect the global namespace.
var ripplyScott = (function() {} var circle = document.getElementById('js-ripple'), ripple = document.querySelectorAll('.js-ripple'); function rippleAnimation(event, timing) {…} })();
To kick things off we’ll grab a few elements and store them in variables; particularly the
use element and it’s containing
svg within
button. The entire animation logic will reside within the
rippleAnimation function. This function will accept arguments for timing of the animation sequence and event information.)); } })();
A ton of variables have been defined so let’s hit them one by one to discuss what they’re in charge of.
var tl = new TimelineMax();
This variable creates the timeline instance for the animation sequence and the way all timelines are instantiated in TweenMax.
var x = event.offsetX; var y = event.offsetY;
An event’s offset is a read-only property that reports the offset value from the mouse pointer to the padding edge of the target node. In this case that would be our
button. The event offset is calculated from left to right for x and top to bottom for y; both starting at zero.
var w = event.target.offsetWidth; var h = event.target.offsetHeight;
These variables are returning the width and height of the button. Final calculations will include the size of the element’s border’s and padding. We’ll need this value to know how large our element is so we can spread the ripple to the farthest edge.
var offsetX = Math.abs( (w / 2) - x ); var offsetY = Math.abs( (h / 2) - y );
The offset values are the click’s offset distance away from the element’s center. In order to fill the entire area of our target, the ripple must be large enough to cover from the point of contact to the farthest corner. Using our initial x and y coordinates won’t cut it as once again the values start from zero going from left to right for x and top to bottom for y. This approach lets us use those values, but detects the distance no matter what side is clicked of the target’s central point.
Notice how the circle will cover the entire element each click no matter where the initial point of input takes place. To cover the entire surface according to the initiated point of interaction we need to do some maths.
Here’s how the offset is calculated using 464 x 82 as our width and height, 391 and 45 as our x and y coordinates:
var offsetX = (464 / 2) - 391 = -159 var offsetY = (82 / 2) - 45 = -4
We find the center by dividing the width and height in half then subtract the values reported detected by our x and y coordinates.
The
Math.abs() method returns the absolute value of a number. Using our arithmetic above that would make the values 159 and 4.
var deltaX = 232 + 159 = 391; var deltaY = 41 + 4 = 45;
Delta calculates the entire distance of our click instead of the distance to the center. The reason for delta is that x and y always start at zero going from left to right so we need a way to detect the click when it’s in the opposite direction; right to left.
For those that participated in basic math courses throughout highschool will recognize the Pythagorean Theorem. This formula takes the altitude squared(a) plus the base squared(b) and results in the hypotenuse squared(c).
a2 + b2 = c2
var scale_ratio = Math.sqrt(Math.pow(deltaX, 2) + Math.pow(deltaY, 2));
Using this formula let’s run through the calculations.
var scale_ratio = Math.sqrt(Math.pow(391, 2) + Math.pow(45, 2));
The method
Math.pow() returns the power of the first argument; in this case doubled. The value 391 to the power of 2 would be 152881. The last value of 45 to power of 2 equals 2025. Adding both these values and taking the square root of the result would leave us with 393.58099547615353 which is the ratio we need to scale the ripple by.; } })();
Using the
fromTo method in TweenMax we’re passing the target—ripple shape—and setting up object literals that contain our directions for the entire motion sequence. Seeing as we’d like to animate form the center outwards, the SVG needs the transform-origin set to the middle position. The scaling also needs to be adjusted to it’s smallest position, given an ease for feeling and setting
opacity to 1 since we’d like to animate in then out. If you recall earlier we set the
use element with an
opacity of 0 in CSS and the reason why we’d like to go from a value of 1 and return to zero. The final part is returning our timeline instance.; } return { init: function(target, timing) { var button = document.getElementById(target); button.addEventListener('click', function(event) { rippleAnimation.call(this, event, timing); }); } }; })();
This object literal returned will control our ripple by attaching an event listener to the desired target, calling upon our
rippleAnimation and finally passing arguments we’ll discuss in our next step.
ripplyScott.init('js-ripple-btn', 0.75);
The final call is made to our button by using our module and passing the
init function that passes our button and the timing for the sequence. Voilà!
We hope you enjoy this little experiment and find it inspiring! Don’t forget to check out the demos with the different shapes and take a look at the source code. Try new shapes, layer shapes, but most importantly stay creative.
- ChromeSupported
- FirefoxSupported
- Internet ExplorerSupported from version 9+
- SafariSupported
- OperaSupported
View demo Download source
This looks awesome :D Will have to give it a try. Thank you for writing such a thorough and easy to understand tutorial :)
You made my heart warm. Makes me feel good to hear the tut was easy to understand. My objective was met! Thanks again for reading.
Awesome! Thank you for sharing this with us, Dennis.
Wow! Love this effect. Will this also work on mobile devices?
Just opened this in Safari on my iPhone 5 and it works nicely :)
Absolutely! Anywhere SVG is supported this effect will be as well \o/
Good tutorial! Very welcome to nowadays. :) Congratulations and thanks for the contribution!
Thanks Giovanni
Looks great. Thanks you :)
Uh, i’m waiting for more days similar articles on codrops! This is very nice effect and i think to use in my work! Thanks for sharing :)
Very nice! The one think I would like to see is using `mousedown` and `touchstart` instead of `click` so the the ripple appears immediately when it’s clicked or touched, instead of when the mouse button is released.
Hey Eden. Great points. The idea of the article was to show how SVG can be used and the rest is for others to run with it. I hope you take it to 11 as they say :)
Cool experiment, but it’s a rather expensive solution considering GASP is a such heavy library (even at minimum) for something so insignificant. In a real world situation I would opt for something that is using vanilla JS, a single HTML element as a circle (border-radius) and scale for transformation. Yes, you probably won’t be able to make it as fancy as it is in the demo, but at least it eliminates the need of yet another library, especially when we should care about speed and performance on mobile devices.
Hi Andy,
TweenMax is 34.8kb gzipped so I don’t really consider it such an expensive operation especially when other parts of a project could potentially be using it too. SVG is super tough to animate with strictly CSS and yes you could do it with HTML elements, but you will notice pixelation as a result when transformations occur such as scaling+border-radius. I use TweenMax quite a bit for projects so I don’t consider it a huge overhead. As with all demo’s here you’re welcome to expand on them and make them suit your needs or build upon them to improve. Appreciate the feedback and thanks for reading :)
Hi Dennis is it possible to have multiple instances on the same page? What would be the easiest way?
It’s ok, I ended up going a slightly different route to achieve what I wanted but it was very much inspired by your advice here let me know what you think!
It’s a fairly simple change to get it working with multiple buttons. First you need to move the querySelector for the ripple effect into rippleAnimation and pass the button in to the function too. You can then do a querySelector on the button itself to get the relevant ripple. I’ve changed the init to do a querySelector on a target which has been passed in rather than getting the element by ID.
var ripplyScott = (function () {
function rippleAnimation(button, event, timing) {
var ripple = button.querySelectorAll(‘.js-ripple’),: ‘50% 50%’,
scale: 0,
opacity: 1,
ease: Linear.easeIn
}, {
scale: scale_ratio,
opacity: 0
});
return tl;
}
return {
init: function (target, timing) {
var buttons = document.querySelectorAll(target);
[].forEach.call(buttons, function (button) {
button.addEventListener(‘click’, function (event) {
rippleAnimation.call(this, button, event, timing);
});
});
}
};
})();
Then you just need to call the init function and pass in the target for the query selector:
ripplyScott.init(‘.button’, 0.75);
The animation will now be bound to any elements with the .button class. Obviously it’s slightly less efficient because you’re doing a DOM lookup each time you run the function but it’s more versatile so it’s a small tradeoff.
Is there a way to put these on a wix.com website?
Just tried this demo on Cent OS 6.7 Firefox ESR 38.3.0 and this does not work. So far the only SVG tutorial that is not working for me here. Would love to be able to start implementing more SVG components as this makes this more ‘flexible’ IMO.
The console outputs:
x is:undefined
ripple-config.js (line 17)
y is:undefined
ripple-config.js (line 18)
offsetX is:NaN
ripple-config.js (line 19)
offsetY is:NaN
ripple-config.js (line 20)
deltaX is:NaN
ripple-config.js (line 21)
deltaY is:NaN
ripple-config.js (line 22)
width is:268
ripple-config.js (line 23)
height is:87
ripple-config.js (line 24)
scale ratio is:NaN
Totally awesome, but a little heavy because of GSAP.
Anyway, I will use it!! :)
Good tutorial, I am trying to do it with angular, it works… but I don’t see svg effect, js changing elements attrs and thats it(
Great tutorial but ripple effect is not working offline. Does anyone have a solution for this?
Hey! There is a little bug when you have an svg icon in the button. To fix it, you just need to get the offsetWidth and the offsetHeight of the button directly instead of getting the event.target offsetWhidth and offsetHeight.
Here’s the code:
var ripplyScott = (function() {
var circle = document.getElementById(‘js-ripple’),
ripple = document.querySelectorAll(‘.js-ripple’);
function rippleAnimation(event, timing, target) {
var tl = new TimelineMax();
x = event.offsetX,
y = event.offsetY,
w = target.offsetWidth,
h = target.offsetHeight,
offsetX = Math.abs( (w / 2) – x ),
offsetY = Math.abs( (h / 2) – y ),
deltaX = (w / 2) + offsetX,
deltaY = (h / 2) + offsetY,
scale_ratio = Math.sqrt(Math.pow(deltaX, 2) + Math.pow(deltaY, 2));
console.log(‘x is:’ + x);
console.log(‘y is:’ + y);
console.log(‘offsetX is:’ + offsetX);
console.log(‘offsetY is:’ + offsetY);
console.log(‘deltaX is:’ + deltaX);
console.log(‘deltaY is:’ + deltaY);
console.log(‘width is:’ + w);
console.log(‘height is:’ + h);
console.log(‘scale ratio is:’ + scale_ratio);
tl.fromTo(ripple, timing, {
x: x,
y: y,
transformOrigin: ‘50% 50%’,
scale: 0,
opacity: 1,
ease: Linear.easeIn
},{
scale: scale_ratio,
opacity: 0
});
return tl;
}
return {
init: function(target, timing) {
var button = document.getElementById(target);
button.addEventListener(‘click’, function(event) {
rippleAnimation.call(this, event, timing, button);
});
}
};
})();
ripplyScott.init(‘js-ripple-btn’, 0.75); | http://tympanus.net/codrops/2015/09/14/creating-material-design-ripple-effects-svg/ | CC-MAIN-2016-22 | refinedweb | 3,282 | 64.51 |
This article is for Delphi developers who want to learn Prism. It covers the most significant changes to the old Delphi language
and the basics about the new parallel computing support.
Delphi Prism is a .NET language based upon Delphi. You might say it is the Delphi.NET. The name also stands for a Visual Studio extension
that makes coding in Prism comfortable. It is a Visual Studio Shell application, so it integrates into an existing VS 2008 (if it is installed
on the machine) or runs as a standalone IDE.
Why should you use Prism at all? First, there are Linux and Macintosh. Maybe you want to write platform independent code for Mono.
Second, desktop applications are not always adequate and Delphi's ISAPI support is not state of the art. Third, you might be switching
from native to managed development in general. Learning to use a new platform will be easier with a language you already know.
There's a fourth possible reason: Your applications are designed for multicore computers.
Delphi Prism is designed especially for heavy multithreading and high responsiveness.
In this absolute beginner's tutorial, we'll write an address book using the Lucene.NET library.
To introduce desktop and web at the same time, there'll be a WPF application to fill the search index and a web page to search it.
Create a new Delphi WPF project. Visual Studio shows you the Forms Designer, where you can design the main dialog as usual.
Change to the code editor. Delphi developers will be surprised: instead of a unit the code generator has declared a namespace.
In the class definition, you find the new keywords partial and method. The latter replaces procedure
as well as function, because .NET doesn't make a difference between those two. (Rather every method has a return value,
for procedures it is void.) The name Create for constructors is replaced by nothing at all: objects get created
with new, just as in the C-like languages.
unit
namespace
partial
method
procedure
function
void
Create
new
namespace LuceneTest;
interface
uses
System.Linq,
System.Windows,
System.Collections.ObjectModel,
System.Collections.Generic,
Lucene.Net.Index,
Lucene.Net.Store,
Lucene.Net.Search,
Lucene.Net.Documents,
Lucene.Net.Analysis.Standard,
Lucene.Net.QueryParsers;
type
Window1 = public partial class(System.Windows.Window)
private
method btnIndex_Click(sender: System.Object; e: RoutedEventArgs);
method btnSearch_Click(sender: System.Object; e: RoutedEventArgs);
method addDocument(name: String; address: String; writer: IndexWriter);
public
constructor;
end;
Let's begin with the address book. A list of names has to be filtered and added to the search index. The new way to search lists
looks quite confusing: the common Delphi developer is used to declare all variables above the procedure! But thanks to LINQ,
there are lists without a defined type (that means, not defined in code), which don't even have to be declared.
method Window1.BuildSearchIndex;
var
persons: Collection<person>;
directory: Directory;
writer: IndexWriter;
analyzer: StandardAnalyzer;
begin
persons := GetPersons;
var filteredPersons := from n in persons
where (not n.Blocked)
order by n
select n;
directory := FSDirectory.GetDirectory('L:\\Index', true);
analyzer := new StandardAnalyzer();
writer := new IndexWriter(directory, analyzer, true);
for each person in IEnumerable<person>(filteredPersons) do
begin
addDocument(person.Name, person.Address, writer);
end;
writer.Optimize();
writer.Close();
end;
The newly built search index is to be searched by a web form. Create a new Delphi ASP.NET project!
Again, Visual Studio shows you a designer window. Open the code behind to meet another new keyword.
partial splits the Delphi class into an editable file Default.aspx.pas and the designer generated file
Default.aspx.designer.pas. While you're typing ASP code, the designer fill its file with all necessary declarations.
Your file will rarely be touched by the designer, unless the generated code must be edited by you. Now, double-click a button
on the web form to insert an event handler.
By the way, this is a good point to introduce the double compare operator. You can make your code more readable using
"0.2 <= score < 0.5" instead of the long version "0.2 <= score and score < 0.5".
0.2 <= score < 0.5
0.2 <= score and score < 0.5
method _Default.btnFind_Click(sender: Object; e: EventArgs);
var
indexDirectory: String;
parser: QueryParser;
query: Query;
searcher: IndexSearcher;
searchResults: TopDocs;
currentDocument: Document;
lblResult: Label;
begin
parser := new QueryParser('name', new StandardAnalyzer());
query := parser.Parse(txtName.Text);
indexDirectory := ConfigurationManager.AppSettings['LuceneIndexDirectory'];
searcher := new IndexSearcher(FSDirectory.GetDirectory(indexDirectory, false));
searchResults := searcher.Search(query, nil, 10);
for each currentResult in searchResults.scoreDocs do
begin
currentDocument := searcher.Reader.Document(currentResult.doc);
lblResult := new Label();
lblResult.Text := string.Format("{0} - {1}, {2}",
ScoreToString(currentResult.score),
currentDocument.Get('name'),
currentDocument.Get('address'));
pResult.Controls.Add(lblResult);
end;
pResult.Visible := true;
end;
method _Default.ScoreToString(score: Single): String;
begin
Result := 'Impossible';
if(0.2 <= score < 0.5)then
Result := 'Improbable'
else if(0.5 <= score < 0.8)then
Result := 'Maybe'
else if(0.8 <= score < 1.0)then
Result := 'Quite sure'
else
Result := 'That is it!';
end;
Performance has always been an argument for using Delphi. Prism focuses on parallel programming and scores with handy new keywords which save lots of code and chaos.
The most handy one is async which simply declares a method as asynchronous. An asynchronous method is executed
in a separate thread - automatically! That way a single word in the declaration line can prevent the main thread from being slowed
down by log output calls. In the declaration of a variable, async is the promise that the variable will - in the future - contain a certain value.
The value itself is calculated in a separate thread. If another thread accesses the variable before the calculation is finished, that thread is blocked until
the value is available. But the most impressive news is the asynchronous block:
async
01 SomethingInTheMainThread(a);
02 var myBlock: future := async
03 begin
04 DoSomethingLong(b);
05 DoEvenMore(c);
06 end;
07 WholeLotInTheMainThread(d);
08 myBlock();
When is line 04 executed? Assuming there are enough processors, simultaneously with line 07.
async makes the block run in another thread. The future variable myBlock is your handle for that thread,
so you can wait for it in line 08. The method call myBlock() doesn't execute the block! Only if it hasn't yet finished, it waits for the thread to end.
future
myBlock
myBlock()
Inside the asynchronous blocks, you may call other asynchronous methods. But be careful: the main thread doesn't wait for them.
Waiting for an asynchronous block means waiting for this one thread, not for any "nested" threads that have been started by the block.
To visualise all that parallel stuff, the web page contains four checkboxes. They'll be evaluated in the background, when the user already sees the response page in his browser.
type
_Default = public partial class(System.Web.UI.Page)
protected
method btnFind_Click(sender: Object; e: EventArgs);
method btnSurvey_Click(sender: Object; e: EventArgs);
private
logFile: String;
logWriter: future StreamWriter := new StreamWriter(logFile);
method ScoreToString(score: Single): String;
method WriteLog(i: Integer; text: String); async;
end;
implementation
method _Default.btnSurvey_Click(sender: Object; e: EventArgs);
begin
logFile := ConfigurationManager.AppSettings['LogFile'];
logWriter.AutoFlush := true;
var backgroundWork: future := async
begin
logWriter.WriteLine("Loop starts at {0:mm:ss:fff}.", DateTime.Now);
for each matching chkSurvey: CheckBox in pSurvey.Controls index i do
if(chkSurvey.Checked)then
WriteLog(i, chkSurvey.Text);
logWriter.WriteLine("Loop stops at {0:mm:ss:fff}.", DateTime.Now);
end;
backgroundWork();
logWriter.WriteLine("Page delivered at {0:mm:ss:fff}.", DateTime.Now);
end;
method _Default.WriteLog(i: Integer; text: String);
begin
Thread.Sleep(1000);
logWriter.WriteLine("{0}. Selection is '{1}' at {2:mm:ss:fff}.", i, text, DateTime.Now);
end;
The StreamWriter seems to be initialised with an empty path. But the keyword future causes the assignment
in the declaration line to be executed shortly before the first access to the object. At that time, the path already is assigned.
The method WriteLog is async, so it always runs in the background.
StreamWriter
WriteLog
In the async block's thread, a for each matching loop iterates through all controls that are checkboxes.
Every iteration can call another asynchronous method. When in the end the main thread waits for the block to finish, it waits only
for the block's thread, not for any additional thread started by the block. The WriteLog calls can still run in the background,
maybe waiting for a free CPU, when the user already sees the complete response.
for each matching
To compile the demo applications, you need the assembly Lucene.Net.dll.
If the latest stable release doesn't work, try version 2.0.004.
A 30 days trial version of Delphi Prism can be downloaded from Embarcadero.
Sadly, they don't offer a free Express. | http://www.codeproject.com/script/Articles/View.aspx?aid=37410 | CC-MAIN-2016-40 | refinedweb | 1,464 | 51.95 |
i am writing a program.. in that i am needed to represent an array using pointers only..(its a constraint i ve to work with).. the prob i am facing can be shown by this small program.. pls help me rectify with
#include <stdio.h> #include <conio.h> void main() { char a[4],*b; a[0]=2; a[1]=2; b[0]=a[0]; printf("%s",a); getch(); }
i have trouble whenever i try to assign b a value.. like here b[0]=a[0] gives the exception.. even if i have b[0]=0 it will give an exception
the program is giving an nullreferenceexception.. saying that i cannot dereference a null object.. how do i fix this.. or are there any alternate ways to handle this.. | https://www.daniweb.com/programming/software-development/threads/27232/help-needed-in-assigning-values | CC-MAIN-2018-43 | refinedweb | 128 | 79.16 |
Opened 7 years ago
Closed 5 years ago
#6138 closed (fixed)
newforms: when accessing directly form.errors, error_class is not used
Description
Tested with SVN Django, rev 6897.
Short guide for reproducing the problem:
- write custom form class and ErrorList-based class
- make instance of the form which defined error_class as our ErrorList-based class and some non-valid data
- watch customform.errors and customform['customfield'].errors, they are instances of ErrorList, not our error_class
The long guide (small app for reproducing the problem):
urls.py (within project dtest)
from django.conf.urls.defaults import * urlpatterns = patterns('', url(r'^form/$', 'dtest.newforms.views.microform', {'form':'form.html'}), url(r'^form2/$', 'dtest.newforms.views.microform', {'form':'form2.html'}), )
newforms/forms.py
from django.utils.encoding import force_unicode from django import newforms as forms attrs_dict = { 'class': 'required' } class ErrList(forms.util.ErrorList): def __unicode__(self): return 'errors: %s' % ''.join([unicode(e) for e in self]) class MicroForm(forms.Form): username = forms.CharField(max_length=30, widget=forms.TextInput(attrs=attrs_dict), label=u'username') def clean(self): if self.cleaned_data.get('username', '') is not 'blah': raise forms.ValidationError('we have a problem here')
newforms/views.py
from django.http import HttpResponse from django.shortcuts import render_to_response from django.template import RequestContext from dtest.newforms.forms import ErrList, MicroForm def microform(request, form='form.html'): if request.method == 'POST': m = MicroForm(request.POST, error_class=ErrList) if m.is_valid(): return HttpResponse('OK') else: m = MicroForm() return render_to_response(form, { 'form': m }, context_instance=RequestContext(request))
templates/form.html
<form action="" method="POST"> <dl> {% for field in form %} <dt>{{ field.label_tag }}</dt> <dd {% if field.errors %}{{ field.errors }}</dd>{% endif %} {% endfor %} </dl> <div class="submit"><input id="submit" type="submit" value="Sign up" /> </form>
templates/form2.html
<form action="" method="POST"> <ul> {{ form.as_ul }} </ul> <div class="submit"><input id="submit" type="submit" value="Sign up" />
- When accessing form/, the ErrList does not work.
- When accessing form2/, the to_ul() (and _html_output() too) method works with ErrList, but non_field_errors() do not.
A simple patch is included below. It fixes the problem, but I do not guarantee working with the rest of the code in all cases.
Attachments (5)
Change History (23)
Changed 7 years ago by Michal Moroz
comment:1 Changed 7 years ago by Italomaia
- Needs documentation unset
- Needs tests unset
- Patch needs improvement unset
The redered errorlist is comming escaped! Shouldn't it come unnescaped? This patch outputs escaped text. Django docs per example, uses <div> in the
returned error message. With unnescaped, that example wouldn't work.
comment:2 Changed 6 years ago by AzMoo
- Resolution set to fixed
- Status changed from new to closed
I've added a patch for this that makes non_field_errors honour error_class to match the behaviour of bound fields.
comment:3 Changed 6 years ago by mtredinnick
- Resolution fixed deleted
- Status changed from closed to reopened
This hasn't been fixed yet. Please read contributing.txt to see what the various stages of a ticket are, but "fixed" happens only when something is committed to the repository.
comment:4 Changed 6 years ago by AzMoo
- Patch needs improvement set
Sorry!
I've realized that this patch only fixes the helper functions, not accessing the errors directly. Obviously to be complete it needs to do this.
comment:5 Changed 6 years ago by ubernostrum
What Malcolm meant is that "fixed" doesn't happen until a Django developer actually checks the code into the repository; just posting a patch doesn't do that, and any patch posted still needs to be reviewed by a Django developer.
comment:6 Changed 6 years ago by jacob
- Triage Stage changed from Unreviewed to Accepted
comment:7 Changed 6 years ago by Leo
the bug is still here in 1,0,alfa version
comment:8 Changed 6 years ago by issya
I can confirm that this is still a problem. If I try to access field.errors, the custom error list does not work. If I just print my form out with {{ form }}, the custom field.errors work.
comment:9 Changed 6 years ago by adunar
- Cc adunar added
- milestone set to post-1.0
+1; it's still a bug in 1.0 and the current svn revision (9232)... is this patch waiting on anything?
Changed 6 years ago by AzMoo
Updated version - applies error_class to non_field_errors as well as the boundfield errors.
comment:10 Changed 5 years ago by anonymous
- milestone post-1.0 deleted
Milestone post-1.0 deleted
comment:11 Changed 5 years ago by gz
- Cc gz added
Is there anything we can do to help getting this fixed?
comment:12 Changed 5 years ago by peter2108
It's still a bug in 1.1 rc1 11,332 so I guess no-one cares.
comment:13 Changed 5 years ago by peter2108
- Cc peter2108 added
comment:14 Changed 5 years ago by kmtracey
- Needs tests set
If the latest patch fixes the reason that "patch needs improvement" was checked then it should be unchecked. Also, I don't see any tests nor any reason why tests aren't possible/appropriate.
comment:15 follow-up: ↓ 17 Changed 5 years ago by Alex
Please put the tests in the same diff as the patch itself, it is possible to use svn add locally.
comment:16 Changed 5 years ago by peter2108
- Needs tests unset
- Owner changed from nobody to peter2108
- Patch needs improvement unset
- Status changed from reopened to new
Forms have an optional parameter 'error_class' which defaults to ErrorList.
ErrorList subclasses 'list'. It holds a list of Form errors and has methods to
present its errors in various formats, typically an HTML <ul>. A custom
error_class might change the HTML display of Form errors. Forms add errors
by trapping a ValidationError
ValidationError.messages is an ErrorList instance. Present code just adds
this ErrorList to the Form's errors. Instead we initialise an error_class
instance with ErrorList.messages and add this instance to Form's errors.
error_class is an optional parameter for BaseForm, BaseFormset and BaseModelForm.
Changes are only needed for the first two.
ValidationError is trapped at:
1. forms/fields.py:805 2. forms/forms.py:245 3. forms/forms.py:252 4. forms/formsets.py:254
Changes are made for 2-4. Any issues there might be with 1. are not addressed.
I have included a group of tests. To run these using the constant
'NON_FIELD_ERRORS' instead of its present value I needed to change the _ _all_ _
list of Forms module.
The changes proposed here are those of AzMoo 12/14/08 except for the change to
_html_output which does not appear to be necessary.
Finally if documentation is added for 'error_class' it would probably be worth
warning error_messages for fields are not strings. I included some tests
to illustrate this
The changes are in error_class2.diff, test for the patch in error_class2_test.py
Changed 5 years ago by peter2108
Changed 5 years ago by peter2108
comment:17 in reply to: ↑ 15 Changed 5 years ago by peter2108
Changed 5 years ago by peter2108
Patch and tests as a single diff
comment:18 Changed 5 years ago by peter2108
- Resolution set to fixed
- Status changed from new to closed
A simple patch | https://code.djangoproject.com/ticket/6138 | CC-MAIN-2014-23 | refinedweb | 1,201 | 58.99 |
Understanding the Replit IDE: a practical guide to building your first project with Replit
This tutorial is also available as a video.
Software developers can get pretty attached to their Integrated Development Environments (IDEs) and if you look for advice on which one to use, you'll find quite a lot of developers advocating strongly for one over another: VS Code, Sublime Text, IntelliJ, Atom, Vim, Emacs, and no shortage of others.
In the end, an IDE is just a glorified text editor. It lets you type text into files and save those files, functionality that has been present in nearly all computers since those controlled by punch cards.
In this lesson, you'll learn how to use the Replit IDE. It has some features you won't find in many other IDEs, namely:
- It's fully online. You can use it from any computer that can connect to the internet and run a web browser, including a phone or tablet.
- It'll fully manage your environment for building and running code: you won't need to mess around with making sure you have the right version of Python or the correct NodeJS libraries.
- You can deploy any code you build to the public in one click: no messing around with servers, or copying code around.
In the first part of this guide, we'll cover the basics and also show you how multiplayer works so that you can code alone or with friends.
Introduction: creating an account and starting a project
Visit and follow the prompts to create a user account, either by entering a username and password or by logging in with Google, GitHub, or Facebook.
Once you're done, hit the
+ new repl button in the top left. In the example below, we choose to create a new Python project. Replit will automatically choose a random name for your project, or you can pick one yourself. Note that by default your repl will be public to anyone on the internet; this is great for sharing and collaboration, but we'll have to be careful to not include passwords or other sensitive information in any of our project files.
You'll also notice an "Import from GitHub" option. Replit allows you to import existing software projects directly from GitHub, but we'll create our own for now. Once your project is created, you'll be taken to a new view with several panes. Let's take a look at what these are.
Understanding the Replit panes
You'll soon see how configurable Replit is and how most things can be moved around to suit your fancy. However, by default, you'll get the following layout.
- Left pane: files and configuration. This, by default, shows all the files that make up your project. Because we chose a Python project, Replit has gone ahead and created a
main.pyfile.
- Middle pane: code editor. You'll probably spend most of your time using this pane. It's a text editor where you can write code. In the screenshot, we've added two lines of Python code, which we'll run in a bit.
- Right pane: output sandbox. This is where you'll see your code in action. All output that your program produces will appear in this pane, and it also acts as a quick sandbox to run small pieces of code, which we'll look at more later.
- Run button. If you click the big green
runbutton, your code will be executed and the output will appear on the right.
- Menu bar. This lets you control what you see in the main left pane (pane 1). By default, you'll see the files that make up your project but you can use this bar to view other things here too by clicking on the various icons. We'll take a look at these options later.
Don't worry too much about all of the functionality offered right away. For now, we have a simple goal: write some code and run it.
Running code from a file
Usually, you'll enter your code as text in a file, and run it from there. Let's do this now. Enter the following code in the middle pane (pane 2), and hit the run button.
print("Hello World")
print(1+2)
Your script will run and the output it generates will appear on the right pane (pane 3). Our code outputs the phrase "Hello World" (it's a long-standing tradition that when you learn something new the first thing you do is build a 'hello world' project), and then output the answer to the sum
1 + 2.
You probably won't be able to turn this script into the next startup unicorn quite yet, but let's keep going.
Running code from Replit's REPL
In computer programming, a REPL is a read-eval-print loop, and a REPL interface is often the simplest way to run short computer programs (and where Replit got its name).
While in the previous example we saved our code to a file and then executed the file, it's sometimes quicker to execute code directly.
You can type code in the right-hand pane (pane 3) and press the "Enter" key to run it. Take a look at the example below where we print "Hello World" again and do a different sum, without changing our code file.
This is useful for prototyping or checking how things work, but for any serious program you write you'll want to be able to save it, and that means writing the code in a file like in our earlier example.
Adding more files to your software project
If you build larger projects, you'll want to use more than a single file to stay organised, grouping related code in different files.
So far, we've been using the 'main.py' file that was automatically created for us when we started the project, but we're not limited to this file. Let's add a new file, write some code in that, and import it into the main file for use.
As an example, we'll write code to solve quadratic equations. If you've done this before, you'll know it can be tedious without a computer to go through all of the steps.
Let's make Python do the repetitive steps for us by creating a program called "solver". This could eventually have a lot of different solvers, but for now we'll just write one:
solve_quadratic.
Add a new file to your project by clicking on the
new file button, as shown below. Call the file
solver.py. You now have two files in your project:
main.py and
solver.py. You can switch between your files by clicking on them.
Open the
solver.py file and add the following code to it.
import math
def solve_quadratic(a, b, c):
d = (b ** 2) - 4 * a * c
s1 = (-b + math.sqrt(d)) / (2 * a)
s2 = (-b - math.sqrt(d)) / (2 * a)
return s1, s2
Note that this won't solve all quadratic equations as it doesn't handle cases where
d, the discriminant, is 0 or negative. However, it'll do for now.
Navigate back to the
main.py file. Delete all the code we had before and add the following code instead.
from solver import solve_quadratic
answer = solve_quadratic(5, 6, 1)
print(answer)
Note how we use Python's import functionality to import the code from our new solver script into the
main.py file so that we can run it. Python looks for
.py (Python) files automatically, so you omit the
.py suffix when importing code. Here we import the
solve_quadratic function (which we just defined) from the
solver.py file.
Run the code and you should see the solution to the equation, as shown below.
Congratulations! You've written your first useful program.
Sharing your application with others
Coding is more fun with friends or as part of a team. If you want to share your code with others, it's as easy as copying the URL and sending it. In this case, the URL is, but yours will be different based on your Replit username and the project name you chose.
You can copy the link and open it in an incognito tab (or a different web browser) to see how others would experience your project if you were to share it. By default, they'll be able to see all of your files and code and run your code, but not make any changes. To be able to make changes they would need to fork the repl to create their own copy. Any changes your friends make will only happen in their copies, and won't affect your code at all.
To understand this, compare the two versions of the same repl below.
- As you see it, with all of the controls
- As your friend or an anonymous user would see it without forking the repl, a read-only version
What does this mean? Because no one else can edit your repl, you can share it far and wide. But because anyone can read your repl, you should be careful that you don't share anything private or secret in it.
Sharing write-access: Multiplayer
Of course, sometimes you might want others to have write access to your repl so that they can contribute, or help you out with a problem. In these cases, you can use Replit's "multiplayer" functionality.
If you invite someone to your repl, it's different from sharing the URL with them. You can invite someone by clicking
Invite in the top right and sending them the secret link that starts with. This link will give people edit access to your repl.
If you have a friend handy, send it to them to try it out. If not, you can try out multiplayer anyway using a separate incognito window again. Below is our main Replit account on the left and a second account which opened the multiplayer invite link on the right. As you can see, all keystrokes can be seen by all parties in real time.
Make it your own
If you followed along, you'll already have your own version of the repl to extend. If not, start from ours. Fork it from the embed below.
Where next?
You can now create basic programs on your own or with friends, and you are familiar with the most important Replit features. There's a lot more to learn though. In the next lessons, you'll work through a series of projects that will teach you more about Replit features and programming concepts along the way.
If you get stuck, you can get help from the Replit community or on the Replit Discord server. | https://docs.replit.com/tutorials/introduction-to-the-repl-it-ide | CC-MAIN-2022-27 | refinedweb | 1,806 | 80.01 |
KDECore
KTempFile Class ReferenceThe KTempFile class creates and opens a unique file for temporary use. More...
#include <ktempfile.h>
Detailed DescriptionThe KTempFile class creates and opens a unique file for temporary use.
This is especially useful if you need to create a file in a world writable directory like /tmp without being vulnerable to so called symlink attacks.
KDE applications, however, shouldn't create files in /tmp in the first place but use the "tmp" resource instead. The standard KTempFile constructor will do that by default.
To create a temporary file that starts with a certain name in the "tmp" resource, one should use: KTempFile(locateLocal("tmp", prefix), extension);
KTempFile does not create any missing directories, but locateLocal() does.
See also KStandardDirs
Definition at line 55 of file ktempfile.h.
Constructor & Destructor Documentation
Creates a temporary file with the name: <filePrefix><six letters><fileExtension>.
The default
filePrefix is "$KDEHOME/tmp-$HOST/appname/" The default
fileExtension is ".tmp"
- Parameters:
-
Definition at line 60 of file ktempfile.cpp.
The destructor closes the file.
If autoDelete is enabled the file gets unlinked as well.
Definition at line 129 of file ktempfile.cpp.
Constructor used by KSaveFile.
Definition at line 79 of file ktempfile.cpp.
Member Function Documentation
Closes the file.
See status() for details about errors.
- Returns:
- true if successful, or false if an error has occurred.
Definition at line 253 of file ktempfile.cpp.
For internal use only.
Create function used internally by KTempFile and KSaveFile
Definition at line 92 of file ktempfile.cpp.
Returns a QDataStream for writing.
- Returns:
- QDataStream open for writing to the file, or 0 if opening the file failed
Definition at line 192 of file ktempfile.cpp.
Definition at line 170 of file ktempfile.cpp.
Returns the FILE* of the temporary file.
- Returns:
- FILE* stream open for writing to the file, or 0 if opening the file failed
Definition at line 155 of file ktempfile.cpp.
An integer file descriptor open for writing to the file.
- Returns:
- The file descriptor, or a negative number if opening the file failed
Definition at line 149 of file ktempfile.cpp.
Returns the full path and name of the file.
Note that in most circumstances the file needs to be closed before you use it by name.
In particular, if another process or software part needs to write data to the file based on the filename, the file should be closed before doing so. Otherwise the act of closing the file later on may cause the file to get truncated to a zero-size, resulting in an unexpected loss of the data.
In some cases there is only interest in the filename itself but where the actual presence of a file with such name is a problem. In that case the file should first be both closed and unlinked. Such usage is not recommended since it may lead to the kind of symlink vulnerabilities that the KTempFile design attempts to prevent.
- Returns:
- The name of the file, or QString::null if opening the file has failed or the file has been unlinked already.
Definition at line 143 of file ktempfile.cpp.
Turn automatic deletion on or off.
Automatic deletion is off by default.
- Parameters:
-
Definition at line 87 of file ktempfile.h.
Definition at line 198 of file ktempfile 137 of file ktempfile.cpp.
Flushes file to disk (fsync).
If you want to be as sure as possible that the file data has actually been physically stored on disk you need to call sync().
See status() for details about errors.
- Returns:
- true if successful, or false if an error has occurred.
- Since:
- 3.3
Definition at line 216 of file ktempfile.cpp.
Returns the QTextStream for writing.
- Returns:
- QTextStream open for writing to the file, or 0 if opening the file failed
Definition at line 182 of file ktempfile.cpp.
Unlinks the file from the directory.
The file is deleted once the last reader/writer closes it.
Definition at line 202 of file ktempfile.cpp.
The documentation for this class was generated from the following files: | http://api.kde.org/3.5-api/kdelibs-apidocs/kdecore/html/classKTempFile.html | CC-MAIN-2015-35 | refinedweb | 675 | 67.35 |
Opened 5 years ago
Closed 5 years ago
#7200 closed Feature Requests (fixed)
Unable to build boost.thread modularized
Description
building cmake modularized boost.thread from master, using xcode 4.4 (apple llvm) fails on : /thread.cpp:27:10: fatal error:
'libs/thread/src/pthread/timeconv.inl' file not found
#include <libs/thread/src/pthread/timeconv.inl>
Replacing the include with : #include "timeconv.inl" passes.
I guess CMakeScript can not fix it, because there is no lib directory in include paths.
Attachments (1)
Change History (7)
comment:1 Changed 5 years ago by
comment:2 Changed 5 years ago by
I'm afraid that i'm not able to add parent of libs/thread to cmake file, because i was using this repository: github.com/ryppl/boost-zero.git
As it was mentioned at boost CMakeModularizationStatus wiki page, the repository above, already have an overlay cmake script, but the directory structure of that repository (after git cloning) looks like:
<root>
boost
...
thread
...
I think that there should not be any requirement for directory structure outside its own, because that would break the idea of modularization (it should depend only on libraries found by ryppl_find_and_use_package). Am i getting it wrong?
comment:3 Changed 5 years ago by
I don't know nothing about CMake and the modularization.
Changed to feature request as CMake is not supported yet.
comment:4 Changed 5 years ago by
Committed in trunk revision 80125. Committed in trunk revision 80126.
comment:5 Changed 5 years ago by
comment:6 Changed 5 years ago by
Changed 5 years ago by
khkgjfhgdytrutggvfdr7
I have replaced #include "timeconv.inl" by #include <libs/thread/src/pthread/timeconv.inl> as other platforms complains. Could you try to add the parent directory of libs/thread on the cmake file? | https://svn.boost.org/trac10/ticket/7200 | CC-MAIN-2017-47 | refinedweb | 296 | 58.38 |
IntelliJ IDEA 2020.3 EAP7: New UX for Extract Method Refactoring, Kubernetes Updates, SSR for Kotlin, and More
We’ve already covered many of the most prominent features that you will use in IntelliJ IDEA 2020.3 in previous EAP blog posts. However, we still have some more in store for you. In this blog post, you will discover a new UX for the Extract Method refactoring, learn how to open any file in IntelliJ IDEA by default, and get to know what’s new in IntelliJ IDEA for Kubernetes.
We invite you to test out all the new features by downloading the EAP from our website, installing it using the free Toolbox App, or updating to this latest EAP using snaps if you’re an Ubuntu user.
Java
New Extract Method layout
We’ve updated the UX for the Extract Method refactoring to make it faster and more accessible. When you select a code fragment you want to extract and press ⌥⌘M or select Refactor / Extract/Introduce / Method…, the IDE will refactor it immediately without displaying a dialog window.
After performing this refactoring, you can click the gear icon next to the method name and select additional settings in the drop-down list. If your method is extracted far from the initial location, it will be preserved in a separate frame. You can click on this frame to navigate back to the original code.
Kubernetes (Ultimate Edition)
Download logs
You can now download your pod logs to work with them locally – select a pod and click the Download Log button in the left pane of the Services tool window. The IDE will then open the downloaded pod in the editor.
By default, your pods will be saved to Scratches and Consoles | Kubernetes Files | “context” | “namespace” | pods.
There are several settings you can edit to customize the download process.
You can specify the download path for pod logs by going to Preferences / Settings | Build, Execution, Deployment | Kubernetes and changing it in the Pod Logs section. Notice that “context” | “namespace” | pods will be added to the specified path automatically.
You can also choose to specify the path every time a download commences. In this case, the logs will be saved to the exact location that you specify.
Another option in this section allows you to version your logs. If you tick the Append timestamp to pod log name when download checkbox, then each downloaded pod log will be saved separately with a timestamp in the file name. If this checkbox is clear, the IDE will overwrite the log with each new download.
Resources deletion
It is now possible to quickly delete any of your Kubernetes resources, either by clicking the garbage bin icon in the left pane of the Services tool window or by selecting Delete Resource from the context menu.
Open Console and Run Shell
You can connect containers that include consoles via Open Console, which you can invoke from the context menu or by clicking the Open Console button in the Services tool window.
If you want to launch Shell for a pod container, select Run Shell from the context menu or click the Run Shell button in the left pane of the Services tool window. The launched shell will then open in a new tab.
You can click the tools icon in the left pane of the Services tool window for quick access to Kubernetes settings. In the Pod Shell section, define which command to use for running a shell inside a container (by default, it is /bin/bash) and choose whether you want to apply this command to all projects or just to the current one.
Load CRDs from Kubernetes
Your CRD schemas provide a set of rules for creating Kubernetes resources. Currently, it is possible to load CRDs from files or from URLs. This is great, but CRDs can vary by cluster or context. For example, you can have three contexts with three different clusters. These clusters do not have the same CRDs, and they may have different versions as well.
In v2020.3, we’ve implemented a solution for such cases. In Preferences / Settings | Languages & Frameworks | Kubernetes, you can select the Use API schema from an active cluster checkbox to automatically load CRD schemas from an active cluster, if there are any.
Kotlin
Structural search and replace
In IntelliJ IDEA 2020.3 EAP7, we’ve introduced support for structural search and replace (SSR) actions for Kotlin. These allow you to find and replace code patterns, taking the syntax and semantics of the source code into account.
To invoke the Structural Search dialog, go to Edit | Find | Search Structurally…. Make sure that you have selected Kotlin as the file type. You can then write a search template or choose Existing Templates… by clicking the tools icon in the top right corner.
You can add filters for variables to narrow down your search. The following example demonstrates how to apply the Type filter:
And here is how the Text filter works:
Improved support of .editorconfig
The Kotlin plugin API fully supports an .editorconfig file that keeps your code formatting settings.
User Experience
Preview tab
Now you can open a file in a preview tab with a single click. To enable this feature, click the gear icon in the Project view and select both Enable Preview Tab and Open Files with Single Click. If you start editing a file opened in this way, it will cease to be a preview and will become an ordinary file.
Setting IntelliJ IDEA as the default application for opening files
Starting with v2020.3, you can make IntelliJ IDEA a default application for opening files. Go to Preferences | Settings / Editor / File Types and click the Associate file types with IntelliJ IDEA… button. In the dialog, select the extensions for files you wish to open in IntelliJ IDEA and click OK.
On macOS you have to restart your computer for changes to be applied.
The selected file extension associations will remain unchanged when you upgrade to a newer version of your IDE.
That’s it for this week! Test out the new features and share your thoughts in the comments below, on Twitter, or via our issue tracker.
If you want to learn more about other improvements coming in IntelliJ IDEA 2020.3, you can check out the release notes for a full list of EAP features.
Happy developing! | https://blog.jetbrains.com/idea/2020/11/intellij-idea-2020-3-eap7/ | CC-MAIN-2020-50 | refinedweb | 1,066 | 70.02 |
So far in this series I have emphasized how one of the great strengths of XML lies in how richly it adds to the developer's toolbox. Now we move to a closer look at many of these tools. One of the most important areas is in Application Programming Interfaces (APIs) that bind XML technologies to other programming and run-time environments. In this article, we shall look closely at the two preeminent APIs for XML: Simple API for XML (SAX) and Document Object Model (DOM). They represent two strongly contrasting processing models for XML, and as such have quite complementary sets of advantages and disadvantages. A basic understanding of XML is required, as well as familiarity with some object-oriented programming language.
SAX is a very interesting species. It was essentially created on a marathon thread on the XML-DEV mailing list, which has long been the prime habitat for XML experts. David Megginson led the discussion and the result was one of the most successful XML initiatives, with no large company or standards-body sponsorship.
SAX is an event-driven API. That is, the developer registers handler code for specific events triggered by different parts of XML mark-up (e.g. start and end tags, text, entities). The parser then sends a stream of these events based on the input XML, which the handler code processes in turn. Figure 1 is an illustration of this process.
The XML parser engine is tied to the SAX system through an appropriate driver, which causes SAX events to be fired in a stream as the parsing progresses. The developer will typically register handlers to capture these events and take appropriate action. This style of processing might be familiar to you if you have done user interface programming using popular systems such as Microsoft* Foundation Classes or many XWindows* APIs. If you are not, however, familiar with this style, such event-based processing might represent a somewhat novel way of thinking. Let us proceed with an example.
Listing 1 is a small SAX program that draws a crude graph of the tree structure of an XML document. It is written in Python*, so users of almost any OO language should be able to follow along.
In object-oriented languages, event-based interfaces are usually implemented by registering objects whose classes have special methods for each event. We define such a class, TreePrintHandler. If you compare with the event names in Figure 1, you will see that the methods in this class are similar to the event names. This is no coincidence: the SAX engine works by calling these particular methods whenever the corresponding event is dispatched. We derive TreePrintHandler from a built-in class, sax.ContentHandler, which provides a default in case we don't define a method to handle a particular event. Note that we don't implement every SAX event. We don't need to do anything special for the "end document" event, for example.
Very often in SAX programming, you need to keep track of where you are in the flow, or perhaps some values that will need to be used at some point. Managing such details is known as managing state. The information comes strictly in the order that the XML parser follows, which is not always the natural order for processing, so the SAX developer must be familiar with state management. Luckily, since we are using a class for event handling, this is not so difficult. You define instance variables that keep track of state. In the example program, the state to be managed is the depth of indentation reached.
The following is an example of running this program using Python, assuming you've copied Listing 1 to a file named listing1.py:
The SAX example shows how an object-oriented language is used to deal with event-based processing. However, the W3C also developed an object model for XML documents that can be used more directly. The Document Object Model (DOM) is the result of this effort. DOM is well known to Web developers as the way to manipulate forms and the like in an HTML Web browser. The XML aspect of DOM is much the same as the HTML aspect. The basic idea is that a document is decomposed into a tree model, where each component of the XML syntax is represented by a node. For instance, the following XML document can be represented by the tree illustrated in Figure 2.
Figure 2 - Click on image to enlarge
Each part of the document is a separate node in the tree. Notice the root node, labeled ("/"). This is a node that in effect represents the document as a whole. It has one element child, known as the document element (ADDR in our case). Elements can have other elements as children, as well as text nodes. Attributes are not quite considered children of their elements, so I represent them using a dashed line to what is known as their owner element. Attribute names are marked with an @ sign.
Imagine an API that allows you to navigate this tree, moving from parent to child node, to siblings, and other steps, taking advantage of special properties of certain types of nodes (for instance, elements can have attributes and text nodes have the text data). If you can imagine this, then you already have a basic handle on the DOM.
The DOM, like SAX, is designed to be language-neutral. In the case of the DOM, the generic interface definition language (IDL) standardized by the Object Management Group (OMG) is used to express the tree node interfaces. For instance, the interface for retrieving a particular attribute from an element is defined as follows:
This uses the special type DOMString to represent a string based on the rules for XML strings. This is typically translated into a method of the same name in the implementation language.
Again, an example should help illustrate. Listing 2 is a program that navigates and mutates an XML document using DOM.
Notice that some very important functions, such as converting XML source into a tree ready for DOM processing, and converting such a tree back to text, are not yet covered in the DOM standard. DOM is evolving through several "levels," each of which builds on the prior one. Level 1 covered the basics, Level 2 added namespace support, iterators, and so forth. Namespaces are a way to avoid clashes in XML element and attribute names. I'll discuss this in more detail in the next article in this series. Iterators are mechanisms for walking over the DOM tree, invoking some action for each node in turn. DOM Level 3 adds loading and saving trees, and other tools, but is still in development as of my writing. Be sure that the DOM library you choose has the support for XML features you need.
As you can see from the example, DOM trees can be manipulated and not just read. One must do this manipulation in small steps, though--by dissociating parents from children and attaching them to other parents. Using the DOM, you can also store arbitrary pointers to any nodes in the tree, and quickly jump to exactly the part you wish to process. If you copy Listing 2 to a file named listing2.py, you can try it out as follows:
DOM and SAX are quite different approaches to XML processing, and both are valuable tools to have around. In deciding when to use one or the other, there are several factors to consider.
- For many people, DOM is easier to understand than SAX at first, because it involves painstaking navigation of a tree that can be readily grasped.
- DOM, however, generally keeps all XML nodes in memory, which can be very inefficient for larger documents. State management in SAX can be very complex to set up. If your processing doesn't flow naturally with the document, it can be hard work.
- SAX tends to use much less memory because only the current bits of the event stream need be instantiated.
- Once you have dealt with any initial difficulties setting up SAX handlers, they tend to be more robust.
It is not unusual to use both in processing, for instance, in skimming over a large document using SAX and then building a small DOM tree for the portion of the document one wishes to process. Whether you need speed of development or speed of execution, regardless of what processing patterns you employ for each particular XML task, one or the other is probably the key to getting things done among the tags.
The XML-DEV mailing list home page:*
Simple API for XML (SAX) project home page:*
The W3C's home page for DOM:*
Read other articles in this series: Part 1, Part 2, Part 4, Part 5
For more complete information about compiler optimizations, see our Optimization Notice. | http://software.intel.com/en-us/articles/taking-applications-to-the-next-level-with-xml-part-3-the-toolbox-of-xml-apis/ | crawl-003 | refinedweb | 1,485 | 61.67 |
Whats better for complete a noob playing a rogue or a cleric
>>43095669
What system?
If it's 3.PF, Cleric, rogues are terrible and Clerics can be built as combat monsters.
If it's a balanced system, do you want to be clerical or roguish?
>>43095669
def cleric
Rogues are pretty difficult because they have to know about tactics to use their backstab/sneakattack.
If you're playing Pathfinder, pick up a Rogue. Not an Unchained Rogue, just a normal one.
If you're playing DnD 5e, do not pick Cleric under any circumstances, they are the weakest class.
>complete noob
>casters
Definitely start with something that doesn't have a bunch of spells to keep track of. Nothing is more frustrating than spending half a session while a guy fumbles through source books to figure out what he can do.
>>43095767
Clerics -> Weakest Class
Nigga, what?
WHAT?
How?
Fighter.
>>43095669
Complete noob here, I like Bard.
>>43096084
This for a complete noob.
>>43095767
>Caster
>Weakest
What?
>>43095669
Choose what appeals to you, learn that.
>>43095669
rogues are shit
clerics are not that easy
if complete noob give him a druid
he gets to summon a bear, and turn into a bear, and have a bear companion, and the three of them get to beargang up on people.
I'm a noob playing 3.5 as a rogue right now and it's going pretty well for me. Yes, I kinda suck at combat, but outside of it I do everything for the party. You get the most random trained skills out of anyone.
It really depends on whether you look forward to fighting or roleplaying more.
>>43095767
The cleric is one of the easiest classes to play but also the most fun one.
Half your personality is pretty much dictated by what god you chose, even someone totally new to the hobby can roleplay a decent cleric in their sleep as long as they read up on the character's religion a bit. That plus basically no restrictions on what you can build your character into.
>>43095767
>they are the weakest class.
That would be rangers.
For 3.5/PF I'd say cleric since you don't have to plan your feats and shit ahead as much
Otherwise it doesn't really matter.
>>43095669
Cleric. In order to fend off >>43095913, make some simple spell cards to represent your each daily spell selection with easy reference for effects. | https://4archive.org/board/tg/thread/43095669/whats-better-for-complete-a-noob-playing-a-rogue-or-a-cleric | CC-MAIN-2018-51 | refinedweb | 411 | 82.54 |
If you can get a spare SSD even a $95 Samsung EVO 250GB you can install it there and it is really easy. Recommend unplugging windows drive during the install to make things easier. You can do two things from there. Setup grub (boot loader) to configure for windows or just use bios boot selection (typically f8,f11,f12 on boot) to select which drive to boot.
Thanks again! I can't afford getting a new SSD, I have already a SSD running W10 and a HDD for data, so my idea is to either make some space in the SSD for Ubuntu (but that would be tight, I don't have much free space) or make a separate partition in the data HDD and then install Ubuntu there. In either case I'd like to set up a dual-boot with W10 booting by default.
@mgarrus and @Estiui here are the steps I did for my 64-bit Win7 with GTX 960 setup:
Install the CUDA ( and).
Then install CuDNN ().
Install Anaconda on your machine...
Now you want to create a GPU environment for Tensorflow and install all these packages into it (and any other packages you want to use):
Note that you HAVE to use Anaconda Python 3.5.... Tensorflow will only work with that specific version on Windows (not 2.7, not 3.6).
Whenever you want to use your new setup, pull up a Windows command prompt, and type this into it:
Change to whatever directory you want, then 'jupyter notebook' to start up Jupyter. It will automatically open a browser window in your default browser.
A few things to note:
Tensorflow uses different dimension ordering than Theano:
For 2D data (e.g. image), "tf" assumes (rows, cols, channels) while "th" assumes (channels, rows, cols).
For 3D data, "tf" assumes (conv_dim1, conv_dim2, conv_dim3, channels) while "th" assumes (channels, conv_dim1, conv_dim2, conv_dim3).
An alternate "quick and dirty" kludge for the class notebooks is to just specify "th" ordering in the keras.json file (in the .keras directory):
{"image_dim_ordering": "th","epsilon": 1e-07,"floatx": "float32","backend": "tensorflow"}
There are a few things you need to change for Python 3.5 -- such as cPickle becomes _Pickle... I don't remember what they all were, but it something worked in 2.7 but you get an error in 3.5, that's likely to be the problem.
I'm trying to remember if I missed anything..... but this is basically what I did. I hope this helps!
Christina
One more thing I did forget.... when specifying directories and files in the notebooks, you will have to use the Windows convention, not the linux, such as path = "data\\fish\\" instead of path = "data/fish/".
Thanks for your explanation, I'll have to see which is the easier way to go for me
@Christina
One thing that might make working with windows more palatable is the pathlib module in Python 3 - it reduces a lot of unnecessary text from os, os.path, glob, etc too.
E.g.
from pathlib import Path
basepath = Path('mypath')
# overloads '/' operator
train = basepath / 'train'
# can create directories without raising an error if it already exists
train.mkdir(parents=True, exist_ok=True)
assert train.exists(), 'does not exist'
assert train.is_dir(), 'not a directory'
#recursively search for files matching a pattern
file_gen = train.rglob('*.png')
filepath = next(file_gen)
#only issue is filepath is a Path object, not str
#some modules know how to deal with that
#others require str(filepath)
Thanks David, great point!
What an incredibly useful answer, Chris. Also a fan of your username spoonerism.
I believe you're referring to the Nvidia NVLink technology here:
But, as far as I can find, the tech seems to be for servers and workstations. Did not find any information about plans for a consumer version.
Yes, that's it. I couldn't find it quickly when I was on mobile. When I looked I couldn't tell if it was going to be exclusive to their high end cards or not either. My guess it very well maybe. They already crippled the Titan X and 10xx cards for machine learning, so it is no surprise this would be held back from them as well.
#deeplearningproblems
I found it annoying to have to constantly restart my jupyter notebooks
With this code then after a reboot jupyter notebook will just be running on the localhost:8888? And from a remote machine I would be able to use the code you gave to forward it with ssh to my laptop?
ssh -NL 8888:localhost:8888 user@host -p portnumber -i ~/.ssh/privatekey
This is awesome. Can't wait to set it up! Thanks @brendan.
I've set up an Ubuntu 16.04 box and configured it for access from my mac laptop via ssh. Everything works well, except sleeping/suspending. After I suspend my box I can use a magic packet to wake it from my phone or laptop either on or off my home lan. But if I wait more than about 15 or 20 minutes neither works.
Has anybody gotten wake on lan to work consistently from outside their home network?
Or should I just leave my rig running 24/7?
I wrote up the steps for setting up a server in Ubuntu (Windows dual boot). For the complete Ubuntu/Windows ignoramus, like I am, or was.
Perhaps someone could add it to the Wiki Installation pages?
Start----------------------------------------------------------------------------------------Setup Ubuntu local server, for beginners (including Windows dual boot)
This guide is geared toward beginners with Ubuntu and Windows, to get you set up for the course with minimal hassles. I will try to clearly lay out every step needed, without assuming that you already have prior skills with these OS's.
I do assume that you are starting with a PC and an nVidia GPU. This guide is current as of 18-March-2017. The Ubuntu version installed is 16.04.2 LTS. For other Ubuntu versions and and hardware, YMMV.
Making the Ubuntu Installer
In this section, we create the Ubuntu installer on a flash drive, from Windows. If you are not starting from Windows, you will need to create the installer a different way. You will need a USB flash drive, 2 GB or larger.
To create the bootable installer drive, follow the instructions at
Installing Ubuntu
You will be installing Ubuntu in its own partition, separate from the Windows partition. You may find instructions that recommend using the Windows Disk Manager to pre-allocate a partition for Ubuntu. This is neither necessary nor advised. WDM is limited in how much it can shrink the Windows partition because there are system files that cannot be moved while Windows runs. The Ubuntu installer itself can do the partitioning better than WDM because Windows is not running and can be shrunk further. Just know your ideal partition sizes before proceeding.
The Ubuntu installer advises that an internet connection will speed up the installation. Actually, a bug in the installer will cause the installation to fail partway through when there is an internet connection. So disconnect internet during the install, and don't waste time figuring this out.
Next, boot from the installer. This will likely require entering the BIOS screens to select the USB flash drive as the boot device.
The installer will let you choose "Install them side by side, choosing between them each startup" (for dual boot), and let you size the two partitions.
Once the installer finishes, remove the flash drive and boot from the hard drive. If all has gone well, you will see a menu that allows the choice between Ubuntu and Windows.
Navigating Ubuntu
At the top of the Launcher is a search tile that allows you to find programs quickly. Terminal is one you will be using soon. Note that Ctrl-v does not work in Terminal. You have to right-click and select Paste from the menu.
The next tile below is the file browser with your Home directory as the root. At this point, go to Edit->Preferences->Views. Select "Show hidden and backup files". You will need to edit some of these later.
System Settings (looks like a gear and wrench) gives access to many settings for personalizing Ubuntu. Be careful with the "Additional Drivers" tab. Ubuntu will offer to install a proprietary driver from nVidia. If you install it, you will be locked out of Ubuntu in a login screen loop. Instructions for escaping this situation are in the notes below.
Shutdown and reboot are found in the gear icon in the upper right corner.
Setting up the GPU and Course MaterialNote: do NOT install the nVidia drivers offered in System Settings->Additional Drivers.
Fortunately, several generous experts have created a script that does the setup automatically. The script is found at
If you are easy with git, you can get the script file directly. Or click the Raw link, and using Text Editor simply copy/paste into a local file named install-GPU.sh.
Note that the script has recently been revised to install an older version of Keras, the one that the course's code was designed for. Later you may want to update to the current Keras 2.
One small problem is that the script calls git, which is not yet installed. To install git, open a Terminal window and enter
sudo apt install git
Now it's time to run the script. From the Terminal window, enter
bash 'path-to/install-gpu.sh'(You may simply type "bash ", and drag the script file to Terminal to enter its path.)
Wait while the script runs.
As part of its operations, the script will install an up-to-date nVidia driver, one that does not have the boot loop problem. At some point, Ubuntu required me to enable Insecure Boot Mode and provided the steps. I do not recall when this occurred.
Reboot now.
Open Terminal, and enter
nvidia-smi
If all has gone well, you will see the GPU and its state.
Running the Notebooks
A configuration change makes this more convenient. Open the .jupyter invisible folder found in Home, and edit jupyter_notebook_config.py. Edit the matching line to
c.NotebookApp.notebook_dir = u'courses/deeplearning1/nbs/'
This way jupyter will always open to the notebooks directory.
Next, enter in Terminal
jupyter notebook
To access the jupyter server, open a browser window and go to
You should see a file list that contains the lesson notebooks for the course. Open one of them and you are ready to work.
Random Notes
Inside a jupyter notebook, use shift-enter to run a cell.
To monitor GPU load, enter in a second Terminal,watch nvidia-smi
Run Software Updater to get security updates that were not part of the installer.
To escape from the nVidia driver boot loop, at login type Ctrl + Alt + F1. At the login prompt, type your user name all lowercase, then your password. This is called TTY login.
typesudo apt-get purge nvidia-*
and reboot.
gksu nautilus
End---------------------------------------------------------------------------------------------------------------
Also, feel free to edit and correct.
On to Lesson 2!
Malcolm
So I just got my 1080 Ti and did a quick run on CatsDogs. First fit time was 190s vs 245 on my old 1080.
Good idea - and thanks! We'll add it.
You should be able to do a lot better than that, I get 229s on a 1070 and when I calculated the cuda stats and terraflops I guestimated you can hit around 140s. I'm waiting for the Gamer X editions to come out with the proper cooling and higher stock clocks.
Hi Malcolm
Thanks for the information I would like to add a fresh disk for linux I guess the dual boot would work in this situation. I have done this before a long long time ago (10+ years ago pre 64 bit) with mixed results, drivers for video cards etc.
If I get to the point of having my USB install then before installing linux install the additional hard drive then run the USB install would there be any issues you can think of. Or does windows 7 need to know about the drive
Thanks
I let the Ubuntu installer re-partition the existing Windows drive. So I imagine the installer would have no trouble formatting and installing onto a separate drive. Windows does not need to know anything.
The only trouble I have with Ubuntu 16.0.4 is that after Suspend, open windows come back stuck to screen garbage. The only cure is to reboot.
Can anyone recommend a hardware / computer store in San Francisco who can assemble a deep learning box? I talked to Central Computer but their Ubuntu guy has been out for months due to family emergency and they will only install Windows. Checked on Yelp but other stores seemed to be mostly focused on minor repairs, not custom boxes. | http://forums.fast.ai/t/making-your-own-server/174?page=10 | CC-MAIN-2017-51 | refinedweb | 2,156 | 73.88 |
Hi all,
When we set the hadoop configuration, we specify a storage directory path.
Once we start running the cluster, we see some directories getting created
inside that specified path.
Current, Detach, tmp, storage.
1. Current directory is the actual storage directory, which is in
accordance with the namespace of the datanode.
2. tmp directory is a temporary directory used for creating Blocks
temporarily in this directory. And when finalized these blocks are moved to
current directory.
3. storage is a file which encodes the storageID of the volume.
*4. Detach:Any idea why this directory is maintained?*
*
*
Correct me, if i am wrong in interpreting the functionality's of the other
directories.
Thanks,
Kartheek. | http://mail-archives.apache.org/mod_mbox/hadoop-hdfs-dev/201112.mbox/%3CCANAqB2hbeHqAod2Jx-tiKEB1C1apgswd7zUEgMD8HjZDetgmsQ@mail.gmail.com%3E | CC-MAIN-2014-41 | refinedweb | 115 | 50.23 |
Displaying and editing an object using the DataForm
Letting a user work with groups of related data is a requirement of almost every application. It includes displaying a group of people, editing product details, and so on. These groups of data are generally contained in forms and the Silverlight DataForm (from the Silverlight Toolkit) is just that—a form.
In the next few recipes, you'll learn how to work with this DataForm. As of now, let's start off with the basics, that is, displaying and editing the data.
Getting ready
For this recipe, we're starting with a blank solution, but you do need to install the Silverlight Toolkit as the assemblies containing the DataForm are offered through this. You can download and install it from. You can find the completed solution in the Chapter05/Dataform_DisplayAndEdit_Completed folder in the code bundle that is available on the Packt website.
How to do it...
We're going to create a Person object, which will be displayed through a DataForm. To achieve this, we'll carry out the following steps:
- Start a new Silverlight solution, name it DataFormExample, and add a reference to System.Windows.Controls.Data.DataForm.Toolkit (from the Silverlight Toolkit). Alternatively, you can drag the DataForm from the Toolbox to the design surface.
- Open MainPage.xaml and add a namespace import statement at the top of this fi le (in the
tag) as shown in the following code. This will allow us to use the DataForm, which resides in the assembly that we've just referenced.
xmlns:df="clr-namespace:System.Windows.Controls;
assembly=System.Windows.Controls.Data.DataForm.Toolkit"
- Add a DataForm to MainPage.xaml and name it as myDataForm. In the DataForm, set AutoEdit to False and CommandButtonsVisibility to All as shown in the following code:
<Grid x:
<Grid.RowDefinitions>
<RowDefinition Height="40" ></RowDefinition>
<RowDefinition></RowDefinition>
</Grid.RowDefinitions>
<TextBlock Text="Working with the DataForm"
Margin="10"
FontSize="14" >
</TextBlock>
<df:DataForm x:Name="myDataForm"
AutoEdit="False"
CommandButtonsVisibility="All"
Grid.
</df:DataForm>
</Grid>
- Add a new class named Person to the Silverlight project having ID, FirstName, LastName, and DateOfBirth as its properties. This class is shown in the following code. We will visualize an instance of the Person class using the DataForm.
public class Person
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime DateOfBirth { get; set; }
}
- Open MainPage.xaml.cs and add a person property of the Person type to it. Also, create a method named InitializePerson in which we'll initialize this property as shown in the following code:
public Person person { get; set; }
private void InitializePerson()
{
person = new Person()
{
ID = 1,
FirstName = "Kevin",
LastName = "Dockx",
DateOfBirth = new DateTime(1981, 5, 5)
};
}
- Add a call to InitializePerson in the constructor of MainPage.xaml.cs and set the CurrentItem property of the DataForm to a person as shown in the following code:
InitializePerson();
myDataForm.CurrentItem = person;
- You can now build and run your solution. When you do this, you'll see a DataForm that has automatically generated the necessary fields in order to display a person. This can be seen in the following screenshot:
How it works...
To start off, we needed something to display in our DataForm: a Person entity. This is why we've created the Person class: it will be bound to the DataForm by setting the CurrentItem property to an object of type Person.
Doing this will make sure that the DataForm automatically generates the necessary fi elds. It looks at all the public properties of our Person object and generates the correct control depending on the type. A string will be displayed as a TextBox, a Boolean value will be displayed as a CheckBox, and so on.
As we have set the CommandButtonsVisibility property on the DataForm to All, we get an Edit icon in the command bar at the top of the DataForm. (Setting AutoEdit to False makes sure that we start in the display mode, rather than the edit mode). When you click on the Edit icon, the DataForm shows the person in the editable mode (using the EditItemTemplate) and an OK button appears. Clicking on the OK button will revert the form to the regular displaying mode. Do keep in mind that the changes you make to the person are persisted immediately in memory (in the case of a TextBox, when it loses focus).
If necessary, you can write extra code to persist the Person object from the memory to an underlying datastore by handling the ItemEditEnded event on the DataForm.
There's more...
At this moment, we've got a DataForm displaying a single item that you can either view or edit. But what if you want to cancel your edit? As of now, the Cancel button appears to be disabled. As the changes you make in the DataForm are immediately persisted to the underlying object in the memory, cancelling the edit would require some extra business logic. Luckily, it's not hard to do.
First of all, you'll want to implement the IEditableObject interface on the Person class, which will make sure that cancelling is possible. As a result, the Cancel button will no longer be disabled. The following code is used to implement this:
public class Person : IEditableObject
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime DateOfBirth { get; set; }
public void BeginEdit()
{}
public void CancelEdit()
{}
public void EndEdit()
{}
}
This interface exposes three methods: BeginEdit, CancelEdit, and EndEdit. If needed, you can write extra business logic in these methods, which is exactly what we need to do. For most applications, you might want to implement only CancelEdit, which would then refetch the person from the underlying data store. In our example, we're going to solve this problem by using a different approach. (You can use this approach if you haven't got an underlying database from which your data can be refetched, or if you don't want to access the database again.) In the BeginEdit method, we save the current property values of the person. When the edit has been cancelled, we put them back to the way they were before. This is shown in the following code:
public void BeginEdit()
{
// save current values
tmpPerson = new Person()
{
ID = this.ID,
FirstName = this.FirstName,
LastName = this.LastName,
DateOfBirth = this.DateOfBirth
};
}
public void CancelEdit()
{
// reset values
ID = tmpPerson.ID;
FirstName = tmpPerson.FirstName;
LastName = tmpPerson.LastName;
DateOfBirth = tmpPerson.DateOfBirth;
}
Now, cancelling an edit is possible and it actually reverts to the previous property values.
More on DataForm behavior
The DataForm exposes various events such as BeginningEdit (when you begin to edit an item), EditEnding (occurs just before an item is saved), and EditEnded (occurs after an item has been saved). It also exposes properties that you can use to defi ne how the DataForm behaves.
Validating a DataForm or a DataGrid
As you might have noticed, the DataForm includes validation on your fields automatically. For example, try inputting a string value into the ID field. You'll see that an error message appears. This is beyond the scope of this recipe, but more on this will be discussed in the Validating the DataForm recipe.
Managing the editing of an object on different levels
There are different levels of managing the editing of an object. You can manage this on the control level itself by handling events such as BeginningEdit or ItemEditEnded in the DataForm. Besides that, you can also handle editing on a business level by implementing the IEditableObject interface and providing custom code for the BeginEdit, CancelEdit, or EndEdit methods in the class itself. Depending on the requirements of your application, you can use either of the levels or even both together.
See also
In this recipe, we've seen how the DataForm is created automatically. For most applications, you require more control over how your fi elds, for example, are displayed. The DataForm is highly customizable, both on a template level (through template customization) and on how the data is generated (through data annotations). If you want to learn about using the DataForm to display or edit a list of items rather than just one, have a look at the next recipe, Displaying and editing a collection using the DataForm.
Displaying and editing a collection using the DataForm
In the previous recipe, you learned how to work with the basic features of the DataForm. You can now visualize and edit an entity. But in most applications, this isn't enough. Often, you'll want to have an application that shows you a list of items with the ability to add a new item or delete an item from the list. You'll want the application to allow you to edit every item and provide an easy way of navigating between them. A good example of this would be an application that allows you to manage a list of employees.
The DataForm can do all of this and most of it is built-in. In this recipe, you'll learn how to achieve this.
Getting ready
For this recipe, we're starting with the basic setup that we completed in the previous recipe. If you didn't complete that recipe, you can find a starter solution in the Chapter05/ Dataform_Collection_Starter folder in the code bundle that is available on the Packt website. The finished solution for this recipe can be found in the Chapter05/Dataform_ Collection_Completed folder.
In any case, you'll need to install the Silverlight Toolkit as the assemblies containing the DataForm are offered through it. You can download and install it from.
How to do it...
We're going to create an application that visualizes a list of people using the DataForm. In order to achieve this, carry out the following steps. (If you're starting from a blank solution, you'll need to add a DataForm to your MainPage and create a Person class having ID, FirstName, LastName, and DateOfBirth as its properties.)
- Open MainPage.xaml.cs and add a new property called lstPerson of the ObservableCollection type of Person to it. This is shown in the following line of code:
public ObservableCollection<Person> lstPerson { get; set; }
- Create a new method called InitializePersons(), which is used to initialize lstPerson. This is shown in the following code:
private void InitializePersons()
{
lstPerson = new ObservableCollection<Person>()
{
new Person()
{
ID=1,
FirstName="Kevin",
LastName="Dockx",
DateOfBirth = new DateTime(1981, 5, 5)
},
new Person()
{
ID=2,
FirstName="Gill",
LastName="Cleeren",
DateOfBirth = new DateTime(2009, 1, 1)
},
new Person()
{
ID=3,
FirstName="Judy",
LastName="Garland",
DateOfBirth = new DateTime(1922, 6, 10)
}
};
}
- In the MainPage constructor, call the InitializePersons() method and set the ItemsSource property of myDataForm to lstPerson as shown in the following code:
public MainPage()
{
InitializeComponent();
InitializePersons();
myDataForm.ItemsSource = lstPerson;
}
- You can now build and run the solution. You'll notice that you can navigate through the list of persons in the DataForm by using the navigation buttons at the top of the DataForm. This can be seen in the following screenshot:
How it works...
In the previous recipe, we set the CurrentItem property of the DataForm to a Person object. This recipe builds on that, but instead of setting the CurrentItem property, we bind the ItemsSource property to our ObservableCollection of Person. While doing this, the DataForm will automatically generate navigation buttons to navigate through the collection and will also generate an Add and a Delete button. In order to access the current item, you can refer to the CurrentItem property, which will change automatically while navigating through the list.
There's more...
In order to change the behavior of the DataForm, you can set a variety of its properties on the DataForm. AutoCommit makes sure changes are saved if the user navigates through the list without clicking on the OK button, while AutoEdit makes sure the DataForm automatically goes in Edit mode when the user selects a record. CancelButtonContent sets the content for the Cancel button. (You need to implement IEditableObject on your Person class for this button to be enabled. Have a look at the previous recipe for more information on this.) CommitButtonContent sets the content for the OK button.
In order to change the ability to add or delete items, you can easily change the CommandButtonsVisibility property to show or hide the corresponding buttons.
Along with that, the DataForm exposes a few events specifi cally for use while binding to collections. AddingNewItem is fi red just before an item is added to the collection, DeletingItem is fi red just before an item is deleted, and CurrentItemChanged is fi red when the current item has been changed (which happens when you navigate through the list of items, or when you add or delete an item).
See also
In this recipe, we've used an ObservableCollection that is bound to the ItemsSource property of the DataForm.
For most applications, you'll require more control over how your fields (for example) are displayed. The DataForm is highly customizable, both on a template level (through template customization) and on how the data is generated (through Data Annotations).
Validating the DataForm
Validation of your data is a requirement for almost every application to make sure that no invalid input is possible. If you're using a DataForm, you can easily implement validation by using Data Annotations on your classes or properties. This control picks up these validation rules automatically and even provides visual feedback. In this recipe, you'll learn how to implement this kind of validation for a DataForm.
Getting ready
We're starting from the solution that we competed in the Displaying and editing a collection using the DataForm recipe. If you didn't complete that recipe, you can fi nd a starter solution located in the Chapter05\Dataform_Validation_Starter folder in the code bundle that is available on the Packt website. The finished solution for this recipe can be found in the Chapter05\Dataform_Validation_Completed folder.
In any case, you'll need to install the Silverlight Toolkit as the assemblies containing the DataForm are offered through it. You can download and install it from.
How to do it...
If you're starting from a blank solution, you'll need to add a DataForm to your MainPage and create a Person class having ID, FirstName, LastName, and DateOfBirth as its properties. The DataForm on the MainPage should be bound to an ObservableCollection of Person.
We're going to make sure that the DataForm reacts to the validation attributes we'll add to the Person class. To achieve this, carry out the following steps:
- Add a reference to System.ComponentModel.DataAnnotations in your Silverlight project.
- Open the Person class and add the following attributes to the FirstName property of this class:
[StringLength(30, MinimumLength=3,
ErrorMessage="First name should have between 3 and 30
characters")]
[Required(ErrorMessage="First name is required")]
public string FirstName { get; set; }
- We can now build and run our solution. When you enter invalid data in the FirstName field, you notice that you get visual feedback for these validation errors and you aren't able to persist your changes unless they are valid. This can be seen in the following screenshot:
How it works...
We've added Data Annotations such as the RequiredAttribute and the StringLengthAttribute to the FirstName property in the Person class. These Data Annotations respectively tell any control that can interpret them that the FirstName is required and it should have between 3 and 30 characters. We've also added a custom error message for both the Data Annotations by fi lling out the ErrorMessage NamedParameter.
As a DataForm is able to look for these validation rules automatically, it will show validation errors if the validation fails. This feature comes out of the box with a DataForm, without you having to do any of the work. Therefore, you can easily enable validation by just using Data Annotations.
By using named parameters in the constructors of your attributes, you can further customize how the attribute should behave. For example, ErrorMessage enables you to customize the message that is shown when validation fails.
There's more...
In this recipe, we've used just a few of the possible data annotations. DataTypeAttribute, RangeAttribute, RegularExpressionAttribute, RequiredAttribute, StringLengthAttribute, and CustomValidationAttribute are all of the data annotations at your disposal.
For all of these attributes, named parameters are possible in order to further customize the way validation should occur. ErrorMessage, ErrorMessageResourceName, and ErrorMessageResourceType are available on all attributes, but many more are available depending on the attribute you use. You can check them by looking at the IntelliSense tooltip you get on the attribute constructor.
Other uses of Data Annotations
In the other recipes of this article, you've already noticed that other non-validating data attributes exist such as the display attributes and the mode attributes. These attributes are used to control how certain information should be displayed or how certain properties should relate to each other
RIA Services and Data Annotations
Data Annotations are heavily used in combination with WCF RIA Services.
Summary
In this article, we learnt:
- Displaying and editing an object using the DataForm
- Displaying and editing a collection using the DataForm
- Validating the DataForm
If you have read this article you may be interested to view : | https://www.packtpub.com/books/content/working-dataform-microsoft-silverlight-4 | CC-MAIN-2015-14 | refinedweb | 2,881 | 52.9 |
This module is a code generator, it can read Django models and outputs corresponding ones for schematics.
Of course, this is code generation, therefore a damn bad idea. This won’t keep your stuff synced.
It’s still useful, however. Sometimes you’re converting a large Django code base to domain models in schematics. In those cases, it’s a royal pain to mechanically retype hundreds of models and thousands of field definitions by hand. We have computers for that, you know.
You can either run this as a stand alone script or use it as a library.
Add django2schematics to your INSTALLED_APPS settings. Then:
python manage.py 2_schematics app_name
You can specify full apps or models to export. By default the script will output to stdout. The –to-file flag will save each app models into [app-dir]/domain-raw.py.
See –help for more options.
If you’d rather process the ouput your self then:
from django2scheamtics.exporter import SchematicsModel SchematicsModel.from_django(the_model_class) # or as a string SchematicsModel.from_django(the_model_class).to_string()
Let me know if this works (or doesn’t) for you. Feedback is always welcome.
Feedback with accompanying pull requests and tests will buy you a beer on me next time you’re in São Paulo. Or tea, if that’s your. | https://pypi.org/project/Django2Schematics/ | CC-MAIN-2017-09 | refinedweb | 215 | 70.5 |
AWS is, in my humble opinion, pricy. However, they provide a nice alternative to the on-demand EC2 instances most people are familiar with: Spot instances. In essence, spot instances allow you to bid on otherwise compute idle time. Recent changes to the web console seem to highlight spot instances a bit more than they used to, but I still don't see them mentioned often.
The advantage is you get the same selection of instance sizes, and they perform the same as a normal on-demand instance for (usually) a fraction of the price. The downside is that they may disappear at a moment's notice if there's not enough spare capacity when someone else spins up a normal on-demand instance, or simply outbids you. It certainly happened to us on occasion, but not as frequently as I originally expected. They also take a couple minutes to evaluate the bid price when you put in a request, which can be a bit of a surprise if you're used to the almost-instantaneous on-demand instance provision time.
We made extensive use of spot instances in some of the software cluster testing we recently did. For our purposes those caveats were no big deal. If we got outbid, the test could always be restarted in a different Availability Zone with a little more capacity, or we just waited until the demand went down.
At the height of our testing we were spinning up 300 m1.xlarge instances at once. Even when getting the best price for those spot instances, the cost of running a cluster that large adds up quickly! Automation was very important. Our test scripts took hold of the entire process, from spinning up the needed instances, kicking off the test procedure and keeping an eye on it, retrieving the results (and all the server metrics, too) once done, then destroying the instances at the end.
Here's how we did it:
In terms of high level key components, first, that test driver script was home-grown and fairly specific to the task. Something like Chef could have been taught to spin up spot instances, but those types of configuration management tools are better at keeping systems up and running. We needed the ability to run a task, and immediately shut down the instances when done. That script was written in Python, and leans on the boto library to control the instances.
Second, a persistent 'head node' was kept up and running as a normal instance. This ran a Postgres instance and provided a centralized place for the worker nodes to report back to. Why Postgres? I needed a simple way to number and count the nodes in a way immune to race conditions, and sequences were what came to mind. It also gave us a place to collect the test results and system metrics, and compress down before transferring out from AWS.
Third, customized AMI's were used. Why script the installation of ssh keys, Java, YCSB or Cassandra or whatever, system configuration like our hyper 10-second interval sysstat, application parameters, etc, onto each of those 300 stock instances? Do it once on a tiny micro instance, get it how you want it, and snapshot the thing into an AMI. Everything's ready to go from the start.
There, those are the puzzle pieces. Now how does it all fit together?
When kicking off a test we give the script a name, a test type, a data node count, and maybe a couple other basic parameters if needed. The script performs the calculations for dataset size, number of client nodes needed to drive those data nodes, etc. Once it has all that figured out the script creates two tables in Postgres, one for data nodes and one for client nodes, and then fires off two batch requests for spot instances. We give them a launch group name to make sure they're all started in the same AZ, our customized AMI, a bit of userdata, and a bid price:
max_price = '0.10' instance_type = 'm1.xlarge' #(snip) ec2.request_spot_instances( max_price, ami, instance_type=instance_type, count=count, launch_group=test_name, availability_zone_group=test_name, security_groups=['epstatic'], user_data=user_data, block_device_map=bdmap )
Okay, at this point I'll admit the AMI's weren't quite that simple, as there's still some configuration that needs to happen on instance start-up. Luckily AWS gives us a handy way to do that directly from the API. When making its request for a bunch of spot instances, our script sets a block of userdata in the call. When userdata is formulated as text that appears to be a script -- starting with a shebang, like #!/bin/bash -- that script is executed on first boot. (If you have cloud-init in your AMI's, to be specific, but that's a separate conversation.) We leaned on that to relay test name and identifier, test parameters, and anything else our driver script needed to communicate to the instances at start. That thus became the glue that tied the instances back to the script execution. It also let us run multiple tests in parallel.
You may have also noticed the call explicitly specifies the block device map. This overrides any default mapping that may (or may not) be built into the selected AMI. We typically spun up micro instances when making changes to the images, and as those don't have any instance storage available we couldn't preconfigure that in the AMI. Setting it manually looks something like:
from boto.ec2.blockdevicemapping import BlockDeviceMapping, BlockDeviceType bdmap = BlockDeviceMapping() sdb = BlockDeviceType() sdb.ephemeral_name = 'ephemeral0' bdmap['/dev/sdb'] = sdb sdc = BlockDeviceType() sdc.ephemeral_name = 'ephemeral1' bdmap['/dev/sdc'] = sdc sdd = BlockDeviceType() sdd.ephemeral_name = 'ephemeral2' bdmap['/dev/sdd'] = sdd sde = BlockDeviceType() sde.ephemeral_name = 'ephemeral3' bdmap['/dev/sde'] = sde
Then, we wait. The process AWS goes through to evalutate, provision, and boot takes a number of minutes. The script actually goes through a couple of stages at this point. Initially we only watched the tables in the Postgres database, and once the right number of instances reported in, the test was allowed to continue. But we soon learned that not all EC2 instances start as they should. Now the script gets the expected instance ID's, and tells us which ones haven't reported in. If a few minutes pass, and one or two still aren't reporting in (more on that in a bit) we know exactly which instances are having problems, and can fire up replacements.
An example output from the test script log, if i-a2c4bfd1 doesn't show up soon and we can't connect to it ourselves, we can be confident it's never going to check in:
2014-01-02 05:01:46 Requesting node allocation from AWS... 2014-01-02 05:02:50 Still waiting on start-up of 300 nodes... 2014-01-02 05:03:51 Still waiting on start-up of 5 nodes... 2014-01-02 05:04:52 Checking that all nodes have reported in... 2014-01-02 05:05:02 I see 294/300 data servers reporting... 2014-01-02 05:05:02 Missing Instances: i-e833499b,i-d63349a5,i-d43349a7,i-c63349b5,i-a2c4bfd1,i-d03349a3 2014-01-02 05:05:12 I see 294/300 data servers reporting... 2014-01-02 05:05:12 Missing Instances: i-e833499b,i-d63349a5,i-d43349a7,i-c63349b5,i-a2c4bfd1,i-d03349a3 2014-01-02 05:05:22 I see 296/300 data servers reporting... 2014-01-02 05:05:22 Missing Instances: i-e833499b,i-c63349b5,i-a2c4bfd1,i-d63349a5 2014-01-02 05:05:32 I see 298/300 data servers reporting... 2014-01-02 05:05:32 Missing Instances: i-a2c4bfd1,i-e833499b 2014-01-02 05:05:42 I see 298/300 data servers reporting... 2014-01-02 05:05:42 Missing Instances: i-a2c4bfd1,i-e833499b 2014-01-02 05:05:52 I see 299/300 data servers reporting... 2014-01-02 05:05:52 Missing Instances: i-a2c4bfd1 2014-01-02 05:06:02 I see 299/300 data servers reporting... 2014-01-02 05:06:02 Missing Instances: i-a2c4bfd1 2014-01-02 05:06:12 I see 299/300 data servers reporting... 2014-01-02 05:06:12 Missing Instances: i-a2c4bfd1 2014-01-02 05:06:22 I see 299/300 data servers reporting... 2014-01-02 05:06:22 Missing Instances: i-a2c4bfd1 2014-01-02 05:06:32 I see 299/300 data servers reporting... 2014-01-02 05:06:32 Missing Instances: i-a2c4bfd1
Meanwhile on the AWS side, as each instance starts up that userdata mini-script writes out its configuration to various files. The instance then kicks off a phone home script, which connects back to the Postgres instance on the head node, adds its own ID, IP address, and hostname, and receives back its node number. (Hurray INSERT ... RETURNING!) It also discovers any local instance storage it has, and configures that automatically. The node is then configured for its application role, which may depend on what it's discovered so far. For example, nodes 2-n the Cassandra cluster will look up the IP address for node 1, and use that for its gossip host, as well as use their node numbers for the ring position calculation. Voila, hands-free cluster creation for Cassandra, MongoDB, or whatever we need.
Back on the script side, once everything's reported in and running as expected, a sanity check is run on the nodes. For example with Cassandra it checks that the ring reports the correct number of data nodes, or similarly for MongoDB that the correct number of shard servers are present. If something's wrong, the human that kicked off the test (who hopefully hasn't run off to dinner expecting that all is well at this point) is given the opportunity to correct the problem. Otherwise, we continue with the tests, and the client nodes are all instructed to begin their work at the same time, beginning with the initial data load phase.
Coordinated parallel execution isn't easy. Spin off threads within the Python script and wait until each returns? Set up asynchronous connections to each, and poll to see when each is done? Nah, pipe the node IP address list using the subprocess module to:
xargs -P (node count) -n 1 -I {} ssh root@{} (command)
It almost feels like cheating. Each step is distributed to all the client nodes at once, and doesn't return until all of the nodes complete.
Between each step, we perform a little sanity check, and push out a sysstat comment. Not strictly necessary, but if we're looking through a server's metrics it makes it easy to see which phase/test we're looking at, rather than try to refer back to timestamps.
run_across_nodes(data_nodes+client_nodes, "/usr/lib/sysstat/sadc -C \\'Workload {0} finished.\\' -".format(workload))
When the tests are all done, it's just a matter of collecting the test results (the output from the load generators) and the metrics. The files are simply scp'd down from all the nodes. The script then issues terminate() commands to AWS for each of the instances it's used, and considers itself done.
Fun AWS facts we learned along the way:
Roughly 1% of the instances we spun up were duds. I didn't record any hard numbers, but we routinely had instances that never made it through the boot process to report in, or weren't at all accessible over the network. Occasionally it seemed like shortly after those were terminated, a subsequent run would be more likely to get a dud instance. Presumably I was just landing back on the same faulty hardware. I eventually learned to leave the dead ones running long enough to kick off the tests I wanted, then terminate them once everything else was running smoothly.
On rare occasion, instances were left running after the script completed. I never got around to figuring out if it was a script bug or if AWS didn't act on a .terminate() command, but I soon learned to keep an eye on the running instance list to make sure everything was shut down when all the test runs were done for the day. | http://blog.endpoint.com/2014/01/spot-on-cost-effective-performance.html | CC-MAIN-2017-13 | refinedweb | 2,056 | 70.43 |
2009/2/13 An updated version of this article using Ubuntu Intrepid can be viewed here.
In my previous setup there were some concerns with the way I was using mod_proxy. The issue is that a request comes in and is received by Apache, if it was a media file Apache would then pass the request to Lighttpd, which would pass the file to Apache, which would then pass the file to the requester. Obviously, this is batshit crazy.
This is why I have reworked my instructions with fewer catastrophic mental lapses. The article has also been reworked for conciseness, and all sections on security have been removed, you can refer back to the original article, but should ideally look for a more specialized resource on securing your server.
The bulk of the process is unchanged, but we will now be using Nginx as a frontend proxy and static media server, and Apache2 with mod_python as the backend server for handling Django. Lighttpd has been dropped in favor of Nginx mostly because Nginx is from Russia, and is thus exotic.
Also relevant is the fact that Lighttpd has an annoying memory leak.
End Product
The end product is still an Ubuntu Feisty server. It will use Nginx as its frontend server (handling media, and proxying other requests to Apache2), and Apache2 as its backend server. It will use memcached for caching, and Postgres8.2 for its database. Django will be our framework of choice.
On to the fun stuff.
Credits and resources can be found in the original article.
Upgrading Ubuntu Dapper to Feisty
Upgrading from Ubuntu Dapper (SliceHost's current Ubuntu OS) to Feisty is quick and painless. You do need to do the upgrades in order: skipping straight to Feisty may make your installation unstable. The final 'lsb_release -a' is simply to confirm that the upgrade has occured. It should confirm that Feisty is installed.
### My article 1. My list entry one 2. My list entry two <code class="python">def x (a, b): return a * b</code>
Adding Apache & Other Libraries
Note: psyco_pg2 in the Ubuntu repository appears to be broken, which is why we are installing it with easy_install instead of apt-get.
### My article 1. My list entry one 2. My list entry two @@ python def x (a, b): return a * b
Setting up nginx
First we need to setup nginx. We will be using the configuration file provided in this article at blog.kovyrin.net. The file is available for download right underneath the sytax highlighted code snippet.
Open up your nginx.conf file:
import myproject.myapp.markdownpp as markdownpp
Then completely delete the contents of the file, and replace them with the contents of the configuration file that we are borrowing from kovyrin.net.
You will have to make several minor changes to the config file:
- Replace "some-server.com" with your actual domain.
- For the static file location change the long regular expression to /media/
- Change the root directory in the static media location to /var/www/yourdomain.com/
So the first altered part will look like this
class Entry(models.Model): title = models.CharField(maxlength=200) body = models.TextField() body_html = models.TextField(blank=True, null=True) use_markdown = models.BooleanField(default=True)
(Yes, I acknowledge how totally unhelpful it is to change the example from some-server.com to yourdomain.com.)
And the second portion will look like
def save(self): if self.use_markdown: self.body_html = markdownpp.markdown(self.html) else: self.body_html = self.body super(Entry,self).save()
We are changing the regular expression to /media/ because we no longer have to perform a number of regular expression matches. Admittedly, the performance increase is probably minimal.
Now lets create a few folders:
class Resource(models.Model): title = models.CharField(maxlength=50) markdown_id = models.CharField(maxlength=50) content = models.FileField(upload_to="myapp/resource")
Okay, now we deal with Apache.
Setting up Apache
The first step is to change the port apache is running on:
class Entry(models.Model): title = models.CharField(maxlength=200) body = models.TextField() body_html = models.TextField(blank=True, null=True) use_markdown = models.BooleanField(default=True)
Change it to 8080 instead of 80. Save the file.
Now we need to make our log folder:()
Then we'll need to edit our apache config file:
refs = entry.resources.all()
That will initially be an empty file, and you'll be adding this to it:
def save: super(Entry,self).save() res = self.resources.all() # etc etc super(Entry,self).save()
Finally we need to enable the virtual host:
import time, thread from django.db import models from django.dispatch import dispatcher from django.db.models import signals ####################### ### your models go here ### #######################
Starting nginx and Apache
Now that we have our two servers running, we need to turn them on.
Go visit and you should get a default Apache page.
Go visit and... you should still get a default Apache page. Only this time if you look at the headers you'll be getting it served via nginx.
Now lets double check that nginx is serving static media like we want it to:
resave_hist = {} dispatcher.connect(resave_object, signal=signals.post_save, sender=Entry)
Write a couple words into the file, save it, and then browse to . It should show your file. Browse to, it shouldn't show the apache page.
Now turn Apache back on:
and delete that file
And our servers are setup.
PostgreSQL
Make sure to use your own password instead of just 'password' in the code below.
qaodmasdkwaspemas15ajkqlsmdqpakldnzsdfls
And then we edit the pg_hba.conf file.
qaodmasdkwaspemas16ajkqlsmdqpakldnzsdfls
Go to the end of the file and comment out all lines that start with host (unless you will be accessing your database remotely). Finally the local line should look like
qaodmasdkwaspemas17ajkqlsmdqpakldnzsdfls
Finally we'll want to restart Postgres:
qaodmasdkwaspemas18ajkqlsmdqpakldnzsdfls
Configuring memcached
Running memcached is easy:
qaodmasdkwaspemas19ajkqlsmdqpakldnzsdfls:
qaodmasdkwaspemas20ajkqlsmdqpakldnzsdfls Django, etc
First lets create a non-root user, it'll hold all our django files. For these examples it will be user django.
qaodmasdkwaspemas21ajkqlsmdqpakldnzsdfls
Now we are going to setup Django. We will first create a postgres user for our Django app:
qaodmasdkwaspemas22ajkqlsmdqpakldnzsdfls).
qaodmasdkwaspemas23ajkqlsmdqpakldnzsdfls
Then we'll want to create some folders for Django. You can feel free to play with the folder layout, its mostly a personal thing, but you'll have to keep any changes you make in mind when you follow the remaining instructions.
qaodmasdkwaspemas24ajkqlsmdqpakldnzsdfls
Now we check out the Django source and link the checked out source into the site-packages so that the python interpreter can find it.
qaodmasdkwaspemas25ajkqlsmdqpakldnzsdfls
Now we get to create our first Django project. Notice how we symlink the project into the site-packages folder so that it available in the python path. This is a matter of preference, you can alteratively add the path to the project to the Apache virtual host file we edited earlier.
qaodmasdkwaspemas26ajkqlsmdqpakldnzsdfls
Now edit your newly minted settings.py file.
qaodmasdkwaspemas27ajkqlsmdqpakldnzsdfls
You'll need to make a number of changes, these are the lines you will need to add (not alter) to your settings.py:
qaodmasdkwaspemas28ajkqlsmdqpakldnzsdfls
I personally use a very long middleware cache because my pages don't change much (I am serving a blog, and thus caching entire pages is not too problematic), the standard value is much lower, around 300. The key prefix is used to distinguish caches between multiple Django projects using the same caching backend. If you are only planning to have one project using your caching backend then it is fine to leave the key as an empty string. If you plan on having:
qaodmasdkwaspemas29ajkqlsmdqpakldnzsdfls:
qaodmasdkwaspemas30ajkqlsmdqpakldnzsdfls.
Quick Fix To For Apache & Python Egg Compatibility
Because we installed psycopg2 via a python egg we will need to add a couple lines to our Apache config file. This process is explained on the Django page for modython, but is fairly simple.
First make a file to hold a few lines of Python:
qaodmasdkwaspemas31ajkqlsmdqpakldnzsdfls
Now eggs.py should contain these lines:
qaodmasdkwaspemas32ajkqlsmdqpakldnzsdfls
Then we need to open our virtual host file
qaodmasdkwaspemas33ajkqlsmdqpakldnzsdfls
And modifying the file to look like this:
qaodmasdkwaspemas34ajkqlsmdqpakldnzsdfls
Save the file and now Apache and eggs should play nicely together.
Weeping with Joy
We're done. Of course your server isn't secure at all, you should go do something about that. While working through these instructions you probably ran into points where you thought "What the hell is wrong with this guy?" and also "This doesn't work... at all." Well I hope you remember those moments, because I'd appreciate knowing which spots caused emotional distress (so I can idly dream about fixing them). | http://lethain.com/dreamier-dream-server-nginx/ | CC-MAIN-2014-52 | refinedweb | 1,433 | 58.28 |
seamless is a TCP proxy that allow you to deploy new code then switch traffic to new backend without downtime.
Switching backends is done with HTTP interface (on a different port) with the following API:
- /switch?backend=address
- switch traffic to new backend
- /current
- return (in plain text) current server
Process
Start first backend at port 4444
Run
seamless 8080 localhost:4444
Direct all traffic to port 8080 on local machine.
When you need to upgrade the backend, start a new one (with new code on a different port, say 4445). Then:
curl
(Note that management port is different from the one we proxy).
Installing
You can download a statically linked executable at the downloads section.
Or if you have a Go development environment, you can
go get bitbucket.org/tebeka/seamless
Miki Tebeka <miki.tebeka@gmail.com> or here. | https://bitbucket.org/tebeka/seamless/src/32a8ef1d7fd4?at=v0.1.2 | CC-MAIN-2015-27 | refinedweb | 140 | 65.12 |
How to: Retrieve the Content Sources for a Shared Services Provider
The Content object in the Enterprise Search Administration object model provides access to the content sources configured for the search service of a Shared Services Provider (SSP).
The following procedure shows how to write out the full list of content source names and IDs from a console application.
To display the list of content source names and IDs from a console application
In your application, set references to the following DLLs:
Microsoft.SharePoint.dll
Microsoft.Office.Server.dll
Microsoft.Office.Server.Search.dll
In your console application's class file, add the following using statements near the top of the code with the other namespace directives.
To retrieve the Content object for the SSP's search context, add the following code. For more information about ways to retrieve the search context, see How to: Return the Search Context for the Search Service Provider.
Retrieve the collection of content sources by using the following code.
To loop through the content sources and display the name and ID for each content source, add the following code.
Example
Following is the complete code for the console application class sample.
Prerequisites
Ensure ContentSourcesSample { class Program { static void Main(string[] args) { /* Replace <SiteName> with the name of a site using the SSP */ string strURL = "http://<SiteName>"; SearchContext context; using (SPSite site = new SPSite(strURL)) { context = SearchContext.GetContext(site); } Content sspContent = new Content(context); ContentSourceCollection sspContentSources = sspContent.ContentSources; foreach (ContentSource cs in sspContentSources) { Console.WriteLine("NAME: " + cs.Name + " ID: " + cs.Id); } } } }
See Also
TasksHow to: Return the Search Context for the Search Service Provider
How to: Add a Content Source
How to: Delete a Content Source
How to: Programmatically Manage the Crawl of a Content Source
How to: Programmatically Configure a Crawl Schedule for a Content Source
ConceptsGetting Started with the Enterprise Search Administration Object Model
Content Sources Overview | https://technet.microsoft.com/en-us/library/aa637145(v=office.12).aspx | CC-MAIN-2016-44 | refinedweb | 314 | 50.26 |
CodeGuru Update eNewsletter - January 25, 2005
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CodeGuru Newsletter
January 25, 2005
This newsletter is part of the Developer.com, EarthWeb, and
internet.com networks.
Jupitermedia Corporation
IBM Cloudscape
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If configuring e-mail or Spam filter rules, please use this
domain name (not the entire "from" address, which varies).
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TOPICS:
--> Editorial -
--> New Articles on CodeGuru:
==> Algorithms
- [Updated] Delaunay Triangles
==> Beginning VB .NET
- Discovering Visual Basic .NET: Repeating Code
==> COM
- Writing Your Own COM Interop in C#
==> Controls
- Changing the Background Color of a Read-Only Edit Control
- True Color Image List
==> Managed C++
- Managed C++: Determining User Security Roles
==> Mathematics (C# /.NET)
- Operator Overloading for Mathematical Libraries
==> Multimedia
- PCM Audio and Wave Files
==> Network
- Access Newly Available Network Information with .NET 2.0
==> Security
- Managed C++: Retrieving User's Windows Security Information
==> System
- Deleting a Directory Along with Sub-Folders
==> Win CE
- How the DesktopRapiInvoker Application Transfers the File
--> Discussion Groups (including Hot threads)
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1. Let The Voting Begin!
2. Understanding Telephony Concepts for Interactive Voice Responses
3. Capturing Keyboard Strokes in Java
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Last week Microsoft announced the 2005 MVP awards. I'm happy to say that there are a number of members of CodeGuru that were given the honor. You can find out about the MVP awards in the press release from Microsoft at:
Congratulations to Paul, Andreas, Mark, and any others who received the award. If you are also an MVP, drop me an email and let me know.
On a different note, Microsoft announced that XBox has been growing strongly. They stated that the XBox was the only gaming console to show positive market share growth in 2004. More specifically, XBox Live has been growing as well with 1.4 members now online.
Last night I spent a few hours of downtime playing Halo 2 online. I was joined by four other members in my "Clan". While I believe my character has a target painted on it, I did find it to be a lot of fun. with over 91,000,000 (that is 91 million) hours logged on Halo 2 on XBox live, apparently a lot of people find it fun.
When you step back and look at something like XBox live, you have to be impressed as a developer. It is an application that has an extremely simple interface. With the push of just a few buttons you are able to interact with others from around the world in real time. Not only is the application networked, but is also allowing for the exchange of data, voice communication, and more.
If you have been developing for more than 10 years, then step back for a minute and think about what it would have taken with technology from 1995 to build something like the networked Halo 2 application. As I do this, I get excited about the types of applications we will be building ten years from now!
Have a thought or opinion? Drop by the Feedback forum or drop me an email and let me Virus Research and
Defense
By Peter Szor for Addison-Wesley
720 pages
I received a draft copy of this book. Looks interesting. It is due out in February. Some of the topics include :
- Introduction to the Game of Nature
- The Fascination of Malicious Code Analysis
- Malicious Code Environments
- File Infection Techniques
- Basic Self Protection Strategies
- Advanced Code Evolution Techniques
- Strategies of Computer Worms
- Antivirus Defense Techniques
- Memory Scanning and Disinfection
- Worm-Blocking Techniques
- Host-Based Intrusion Prevention
- Network-Level Defense Strategies
- Malicious Code Analysis Techniques
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New & Updated Articles on CodeGuru
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Following are short descriptions of new articles on CodeGuru. If you are interested in submitting your own article for inclusion on the site, then you will find guidelines located at
This week's posted CodeGuru articles:
==> Algorithms
- [Updated] Delaunay Triangles
By Sjaak Priester
Learn about an algorithm to calculate this intriguing and important data structure in computer graphics.
==> Beginning VB .NET
- Discovering Visual Basic .NET: Repeating
Code
By Bill Hatfield
For those new to Visual Basic, here is your chance to learn about the topic of looping and how to get your program to execute several lines of code again and again.
==> COM
- Writing Your Own COM Interop in C#
By darwen.
==> Controls
- Changing the Background Color of a Read-Only Edit
Control
By Kevin Bond
Learn how to change the background color of a read-only text box so it isn't grey.
- True Color Image List
By Marius Bancila
Create true color (24 or 32 bits) image list for trees, lists, and toolbars.
==> Managed C++
- Managed C++: Determining User Security
Roles
By Tom Archer -
For those who don't have the desire or time to become experts on Windows security, follow this demonstration of using various .NET classes to test for a user's inclusion in one or more security groups.
==> Mathematics (C# /.NET)
- Operator Overloading for Mathematical
Libraries
By VijayaSekhar Gullapalli
Discover the concept of operator overloading in C# and its application in mathematical libraries.
==> Multimedia
- PCM Audio and Wave Files
By raghuvamshi
Provides a broad overview of what PCM audio is and how it is implemented in WAVE files.
==> Network
- Access Newly Available Network Information with .NET
2.0
By Mark Strawmyer
A new namespace in the upcoming 2.0 release of the Microsoft .NET Framework adds support for some very useful network-related items. Explores some of these new items and how you can use them to your advantage.
==> Security
- Managed C++: Retrieving User's Windows Security
Information
By Tom Archer -
Learn how to retrieve a current user's basic security information, such as the fully qualified user name (with domain or workgroup), whether the user is authenticated, and the authentication type.
==> System
- Deleting a Directory Along with
Sub-Folders
By Feroz Zahid
==> Win CE
- How the DesktopRapiInvoker Application Transfers the
File
By Nancy Nicolaisen
Look into how the DesktopRAPIInvoker application transfers files between the desktop and the CE-side device.
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==> Vanishing Application
==> Adding values into combobox using mfc in vc++
==> Polynomial Class
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New Articles on Developer.com
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Below are some of the new articles that have been posted to Developer.com ().
1. Let The Voting Begin!
By Rosemarie Graham -
The finalists for the Developer.com Product of the Year 2005 contest have been chosen. Vote for your favorite products now.
2. Understanding Telephony Concepts for Interactive Voice
Responses
By Xiaole Song -
Wanting to use interactive voice responses with your users? Start by learning about telephony concepts and about the telephony functionality within Microsoft's Speech Server and Speech Application SDK.
3. Capturing Keyboard Strokes in Java
By Richard G. Baldwin -
Discover how to use a KeyEventPostProcessor object to process KeyEvents after they have been processed by KeyEventDispatchers or by the components that fired the! | http://www.codeguru.com/announcements/article.php/3464441/CodeGuru-Update-eNewsletter--January-25-2005.htm | CC-MAIN-2016-26 | refinedweb | 1,210 | 53.1 |
if($DataEntry =~ !/d.*+)
{
print "bad entry";
}
else
{
print "good entry";
}
[download]
While !/d.*+ vaguely resembles a regular expression, I suspect you want to read perlre, because what you have there is not a regular expression (or perl for that matter, since it won't even compile.)
if ( $DataEntry =~ /^\d+$/ ) {
print "good entry";
} else {
print "bad entry";
}
[download]
Add in a test for zero -- that passes through this regex, but is not a positive integer by any definition I'm aware of.
You might want to look at Regexp::Common::number in general, but I don't see anything ready-made to do what you want. Here's a pattern I might use:
$dataEntry =~ m{ \A # beginning of string
\+? # optional plus sign
\d+ # one or more digits
\z # end of string
}xms
[download]
Using Regexp::Common, that might be:
use Regexp::Common qw( number );
$dataEntry =~ /$RE{num}{int}/ && $dataEntry == abs $dataEntry
[download]
If you want to allow for white space in your data entry, you could add \s* into your patterns.
Update: After consideration of the contributions of the other monks, I think this is a better expression than the one I have above:
m{ \A # beginning of string
\+? # optional plus sign
[0-9]* # optional digits, including zero
[1-9] # mandatory non-zero digit
[0-9]* # optional digits, including zero
\z # end of string
}xms
[download]
This incorporates Nkuvu's observation that a value of zero should not be allowed and mreece's suggestion that \d is not always the best way to match digits (though I find this counterintuitive). It also passes my own test suite.
Is there a place to donate or help fund this great site??
See the Offering Plate for contribution details.
I think that this exact case is handled in the Camel Book.
The logic is quite straightforward:
#!perl
use strict;
use warnings;
while (<DATA>) {
chomp; # get rid of pesky newlines
if(is_integer_string($_)){
print "$_ is a valid integer string\n";
}
else {
print "$_ isn't a valid integer string\n";
}
}
sub is_integer_string {
# a valid integer is any amount of white space, followed
# by an optional sign, followed by at least one digit,
# followed by any amount of white space
return $_[0] =~ /^\s*[\+\-]?\d+\s*$/;
}
__DATA__
1
1234
+1234
-1234
A
1234+
+ 1234
[download]
Note that this does not check to see if the integer can be represented on your system. It also does not permit white space between the sign and the leading digit of the number being examined.
return $_[0] =~ /^\s*[\+\-]?\d+\s*$/;
[download]
if(( $_[0] =~ /^\s*[\+\-]?\d+\s*$/) and ($_[0] > 0)) {
return 1;
}
else{
return undef;
}
[download]
Doubtless, this is not the most efficient method.
emc
Insisting on perfect safety is for people who don't have the balls to live in the real world.
Can't we simply check for >0?
print 'no' if '1a' > 0;
print 'no' if .1 > 0;
[download]
Close. I think ($_ eq int($_) && $_ > 0) will work as a condition though.
use strict;
use warnings;
my @tests = qw/12 1a 4 -3 0 0.1 .1/;
for (@tests) {
print "$_ => ";
no warnings qw/numeric/;
if ($_ eq int($_) && $_ > 0) {
print 'ok';
} else {
print 'bad';
}
print "\n";
}
__END__
C:\Perl\test>perl int_test.pl
12 => ok
1a => bad
4 => ok
-3 => bad
0 => bad
0.1 => bad
.1 => bad
[download]
use strict;
use warnings;
use Test::More;
my @good = qw( 12 1 +1 1234 );
my @bad = qw( 1a -3 0.1 .1 0 +0 -0 );
plan 'tests' => scalar @good + scalar @bad;
ok( is_int( $_ ), "[$_] is int" ) for @good;
ok( ! is_int( $_ ), "[$_] is not int" ) for @bad;
sub is_int {
return ( $_[0] eq int( $_[0] ) && $_[0] > 0 );
}
__END__
1..11
ok 1 - [12] is int
ok 2 - [1] is int
not ok 3 - [+1] is int
# Failed test '[+1] is int'
# in perlmonks.pl at line 14.
ok 4 - [1234] is int
Argument "1a" isn't numeric in int at perlmonks.pl line 18.
ok 5 - [1a] is not int
ok 6 - [-3] is not int
ok 7 - [0.1] is not int
ok 8 - [.1] is not int
ok 9 - [0] is not int
ok 10 - [+0] is not int
ok 11 - [-0] is not int
# Looks like you failed 1 test of 11.
[download]
Oops. I should have named that is_positive_int, etc.
what you probably want here is a string that starts with a number 1-9, followed by more numbers 0-9 (assuming that 03 is a bad entry), or just one or more numbers 0-9 (if 03 is a good entry).
if ($DataEntry =~ /^[1-9][0-9]*$/) {
print "good entry\n";
} else {
print "bad entry\n";
}
[download]
if ($DataEntry =~ /^[0-9]+$/) {
print "good entry\n";
} else {
print "bad entry\n";
}
[download]
# +ve int, not inc zero, optional space, optional sign
$var1 =~ s/^\s+//; # leading whitespace
$var1 =~ s/\s+$//; # trailing whitespace
if( $var1 =~ /^[+]?\d+$/ && $var1 != 0 )
{
print "+ve | http://www.perlmonks.org/?node_id=614452 | CC-MAIN-2015-06 | refinedweb | 825 | 78.08 |
Alright alright, I know for a lot of the last article seemed like a big ad for Lit. That said, I promise I’m not unable to see the advantages of other frameworks. Lit is a tool in a web developer’s toolbox. Like any tool, it has its pros and cons: times when it’s the right tool for the job, and other times when it’s less so.
That said, I’d argue that using an existing framework is more often the better tool for the job than vanilla web components.
To showcase this, let’s walk through some of these frameworks and compare and contrast them to home-growing web components.
Pros and Cons of Vanilla Web Components
While web frameworks are the hot new jazz - it’s not like we couldn’t make web applications before them. With the advent of W3C standardized web components (without Lit), doing so today is better than it’s ever been.
Here are some pros and cons of Vanilla JavaScript web components:
To the vanilla way of doing things’ credit, there’s a bit of catharsis knowing that you’re relying on a smaller pool of upstream resources. There’s also a lessened likelihood of some bad push to NPM from someone on the Lit team breaking your build.
Likewise - for smaller apps - you’re likely to end up with a smaller output bundle. That’s a huge win!
For smaller applications where performance is critical, or simply for the instances where you need to be as close to the DOM as possible, vanilla web components can be the way to go.
That said, it’s not all roses. After all, this series has already demonstrated that things like event passing and prop binding are verbose compared to Lit. Plus, things may not be as good as they seem when it comes to performance.
Incremental Rendering
On top of the aforementioned issues with avoiding a framework like Lit, something we haven’t talked about much is incremental rendering. A great example of this would come into play if we had an array of items we wanted to render, and weren’t using Lit.
Every time we needed to add a single item to that list, our
innerHTML trick would end up constructing a new element for every single item in the list. What’s worse is that every subelement would render as well!
This means that if you have an element like this:
html
<li><a href=””><div class=”flex p-12 bg-yellow”><span>Go to this location</span></div></a></li><li><a href=””><div class=”flex p-12 bg-yellow”><span>Go to this location</span></div></a></li>
And only needed to update the text for a single item in the list, you’d end up creating 4 more elements for the item you wanted to update… On top of recreating the 5 nodes (including the Text Node) for every other item in the list.
Building Your Own Framework
As a result of the downsides mentioned, many that choose to utilize vanilla web components often end up bootstrapping their own home-grown version of Lit.
Here’s the problem with that: You’ll end up writing Lit yourself, sure, but with none of the upsides of an existing framework.
This is the problem with diving headlong into vanilla web components on their own. Even in our small examples in the article dedicated to vanilla web components, we emulated many of the patterns found within Lit. Take this code from the article:
html
<script>class MyComponent extends HTMLElement {todos = [];connectedCallback() {this.render();}// This function can be accessed in element query to set internal data externallysetTodos(todos) {this.todos = todos;this.clear();this.render();}clear() {for (const child of this.children) {child.remove();}}render() {this.clear();// Do logic}}customElements.define('my-component', MyComponent);</script><script> class MyComponent extends HTMLElement { todos = []; connectedCallback() { this.render(); } // This function can be accessed in element query to set internal data externally setTodos(todos) { this.todos = todos; this.clear(); this.render(); } clear() { for (const child of this.children) { child.remove(); } } render() { this.clear(); // Do logic } } customElements.define('my-component', MyComponent);</script>
Here, we’re writing our own
clear logic, handling dynamic value updates, and more.
The obvious problem is that we’d then have to copy and paste most of this logic in many components in our app. But let’s say that we were dedicated to this choice, and broke it out into a class that we could then extend.
Heck, let’s even add in some getters and setters to make managing state easier:
html
<script>// Base.jsclass OurBaseComponent extends HTMLElement {connectedCallback() {this.doRender();}createState(obj) {return Object.keys(obj).reduce((prev, key) => {// This introduces bugsprev["_" + key] = obj[key];prev[key] = {get: () => prev["_" + key],set: (val) => this.changeData(() => prev["_" + key] = val);}}, {})}changeData(callback) {callback();this.clear();this.doRender();}clear() {for (const child of this.children) {child.remove();}}doRender(callback) {this.clear();callback();}}</script><script> // Base.js class OurBaseComponent extends HTMLElement { connectedCallback() { this.doRender(); } createState(obj) { return Object.keys(obj).reduce((prev, key) => { // This introduces bugs prev["_" + key] = obj[key]; prev[key] = { get: () => prev["_" + key], set: (val) => this.changeData(() => prev["_" + key] = val); } }, {}) } changeData(callback) { callback(); this.clear(); this.doRender(); } clear() { for (const child of this.children) { child.remove(); } } doRender(callback) { this.clear(); callback(); } }</script>
Now our usage should look fairly simple!
html
<script>// MainFile.jsclass MyComponent extends OurBaseComponent {state = createState({todos: []});render() {this.doRender(() => {this.innerHTML = `<h1>You have ${this.state.todos.length} todos</h1>`})}}customElements.define('my-component', MyComponent);</script><script> // MainFile.js class MyComponent extends OurBaseComponent { state = createState({todos: []}); render() { this.doRender(() => { this.innerHTML = `<h1>You have ${this.state.todos.length} todos</h1>` }) } } customElements.define('my-component', MyComponent);</script>
That’s only 13 lines to declare a UI component!
Only now you have a bug with namespace collision of state with underscores, your
doRender doesn’t handle async functions, and you still have many of the downsides listed below!
You could work on fixing these, but ultimately, you’ve created a basis of what Lit looks like today, but now you’re starting at square one. No ecosystem on your side, no upstream maintainers to lean on.
Pros and Cons of Lit Framework
With the downsides (and upsides) of vanilla web components in mind, let’s compare the pros and cons of what building components using Lit looks like:
While there is some overlap between this list of pros and cons and the one for avoiding Lit in favor of home-growing, there’s a few other items here.
Namely, this table highlights the fact that Lit isn’t the only framework for building web components. There’s huge alternatives like React, Vue, and Angular. These ecosystems have wider adoption and knowledge than Lit, which may make training a team to use Lit more difficult.
However, Lit has a key advantage over them, ignoring being able to output to web components for a moment - we’ll come back to that.
Even compared to other frameworks, Lit is uniquely lightweight.
Compare the bundle sizes of Vue - a lightweight framework in it’s own right - compared to Lit.
While tree shaking will drastically reduce the bundle size of Vue for smaller applications, Lit will still likely win out for a simple component system.
Other Frameworks
Lit framework isn’t alone in being able to output to web components, however. In recent years, other frameworks have explored and implemented various methods of writing code for a framework that outputs to web components.
For example, the following frameworks have official support for creating web components without changing implementation code:
Vue 3, in particular, has made massive strides in improving the web component development experience for their users.
What’s more is that these tools tend to have significantly larger ecosystems. Take Vue for example.
Want the ability to change pages easily? Vue Router
Want a global store solution? Vuex Prefer similar class based components? Vue Class Component Library
Prebuilt UI components? Ant Design
While some ecosystem tools might exist in Lit, they certainly don’t have the same breadth.
That’s not to say it’s all good in the general web component ecosystem. Some frameworks, like React, have issues with Web Component interop, that may impact your ability to merge those tools together.
Why Web Components?
You may be asking - if you’re going to use a framework like Vue or React anyway, why even bother with web components? Couldn’t you instead write an app in one of those frameworks, without utilizing web components?
You absolutely can, and to be honest - this is how most apps that use these frameworks are built.
But web components play a special role in companies that have multiple different projects: Consolidation.
Let’s say that you work for BigCorp - the biggest corporation in Corpville.
BigCorp has dozens and dozens of full-scale applications, and not all of them are using the same frontend framework. This might sound irresponsible of BigCorp’s system architects, but in reality, sometimes a framework is better geared towards specific applications. Additionally, maybe some of the apps were part of an acquisition or merger that brought them into the company.
After all, the user doesn’t care (or often, know) about what framework a tool is built with. You know what a user does care about? The fact that each app in a collection all have vastly different UIs and buttons.
While this is clearly a bug, if both codebases implement the buttons on their own, you’ll inevitably end up with these types of problems; this being on top of the work-hours your teams have to spend redoing one-another’s work for their respective frameworks.
And that’s all ignoring how difficult it can be to get designers to have consistency between different project’s design components - like buttons.
Web Components solve this problem.
If you build a shared component system that exports web components, you can then use the same codebase across multiple frameworks.
Once the code is written and exported into web components, it’s trivial to utilize these new web components in your application. Like, it can be a single line of code trivial.
From this point, you’re able to make sure the logic and styling of these components are made consistent between applications - even if different frameworks.
Conclusion
While web components have had a long time in the oven, they came out swinging! And while Lit isn’t the only one at the table, they’ve certainly found a strong foothold in capabilities.
Lit’s lightweightness, paired with web component’s abilities to integrate between multiple frameworks is an incredible one-two punch that makes it a strong candidate for any shared component system.
What’s more, the ability to transfer knowledge from other frameworks makes it an easy tool to place in your toolbox for usage either now or in the future.
Regardless; whether you’re using Vue, React, Angular, Lit, Vanilla Web Components, or anything else, we wish you happy engineering! | https://unicorn-utterances.com/posts/web-components-101-framework-comparison | CC-MAIN-2022-33 | refinedweb | 1,854 | 55.64 |
0
Im into the last stages of my C++ class and am having trouble with a project that has been assigned. Here is the problem and thanks in advance for whoever helps out!
Declare an object of type bucket
1). Use the SetGallonSize() method to set the bucket size to 5.0 gallons
2). Use the FillBucket() method to fill the bucket to 3.2 gallons of water
3). Use the GetWeight() method to output the weight of the 3.2 gallons of water
Here is the header file that was provided
// bucket.h #ifndef _BUCKET_H #define _BUCKET_H const double WEIGHT_OF_WATER = 8.3; class bucket { public: // constructors bucket(); bucket(bucket & Object); // member functions void SetGallonSize(double Size); void FillBucket(double Amount); double GetWeight(); private: // data double MySize, MyAmount; }; bucket::bucket() { MySize = 0; MyAmount = 0; } bucket::bucket(bucket & Object) { MySize = Object.MySize; MyAmount = Object.MyAmount; } void bucket::SetGallonSize(double Size) { MySize = Size; } void bucket::FillBucket(double Amount) { if(Amount <= MySize) { MyAmount = Amount; } else { MyAmount = MySize; } } double bucket::GetWeight() { return(MyAmount*WEIGHT_OF_WATER); } #endif
Here is my code I have so far. I dont know if Im on the right track, because the output is 53.20.
// bucket.cpp #include <iostream> #include <bucket.h> using namespace std; int main () { bucket Bucket_Size; bucket Bucket_Amount; double MySize = 5.0; double MyAmount = 3.2; Bucket_Size.SetGallonSize(MySize); Bucket_Amount.FillBucket (MyAmount); cout << "The bucket amount is " << MySize << MyAmount << Bucket_Size.GetWeight() << endl << endl; return 0; } | https://www.daniweb.com/programming/software-development/threads/328435/oop-issue-with-calculation | CC-MAIN-2017-26 | refinedweb | 237 | 60.41 |
03-26-2018 02:03 PM
06-20-2018 12:49 PM
06-20-2018 01:47 PM
Hi,
Yes still looking, just dropped down in priorty on my list. But that would be fantastic if you could share what you have.
Thank you
David
06-21-2018 08:25 AM - edited 06-21-2018 08:27 AM
Why use CLI? If you're going for automation, API is usually a much better option. You could use any of our API libraries to do this quickly. Here's an example using the Palo Alto Networks Device Framework:
from pandevice import firewall, device fw = firewall.Firewall('10.0.1.1', 'admin', 'password', vsys=None) fw.add(device.Vsys('vsys2', 'My New Vsys1')).create() fw.add(device.Vsys('vsys3', 'My New Vsys2')).create() fw.add(device.Vsys('vsys4', 'My New Vsys3')).create() fw.add(device.Vsys('vsys5', 'My New Vsys4')).create() fw.commit()
That creates 4 vsys on the firewall. If you need vsys each with their own virtual router you'd do something like this:
from pandevice import firewall, network, device fw = firewall.Firewall('10.0.1.1', 'admin', 'password', vsys=None) vr2 = fw.add(network.VirtualRouter('vsys2-vr') vsys2 = fw.add(device.Vsys('vsys2', 'My New Vsys2'), virtual_routers=[vr2]) vr2.create() vsys2.create() fw.commit()
That would give you a new virtual router in a new vsys.
More information:
06-21-2018 01:38 PM
@btorresgil This is why it's nice to see others work sometimes. I had a very similar thing to part two I was going to share, but I was defining my variable, then adding it in another line and then creating it in another line. I hadn't even thought about that I could be slimming it down to one line for the add and create!
06-21-2018 01:45 PM
Thank you very much, this would work out super, we do what to automate the entire vsys/vr and bgp router configs. So it is not done! | https://live.paloaltonetworks.com/t5/automation-api-discussions/creating-a-vsys-vr-via-cli/m-p/207520 | CC-MAIN-2022-40 | refinedweb | 334 | 76.32 |
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