audio
audioduration (s) 0.62
28.4
| text
stringlengths 2
287
|
|---|---|
versus epochs and this can be a typical graph so you would often be seeing that you start
|
|
slightly then goes down it may keep on jittering and these are all aspects about whats happening
|
|
be a very smooth transition which it will be getting if your value of is very high
|
|
to the local minima and these are different issues which we would be tackling down through
|
|
experimental processes and some more learning experiences subsequently now looking at the
|
|
so here what i am doing is typically i am looking into two different plots so one is
|
|
my plot of epoch versus cost function the other is my plot of weight space versus cost
|
|
goes to the next one then to the next one and and finally to my convergence now if you
|
|
you would be seeing that the error function over there form some sort of a very structure
|
|
troughs present over there so as these points of my weights they keep on moving down they
|
|
would always be encircling and coming down to my local minimum point as soon as possible
|
|
and the way it comes down to this local minima is what is my learning which is happening
|
|
is that we can actually initialize a network at any random point over there and based on
|
|
that it can start converging and oscillating around any of these trucks and that definitely
|
|
these non global minima positions but rather somehow escape into this from these small
|
|
all of this what comes down to our mind is something interesting so you have seen that
|
|
there is for any kind of a given network if i have three different scalar values over
|
|
there then i can take in these scalar values and i can predict out one of these predicted
|
|
that i have my weights w one w two and w three i take all of these weights together and then
|
|
down to my output over there ok
|
|
doing so in order to solve it out the best possible way is basically trying to look into
|
|
something which is called as the chain rule of differentiation which you have done in
|
|
so i can take a derivative of the cost function with respect to this output next is my output
|
|
now be represented as a product of del del p of jw and del del y of p so together these
|
|
of the cost function if you look into the second part of the gradient then you see that
|
|
of the derivative thats a derivative of the linear network itself and these three things
|
|
together are what will be helping me in finding out the gradient part for my whole network
|
|
then enter into eventually the deep learning and how to train down these deep neural networks
|
|
thank you and stay tuned for the next lecture
|
|
so welcome and so in the ah we will be continuing down with the from where we left in the last
|
|
lecture and thats on multi layer perceptrons to deep neural networks and this is where
|
|
and a recap of the learning rules and how to create down this single model and then
|
|
a single perceptron and then a whole collection of perceptrons in terms of its matrix and
|
|
the matrix form of representing the data from there going down to the gradient and what
|
|
it gets broken down into partial products over there and using these partial derivative
|
|
last class so that was on the gradient computation part say i have three scalars x one x two
|
|
and x three and then i would like to map it down to another predictor scalar which is
|
|
is from x how to get down to p hat the question which we had raised is how to get down this
|
|
to y which is the output from the summation block and you take a derivative of y with
|
|
respect to w which is known as the derivative of the linear part of the network ok now and
|
|
now the point is that this kind of a computation is what holds true for just one single neuron
|
|
ok and the next point is that if it is not just one single neuron but you have a collection
|
|
of neurons or something which is a deep neural network
|
|
as a multi layer perceptron due to its multiple layers form over there so thats exactly what
|
|
nodes over there that connects to another set of intermediate nodes and that subsequently
|
|
to get down the derivative in its own way but then in order to get this one you see
|
|
case is something tricky so lets look into this
|
|
small part of the network so what we do is say that i am looking at one of my particular
|
|
layer which is say called as the d th layer ok now for my a d th layer what will i will
|
|
now that can be done as an extended product of del del w of y d which is output which
|
|
is the linear part of summation which comes down to that particular plot now if i go down
|
|
to my d minus one th layer so this is my w d which is just connecting down my output
|
|
to the d th layer now if i go down to one layer before it now what we can see is that
|
|
this linear part of this block with respect to the weights which are connecting these
|
|
of the linear part of this one with respect to the block earlier it ok so this is my d
|
|
this is my w of d minus one and thats where my expansion happens now and similarly i keep
|
|
on repeating this whole thing together on the chain and finally what i would get down
|
|
is on the final part which is del del w of y one which is my first output layer over
|
|
it which is my x over here so this is a typical way in which we calculate now our whole networks
|
|
gradient over there so if i want that my total network has to be solved out so this is exactly
|
|
what i would be doing in terms of my calculations so you can typically look so now that i dont
|
|
have what is my input coming from here so what i would be doing is i dont know exactly
|
|
what values are over here so i will be again differentiating this with respect to this
|
|
it stops is a del del w one of y one and thats equal to my input which is x ok so i i believe
|
|
this part is quite clear to you guys and and quite intuitive actually not so hard to calculate
|
|
down something like this now that i have this form going down so my first part of it is
|
|
is what is called as a derivative of the network and finally is the input to the network which
|
|
is my x ok so these together is what constitutes of any
|
|
sort of a learning mechanism within a multi layer perceptron or any kind of a deep neural
|
|
network so what you will have to do is you will have to find out what is my derivative
|
|
of my cost function you will have to find out the derivative of the network which together
|
|
and derivative of the perceptron together and you will have to find out what is that
|
|
now by solving out this complete derivative over here is what we are able to get down
|
|
as our neural network learning algorithm in terms of gradient descent and thats where
|
|
criteria so what this essentially means is that in order for the total derivative of
|
|
fraction of the derivative exists so every single part over there we were doing a chain
|
|
rule of expansion so if every single component of the chain
|
|
rule exists only in that case you would see that the total derivative of the network as
|
|
which is lets take down these two cost functions so the first one is what is called as the
|
|
you can do is quite simple i mean you can just take a del del w ah del del p of j over
|
|
happen is definitely it does exist for the first case which is euclidean norm
|
|
have the second one ok and this is where the fun is so do you think that the derivative
|
|
of this one will exist as well or not just just take down a few seconds over here while
|
|
at zero you see you have an l one norm or just a mod ok so mod of p minus p hat this
|
|
one over there is basically a value which is always a nonzero value and this hat does
|
|
of the rest part of the network and now over here one important point is that the derivative
|
|
del del y of p that will not come into existence whereas del del y of z that does not have
|
|
question is does the derivative of each of them exist or not so lets give you some time
|
|
the derivative does exist and thats a perfectly differentiable function whereas look into
|
|
the second part of that that again is something which is not differentiable because of the
|
|
property so one property was definitely to make it bounded in some form ok but we also
|
|
mentioned that the there are other properties and one of those important properties is that
|
|
the cost function itself sorry not the cost function but the transfer function itself
|
|
end over there until and unless a transfer function is differentiable the derivative
|
|
function and thats the reason why these kind of functions cannot be made cannot be used
|
|
through intermediate weights w one up to w d and ah go down to my final output which
|
|
is p hat and the way of how we are doing down is something of this sort and the first step
|
|
which is called as the forward pass of the network and this is something similar to what
|
|
pass of this x in order to obtain your p hat now that you have your forward pass and you
|
|
that i need to compute out my j which is my cost function the way of computing this j
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.