Questions tagged [gradient-descent]

For questions surrounding gradient descent, a method for finding the optimum state of a parameterized function based on another function often called the loss or error function. It iteratively descends the loss surface to the minimum loss by adjusting parameters based on the product of the partial derivatives comprising the gradient and a learning rate.

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1answer
33 views

Is it possible with stochastic gradient descent for the error to increase?

As simple as that. Is there any scenario where the error might increase, if only by a tiny amount, when using SGD (no momentum)?
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2answers
129 views

Can neuroevolution be combined with gradient descent?

Is there any precedent for using a neuroevolution algorithm, like NEAT, as a way of getting to an initialization of weights for a network that can then be fine-tuned with gradient descent and back-...
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1answer
22 views

In NN, as iterations of Gradient descent increases, the accuracy of Test/CV set decreases. how can i resolve this?

As mentioned in the title I'm using 300 Dataset example with 500 feature as an input. As I'm training the dataset, I found something peculiar. Please look at the data shown below. Iteration 5000 |...
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1answer
15 views

Sensitivity of neural network to inputs

I am trying to build intution regarding neural networks and their working and this is a question, I am interested in: I understand that we normalise inputs. The reason this is done is to capture the ...
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0answers
50 views

Neural networks when gradient descent is not possible

I am looking for an example in which it is simply impossible to use some sort of gradient descent to train a neural network. Is this available? I have read quite some papers about gradient-free ...
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1answer
59 views

How does NEAT find the most successful generation without gradients?

I'm new to NEAT, so, please, don't be too harsh. How does NEAT find the most successful generation without gradient descent or gradients?
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3answers
184 views

Which function $(\hat{y} - y)^2$ or $(y - \hat{y})^2$ should I use to compute the gradient?

The MSE can be defined as $(\hat{y} - y)^2$, which should be equal to $(y - \hat{y})^2$, but I think their derivative is different, so I am confused of what derivative will I use for computing my ...
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0answers
13 views

What is the right formula for weight update rule in Logistic Regression using stochastic gradient descent

Apologies for the lengthy title. My question is about the weight update rule for logistic regression using stochastic gradient descent. I have just started experimenting on Logistic Regression. I ...
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3answers
182 views

How is local minima possible in gradient descent?

Gradient descent works on the equation of mean squared error, which is an equation of a parabola $y=x^2$. We often say that weight adjustment in a neural network by gradient descent algorithm can hit ...
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1answer
51 views

How can we reach global optimum?

Gradient descent can get stuck into local optimum. Which techniques are there to reach global optimum?
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1answer
31 views

When is bias values updated in back propagation?

I am new to deep learning. I have doubts on modifying bias values during back propagation. My doubts are Does the back propagation algorithm modifies the weigh values and bias values in the same pass?...
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1answer
71 views

Is back propagation applied for each data point or for a batch of data points?

I am new to deep learning and trying to understand the concept of back propagation. I have a doubt on when the back propagation is applied. Assume that I have a training data set of 1000 images for ...
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2answers
100 views

Are on-line backpropagation iterations perpendicular to the constraint?

Raul Rojas' Neural Networks A Systematic Introduction, section 8.1.2 relates off-line backpropagation and on-line backpropagation with Gauss-Jacobi and Gauss-Seidel methods for finding the ...
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1answer
38 views

Which local minima to choose according to the shape of the error surface?

The following plot shows error function output based on system weights. Two equal local minima are shown in green pointers. Note that the red dots are not related to the question. Considering the ...
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2answers
55 views

Could error surface shape be useful to detect which local minima is better for generalization?

The following plot shows error function output based on system weights. Two equal local minima are shown in green pointers. Note that the red dots are not related to the question. Does the right one ...
2
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1answer
60 views

What is the gradient of the objective function in the Soft Actor-Critic paper?

In the paper "Soft Actor-Critic: Off-Policy Maximum Entropy Deep Reinforcement Learning with a Stochastic Actor", they define the loss function for the policy network as $$ J_\pi(\phi)=\mathbb E_{...
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1answer
64 views

How to obtain a formula for loss, when given an iterative update rule in gradient descent?

From the reinforcement learning book section 13.3: Using pytorch, I need to calculate a loss, and then the gradient is calculated internally. How to obtain the loss from equations which are stated ...
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1answer
23 views

How to shape the weights or nodes during gradient training of neural network? Training with constraints?

Gradient training changes indiscriminately all the weights and nodes of the neural network. But one can imagine the situations when the training should be shaped, e.g.: One can put constraints on ...
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1answer
32 views

Will LMS always be convex function? If yes, then why do we change it for neural networks?

In LMS(least mean square) since, we use a quadratic error function, and quadratic functions are generally parabola in (some convex like shape). I wonder whether that is the reason why we use least ...
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1answer
27 views

Neural network with logical hidden layer - how to train it? Is it policy gradient problem? Chaining NNs?

I am doing neural machine translation task from language S to language T via interlingua L. So - there is the structure: ...
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3answers
149 views

How can a neural network learn when the derivative of the activation function is 0?

Imagine that I have an artificial neural network with a single hidden layer and that I am using ReLU as my activating function. If by change I initialize my bias and my weights in such a form that: $$ ...
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1answer
75 views

Can gradient descent training be used for nonsmooth loss functions?

I have non-smooth loss function - e.g. loss(x)=min(x, 0.5). Can gradient descent be used for training neural networks with such functions. Can gradient descent be used for fairly general, ...
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1answer
138 views

Cost function increasing with SGD

In Deep Learning by Goodfellow et al., I came across the following line on the chapter on Stochastic Gradient Descent (pg. 287): The main question is how to set $\epsilon_0$. If it is too large, ...
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0answers
25 views

neuralnetworksanddeeplearning.com chapter 5 problems

For http://neuralnetworksanddeeplearning.com/chap5.html , could anyone suggest: 1) how to approach the derivation of expression (123) ? 2) what constitutes value ~ 0.45 ? 3) why the need of taylor ...
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1answer
225 views

Feed forward neural network using numpy for IRIS dataset

I tried to build a neural network for working on IRIS dataset using only numpy after reading an article (link: https://iamtrask.github.io/2015/07/12/basic-python-network/). I tried to search the ...
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2answers
175 views

SARSA won't work for linear function approximator for MountainCar-v0 in OpenAI environment. What are the possible causes?

I am learning Reinforcement Learning from the lectures from David Silver. I finished lecture 6 and went on to try SARSA with linear function approximator for MountainCar-v0 environment from OpenAI. A ...
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2answers
64 views

Gradient Descent Feature Scaling

When feature scaling for a Multivariate Linear Regression housing predictor (housing area and # bedrooms), the exercise suggested "scale both types of inputs by their standard deviations and set their ...
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2answers
898 views

Can the value of a cost function be negative?

I'm new to machine learning and I was watching a video about gradient descent.It said that we want our cost function(Mean squared error) to have the minimum value but that minimum value shown in the ...
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0answers
29 views

Neural network backpropagation gradient descent better than conjugate gradient descent?

My understanding is that the conjugate gradient method is faster than gradient descent because it does less zig zags while descending. How come the state of the art papers I see all use gradient ...
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1answer
166 views

Deep Q-Learning: why don't we use mini-batches during experience reply?

In examples and tutorial about DQN, I've often noticed that during the experience replay (training) phase people tend to use stochastic gradient descent / online learning. (e.g. link1, link2) ...
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4answers
2k views

How do I choose the optimal batch size?

Batch size is a term used in machine learning and refers to the number of training examples utilised in one iteration. The batch size can be one of three options: batch mode: where the batch ...
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1answer
52 views

Weight Normalization paper

I am trying to dissect paper about weight normalization: https://papers.nips.cc/paper/6114-weight-normalization-a-simple-reparameterization-to-accelerate-training-of-deep-neural-networks.pdf ...
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1answer
87 views

Do good approximations produce good gradients?

Let’s say I have a neural net doing classification and I’m doing stochastic gradient descent to train it. If I know that my current approximation is a decent approximation, can I conclude that my ...
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1answer
812 views

Can non-differentiable layer be used in a neural network, if it's not learned?

For example, AFAIK pooling layer in CNN is not differentiable, but it can be used because it's not learning. Is it always true?
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0answers
25 views

Has anyone investigated iteration awareness beyond RNN and LSTM?

This question considers the convergence of an artificial networks (MLPs, RNNs, LSTM nets, CNNs) over time or over the course of epochs made up of iterations through training examples. In this ...
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2answers
92 views

Mini-batch training and the gradient

I am reading a book that states, "As the mini-batch size increases, the gradient computed is closer to the 'true' gradient". So basically what they are saying is mini-batch training only focuses on ...
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2answers
53 views

Behaviour of cost

In doing a project using neural networks with an input layer, 4 hidden layers and an output layer ,I used mini batch gradient descent. I noticed that the randomly initialised weights seemed to do a ...
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2answers
144 views

Working with large datasets

If one has a dataset large enough to learn a highly complex function, say learning chess game-play, and the processing time to run mini batch gradient descent on this entire dataset is too high, can I ...
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1answer
146 views

Gradient of boltzmann policy over reward function

I'm struggling with an inverse reinforcement learning problem which seems to appear quite often around the literature, yet I can't find any resources explaining it. The problem is that of calculating ...
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1answer
47 views

Gradient descent update

In the following, I put the link for the general algorithm of maximum entropy inverse reinforcement learning. http://178.79.149.207/assets/maxent/maxent_slide.jpg This uses a gradient descent ...
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1answer
256 views

Why Feature Scaling for skewed contour?

Why is it that the skewed contour (unscaled features) will result in slow performance of gradient descent? In other words, how (or why) will the gradients end up taking a long time before finding the ...
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1answer
43 views

What can be deduced about the “algorithm” of backpropagation/gradient descent?

On this video Link to video a neurologist starts by saying that we do not know how neurons calculate gradients for backpropagation. At minute 30:39 hes showing faster convergence for "our algorithm"...
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1answer
1k views

How do I implement softmax forward propagation and backpropagation to replace sigmoid in a neural network?

I'm currently using 3Blue1Brown's tutorial series on neural networks and lack extensive calculus knowledge/experience. I'm using the following equations to calculate the gradients for weights and ...
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1answer
40 views

How to change a weight/bias with gradient

After watching 3Blue1Brown's tutorial series, and an array of others, I'm attempting to make my own neural network from scratch. So far, I'm able to calculate the gradient for each of the weights and ...
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1answer
474 views

Why use semi-gradient instead of full gradient in RL problems, when using function approximation?

Semi-gradient methods work well in reinforcement learning, but what is there a reason of not using the true gradient if it can be computed? I tried it on the cart pole problem with a deep Q-network ...
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2answers
928 views

How to perform gradient checking in a neural network with batch normalization?

I have implemented a neural network (NN) using python and numpy only for learning purposes. I have already coded learning rate, momentum, and L1/L2 regularization and checked the implementation with ...
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0answers
457 views

How to calculate gradient of filter in convolution network

I have similar architecture like in image:CNN. I don't understand how to calculate gradient of filter F. I found these equations(source): Gradient and delta, where first equation calculate gradient ...
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3answers
464 views

CNN backpropagation with stride>1

I read that to compute the derivative of the error with respect to the input of a convolution layer is the same to make of a convolution between deltas of the next layer and the weight matrix rotated ...
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2answers
191 views

How is direction of weight change determined by Gradient Descent algorithm

The result of gradient descent algorithm is a vector. So how does this algorithm decide the direction for weight change? We Give hyperparameters for step size. But how is the vector direction for ...
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2answers
4k views

How is gradient calculated for middle layer weights?

I am trying to understand backpropagation. I used a simple neural network with one input x, one hidden layer h and one output layer y, with weight w1 connecting x to h, and w2 connecting h to y. x--...