Questions tagged [backpropagation]

For questions about the back-propagation (aka "backprop", and often abbreviated as "BP") algorithm, which is used to compute the gradient of the objective function (e.g. the mean squared error) with respect to the parameters (or weights) of the neural network, when trained with gradient descent.

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Difficulties to implement the layer-wise relevance propagation in MATLAB

I'm having serious issues with the implementation of the LRP algorithm for neural networks in MATLAB. The challenge is to implement the equations correctly. I'm trying to implement the deep-Taylor $\...
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109 views

When do you back-propagate errors through a neural network when using TD($\lambda$)?

I have a neural network that I'm want to use to self-play Connect Four. The neural network receives the board state and is to provide an estimate of the state's value. I would then, for each move, ...
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258 views

Simple three layer neural network with backpropagation is not approximating tanh function

I have this simple neural network in Python which I'm trying to use to aproximation tanh function. As inputs I have x - inputs to the function, and as outputs I want tanh(x) = y. I'm using sigmoid ...
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16 views

Gradient of Scalar objective cannot be efficiently calculated?

Suppose we generate the vector output $y$ from model $h(x, \theta)$, with input $x$ and parameters $\theta$. Reverse mode differentiation says that we can calculate the gradient \begin{align*} \...
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15 views

Are there any good references that describe the equations of the forward pass of Graph Neural Networks?

I am trying to program Graph Neural Network from scratch. Can the community please suggest a good reference/s to read about the equations of the forward pass in Graph Neural Networks, especially in ...
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41 views

What is the correct formula for updating the weights in a 1-single hidden layer neural network?

I'm creating a neural network with 3 layers and no bias. On internet I saw that the expression for the derivative of the weights between the hidden layer and the output layer was: $$\Delta W_{j,k} = (...
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21 views

Backpropagation - what does rate of change calculated from the partial derivatives actually relate to?

I understand conceptually how backpropagation works according to the chain rule, and I understand that partial derivatives calculate the rate of change of a function containing multiple variables with ...
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22 views

Do $V_\theta$ and $V_s$ represent partial or total derivatives in the paper “Learning Continuous Control Policies by Stochastic Value Gradients”?

I was reading up on the Stochastic Value Gradients paper by Heess et al. In the paper, they describe a recursive process to calculate path-wise derivatives via equations (3) and (4), at the bottom of ...
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31 views

Double DQN backpropagation of negative final rewards?

My problem is that in my Double DQN model, negative final rewards are not being backpropagated into action Q-values, and so some Q-values are positive, when they should be negative, and hence ...
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33 views

Backpropagation in REINFORCE algorithms with Categorical / Multinomial Distribution

From a paper by Williams, I know in general how to backpropagate log-probabilities of chosen actions when applying the REINFORCE weight update rule. However, I was wondering about a case not being ...
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32 views

Is vectorizing backpropagation feasible?

Does it make sense to have the backpropagation of a neural network layer happen all at once if the learning rate is lowered? This would mean the new weights of that layer would be independent of each ...
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11 views

How to update all the weights in case only one data out of n signals is observable

If we have cost function as $$E_i = (D_i -Y_i)^T Q (D_i -Y_i)$$, where $$Q=\begin{bmatrix} 1 & 0 & 0\\ 0 & 0 & 0\\ 0 & 0 & 0 \end{bmatrix}$$( in case only one data signal can ...
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49 views

Why is the error curve of a neural network trained with MSE to output $\frac{3 I_1 + 5 I_2}{2}$ given inputs $I_1$ and $I_2$ oscillating weirdly?

I just "finished" my first AI program. I programmed in Excel VBA, and I think it works well. I was checking every formula and the whole algorithm several times to make sure every formula is ...
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18 views

Neural Network trains towards 1 despite target

So I'm trying to make my first neural network and have just finished my back propagation functions. I got the algebra from brilliant and thought I'd understood it, but my bug proves otherwise. The bug ...
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23 views

During Backpropagation in LSTM, why is the previous output $h_{t-1}$ considered constant w.r.t any $W$ while computing derivative?

I've just started learning LSTM, and some points in the process of calculating the gradients are getting me confused. Say, for example, we want to compute $\frac{\partial}{\partial W_i}L$, where $L$ ...
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32 views

Backpropagation implementation not applicable for other cases

I saw this implementation of backpropagation in MATLAB, where the loss function used is MSE, and the last layer's activation function was sigmoid. I denoted the portions of the formula for what I ...
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14 views

Explanation of the partial derivatives in back-propogation algorithm

I understand that this is the method for conducting back-propogation: With a three layer network (input layer, one hidden layer, one output layer); start with input $I_i$ as an exemplar input. ...
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12 views

How to update the error on hidden nodes using back-propogation, given the error on the output nodes and weights

I'm trying to solve question 30 of this paper. The short version of the question is if someone could show me how to do this, I would appreciate it (the answer should be A; -0.0660). The long version ...
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33 views

XOR problem with bipolar representation

I am taking a course in Machine Learning and the Professor introduced us to the XOR problem. I understand the XOR problem is not linearly separable and we need to employ Neural Network for this ...
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30 views

In LSTMs, how does the additive property enables better balancing of gradient values during backpropagation?

There are two sources that I'm using to to try and understand why LSTMs reduce the likelihood of the vanishing gradient problem associated with RNNs. Both of these sources mention the reason LSTMs are ...
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41 views

How to normalise image input to backpropogation algorithm?

I am implementing a simple backpropagation neural network for classifying images. One set of images are cars another set of images are buildings (houses). So far I have used Sobel Edge detector after ...
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27 views

How to find the derivative of a dynamic neuron model, which depends on previous states of the neuron?

This is the equation where n denotes the current state, (n-1) denotes the state in the previous step etc. And to do back-propagation I need to find partial derivatives over each of the variables. For ...
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24 views

Finding the energy function given update rule of a single layer non-linear neural network

Consider the network with N neurons, each of which takes a $2 \times k$ input specified by the tuple $(\vec c_t, \vec \theta_t)$ to produce output $\vec{R}_t$ through an update rule on the pairwise ...
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109 views

Backpropagation implementation with Java

I've been trying to implement a Multilayer Perceptron Network using java language with the ultimate goal of creating and teaching a neural network to recognize handwritten digits. Pretty simple and ...
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42 views

Why is it that having a duplicate in features set makes training to work bad

I'm defining a deep network to emulate a multitarget regression. When I costruct my training set, I take information from a graph; without going into too much detail, it could happen that I take 2 ...
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78 views

Derivation of regularized cost function w.r.t activation and bias

In regularzied cost function a L2 regularization cost has been added. Here we have already calculated cross entropy cost w.r.t $A, W$. As mentioned in the regularization notebook (see below) in ...
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1answer
29 views

Positive bias causes the calculation of incorrect gradients

I have a data set with a positive bias (an image, where the values range from 0 to 1), that seems to be causing my network to calculate incorrect gradients. If I just use the raw image as input, of ...
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51 views

Confused about NeuralODE

I am a bit confused about NeuralODE and I want to make sure that what I understood so far is correct. Assume we have (for simplicity) 2 data points $z_0$ measured at $t_0$ and $z_1$ measured at $t_1$...
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219 views

How to back-propagate illegal actions for policy gradient learning

When training a AI RL agent to play a game there'll be situations where the AI cannot perform certain actions lest they violate the game rules. That's easy to handle, and I can set illegal actions to ...
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97 views

Back propagation on matrix of weights

I am trying to implement a Neural Network for binary classification using python and numpy only. My network structure is as follows: input features: 2 [1X2] matrix Hidden layer1: 5 neurons [2X5] ...

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