Questions tagged [loss-functions]

For questions related to the concept of loss (or cost) function in the context of machine learning.

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21 views

setting up last layer in tensoflow for class type of label [closed]

I am creating a NN in tensorflow keras. the inputs are all float and the output is a class. The output currently encoded as a float, but only has 4 values (0,1,2,3). My model is similar to this: ...
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1answer
110 views

What is the difference between a fitness function and a reward function?

In reinforcement learning (RL), the reward function (RF), which can be denoted as $r(s)$, $r(s, a)$, $r(s, a, s')$, $r(s, s')$ depending on its specific definition, provides the learning signal, which ...
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0answers
44 views

BlackOut - ICLR 2016: need help understanding the cost function derivative

In the ICLR 2016 paper BlackOut: Speeding up Recurrent Neural Network Language Models with very Large Vocabularies, on page 3, for eq. 4: $$ J_{ml}^s(\theta) = log \ p_{\theta}(w_i | s) $$ They have ...
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2answers
105 views

If the training data are linearly separable, which of the following $L(w)$ has less optimum answer for $w$, when $y = w^Tx$?

I'm studying machine learning and I came into a challenging question. The answer is 2. But based on my ML notes, all of them are true. Where are the wrong points?
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1answer
75 views

Why doesn't the set $\{ -2, +2 \}$ in $E(X) = (y − \text{sign}\{\overline{W} \cdot \overline{X} \}) \in \{ −2, +2 \}$ include $0$?

I am currently studying the textbook Neural Networks and Deep Learning by Charu C. Aggarwal. Chapter 1.2.1.2 Relationship with Support Vector Machines says the following: The perceptron criterion is ...
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1answer
90 views

RealNVP gives wrong probabilities

I am trying to use RealNVP with some data I have (the input size is a 1D vector of size 22). Here is the link to the RealNVP paper and here is a nice, short explanation of it (the paper is pretty long)...
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1answer
50 views

What error should I use for RNN?

I'm relatively new to machine learning, and I don't know what error I should use for an RNN. I want to use a simple Elman RNN to predict the cases of Covid-19 there will be in a hospital for the next ...
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2answers
208 views

How should we interpret this figure that relates the perceptron criterion and the hinge loss?

I am currently studying the textbook Neural Networks and Deep Learning by Charu C. Aggarwal. Chapter 1.2.1.2 Relationship with Support Vector Machines says the following: The perceptron criterion is ...
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1answer
68 views

How to understand marginal loglikelihood objective function as loss function (explanation of an article)?

I am reading article https://allenai.org/paper-appendix/emnlp2017-wt/ http://ai2-website.s3.amazonaws.com/publications/wikitables.pdf about training neural network and the loss function is mentioned ...
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1answer
64 views

How to incorporate a symmetry constraint in the loss function to train a CNN?

I have a task of extremely sparse binary segmentation, i.e. the segmentation mask contains either 0 or 1, and there are ~95% zeros and only ~5% ones. I use the focal loss to address the sparseness (...
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1answer
80 views

How does the DQN loss from td_targets against q_values make sense?

Why td_loss is calculated from (td_targets against q_values)? Why I am lost is because: <...
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0answers
28 views

Single-value loss/training in a CNN with a tensor output

I am playing around with an idea of using using Q-learning with a DQN (Deep Q-Network), to determine the optimal position of a number of 'units' on a grid of allowed locations, according to some ...
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1answer
29 views

In this implementation of pix2pix, why are the weights for the discriminator and generator losses set to 1 and 100 respectively?

I am working on a pix2pix GAN model that was inspired by the code in this Github repository. The original code is working and I have already customized most of the code for my needs. However, there is ...
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16 views

What does Dice Loss should receive in case of binary segmentation

I implemented Dice loss class in pytorch: ...
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1answer
7k views

What is an objective function?

Local search algorithms are useful for solving pure optimization problems, in which the aim is to find the best state according to an objective function. My question is what is the objective function?
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0answers
33 views

How to make SAC (Soft-Actor-Critic) learn a policy?

I cannot make SAC learn a task in a certain environment. The point is that it actually sometimes finds a very good policy, but it never learns the policy in the end. I am using the SAC implementation ...
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1answer
52 views

When calculating the cost in deep Q-learning, do we use both the input and target states?

I just finished Andrew Ngs's deep learning specialization, but RL was not covered, so I don't know the basics of RL. So, I have been having trouble understanding the cost function in deep Q-learning. ...
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1answer
364 views

How do I get multiple loss per sample in keras evaluate? [closed]

Usually, when I evaluate() a model, I would get a single loss that is already averaged over all samples. How do I get the loss per each sample and return all of them? E.g. if my dataset has 100 ...
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0answers
17 views

Which loss function should I use to train DDGP with multiple q values, one for each of the output dimensions?

I'm trying to come up with a loss function for the case, in DDPG, where we have as many outputs from the critic as there are from the actor. So, there will be one Q value for each dimension in the ...
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1answer
69 views

How to understand 'losses' in Spacy's custom NER training engine?

From the tid-bits, I understand of neural networks (NN), the Loss function is the difference between predicted output and expected output of the NN. I am following this tutorial, the losses are ...
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1answer
49 views

Have I understood the loss function from the original U-Net paper correctly?

In the original U-Net paper, it is written The energy function is computed by a pixel-wise soft-max over the final feature map combined with the cross entropy loss function. ... $$ E=\sum_{\mathbf{x} ...
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0answers
25 views

Correct way to work with both categorical and continuous features together

I have a time series with both continuous and categorical features, and I want to do a prediction task. I will elaborate: The data is composed of 100Hz sampling of some voltages, kind of like an ecg ...
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1answer
71 views

Why is the derivative of the softmax layer shaped differently than the derivative of other neurons?

If the derivative is supposed to give the rate of change of a function at that point, then why is the derivative of the softmax layer (a vector) the Jacobian matrix, which has a different shape than ...
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1answer
44 views

Explanation of this L2 minimization equation

I am trying to understand the last two lines of this math notation. How Var and double summation of Cov came to the equation. The first two lines I understood something like $(a-b)^2 = a^2 -2ab +b^2$.
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1answer
37 views

Loss randomly changing, incorrect output (even for low loss) when trying to overfit on a single set of input and output

I am trying to make a neural network framework from scratch in C++ just for fun, and to test my backpropagation, I thought it would be an easy way to test the functionality if I give it one input - a ...
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0answers
29 views

What is the effect of too harsh regularization?

While training a CNN model, I used an l1_l2 regularization (i.e. I applied both $L_1$ and $L_2$ regularization) on the final layers. While training, I saw the ...
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2answers
350 views

Why does TensorFlow docs discourage using softmax as activation for the last layer?

The beginner colab example for tensorflow states: Note: It is possible to bake this tf.nn.softmax in as the activation function for the last layer of the network....
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1answer
40 views

Which NN would you choose to estimate a continuous function $f:\mathbb R^2 \rightarrow \mathbb R$?

Suppose we want to estimate a continuous function $f:\mathbb R^2 \rightarrow \mathbb R$ based on a sample using a NN (around 1000 examples). This function is not bounded. Which architecture would you ...
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1answer
97 views

When should I create a custom loss function?

I'm using a neural network to solve a multi regression problem because I'm trying to predict continuous values. To be more specific, I'm making a tracking algorithm to track the position of an object, ...
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2answers
43 views

Maximize loss on non-target variable

I have a neural network that should be able to classify documents to target label A. The problem is that the network is actually classifying label B, which is an easier task. To make the problem more ...
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1answer
44 views

Explain the difference in graphical patterns between discriminator fake loss and generator loss in GAN

In GAN (generative adversarial networks), let us take "binary cross-entropy" as the loss function for discriminator $$(overall \; loss = -\sum log(D(x_i)) -\sum log(1-D(G(z_i))) $$ $$ where \...
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1answer
83 views

How is the DQN loss derived from (or theoretically motivated by) the Bellman equation, and how is it related to the Q-learning update?

I'm doing a project on Reinforcement Learning. I programmed an agent that uses DDQN. There are a lot of tutorials on that, so the code implementation was not that hard. However, I have problems ...
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1answer
50 views

What is the cost function of a transformer?

The paper Attention Is All You Need describes the transformer architecture that has an encoder and a decoder. However, I wasn't clear on what the cost function to minimize is for such an architecture. ...
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1answer
94 views

How do you perform a gradient based adversarial attack on an SVM based model?

I have an SVM currently and want to perform a gradient based attack on it similar to FGSM discussed in Explaining And Harnessing Adversarial Examples. I am struggling to actually calculate the ...
2
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1answer
115 views

What is the impact of scaling the KL divergence and reconstruction loss in the VAE objective function?

Variational autoencoders have two components in their loss function. The first component is the reconstruction loss, which for image data, is the pixel-wise difference between the input image and ...
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0answers
24 views

Implementing Multiclass Dice Loss Function

I am doing multi class segmentation using UNet. My input to the model is HxWxC and my output is, ...
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0answers
17 views

What is the intuition behind equations 10, 11 and 12 of the paper “Noise2Noise: Learning Image Restoration without Clean Data”?

Can anyone help me understand these functions described in the paper Noise2Noise: Learning Image Restoration without Clean Data I have read the portion A.4 in the appendix but need a more detailed and ...
2
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1answer
61 views

How to perform binary classification when one class is more predominant than the other?

Assuming we have big $m \times n$ input dataset, with $m \times 1$ output vector. It's a classification problem with only two possible values: either $1$ or $0$. Now, the problem is that almost all ...
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3answers
25k views

How can we process the data from both the true distribution and the generator?

I'm struggling to understand the GAN loss function as provided in Understanding Generative Adversarial Networks (a blog post written by Daniel Seita). In the standard cross-entropy loss, we have an ...
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0answers
26 views

Loss function decays linearly in segmentation MRI fascia

I am working on a segmentation of MRI images of the thigh. I am trying to segment the fascia, there is a slight imbalance between the background and the mask. I have about 1400 images from 30 patients ...
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1answer
171 views

Why is the evidence equal to the KL divergence plus the loss?

Why is the equation $$\log p_{\theta}(x^1,...,x^N)=D_{KL}(q_{\theta}(z|x^i)||p_{\phi}(z|x^i))+\mathbb{L}(\phi,\theta;x^i)$$ true, where $x^i$ are data points and $z$ are latent variables? I was ...
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28 views

What is a “center loss”?

I have seen that a center loss is beneficial in computer vision, especially in face recognition. I have tried to understand this concept from the following material A Discriminative Feature Learning ...
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0answers
21 views

Understanding the MuZero loss function for a two-player game

This question is connected to a question that I asked some time ago. This is how I understood the training procedure takes place (please correct any conceptual mistakes here): Many complete games are ...
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1answer
27 views

Loss function definition

I have read what the loss function is but I am not sure if I have understood it. For each neuron in the output layer the loss function is equal most usually to the square of the difference value of ...
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0answers
24 views

Could the data augmentation lead to the model learning features which corresponds to data augmented data and not to the real data?

I am trying to train a Unet network with Synthetic data to do binary segmentation due to the fact that is is not easy to collect real data. And there is something in the training process that I do not ...
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1answer
378 views

Why is this PyTorch implementation of the actor-critic algorithm inconsistent with the mathematical formulas?

This PyTorch implementation of the actor-critic algorithm calculates the losses like so: ...
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0answers
18 views

How to afine the extremity values in regression prediction with Keras?

I made a stack of bidirectional LSTM layers following by Dense layers (with swish activation functions) in order to predict a continuous value between 0 and 2. I compiled the model with ...
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2answers
1k views

How do we design a neural network such that the $L_1$ norm of the outputs is less than or equal to 1?

What are some ways to design a neural network with the restriction that the $L_1$ norm of the output values must be less than or equal to 1? In particular, how would I go about performing back-...
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0answers
26 views

Wasserstein GAN with gradient penality - Loss values

I have trained a WAN with gradient penalty and the loss values ​​seem to me much higher than the examples I have seen on the net. The generator receives 2 images as input and must generate a ...
2
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1answer
42 views

Evaluate model multiple times in loss function? Is this reinforcement learning?

I am interested in models that exhibit behavior. My goal is a model that survives indefinitely on a two dimensional resource landscape. One dimension represents the location (0 to 1) and the second ...