# Questions tagged [notation]

For questions related to notation (in general).

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### Notation used in paper on Continuous Time Reinforcement Learning

I am working on implementing the learning shown in this paper: https://homes.cs.washington.edu/~todorov/courses/amath579/reading/Continuous.pdf In the paper, the authors devise a continuous time ...
1 vote
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### What does the notation $\hat{A}_t\left(s_{0: \infty}, a_{0: \infty}\right)$ appearing in Generalized Advantage Estimation mean?

In general, the advantage function is defined as: $A^\pi\left(s_t, a_t\right):=Q^\pi\left(s_t, a_t\right)-V^\pi\left(s_t\right)$ So far, I understand this formular like this: With the advantage ...
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### Is there a standard nomenclature for model names suffixed by strings such as "Q4_K_S"?

Many models specify details using prefixes such as Q6_K or Q4_K_S. It seems obvious that the ...
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• 145
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### What do we mean by the notation $\mathbf{x}_{p} \in \mathbb{R}^{N \times\left(P^{2} \cdot C\right)}$?

I was going through this VIT paper, what will it look like in torch , if we are trying to write this expression.
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### What is the meaning of $p_{\text {data }}(y)$ in the CycleGAN?

In the original CycleGAN paper, on the second page, there is a sentence that I didn't quite understand In theory, this objective can induce an output distribution over $\hat{y}$ that matches the ...
1 vote
365 views

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1 vote
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### What do the square brackets $[ ]$ and $\mid$ mean in $[G_t \mid S_t=s]$?

Here is the formula of state-value function in Reinforcement Learning. What do the square brackets $[ ]$ and $\mid$ mean in $[G_t \mid S_t=s]$? Why use square brackets? Why use $\mid$? Why do ...
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### Where are the parentheses in the Bellman update rule?

I'm not having a lot of intuition about the equation. I have this Bellman update rule: $$v_{\pi}(s) =\sum_a \pi(a|s)\sum_{s',r} p(s',r|s,a)[r+ \gamma v_{k}(s')]$$ But where are the parenthesis? Is the ...
• 216
1 vote
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### What does the complexity equation constitute exactly in “Why Should I Trust You?” LIME paper

I've recently been reading this paper on LIME, an algorithm to interpret ANY machine learning model. I encountered this equation (in red) on page 4 and have just been having a hard time deciphering ...
1 vote
77 views

### Why do we use $q_{\phi}(z \mid x^{(i)})$ in the objective function of amortized variational inference, while sometimes we use $q(z)$?

In page 21 here, it states: General Idea of Amortization: if same inference problem needs to be solved many times, can we parameterize a neural network to solve it? Our case: for all $x^{(i)}$ we ...
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### Are the authors of the VAE paper writing the PDFs as a function of the random variables?

Usually, I see the conventions: discrete random variable is denoted as $X$, the pmf is written as $P(X=x)$ or $p(X=x)$ or $p_{X}(x)$ or $p(x)$, where $x$ is an instance of $X$ a continuous random ...
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### Which is more popular/common way of representing a gradient in AI community: as a row or column vector?

Consider the following remark about writing gradients from the chapter named Vector Calculus from the test book titled Mathematics for Machine Learning by Marc Peter Deisenroth et al. Remark (...
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1 vote
150 views

### What is the name of this letter $\mathcal{J}$?

What is the name of this letter $\mathcal{J}$ in the following deep learning equation? And what alphabet it is from? $$\mathcal{J} = \frac{1}{m} \sum_{i=1}^m \mathcal{L}^{(i)}$$
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1 vote
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### What is a filter in the context of graph convolutional networks?

In Section 2.1 of the research paper titled Semi-Supervised Classification with Graph Convolutional Networks by Thomas N. Kipf et al., Spectral convolution on graphs defined as The multiplication of ...
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### In this example of fuzzy c-means, what is the difference between "sigma" and "center" for the clusters?

In this example, what exactly do "Cluster" and "Sigma" mean? (They chose random coordinates for the three centroids of the groups) Centers: Cluster centers, returned as a ...
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### Why using negative integers (as dimensions?) in tensor shapes rather than natural numbers?

Consider the following paragraph from A.1 MULTI-MNIST AND CLEVR of A IMPLEMENTATION DETAILS from the research paper titled ...
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### What, exactly, do mlp(64,64) and mlp(64,128,1024) mean in PointNet, and how many input neurons does 1 (x,y,z) point have?

I couldn't find out how to interpret the multilayer perceptron notation given in PointNet. Specifically, I am looking to find out what the numbers inside the parentheses of ...
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### Is there any difference between 'input' and 'conditional input' in the case of neural networks?

In the research paper titled Conditional Generative Adversarial Nets by Mehdi Mirza and Simon Osindero, there is a notion of conditioning a neural network on a class label. It is mentioned in the ...
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### Does generator in conditonal GAN obey probability laws?

In probability, we have two types of probability functions: unconditional probability $p(x)$ and conditional probability $p(x | y)$. Both are fundamentally different and the latter can be obtained by ...
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1 vote
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### What is the meaning of these equations in Noise2Noise paper?

I am trying to understand what is meant by following equations in the Noise2Noise paper by Nvidia. What is meant by the equation in this image? What is $\mathbb{E}_y\{y\}$? And how should I try to ...
• 41
1 vote
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### In the definition of the state-action value function, what is the random variable we take the expectation of?

I know that $$\mathbb{E}[g(X) \mid A] = \sum\limits_{x} g(x) p_{X \mid A}(x)$$ for any random variable $X$. Now, consider the following expression. \mathbb{E}_{\pi} \left[ \sum \limits_{k=0}^{\infty}...
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### Do the rows of the design matrix refer to the observations or predictors?

I attempt to understand the formulation of dictionary learning for this paper: Depression Detection via Harvesting Social Media: A Multimodal Dictionary Learning Solution Multimodal Task-Driven ...
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### What does the notation $\mathcal{N}(z; \mu, \sigma)$ stand for in statistics?

I know that the notation $\mathcal{N}(\mu, \sigma)$ stands for a normal distribution. But I'm reading the book "An Introduction to Variational Autoencoders" and in it, there is this notation:...
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### Why do we use $X_{I_t,t}$ and $v_{I_t}$ to denote the reward received and the at time step $t$ and the distribution of the chosen arm $I_t$?

I'm doing some introductory research on classical (stochastic) MABs. However, I'm a little confused about the common notation (e.g. in the popular paper of Auer (2002) or Bubeck and Cesa-Bianchi (2012)...
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### What does the term $|\mathcal{A}(s)|$ mean in the $\epsilon$-greedy policy?

I've been looking online for a while for a source that explains these computations but I can't find anywhere what does the $|A(s)|$ mean. I guess $A$ is the action set but I'm not sure about that ...
119 views

### What does the notation "for t=T to 1,−1 do" in terms of time steps, in deep recurrent q network?

In looking at an algorithm in the paper Learning to Communicate with Deep Multi-Agent Reinforcement Learning. Here is the full algorithm: What does the notation ...
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1 vote
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### What do the notations $\sim$ and $\Delta (A)$ mean in the paper "Fairness Through Awareness"?

In this paper Fairness Through Awareness, the notation $\mathbb{E}_{x \sim V} \mathbb{E}_{a \sim \mu_x} L(x,a)$ is being used (page 5 top line), where $V$ denotes the set of individuals (so I guess ...
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