# Tag Info

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• 278
Accepted

### How is the log-derivative trick of a trajectory derived?

The identity $$\nabla_{\theta} P(\tau \mid \theta) = P(\tau \mid \theta) \nabla_{\theta} \log P(\tau \mid \theta)\tag{1}\label{1},$$ which can also be written as \begin{align} \nabla_{\theta} \log ...
• 41k

### Why the partial derivative is $0$ when $F_{ij}^l < 0$?. Math behind style transfer

$F_l$ is the activation of the filter. They state in the paper that they base their method on VGG-Network, which uses ReLU as its activation function. In fact, VGG uses it in all of its hidden layers. ...
• 496
Accepted

### How do policy gradients work?

From the equation you wrote: $U(\theta)$ is the total expected reward of a policy $\pi_\theta$ (with parameters/weights $\theta$) over all possible trajectories $\tau$ sampled under the environment ...
• 2,976
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### What is a bad local minimum in machine learning?

The adjective bad isn't mathematically descriptive. A better term is sub-optimal, which implies the state of learning might appear optimal based on current information but the optimal solution from ...
• 7,513

### What are the Calculus books recommended for beginner to advanced researchers in artificial intelligence?

Answer: Calculus James Stewart is the best for a beginner. I started to learn Calculus studying engineering with James Stewart Calculus ( maybe the best for beginners and is really didactic ), ...
1 vote

1 vote

### Which linear algebra book should I read to understand vectorized operations?

Linear Algebra Done Right by Axler seems to be the best book on linear algebra, with a brisk and modern approach.
• 2,101
1 vote

### Why is the change in cost wrt bias in neural network equal to error in the neuron?

This is just an application of the chain rule. The same chapter has "Proof of the four fundamental equations" section, which proves BP1-2, while PB3-4 are left as exercise to the reader. I agree that ...
• 1,967

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