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PyTorch 1.x Reinforcement Learning Cookbook

You're reading from   PyTorch 1.x Reinforcement Learning Cookbook Over 60 recipes to design, develop, and deploy self-learning AI models using Python

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Product type Paperback
Published in Oct 2019
Publisher Packt
ISBN-13 9781838551964
Length 340 pages
Edition 1st Edition
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Author (1):
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Yuxi (Hayden) Liu Yuxi (Hayden) Liu
Author Profile Icon Yuxi (Hayden) Liu
Yuxi (Hayden) Liu
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Toc

Table of Contents (11) Chapters Close

Preface 1. Getting Started with Reinforcement Learning and PyTorch FREE CHAPTER 2. Markov Decision Processes and Dynamic Programming 3. Monte Carlo Methods for Making Numerical Estimations 4. Temporal Difference and Q-Learning 5. Solving Multi-armed Bandit Problems 6. Scaling Up Learning with Function Approximation 7. Deep Q-Networks in Action 8. Implementing Policy Gradients and Policy Optimization 9. Capstone Project – Playing Flappy Bird with DQN 10. Other Books You May Enjoy

Developing the REINFORCE algorithm with baseline

In the REINFORCE algorithm, Monte Carlo plays out the whole trajectory in an episode that is used to update the policy afterward. However, the stochastic policy may take different actions at the same state in different episodes. This can confuse the training, since one sampled experience wants to increase the probability of choosing one action while another sampled experience may want to decrease it. To reduce this high variance problem in vanilla REINFORCE, we will develop a variation algorithm, REINFORCE with baseline, in this recipe.

In REINFORCE with baseline, we subtract the baseline state-value from the return, G. As a result, we use an advantage function A in the gradient update, which is described as follows:

Here, V(s) is the value function that estimates the state-value given a state. Typically, we can use a linear function...

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