Book Image

Python Reinforcement Learning

By : Sudharsan Ravichandiran, Sean Saito, Rajalingappaa Shanmugamani, Yang Wenzhuo
Book Image

Python Reinforcement Learning

By: Sudharsan Ravichandiran, Sean Saito, Rajalingappaa Shanmugamani, Yang Wenzhuo

Overview of this book

Reinforcement Learning (RL) is the trending and most promising branch of artificial intelligence. This Learning Path will help you master not only the basic reinforcement learning algorithms but also the advanced deep reinforcement learning algorithms. The Learning Path starts with an introduction to RL followed by OpenAI Gym, and TensorFlow. You will then explore various RL algorithms, such as Markov Decision Process, Monte Carlo methods, and dynamic programming, including value and policy iteration. You'll also work on various datasets including image, text, and video. This example-rich guide will introduce you to deep RL algorithms, such as Dueling DQN, DRQN, A3C, PPO, and TRPO. You will gain experience in several domains, including gaming, image processing, and physical simulations. You'll explore TensorFlow and OpenAI Gym to implement algorithms that also predict stock prices, generate natural language, and even build other neural networks. You will also learn about imagination-augmented agents, learning from human preference, DQfD, HER, and many of the recent advancements in RL. By the end of the Learning Path, you will have all the knowledge and experience needed to implement RL and deep RL in your projects, and you enter the world of artificial intelligence to solve various real-life problems. This Learning Path includes content from the following Packt products: • Hands-On Reinforcement Learning with Python by Sudharsan Ravichandiran • Python Reinforcement Learning Projects by Sean Saito, Yang Wenzhuo, and Rajalingappaa Shanmugamani
Table of Contents (27 chapters)
Title Page
About Packt
Contributors
Preface
Index

Trust region policy optimization


The trust region policy optimization (TRPO) algorithm was proposed to solve complex continuous control tasks in the following paper: Schulman, S. Levine, P. Moritz, M. Jordan and P. Abbeel. Trust Region Policy Optimization. In ICML, 2015.

To understand why TRPO works requires some mathematical background. The main idea is that it is better to guarantee that the new policy, 

, optimized by one training step, not only monotonically decreases the optimization loss function (and thus improves the policy), but also does not deviate from the previous policy 

much, which means that there should be a constraint on the difference between 

and

, for example, 

for a certain constraint function 

constant

.

Theory behind TRPO

Let's see the mechanism behind TRPO. If you feel that this part is hard to understand, you can skip it and go directly to how to run TRPO to solve MuJoCo control tasks. Consider an infinite-horizon discounted Markov decision process denoted by

, where...