Book Image

Reinforcement Learning Algorithms with Python

By : Andrea Lonza
Book Image

Reinforcement Learning Algorithms with Python

By: Andrea Lonza

Overview of this book

Reinforcement Learning (RL) is a popular and promising branch of AI that involves making smarter models and agents that can automatically determine ideal behavior based on changing requirements. This book will help you master RL algorithms and understand their implementation as you build self-learning agents. Starting with an introduction to the tools, libraries, and setup needed to work in the RL environment, this book covers the building blocks of RL and delves into value-based methods, such as the application of Q-learning and SARSA algorithms. You'll learn how to use a combination of Q-learning and neural networks to solve complex problems. Furthermore, you'll study the policy gradient methods, TRPO, and PPO, to improve performance and stability, before moving on to the DDPG and TD3 deterministic algorithms. This book also covers how imitation learning techniques work and how Dagger can teach an agent to drive. You'll discover evolutionary strategies and black-box optimization techniques, and see how they can improve RL algorithms. Finally, you'll get to grips with exploration approaches, such as UCB and UCB1, and develop a meta-algorithm called ESBAS. By the end of the book, you'll have worked with key RL algorithms to overcome challenges in real-world applications, and be part of the RL research community.
Table of Contents (19 chapters)
Free Chapter
1
Section 1: Algorithms and Environments
5
Section 2: Model-Free RL Algorithms
11
Section 3: Beyond Model-Free Algorithms and Improvements
17
Assessments

Trust region policy optimization

Trust region policy optimization (TRPO) is the first successful algorithm that makes use of several approximations to compute the natural gradient with the goal of training a deep neural network policy in a more controlled and stable way. From NPG, we saw that it isn't possible to compute the inverse of the FIM for nonlinear functions with a lot of parameters. TRPO overcomes these difficulties by building on top of NPG. It does this by introducing a surrogate objective function and making a series of approximations, which means it succeeds in learning about complex policies for walking, hopping, or playing Atari games from raw pixels.

TRPO is one of the most complex model-free algorithms and though we already learned the underlying principles of the natural gradient, there are still difficult parts behind it. In this chapter, we'll only...