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

Deep neural networks and Q-learning

The Q-learning algorithm, as we saw in Chapter 4, Q-Learning and SARSA Applications, has many qualities that enable its application in many real-world contexts. A key ingredient of this algorithm is that it makes use of the Bellman equation for learning the Q-function. The Bellman equation, as used by the Q-learning algorithm, enables the updating of Q-values from subsequent state-action values. This makes the algorithm able to learn at every step, without waiting until the trajectory is completed. Also, every state or action-state pair has its own values stored in a lookup table that saves and retrieves the corresponding values. Being designed in this way, Q-learning converges to optimal values as long as all the state-action pairs are repeatedly sampled. Furthermore, the method uses two policies: a non-greedy behavior policy to gather experience...