Book Image

Deep Reinforcement Learning Hands-On - Second Edition

By : Maxim Lapan
5 (2)
Book Image

Deep Reinforcement Learning Hands-On - Second Edition

5 (2)
By: Maxim Lapan

Overview of this book

Deep Reinforcement Learning Hands-On, Second Edition is an updated and expanded version of the bestselling guide to the very latest reinforcement learning (RL) tools and techniques. It provides you with an introduction to the fundamentals of RL, along with the hands-on ability to code intelligent learning agents to perform a range of practical tasks. With six new chapters devoted to a variety of up-to-the-minute developments in RL, including discrete optimization (solving the Rubik's Cube), multi-agent methods, Microsoft's TextWorld environment, advanced exploration techniques, and more, you will come away from this book with a deep understanding of the latest innovations in this emerging field. In addition, you will gain actionable insights into such topic areas as deep Q-networks, policy gradient methods, continuous control problems, and highly scalable, non-gradient methods. You will also discover how to build a real hardware robot trained with RL for less than $100 and solve the Pong environment in just 30 minutes of training using step-by-step code optimization. In short, Deep Reinforcement Learning Hands-On, Second Edition, is your companion to navigating the exciting complexities of RL as it helps you attain experience and knowledge through real-world examples.
Table of Contents (28 chapters)
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Index

What's wrong with -greedy?

Throughout the book, we have used the -greedy exploration strategy as a simple, but still acceptable, approach to exploring the environment. The underlying idea behind -greedy is to take a random action with the probability of ; otherwise, (with probability) we act greedily. By varying the hyperparameter, we can change the exploration ratio. This approach was used in most of the value-based methods described in the book.

Quite a similar idea was used in policy-based methods, when our network returns the probability distribution over actions to take. To prevent the network from becoming too certain about actions (by returning a probability of 1 for a specific action and 0 for others), we added the entropy loss, which is just the entropy of the probability distribution multiplied by some hyperparameter. In the early stages of the training, this entropy loss pushes our network toward taking random actions (by regularizing the probability distribution...