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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27
Index

A3C with data parallelism

The first version of A3C parallelization that we will check (which was outlined in Figure 13.2) has both one main process that carries out training and several child processes communicating with environments and gathering experience to train on.

Implementation

For simplicity and efficiency, the NN weights broadcasting from the trainer process are not implemented. Instead of explicitly gathering and sending weights to child processes, the network is shared between all processes using PyTorch built-in capabilities, allowing us to use the same nn.Module instance with all its weights in different processes by calling the share_memory() method on NN creation. Under the hood, this method has zero overhead for CUDA (as GPU memory is shared among all the host's processes), or shared memory inter-process communication (IPC) in the case of CPU computation. In both cases, the method improves performance, but limits our example of one single machine using one...