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Deep Reinforcement Learning Hands-On. - Second Edition

You're reading from  Deep Reinforcement Learning Hands-On. - Second Edition

Product type Book
Published in Jan 2020
Publisher Packt
ISBN-13 9781838826994
Pages 826 pages
Edition 2nd Edition
Languages
Author (1):
Maxim Lapan Maxim Lapan
Profile icon Maxim Lapan

Table of Contents (28) Chapters

Preface 1. What Is Reinforcement Learning? 2. OpenAI Gym 3. Deep Learning with PyTorch 4. The Cross-Entropy Method 5. Tabular Learning and the Bellman Equation 6. Deep Q-Networks 7. Higher-Level RL Libraries 8. DQN Extensions 9. Ways to Speed up RL 10. Stocks Trading Using RL 11. Policy Gradients – an Alternative 12. The Actor-Critic Method 13. Asynchronous Advantage Actor-Critic 14. Training Chatbots with RL 15. The TextWorld Environment 16. Web Navigation 17. Continuous Action Space 18. RL in Robotics 19. Trust Regions – PPO, TRPO, ACKTR, and SAC 20. Black-Box Optimization in RL 21. Advanced Exploration 22. Beyond Model-Free – Imagination 23. AlphaGo Zero 24. RL in Discrete Optimization 25. Multi-agent RL 26. Other Books You May Enjoy
27. Index

The Connect 4 bot

To see the method in action, let's implement AlphaGo Zero for Connect 4. The game is for two players with fields 6×7. Players have disks of two different colors, which they drop in turn into any of the seven columns. The disks fall to the bottom, stacking vertically. The game objective is to be the first to form a horizontal, vertical, or diagonal group of four disks of the same color. Two game situations are shown in the following diagram. In the first situation, the first player has just won, while in the second, the second player is going to form a group.

Figure 23.2: Two game positions in Connect 4

Despite its simplicity, this game has 4.5*1012 different game states, which is challenging for computers to solve with brute force. This example consists of several tools and library modules:

  • Chapter23/lib/game.py: A low-level game representation that contains functions to make moves, encode, and decode the game state, and other game-related...
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