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Deep Reinforcement Learning Hands-On

You're reading from   Deep Reinforcement Learning Hands-On A practical and easy-to-follow guide to RL from Q-learning and DQNs to PPO and RLHF

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Product type Paperback
Published in Nov 2024
Publisher Packt
ISBN-13 9781835882702
Length 716 pages
Edition 3rd Edition
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Author (1):
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Maxim Lapan Maxim Lapan
Author Profile Icon Maxim Lapan
Maxim Lapan
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Toc

Table of Contents (29) Chapters Close

Preface 1. Part 1 Introduction to RL FREE CHAPTER
2. What Is Reinforcement Learning? 3. OpenAI Gym API and Gymnasium 4. Deep Learning with PyTorch 5. The Cross-Entropy Method 6. Part 2 Value-based methods
7. Tabular Learning and the Bellman Equation 8. Deep Q-Networks 9. Higher-Level RL Libraries 10. DQN Extensions 11. Ways to Speed Up RL 12. Stocks Trading Using RL 13. Part 3 Policy-based methods
14. Policy Gradients 15. Actor-Critic Method: A2C and A3C 16. The TextWorld Environment 17. Web Navigation 18. Part 4 Advanced RL
19. Continous Action Space 20. Trust Region Methods 21. Black-Box Optimizations in RL 22. Advanced Exploration 23. Reinforcement Learning with Human Feedback 24. AlphaGo Zero and MuZero 25. RL in Discrete Optimization 26. Multi-Agent RL 27. Bibliography
28. Index

The value iteration method

In the simplistic example you just saw, to calculate the values of the states and actions, we exploited the structure of the environment: we had no loops in transitions, so we could start from terminal states, calculate their values, and then proceed to the central state. However, just one loop in the environment builds an obstacle in our approach. Let’s consider such an environment with two states:

ssrrγ12==12= 0.9

Figure 5.7: A sample environment with a loop in the transition diagram

We start from state s1, and the only action we can take leads us to state s2. We get the reward, r = 1, and the only transition from s2 is an action, which brings us back to s1. So, the life of our agent is an infinite sequence of states [s1,s2,s1,s2,]. To deal with this infinity loop, we can use a discount factor: γ = 0.9. Now, the question is, what are the values for both the states? The answer is not very complicated, in...

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