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Deep Reinforcement Learning Hands-On

Deep Reinforcement Learning Hands-On

By : Maxim Lapan
4.3 (34)
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Deep Reinforcement Learning Hands-On

Deep Reinforcement Learning Hands-On

4.3 (34)
By: Maxim Lapan

Overview of this book

Deep Reinforcement Learning Hands-On is a comprehensive guide to the very latest DL tools and their limitations. You will evaluate methods including Cross-entropy and policy gradients, before applying them to real-world environments. Take on both the Atari set of virtual games and family favorites such as Connect4. The book provides an introduction to the basics of RL, giving you the know-how to code intelligent learning agents to take on a formidable array of practical tasks. Discover how to implement Q-learning on 'grid world' environments, teach your agent to buy and trade stocks, and find out how natural language models are driving the boom in chatbots.
Table of Contents (21 chapters)
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20
Index

Value, state, and optimality

You may remember our definition of the value of the state in Chapter 1, What is Reinforcement Learning?. This is a very important notion and the time has come to explore it further. This whole part of the book is built around the value and how to approximate it. We defined value as an expected total reward that is obtainable from the state. In a formal way, the value of the state is: Value, state, and optimality, where Value, state, and optimality is the local reward obtained at the step t of the episode.

The total reward could be discounted or not; it's up to us how to define it. Value is always calculated in the respect of some policy that our agent follows. To illustrate, let's consider a very simple environment with three states:

  1. The agent's initial state.
  2. The final state that the agent is in after executing action "left" from the initial state. The reward obtained from this is 1.
  3. The final state that the agent is in after action "down". The reward obtained from this is 2...

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