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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

A2C on Pong

In the previous chapter, we saw a (not very successful) attempt to solve our favorite Pong environment with PG. Let's try it again with the actor-critic method at hand.

GAMMA = 0.99
LEARNING_RATE = 0.001
ENTROPY_BETA = 0.01
BATCH_SIZE = 128
NUM_ENVS = 50

REWARD_STEPS = 4
CLIP_GRAD = 0.1

We're starting, as usual, by defining hyperparameters (imports are omitted). These values are not tuned, as we'll do this in the next section of this chapter. We have one new value here: CLIP_GRAD. This hyperparameter is specifying the threshold for gradient clipping, which, basically, prevents our gradients at optimization stage from becoming too large and pushing our policy too far. Clipping is implemented using the PyTorch functionality, but the idea is very simple: if the L2 norm of the gradient is larger than this hyperparameter, then the gradient vector is clipped to this value.

The REWARD_STEPS hyperparameter determines how many steps ahead we'll take to approximate the...

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