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Reinforcement Learning with TensorFlow

You're reading from  Reinforcement Learning with TensorFlow

Product type Book
Published in Apr 2018
Publisher Packt
ISBN-13 9781788835725
Pages 334 pages
Edition 1st Edition
Languages
Author (1):
Sayon Dutta Sayon Dutta
Profile icon Sayon Dutta

Table of Contents (21) Chapters

Title Page
Packt Upsell
Contributors
Preface
1. Deep Learning – Architectures and Frameworks 2. Training Reinforcement Learning Agents Using OpenAI Gym 3. Markov Decision Process 4. Policy Gradients 5. Q-Learning and Deep Q-Networks 6. Asynchronous Methods 7. Robo Everything – Real Strategy Gaming 8. AlphaGo – Reinforcement Learning at Its Best 9. Reinforcement Learning in Autonomous Driving 10. Financial Portfolio Management 11. Reinforcement Learning in Robotics 12. Deep Reinforcement Learning in Ad Tech 13. Reinforcement Learning in Image Processing 14. Deep Reinforcement Learning in NLP 1. Further topics in Reinforcement Learning 2. Other Books You May Enjoy Index

Q-learning


In reinforcement learning, we want the Q-function Q(s,a) to predict the best action for a state s in order to maximize the future reward. The Q-function is estimated using Q-learning, which involves the process of updating the Q-function using Bellman equations through a series of iterations as follows:

Here:

Q(s,a) = Q value for the current state s and action a pair

 = learning rate of convergence

 = discounting factor of future rewards

Q(s',a') = Q value for the state action pair at the resultant state s' after action a was taken at state s

R = refers to immediate reward

 = future reward

In simpler cases, where state space and action space are discrete, Q-learning is implemented using a Q-table, where rows represent the states and columns represent the actions. 

Steps involved in Q-learning are as follows:

  1. Initialize Q-table randomly
  2. For each episode, perform the following steps:
    1. For the given state s, choose action a from the Q-table
    2. Perform action a
    3. Reward R and state s' is observed
    4. Update...
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