Book Image

Python Reinforcement Learning

By : Sudharsan Ravichandiran, Sean Saito, Rajalingappaa Shanmugamani, Yang Wenzhuo
Book Image

Python Reinforcement Learning

By: Sudharsan Ravichandiran, Sean Saito, Rajalingappaa Shanmugamani, Yang Wenzhuo

Overview of this book

Reinforcement Learning (RL) is the trending and most promising branch of artificial intelligence. This Learning Path will help you master not only the basic reinforcement learning algorithms but also the advanced deep reinforcement learning algorithms. The Learning Path starts with an introduction to RL followed by OpenAI Gym, and TensorFlow. You will then explore various RL algorithms, such as Markov Decision Process, Monte Carlo methods, and dynamic programming, including value and policy iteration. You'll also work on various datasets including image, text, and video. This example-rich guide will introduce you to deep RL algorithms, such as Dueling DQN, DRQN, A3C, PPO, and TRPO. You will gain experience in several domains, including gaming, image processing, and physical simulations. You'll explore TensorFlow and OpenAI Gym to implement algorithms that also predict stock prices, generate natural language, and even build other neural networks. You will also learn about imagination-augmented agents, learning from human preference, DQfD, HER, and many of the recent advancements in RL. By the end of the Learning Path, you will have all the knowledge and experience needed to implement RL and deep RL in your projects, and you enter the world of artificial intelligence to solve various real-life problems. This Learning Path includes content from the following Packt products: • Hands-On Reinforcement Learning with Python by Sudharsan Ravichandiran • Python Reinforcement Learning Projects by Sean Saito, Yang Wenzhuo, and Rajalingappaa Shanmugamani
Table of Contents (27 chapters)
Title Page
About Packt
Contributors
Preface
Index

Implementation of A3C


We will now look at how to implement A3C using Python and TensorFlow. Here, the policy network and value network share the same feature representation. We implement two kinds of policies: one is based on the CNN architecture used in DQN, and the other is based on LSTM.

We implement the FFPolicy class for the policy based on CNN:

class FFPolicy:

    def __init__(self, input_shape=(84, 84, 4), n_outputs=4, network_type='cnn'):

        self.width = input_shape[0]
        self.height = input_shape[1]
        self.channel = input_shape[2]
        self.n_outputs = n_outputs
        self.network_type = network_type
        self.entropy_beta = 0.01

        self.x = tf.placeholder(dtype=tf.float32, 
                                shape=(None, self.channel, self.width, self.height))
        self.build_model()

The constructor requires three arguments:

  1.  input_shape
  2. n_outputs
  3. network_type

 

input_shape is the size of the input image. After data preprocessing, the input is an 84x84x4...