Book Image

Hands-On Q-Learning with Python

By : Nazia Habib
Book Image

Hands-On Q-Learning with Python

By: Nazia Habib

Overview of this book

Q-learning is a machine learning algorithm used to solve optimization problems in artificial intelligence (AI). It is one of the most popular fields of study among AI researchers. This book starts off by introducing you to reinforcement learning and Q-learning, in addition to helping you become familiar with OpenAI Gym as well as libraries such as Keras and TensorFlow. A few chapters into the book, you will gain insights into model-free Q-learning and use deep Q-networks and double deep Q-networks to solve complex problems. This book will guide you in exploring use cases such as self-driving vehicles and OpenAI Gym’s CartPole problem. You will also learn how to tune and optimize Q-networks and their hyperparameters. As you progress, you will understand the reinforcement learning approach to solving real-world problems. You will also explore how to use Q-learning and related algorithms in scientific research. Toward the end, you’ll gain insight into what’s in store for reinforcement learning. By the end of this book, you will be equipped with the skills you need to solve reinforcement learning problems using Q-learning algorithms with OpenAI Gym, Keras, and TensorFlow.
Table of Contents (14 chapters)
Free Chapter
1
Section 1: Q-Learning: A Roadmap
6
Section 2: Building and Optimizing Q-Learning Agents
9
Section 3: Advanced Q-Learning Challenges with Keras, TensorFlow, and OpenAI Gym

Building further on DQNs

There are several improvements and additions to deep Q-networks that are worth exploring broadly here. We won't be working with these algorithms directly in this chapter, but this is a good starting point for finding ways to improve the performance of the DQNs you've built so far.

Calculating DQN loss

Calculating the prediction loss in a DQN (also called the TD or Temporal Difference error) is a matter of finding the difference between the true Q-value of a state-action pair and the value estimated by the network. We then backpropagate the loss to the earlier nodes in the network to update their weights.

The issue we run into is that we don't actually know the true Q-value of a state...