qlearning.py

# coding: utf-8

# Python Machine Learning, PyTorch Edition by Sebastian Raschka (https://sebastianraschka.com), Yuxi (Hayden) Liu
# (https://www.mlexample.com/) & Vahid Mirjalili (http://vahidmirjalili.com), Packt Publishing Ltd. 2021
#
# Code Repository:
#
# Code License: MIT License (https://github.com/   /LICENSE.txt)

#################################################################################
# Chapter 19 - Reinforcement Learning for Decision Making in Complex Environments
#################################################################################

# Script: qlearning.py

from gridworld_env import GridWorldEnv
from agent import Agent
from collections import namedtuple
import matplotlib.pyplot as plt
import numpy as np

np.random.seed(1)

Transition = namedtuple(
    'Transition', ('state', 'action', 'reward', 'next_state', 'done'))


def run_qlearning(agent, env, num_episodes=50):
    history = []
    for episode in range(num_episodes):
        state = env.reset()
        env.render(mode='human')
        final_reward, n_moves = 0.0, 0
        while True:
            action = agent.choose_action(state)
            next_s, reward, done, _ = env.step(action)
            agent._learn(Transition(state, action, reward,
                                    next_s, done))
            env.render(mode='human', done=done)
            state = next_s
            n_moves += 1
            if done:
                break
            final_reward = reward
        history.append((n_moves, final_reward))
        print(f'Episode {episode}: Reward {final_reward:.2} #Moves {n_moves}')

    return history


def plot_learning_history(history):
    fig = plt.figure(1, figsize=(14, 10))
    ax = fig.add_subplot(2, 1, 1)
    episodes = np.arange(len(history))
    moves = np.array([h[0] for h in history])
    plt.plot(episodes, moves, lw=4,
             marker="o", markersize=10)
    ax.tick_params(axis='both', which='major', labelsize=15)
    plt.xlabel('Episodes', size=20)
    plt.ylabel('# moves', size=20)

    ax = fig.add_subplot(2, 1, 2)
    rewards = np.array([h[1] for h in history])
    plt.step(episodes, rewards, lw=4)
    ax.tick_params(axis='both', which='major', labelsize=15)
    plt.xlabel('Episodes', size=20)
    plt.ylabel('Final rewards', size=20)
    plt.savefig('q-learning-history.png', dpi=300)
    plt.show()


if __name__ == '__main__':
    env = GridWorldEnv(num_rows=5, num_cols=6)
    agent = Agent(env)
    history = run_qlearning(agent, env)
    env.close()

    plot_learning_history(history)