视频讲解：

1. 仅考虑局部合并奖励：目前的奖励只设置为合并方块时获得的分数，只关注了每一步的即时合并收益，而没有对最终达成 2048 这个目标给予额外的激励，如果没有对达成 2048 给予足够的奖励信号，Agent 可能不会将其作为一个重要的目标

2. 训练硬件资源利用不高，没有使用GPU进行加速，默认为CPU，较慢

代码修改如下：

step函数里面，输入维度增加max_tile最大的数是多少

if 2048 in self.board:
    reward += 10000
    done = True
state = self.board.flatten()
max_tile = np.max(self.board)
state = np.append(state, max_tile)
return state, reward, done

input_size = 17

检查系统中是否有可用的 GPU，如果有则使用 GPU 进行计算，否则使用 CPU。

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

在 train ，创建模型实例后，使用 .to(device) 将模型移动到指定的设备（GPU 或 CPU）

model = DQN(input_size, output_size).to(device)
target_model = DQN(input_size, output_size).to(device)

在训练和推理过程中，将输入数据（状态、动作、奖励等）也移动到指定的设备上。

state = torch.FloatTensor(state).unsqueeze(0).to(device)

next_state = torch.FloatTensor(next_state).unsqueeze(0).to(device)

states = torch.FloatTensor(states).to(device)
actions = torch.LongTensor(actions).to(device)
rewards = torch.FloatTensor(rewards).to(device)
next_states = torch.FloatTensor(next_states).to(device)
dones = torch.FloatTensor(dones).to(device)

将 state 和 next_state 先使用 .cpu() 方法移动到 CPU 上，再使用 .numpy() 方法转换为 NumPy 数组

replay_buffer.add(state.cpu().squeeze(0).numpy(), action, reward, next_state.cpu().squeeze(0).numpy(), done)

这个不改的话，会出现 TypeError: can't convert cuda:0 device type tensor to numpy 错误

完整代码如下：

import numpy as np
import torch
import torch.nn as nn
import torch.optim as optim
import random
from collections import deque
import matplotlib.pyplot as plt
import matplotlib.colors as mcolors
from matplotlib.table import Table

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

# 2048 游戏环境类
class Game2048:
    def __init__(self):
        self.board = np.zeros((4, 4), dtype=int)
        self.add_random_tile()
        self.add_random_tile()

    def add_random_tile(self):
        empty_cells = np.argwhere(self.board == 0)
        if len(empty_cells) > 0:
            index = random.choice(empty_cells)
            self.board[index[0], index[1]] = 2 if random.random() < 0.9 else 4

    def move_left(self):
        reward = 0
        new_board = np.copy(self.board)
        for row in range(4):
            line = new_board[row]
            non_zero = line[line != 0]
            merged = []
            i = 0
            while i < len(non_zero):
                if i + 1 < len(non_zero) and non_zero[i] == non_zero[i + 1]:
                    merged.append(2 * non_zero[i])
                    reward += 2 * non_zero[i]
                    i += 2
                else:
                    merged.append(non_zero[i])
                    i += 1
            new_board[row] = np.pad(merged, (0, 4 - len(merged)), 'constant')
        if not np.array_equal(new_board, self.board):
            self.board = new_board
            self.add_random_tile()
        return reward

    def move_right(self):
        self.board = np.fliplr(self.board)
        reward = self.move_left()
        self.board = np.fliplr(self.board)
        return reward

    def move_up(self):
        self.board = self.board.T
        reward = self.move_left()
        self.board = self.board.T
        return reward

    def move_down(self):
        self.board = self.board.T
        reward = self.move_right()
        self.board = self.board.T
        return reward

    def step(self, action):
        if action == 0:
            reward = self.move_left()
        elif action == 1:
            reward = self.move_right()
        elif action == 2:
            reward = self.move_up()
        elif action == 3:
            reward = self.move_down()
        done = not np.any(self.board == 0) and all([
            np.all(self.board[:, i] != self.board[:, i + 1]) for i in range(3)
        ]) and all([
            np.all(self.board[i, :] != self.board[i + 1, :]) for i in range(3)
        ])
        if 2048 in self.board:
            reward += 10000
            done = True
        state = self.board.flatten()
        max_tile = np.max(self.board)
        state = np.append(state, max_tile)
        return state, reward, done

    def reset(self):
        self.board = np.zeros((4, 4), dtype=int)
        self.add_random_tile()
        self.add_random_tile()
        state = self.board.flatten()
        max_tile = np.max(self.board)
        state = np.append(state, max_tile)
        return state

# 深度 Q 网络类
class DQN(nn.Module):
    def __init__(self, input_size, output_size):
        super(DQN, self).__init__()
        self.fc1 = nn.Linear(input_size, 128)
        self.fc2 = nn.Linear(128, 128)
        self.fc3 = nn.Linear(128, output_size)

    def forward(self, x):
        x = torch.relu(self.fc1(x))
        x = torch.relu(self.fc2(x))
        return self.fc3(x)

# 经验回放缓冲区类
class ReplayBuffer:
    def __init__(self, capacity):
        self.buffer = deque(maxlen=capacity)

    def add(self, state, action, reward, next_state, done):
        self.buffer.append((state, action, reward, next_state, done))

    def sample(self, batch_size):
        batch = random.sample(self.buffer, batch_size)
        states, actions, rewards, next_states, dones = zip(*batch)
        return np.array(states), np.array(actions), np.array(rewards), np.array(next_states), np.array(dones)

    def __len__(self):
        return len(self.buffer)

# 可视化函数
def visualize_board(board, ax):
    ax.clear()
    table = Table(ax, bbox=[0, 0, 1, 1])
    nrows, ncols = board.shape
    width, height = 1.0 / ncols, 1.0 / nrows

    # 定义颜色映射
    cmap = mcolors.LinearSegmentedColormap.from_list("", ["white", "yellow", "orange", "red"])

    for (i, j), val in np.ndenumerate(board):
        color = cmap(np.log2(val + 1) / np.log2(2048 + 1)) if val > 0 else "white"
        table.add_cell(i, j, width, height, text=val if val > 0 else "",
                       loc='center', facecolor=color)

    ax.add_table(table)
    ax.set_axis_off()
    plt.draw()
    plt.pause(0.1)

# 训练函数
def train():
    env = Game2048()
    input_size = 17
    output_size = 4
    model = DQN(input_size, output_size).to(device)
    target_model = DQN(input_size, output_size).to(device)
    target_model.load_state_dict(model.state_dict())
    target_model.eval()

    optimizer = optim.Adam(model.parameters(), lr=0.001)
    criterion = nn.MSELoss()
    replay_buffer = ReplayBuffer(capacity=10000)
    batch_size = 32
    gamma = 0.99
    epsilon = 1.0
    epsilon_decay = 0.995
    epsilon_min = 0.01
    update_target_freq = 10

    num_episodes = 1000
    fig, ax = plt.subplots()
    for episode in range(num_episodes):
        state = env.reset()
        state = torch.FloatTensor(state).unsqueeze(0).to(device)
        done = False
        total_reward = 0
        while not done:
            visualize_board(env.board, ax)
            if random.random() < epsilon:
                action = random.randint(0, output_size - 1)
            else:
                q_values = model(state)
                action = torch.argmax(q_values, dim=1).item()

            next_state, reward, done = env.step(action)
            next_state = torch.FloatTensor(next_state).unsqueeze(0).to(device)
            replay_buffer.add(state.cpu().squeeze(0).numpy(), action, reward, next_state.cpu().squeeze(0).numpy(), done)

            if len(replay_buffer) >= batch_size:
                states, actions, rewards, next_states, dones = replay_buffer.sample(batch_size)
                states = torch.FloatTensor(states).to(device)
                actions = torch.LongTensor(actions).to(device)
                rewards = torch.FloatTensor(rewards).to(device)
                next_states = torch.FloatTensor(next_states).to(device)
                dones = torch.FloatTensor(dones).to(device)

                q_values = model(states)
                q_values = q_values.gather(1, actions.unsqueeze(1)).squeeze(1)

                next_q_values = target_model(next_states)
                next_q_values = next_q_values.max(1)[0]
                target_q_values = rewards + gamma * (1 - dones) * next_q_values

                loss = criterion(q_values, target_q_values)
                optimizer.zero_grad()
                loss.backward()
                optimizer.step()

            state = next_state
            total_reward += reward

        if episode % update_target_freq == 0:
            target_model.load_state_dict(model.state_dict())

        epsilon = max(epsilon * epsilon_decay, epsilon_min)
        print(f"Episode {episode}: Total Reward = {total_reward}, Epsilon = {epsilon}")

    plt.close()

if __name__ == "__main__":
    train()