96 lines
4.3 KiB
Python
96 lines
4.3 KiB
Python
#!/usr/bin/env python
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# coding=utf-8
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'''
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@Author: John
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@Email: johnjim0816@gmail.com
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@Date: 2020-06-12 00:50:49
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@LastEditor: John
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LastEditTime: 2022-08-11 09:52:23
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@Discription:
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@Environment: python 3.7.7
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'''
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'''off-policy
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'''
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import torch
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import torch.nn as nn
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import torch.optim as optim
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import random
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import math
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import numpy as np
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class DQN:
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def __init__(self,n_actions,model,memory,cfg):
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self.n_actions = n_actions
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self.device = torch.device(cfg.device) # cpu or cuda
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self.gamma = cfg.gamma # 奖励的折扣因子
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# e-greedy策略相关参数
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self.sample_count = 0 # 用于epsilon的衰减计数
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self.epsilon = cfg.epsilon_start
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self.sample_count = 0
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self.epsilon_start = cfg.epsilon_start
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self.epsilon_end = cfg.epsilon_end
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self.epsilon_decay = cfg.epsilon_decay
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self.batch_size = cfg.batch_size
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self.policy_net = model.to(self.device)
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self.target_net = model.to(self.device)
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for target_param, param in zip(self.target_net.parameters(),self.policy_net.parameters()): # 复制参数到目标网路targe_net
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target_param.data.copy_(param.data)
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self.optimizer = optim.Adam(self.policy_net.parameters(), lr=cfg.lr) # 优化器
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self.memory = memory # 经验回放
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def sample(self, state):
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''' 选择动作
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'''
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self.sample_count += 1
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self.epsilon = self.epsilon_end + (self.epsilon_start - self.epsilon_end) * \
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math.exp(-1. * self.sample_count / self.epsilon_decay) # epsilon是会递减的，这里选择指数递减
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if random.random() > self.epsilon:
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with torch.no_grad():
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state = torch.tensor(state, device=self.device, dtype=torch.float32).unsqueeze(dim=0)
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q_values = self.policy_net(state)
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action = q_values.max(1)[1].item() # 选择Q值最大的动作
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else:
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action = random.randrange(self.n_actions)
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return action
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def predict(self,state):
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with torch.no_grad():
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state = torch.tensor(state, device=self.device, dtype=torch.float32).unsqueeze(dim=0)
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q_values = self.policy_net(state)
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action = q_values.max(1)[1].item() # 选择Q值最大的动作
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return action
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def update(self):
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if len(self.memory) < self.batch_size: # 当memory中不满足一个批量时，不更新策略
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return
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# 从经验回放中(replay memory)中随机采样一个批量的转移(transition)
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state_batch, action_batch, reward_batch, next_state_batch, done_batch = self.memory.sample(
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self.batch_size)
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state_batch = torch.tensor(np.array(state_batch), device=self.device, dtype=torch.float)
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action_batch = torch.tensor(action_batch, device=self.device).unsqueeze(1)
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reward_batch = torch.tensor(reward_batch, device=self.device, dtype=torch.float)
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next_state_batch = torch.tensor(np.array(next_state_batch), device=self.device, dtype=torch.float)
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done_batch = torch.tensor(np.float32(done_batch), device=self.device)
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q_values = self.policy_net(state_batch).gather(dim=1, index=action_batch) # 计算当前状态(s_t,a)对应的Q(s_t, a)
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next_q_values = self.target_net(next_state_batch).max(1)[0].detach() # 计算下一时刻的状态(s_t_,a)对应的Q值
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# 计算期望的Q值，对于终止状态，此时done_batch[0]=1, 对应的expected_q_value等于reward
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expected_q_values = reward_batch + self.gamma * next_q_values * (1-done_batch)
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loss = nn.MSELoss()(q_values, expected_q_values.unsqueeze(1)) # 计算均方根损失
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# 优化更新模型
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self.optimizer.zero_grad()
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loss.backward()
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for param in self.policy_net.parameters(): # clip防止梯度爆炸
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param.grad.data.clamp_(-1, 1)
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self.optimizer.step()
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def save(self, path):
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from pathlib import Path
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Path(path).mkdir(parents=True, exist_ok=True)
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torch.save(self.target_net.state_dict(), path+'checkpoint.pth')
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def load(self, path):
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self.target_net.load_state_dict(torch.load(path+'checkpoint.pth'))
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for target_param, param in zip(self.target_net.parameters(), self.policy_net.parameters()):
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param.data.copy_(target_param.data)
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