【深度强化学习】如何使用多进程（multiprocessing、pipe）来加速训练

荒野火狐2024-06-30 19:43

文章目录

实验结果

实验平台：cpu:i7-10870 8核16线程（intel处理器采用超线程技术，一个核心有两个线程，故物理上是8核，逻辑核心是16核）

pytorch 版本：2.2.2+cu121

numpy 版本：1.24.3

gym 版本：0.26.2

模块：

python 复制代码 
from torch.multiprocessing import Process, Pipe #这两个结果一致，第一种继承了第二个使得可以应用在GPU上
#from multiprocessing import Process, Pipe

最后一行为 未使用多进程加速的原始代码。前面几行的进程数为 number/10。

实验结果表明：进程数为cpu物理核心数一半的时候最佳，我是8核，这里实验结果也是4进程的最佳，快了两倍，不过二进程的可能更稳定点，快了1.6倍。其他进程数就不稳定了。

推荐进程数为：物理核心数的一半

以下为8进程时 不稳定展示：

以下为4进程时 稳定性展示：

参考：

1、github代码（参考并修改了这里代码）

2、DPPO深度强化学习算法实现思路(分布式多进程加速)（这里参考了思路2）

3、在Python中优雅地用多进程（->1、这里说明使用Pipe技术运行更快，2、默认为multiprocessing.set_start_method('spawn')好）

4、pytorch模型在multiprocessing下前馈速度明显降低的原因是什么？（->解决了进程中资源抢占的问题）

实现思路

思路1

对于参考2的实现思路1，我感觉作者只是在训练过程中，用了多个进程训练，并在训练后取了平均，也就是说本来是由一个进程训练，现在是多个进程同时训练，两者都在同一个时间线内，并没有起到加速效果，可以说只是起到了平稳训练的作用。（以下为参考2的作者思路1）

在作者的后续实验也表明,确实是这样的效果

其作者的本来想法，我猜测意思是：在训练的时候利用多进程加速。但是训练的时候用的是同一个网络，无法做到在更新完这个网络的同时发送这个网络给训练前的时间点。于是作废。

思路2

这里的实现思路和这里的参考2的思路2本质上是一样的，也是常见的一种思路。

即，在环境采样中使用多进程采样，在训练中单进程更新（训练）。

比方说，在同一时间线内，4个进程同时采样，这样就是同样的时间采样了4条episode,然后在更新时依旧是单条更新。也就是说更新的次数不变，时间不变，且采样次数不变，但采样时间减少了4倍。（由于更新的时间没有减少4倍，所以理论上比原先的速度快1-4倍）

也可以叫做DPPO,D为distributed,分布式的意思，也意为这里的分布式采样。

类似的思想如：A3C

进程与线程介绍

进程：相当于电脑多开了很多应用。

线程：相当于一个应用里，比方说：一个网页浏览器里有一个线程负责渲染页面，另一个线程负责处理用户输入，还有一个线程负责下载文件。这些线程在同一个进程内协作，共同完成浏览器的功能。

比方说上图的VScode是32进程，

这里显示每个进程里有多少个线程，如上图第一个code进程有32个线程。（设置方法见：任务管理器查看线程数、PID值等方法）

了解到此，我们可以了解到上述线程和平时电脑上所说的8核16线程中的线程所区分开，第二个线程说的可以看作逻辑核心数。

实际效果：我这里开了4个进程。看下面python.exe，上面4个为子进程均有34个线程，第5个为主进程，有45个线程。

而原始单进程的话，只有一个进程，这也就解释了为什么多进程会比单进程快的原因。（上述PID = Process ID 进程标识）

如何实现

multiprocessing、Pipe的范例

创建一个子进程、一个管道

python 复制代码 
## study multiprocessing pipe

from torch.multiprocessing import Process, Pipe
#from multiprocessing import Process, Pipe
import numpy as np
def f(conn):
    conn.send([42, None, 'hello']) # 子管道发送数据
    conn.close()

if __name__ == '__main__':
    parent_conn, child_conn = Pipe() # 创建一个管道(双向通信)
    p = Process(target=f, args=(child_conn,)) # 创建一个子进程 进程函数为f
    p.start() # 子进程开始
    print(parent_conn.recv()) #父管道接收 
    p.join() # 等待子进程结束
'''
[42, None, 'hello']
'''

创建多个子进程、多个管道

python 复制代码 
from torch.multiprocessing import Process, Pipe
import numpy as np

def f(conn, i):
    conn.send([42 + i, None, f'hello from process {i}'])  # 子管道发送数据
    conn.close()

if __name__ == '__main__':
    num_processes = 3  # 创建3个进程

    # 使用列表推导式创建管道和进程
    parent_conns, child_conns = zip(*[Pipe() for _ in range(num_processes)])
    processes = [Process(target=f, args=(child_conn, i)) for i, child_conn in enumerate(child_conns)]

    # 启动所有进程
    [p.start() for p in processes]

    # 接收来自所有子进程的数据
    [print(parent_conn.recv()) for parent_conn in parent_conns]

    # 等待所有进程结束
    [p.join() for p in processes]
'''
[42, None, 'hello from process 0']
[43, None, 'hello from process 1']
[44, None, 'hello from process 2']
'''

关于时间对比上的问题

在作者2或者其他部分github上的代码（如下文中的fast-ppo）,对比的是在同一个episode下（同一时间下）对比收敛程度，而 多进程的收敛太具有不稳定性，（我也完全可以堆一个40进程且某次效果表现良好的一次作为实验对比对象，并且可以吹嘘说比原始的快了近30倍），且如此对比没有显示的对比真实时间。

究其原因，实际是多进程在一个episode时，采样了4条episode,并更新了4次，所以在单个episode时，自然收敛的更快，类似于下图这种形式。

于是采用以环境采样的step为横坐标(现大多库里也都这么写了)，看运行同样步数下所需要的时间。

此步数为原始代码中收敛所需要的步数，这样可以把收敛的程度控制，也能显示的对比时间。

这里用了tensorboard来展示训练过程，tensorboard原本也是step为横坐标，这样更贴合

python 复制代码 
from torch.utils.tensorboard import SummaryWriter 
# Build a tensorboard
writer = SummaryWriter(log_dir='runs/PPO_mul_raw/env_{}_raw_number_{}_seed_{}'.format(env_name, number, seed)) #存的位置
writer.add_scalar('return', episode_return, total_steps) #存的数据

终端启动

python 复制代码 
tensorboard --logdir runs #runs为文件夹名字

代码修改

修改主要部分为训练部分

以下面代码为例

raw代码

python 复制代码 
def train_on_policy_agent(env, agent, max_train_steps,number,seed):
    return_list = []
    # Build a tensorboard
    writer = SummaryWriter(log_dir='runs/PPO_mul_raw/env_{}_raw_number_{}_seed_{}'.format(env_name, number, seed))
    total_steps = 0 
    while total_steps < max_train_steps: 
        episode_return = 0
        transition_dict = {'states': [], 'actions': [], 'next_states': [], 'rewards': [], 'dones': []}
        state = env.reset(seed =0)[0] #1.改 gym 0.26.0版本后，env.reset()返回的是一个字典，所以需要加上[0]
        done = False
        while not done:
            #action = agent.take_action(state) #action 这里是[-2,2]的动作 
            action = agent.take_action(state) # forward 无2 这里是[-1,1]的动作
            next_state, reward,terminated, truncated, _ = env.step([action[0]*2]) 
            done = terminated or truncated
            transition_dict['states'].append(state)
            transition_dict['actions'].append(action)
            transition_dict['next_states'].append(next_state)
            transition_dict['rewards'].append(reward)
            transition_dict['dones'].append(done)

            state = next_state
            episode_return += reward
            total_steps += 1
        return_list.append(episode_return)
        agent.update(transition_dict)
        writer.add_scalar('return', episode_return, total_steps)

    return return_list



actor_lr = 1e-4
critic_lr = 5e-3#1e-1#5e-3
num_episodes = 1000
max_train_steps = 2e5 #1000*200
hidden_dim = 128
gamma = 0.9
lmbda = 0.9
epochs = 10
eps = 0.2
#device = torch.device("cuda") if torch.cuda.is_available() else torch.device("cpu")
device = torch.device("cpu")
env_name = 'Pendulum-v1'
env = gym.make(env_name)
#env.seed(0)
torch.manual_seed(0)
state_dim = env.observation_space.shape[0]
action_dim = env.action_space.shape[0]  # 连续动作空间

agent = PPOContinuous(state_dim, hidden_dim, action_dim, actor_lr, critic_lr,
                      lmbda, epochs, eps, gamma, device)

return_list = train_on_policy_agent(env, agent, max_train_steps,number=5,seed=0)

修改为如下:episode 原本为1000，由于环境的最大长度为200，所以步数为200*1000步，即2e5步

思想：

1.新增一个子进程函数：为每个子进程都创建一个环境用来采样步数

2.利用管道技术：在主进程中每次环境采样前传入已更新的网络->在子进程中接收网络并传出episode数据->在主进程中利用episode数据更新网络->回到第一步，直到达到最大步数。

3.利用多进程：在初始位置新增多个子进程，多个管道（两者数目一致），RL开始前子进程开始，RL结束后子进程强制结束。（因为子进程一制开着，得强制结束）

以下代码中： ### 为新增 ## 为4个注意点

python 复制代码 
###
def child_process(conn, env_name):
    env = gym.make(env_name)
    while True:
        agent = conn.recv()  ## 1.这个位置，先传入agent
        transition_dict = {'states': [], 'actions': [], 'next_states': [], 'rewards': [], 'dones': []}
        episode_return = 0
        episode_steps =0
        state = env.reset(seed=0)[0]
        done = False
        while not done:
            action = agent.take_action(state)
            next_state, reward, terminated, truncated, _ = env.step([action[0] * 2])
            done = terminated or truncated
            transition_dict['states'].append(state)
            transition_dict['actions'].append(action)
            transition_dict['next_states'].append(next_state)
            transition_dict['rewards'].append(reward)
            transition_dict['dones'].append(done)
            state = next_state  ## 2.先append再赋值
            episode_return += reward
            episode_steps +=1

        conn.send((transition_dict, episode_return, episode_steps))
###
def main():
    actor_lr = 1e-4
    critic_lr = 5e-3
    num_episodes = 200
    hidden_dim = 128
    gamma = 0.9
    lmbda = 0.9
    epochs = 10
    eps = 0.2
    device = torch.device("cpu")
    env_name = 'Pendulum-v1'
    env = gym.make(env_name)
    torch.manual_seed(0)
    state_dim = env.observation_space.shape[0]
    action_dim = env.action_space.shape[0]
    # Build a tensorboard
    number = 45 #5
    seed = 0
    writer = SummaryWriter(log_dir='runs/PPO_mul_raw/env_{}_mul_number_{}_seed_{}'.format(env_name, number, seed))
    agent = PPOContinuous(state_dim, hidden_dim, action_dim, actor_lr, critic_lr, lmbda, epochs, eps, gamma, device)
    ###
    process_num = 4  #
    #pipe_dict = dict((i, (pipe1, pipe2)) for i in range(process_num) for pipe1, pipe2 in (Pipe(),)) 
    pipe_dict = {i: Pipe() for i in range(process_num)} #Pipe()返回一个元组: (conn1, conn2) #与上行相同
    child_process_list = [Process(target=child_process, args=(pipe_dict[i][1], env_name)) for i in range(process_num)]
    total_steps = 0
    max_train_steps = 2e5 
    [p.start() for p in child_process_list]
    ###
    return_list = []
    while total_steps < max_train_steps:
        episode_return = 0
        [pipe_dict[j][0].send(agent) for j in range(process_num)]   ##3.先传入agent
        for j in range(process_num): ##4. i,j区分
            transition_dict, episode_return_,episode_steps = pipe_dict[j][0].recv()
            agent.update(transition_dict)
            total_steps += episode_steps
            writer.add_scalar('return', episode_return_, total_steps)
            return_list.append(episode_return_)
            
    [p.terminate() for p in child_process_list] #child 用了while True，所以要terminate
    return return_list #单位为episode

if __name__ == '__main__':
    main()

收敛为何不稳定

管道的传输顺序是固定的，那么收敛不稳定可能是进程导致的，因为进程在同一时刻采样，由于每次采样时智能体的动作实际是不同的，导致最后结果的不同。即使设置了 torch.manual_seed(0)，我们不能顺序 执行完一个episode的随机种子的同时，将下一个随机种子数发送到另外一个进程的开始时间 。顺序上不允许，时间上不允许

（即使设置进程按照进程优先级执行进程也无法实现。）

技巧

进程资源抢占问题

pytorch模型在multiprocessing下前馈速度明显降低的原因是什么？（->解决了进程中资源抢占的问题）

python 复制代码 
# 设置OMP_WAIT_POLICY为PASSIVE，让等待的线程不消耗CPU资源 #确保在pytorch前设置
os.environ['OMP_WAIT_POLICY'] = 'PASSIVE' #
import torch

设置如上操作时，1、2为设置前，6，7为设置后。

时间快了5s左右且在任务管理器中，cpu的占用也从97%占用降低到了28%左右

线程问题

参考： pytorch官方

根据此和实践实验下，不设置时（线程数为物理核心数）效果最佳。

设置方法1

python 复制代码 
import os
os.environ['OMP_NUM_THREADS'] = str(8) #默认物理核心数 #我这里是8

设置方法2

python 复制代码 
torch.set_num_threads(8)

mp中的cpu数和默认线程数查看

python 复制代码 
#import torch.multiprocessing as mp
import torch
import multiprocessing as mp
num_cpu = int(mp.cpu_count()) 
print('num_cpu:',num_cpu)
print(torch.get_num_threads())
'''
num_cpu: 16
8
'''

cpu和gpu问题

关于大多数github上代码以及上面作者提到的利用cpu采样、gpu训练加速的技巧，

改法和实现我写在【深度强化学习】如何平衡cpu和gpu来加快训练速度（实录）这里

进阶（还没看懂/还没实验）

并行环境让采样速度快两个量级：Isaac Gym提速强化学习 (利用异步？Envpool)
fast-ppo（利用每个核心的超线程技术？[env1,env2,env3,env4]->[[env1,env2],[env1,env2]]）
深度强化学习库的设计思想（还没写完）(双-CPU群-单-GPU?)

附代码

raw代码

python 复制代码 
import gym
import os
# 设置OMP_WAIT_POLICY为PASSIVE，让等待的线程不消耗CPU资源
os.environ['OMP_WAIT_POLICY'] = 'PASSIVE'
import torch
import torch.nn.functional as F
import numpy as np
import matplotlib.pyplot as plt
import rl_utils
import time

from torch.utils.tensorboard import SummaryWriter  ##1.TB

def compute_advantage(gamma, lmbda, td_delta):
    td_delta = td_delta.detach().numpy()
    advantage_list = []
    advantage = 0.0
    for delta in td_delta[::-1]:
        advantage = gamma * lmbda * advantage + delta
        advantage_list.append(advantage)
    advantage_list.reverse()
    return torch.tensor(np.array(advantage_list), dtype=torch.float)

class PolicyNetContinuous(torch.nn.Module):
    def __init__(self, state_dim, hidden_dim, action_dim):
        super(PolicyNetContinuous, self).__init__()
        self.fc1 = torch.nn.Linear(state_dim, hidden_dim)
        self.fc_mu = torch.nn.Linear(hidden_dim, action_dim) # 均值 #虽然步骤一样，但里面的权重和偏置不一样
        self.fc_std = torch.nn.Linear(hidden_dim, action_dim) # 方差
 
    def forward(self, x):
        x = F.relu(self.fc1(x)) # 激活函数
        mu = torch.tanh(self.fc_mu(x)) #从[-1,1]*2 确保均值范围为[-2,2]  #测试时候归一化时无2
        std = F.softplus(self.fc_std(x)) # 保证方差为正数 softplus = log(1+exp(x))
        return mu, std # 返回高斯分布的均值和方差

class ValueNet(torch.nn.Module):
    def __init__(self, state_dim, hidden_dim):
        super(ValueNet, self).__init__()  # 继承父类的所有属性
        self.fc1 = torch.nn.Linear(state_dim, hidden_dim)
        self.fc1_2 = torch.nn.Linear(hidden_dim, hidden_dim)
        self.fc2 = torch.nn.Linear(hidden_dim, 1)

    def forward(self, x):
        x = F.relu(self.fc1(x))
        x = F.relu(self.fc1_2(x))
        return self.fc2(x)
    
class PPOContinuous:
    ''' 处理连续动作的PPO算法 '''
    def __init__(self, state_dim, hidden_dim, action_dim, actor_lr, critic_lr,
                 lmbda, epochs, eps, gamma, device):
        self.actor = PolicyNetContinuous(state_dim, hidden_dim,action_dim).to(device)
        self.critic = ValueNet(state_dim, hidden_dim).to(device)
        self.actor_optimizer = torch.optim.Adam(self.actor.parameters(),lr=actor_lr)
        self.critic_optimizer = torch.optim.Adam(self.critic.parameters(),lr=critic_lr)
        self.gamma = gamma
        self.lmbda = lmbda
        self.epochs = epochs
        self.eps = eps
        self.device = device

    def take_action(self, state):
        state = torch.tensor(np.array([state]), dtype=torch.float).to(self.device)
        mu, sigma = self.actor(state)
        action_dist = torch.distributions.Normal(mu, sigma)  # normal是正态分布
        action = action_dist.sample()
        return [action.item()] # 返回一个动作 这里[]是因为返回的是一个列表

    def update(self, transition_dict):
        states = torch.tensor(np.array(transition_dict['states']),
                              dtype=torch.float).to(self.device)
        actions = torch.tensor(np.array(transition_dict['actions']),
                               dtype=torch.float).view(-1, 1).to(self.device)
        rewards = torch.tensor(np.array(transition_dict['rewards']),
                               dtype=torch.float).view(-1, 1).to(self.device)
        next_states = torch.tensor(np.array(transition_dict['next_states']),
                                   dtype=torch.float).to(self.device)
        dones = torch.tensor(np.array(transition_dict['dones']),
                             dtype=torch.float).view(-1, 1).to(self.device)
        rewards = (rewards + 4.0) / 4.0  # 和TRPO一样,对奖励进行修改,方便训练 
        #其中rewards  +8

        td_target = rewards + self.gamma * self.critic(next_states) * (1 -dones)
        td_delta = td_target - self.critic(states)
        #print(td_target)
        #print(self.critic(states))   #.cpu 当你需要将张量转换为 NumPy 数组时，因为 NumPy 不能直接处理 GPU 上的张量。
        advantage = compute_advantage(self.gamma, self.lmbda,td_delta.cpu()).to(self.device)

        # 这三步和离散动作的PPO不一样
        mu, std = self.actor(states)  
        action_dists = torch.distributions.Normal(mu.detach(), std.detach())### # 动作是正态分布 得出动作的概率
        old_log_probs = action_dists.log_prob(actions)
        #print("mu",mu,"std",std)
        for _ in range(self.epochs):
            mu, std = self.actor(states) ##
            action_dists = torch.distributions.Normal(mu, std) ##
            log_probs = action_dists.log_prob(actions)
            ratio = torch.exp(log_probs - old_log_probs)
            surr1 = ratio * advantage
            surr2 = torch.clamp(ratio, 1 - self.eps, 1 + self.eps) * advantage
            actor_loss = torch.mean(-torch.min(surr1, surr2))  
            critic_loss = torch.mean(F.mse_loss(self.critic(states), td_target.detach()))
            self.actor_optimizer.zero_grad()
            self.critic_optimizer.zero_grad()
            actor_loss.backward()
            critic_loss.backward()
            self.actor_optimizer.step()
            self.critic_optimizer.step()


def train_on_policy_agent(env, agent, max_train_steps,number,seed):
    return_list = []
    # Build a tensorboard
    writer = SummaryWriter(log_dir='runs/PPO_mul_raw/env_{}_raw_number_{}_seed_{}'.format(env_name, number, seed))
    total_steps = 0 
    while total_steps < max_train_steps: 
        episode_return = 0
        transition_dict = {'states': [], 'actions': [], 'next_states': [], 'rewards': [], 'dones': []}
        state = env.reset(seed =0)[0] #1.改 gym 0.26.0版本后，env.reset()返回的是一个字典，所以需要加上[0]
        #print('state:',state)
        #state= state_norm(state)  ### 这里状态归一化
        done = False
        while not done:
            #action = agent.take_action(state) #action 这里是[-2,2]的动作 
            action = agent.take_action(state) # forward 无2 这里是[-1,1]的动作
            #next_state, reward, done, _ = env.step(action)[0:4] #2.改
            #next_state, reward,terminated, truncated, _ = env.step(action) #2.改看gym版本0.26.2版本的
            #next_state, reward,terminated, truncated, _ = env.step([np.clip(action[0]*2,-2,2)]) 
            next_state, reward,terminated, truncated, _ = env.step([action[0]*2]) 
            done = terminated or truncated
            transition_dict['states'].append(state)
            transition_dict['actions'].append(action)
            transition_dict['next_states'].append(next_state)
            transition_dict['rewards'].append(reward)
            transition_dict['dones'].append(done)
            #print(transition_dict)
            state = next_state
            episode_return += reward
            total_steps += 1
        return_list.append(episode_return)
        agent.update(transition_dict)
        # if (i_episode+1) % 10 == 0:
        #     pbar.set_postfix({'episode': '%d' % (num_episodes/10 * i + i_episode+1), 'return': '%.3f' % np.mean(return_list[-10:])})
        # pbar.update(1)
        #if (total_steps) % 200 == 0:
            #print('episode:',total_steps,'return:',np.mean(return_list[-10:]))
        writer.add_scalar('return', episode_return, total_steps)

    return return_list



actor_lr = 1e-4
critic_lr = 5e-3#1e-1#5e-3
num_episodes = 1000
max_train_steps = 2e5 #1000*200
hidden_dim = 128
gamma = 0.9
lmbda = 0.9
epochs = 10
eps = 0.2
#device = torch.device("cuda") if torch.cuda.is_available() else torch.device("cpu")
device = torch.device("cpu")
env_name = 'Pendulum-v1'
env = gym.make(env_name)
#env.seed(0)
torch.manual_seed(0)
state_dim = env.observation_space.shape[0]
action_dim = env.action_space.shape[0]  # 连续动作空间

agent = PPOContinuous(state_dim, hidden_dim, action_dim, actor_lr, critic_lr,
                      lmbda, epochs, eps, gamma, device)

return_list = train_on_policy_agent(env, agent, max_train_steps,number=5,seed=0)

mul代码

python 复制代码 
import gym
import os
# 设置OMP_WAIT_POLICY为PASSIVE，让等待的线程不消耗CPU资源 #确保在pytorch前设置
os.environ['OMP_WAIT_POLICY'] = 'PASSIVE' #
import torch
import torch.nn.functional as F
import numpy as np
from multiprocessing import Process, Pipe
from tqdm import tqdm
import time
from torch.utils.tensorboard import SummaryWriter  ##1.TB


def compute_advantage(gamma, lmbda, td_delta):
    td_delta = td_delta.detach().numpy()
    advantage_list = []
    advantage = 0.0
    for delta in td_delta[::-1]:
        advantage = gamma * lmbda * advantage + delta
        advantage_list.append(advantage)
    advantage_list.reverse()
    return torch.tensor(np.array(advantage_list), dtype=torch.float32)

class PolicyNetContinuous(torch.nn.Module):
    def __init__(self, state_dim, hidden_dim, action_dim):
        super(PolicyNetContinuous, self).__init__()
        self.fc1 = torch.nn.Linear(state_dim, hidden_dim)
        self.fc_mu = torch.nn.Linear(hidden_dim, action_dim)
        self.fc_std = torch.nn.Linear(hidden_dim, action_dim)

    def forward(self, x):
        x = F.relu(self.fc1(x))
        mu = torch.tanh(self.fc_mu(x))
        std = F.softplus(self.fc_std(x))
        return mu, std

class ValueNet(torch.nn.Module):
    def __init__(self, state_dim, hidden_dim):
        super(ValueNet, self).__init__()
        self.fc1 = torch.nn.Linear(state_dim, hidden_dim)
        self.fc2 = torch.nn.Linear(hidden_dim, 1)

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

class PPOContinuous:
    def __init__(self, state_dim, hidden_dim, action_dim, actor_lr, critic_lr, lmbda, epochs, eps, gamma, device):
        self.actor = PolicyNetContinuous(state_dim, hidden_dim, action_dim).to(device)
        self.critic = ValueNet(state_dim, hidden_dim).to(device)
        self.actor_optimizer = torch.optim.Adam(self.actor.parameters(), lr=actor_lr)
        self.critic_optimizer = torch.optim.Adam(self.critic.parameters(), lr=critic_lr)
        self.gamma = gamma
        self.lmbda = lmbda
        self.epochs = epochs
        self.eps = eps
        self.device = device

    def take_action(self, state):
        state = torch.tensor(np.array([state]), dtype=torch.float).to(self.device)
        mu, sigma = self.actor(state)
        action_dist = torch.distributions.Normal(mu, sigma)
        action = action_dist.sample()
        return [action.item()]

    def update(self, transition_dict):
        states = torch.tensor(np.array(transition_dict['states']), dtype=torch.float).to(self.device)
        actions = torch.tensor(np.array(transition_dict['actions']), dtype=torch.float).view(-1, 1).to(self.device)
        rewards = torch.tensor(np.array(transition_dict['rewards']), dtype=torch.float).view(-1, 1).to(self.device)
        next_states = torch.tensor(np.array(transition_dict['next_states']), dtype=torch.float).to(self.device)
        dones = torch.tensor(np.array(transition_dict['dones']), dtype=torch.float).view(-1, 1).to(self.device)
        rewards = (rewards + 4.0) / 4.0

        td_target = rewards + self.gamma * self.critic(next_states) * (1 - dones)
        td_delta = td_target - self.critic(states)
        advantage = compute_advantage(self.gamma, self.lmbda, td_delta.cpu()).to(self.device)

        mu, std = self.actor(states)
        action_dists = torch.distributions.Normal(mu.detach(), std.detach())
        old_log_probs = action_dists.log_prob(actions)

        for _ in range(self.epochs):
            mu, std = self.actor(states)
            action_dists = torch.distributions.Normal(mu, std)
            log_probs = action_dists.log_prob(actions)
            ratio = torch.exp(log_probs - old_log_probs)
            surr1 = ratio * advantage
            surr2 = torch.clamp(ratio, 1 - self.eps, 1 + self.eps) * advantage
            actor_loss = torch.mean(-torch.min(surr1, surr2))
            critic_loss = torch.mean(F.mse_loss(self.critic(states), td_target.detach()))
            self.actor_optimizer.zero_grad()
            self.critic_optimizer.zero_grad()
            actor_loss.backward()
            critic_loss.backward()
            self.actor_optimizer.step()
            self.critic_optimizer.step()
###
def child_process(conn, env_name):
    #os.environ['OMP_NUM_THREADS'] = str(4) #默认8
    env = gym.make(env_name)
    while True:
        agent = conn.recv()  ## 1.这个位置，先传入agent
        transition_dict = {'states': [], 'actions': [], 'next_states': [], 'rewards': [], 'dones': []}
        episode_return = 0
        episode_steps =0
        state = env.reset(seed=0)[0]
        done = False
        while not done:
            action = agent.take_action(state)
            next_state, reward, terminated, truncated, _ = env.step([action[0] * 2])
            done = terminated or truncated
            transition_dict['states'].append(state)
            transition_dict['actions'].append(action)
            transition_dict['next_states'].append(next_state)
            transition_dict['rewards'].append(reward)
            transition_dict['dones'].append(done)
            state = next_state  ## 2.先append再赋值
            episode_return += reward
            episode_steps +=1

        conn.send((transition_dict, episode_return, episode_steps))
###
def main():

    actor_lr = 1e-4
    critic_lr = 5e-3
    num_episodes = 200
    hidden_dim = 128
    gamma = 0.9
    lmbda = 0.9
    epochs = 10
    eps = 0.2
    device = torch.device("cpu")
    env_name = 'Pendulum-v1'
    env = gym.make(env_name)
    torch.manual_seed(0)
    state_dim = env.observation_space.shape[0]
    action_dim = env.action_space.shape[0]
    # Build a tensorboard
    number = 46 #5
    seed = 0
    writer = SummaryWriter(log_dir='runs/PPO_mul_raw/env_{}_mul_number_{}_seed_{}'.format(env_name, number, seed))
    agent = PPOContinuous(state_dim, hidden_dim, action_dim, actor_lr, critic_lr, lmbda, epochs, eps, gamma, device)
    ###
    process_num = 4  #
    #pipe_dict = dict((i, (pipe1, pipe2)) for i in range(process_num) for pipe1, pipe2 in (Pipe(),)) 
    pipe_dict = {i: Pipe() for i in range(process_num)} #Pipe()返回一个元组: (conn1, conn2) #与上行相同
    child_process_list = [Process(target=child_process, args=(pipe_dict[i][1], env_name)) for i in range(process_num)]
    
    
    #timeList = list()
    total_steps = 0
    max_train_steps = 2e5
    #begin = time.time()
    # for p in child_process_list:
    #     p.start()
    [p.start() for p in child_process_list]
    return_list = []
    while total_steps < max_train_steps:
        episode_return = 0
        # for j in range(process_num):
        #     pipe_dict[j][0].send(agent)
        [pipe_dict[j][0].send(agent) for j in range(process_num)]   ##3.先传入agent
        for j in range(process_num): ##4. i,j区分
            transition_dict, episode_return_,episode_steps = pipe_dict[j][0].recv()
            agent.update(transition_dict)
            #episode_return += episode_return_
            total_steps += episode_steps
            writer.add_scalar('return', episode_return_, total_steps)
            return_list.append(episode_return_)

            
            

        #return_list.append(episode_return / process_num)
        #timeList.append(time.time()-begin)
        # if (i + 1) % 10 == 0:
        #      print(f'Episode: {i + 1}, Average Return: {np.mean(return_list[-10:])}, Time: {timeList[-1]}')
        # if (total_steps) % 200 == 0:
        #     print('episode:',total_steps,'return:',np.mean(return_list[-10:]))
        

    # for p in child_process_list:
    #     p.terminate()
    [p.terminate() for p in child_process_list] #child 用了while True，所以要terminate
    return return_list #单位为episode
if __name__ == '__main__':
    main()
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