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johnjim0816
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## 原理简介
PPO是一种on-policy算法具有较好的性能其前身是TRPO算法也是policy gradient算法的一种它是现在 OpenAI 默认的强化学习算法,具体原理可参考[PPO算法讲解](https://datawhalechina.github.io/easy-rl/#/chapter5/chapter5)。PPO算法主要有两个变种一个是结合KL penalty的一个是用了clip方法本文实现的是后者即```PPO-clip```。
## 伪代码
要实现必先了解伪代码,伪代码如下:
![在这里插入图片描述](assets/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0pvaG5KaW0w,size_16,color_FFFFFF,t_70.png)
这是谷歌找到的一张比较适合的图,本人比较懒就没有修改,上面的```k```就是第```k```个episode第六步是用随机梯度下降的方法优化这里的损失函数(即```argmax```后面的部分)可能有点难理解,可参考[PPO paper](https://arxiv.org/abs/1707.06347),如下:
![在这里插入图片描述](assets/20210323154236878.png)
第七步就是一个平方损失函数,即实际回报与期望回报的差平方。
## 代码实战
[点击查看完整代码](https://github.com/JohnJim0816/rl-tutorials/tree/master/PPO)
### PPOmemory
首先第三步需要搜集一条轨迹信息,我们可以定义一个```PPOmemory```来存储相关信息:
```python
class PPOMemory:
def __init__(self, batch_size):
self.states = []
self.probs = []
self.vals = []
self.actions = []
self.rewards = []
self.dones = []
self.batch_size = batch_size
def sample(self):
batch_step = np.arange(0, len(self.states), self.batch_size)
indices = np.arange(len(self.states), dtype=np.int64)
np.random.shuffle(indices)
batches = [indices[i:i+self.batch_size] for i in batch_step]
return np.array(self.states),\
np.array(self.actions),\
np.array(self.probs),\
np.array(self.vals),\
np.array(self.rewards),\
np.array(self.dones),\
batches
def push(self, state, action, probs, vals, reward, done):
self.states.append(state)
self.actions.append(action)
self.probs.append(probs)
self.vals.append(vals)
self.rewards.append(reward)
self.dones.append(done)
def clear(self):
self.states = []
self.probs = []
self.actions = []
self.rewards = []
self.dones = []
self.vals = []
```
这里的push函数就是将得到的相关量放入memory中sample就是随机采样出来方便第六步的随机梯度下降。
### PPO model
model就是actor和critic两个网络了
```python
import torch.nn as nn
from torch.distributions.categorical import Categorical
class Actor(nn.Module):
def __init__(self,n_states, n_actions,
hidden_dim=256):
super(Actor, self).__init__()
self.actor = nn.Sequential(
nn.Linear(n_states, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, n_actions),
nn.Softmax(dim=-1)
)
def forward(self, state):
dist = self.actor(state)
dist = Categorical(dist)
return dist
class Critic(nn.Module):
def __init__(self, n_states,hidden_dim=256):
super(Critic, self).__init__()
self.critic = nn.Sequential(
nn.Linear(n_states, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, 1)
)
def forward(self, state):
value = self.critic(state)
return value
```
这里Actor就是得到一个概率分布(Categorica也可以是别的分布可以搜索torch distributionsl)critc根据当前状态得到一个值这里的输入维度可以是```n_states+n_actions```即将action信息也纳入critic网络中这样会更好一些感兴趣的小伙伴可以试试。
### PPO update
定义一个update函数主要实现伪代码中的第六步和第七步
```python
def update(self):
for _ in range(self.n_epochs):
state_arr, action_arr, old_prob_arr, vals_arr,\
reward_arr, dones_arr, batches = \
self.memory.sample()
values = vals_arr
### compute advantage ###
advantage = np.zeros(len(reward_arr), dtype=np.float32)
for t in range(len(reward_arr)-1):
discount = 1
a_t = 0
for k in range(t, len(reward_arr)-1):
a_t += discount*(reward_arr[k] + self.gamma*values[k+1]*\
(1-int(dones_arr[k])) - values[k])
discount *= self.gamma*self.gae_lambda
advantage[t] = a_t
advantage = torch.tensor(advantage).to(self.device)
### SGD ###
values = torch.tensor(values).to(self.device)
for batch in batches:
states = torch.tensor(state_arr[batch], dtype=torch.float).to(self.device)
old_probs = torch.tensor(old_prob_arr[batch]).to(self.device)
actions = torch.tensor(action_arr[batch]).to(self.device)
dist = self.actor(states)
critic_value = self.critic(states)
critic_value = torch.squeeze(critic_value)
new_probs = dist.log_prob(actions)
prob_ratio = new_probs.exp() / old_probs.exp()
weighted_probs = advantage[batch] * prob_ratio
weighted_clipped_probs = torch.clamp(prob_ratio, 1-self.policy_clip,
1+self.policy_clip)*advantage[batch]
actor_loss = -torch.min(weighted_probs, weighted_clipped_probs).mean()
returns = advantage[batch] + values[batch]
critic_loss = (returns-critic_value)**2
critic_loss = critic_loss.mean()
total_loss = actor_loss + 0.5*critic_loss
self.actor_optimizer.zero_grad()
self.critic_optimizer.zero_grad()
total_loss.backward()
self.actor_optimizer.step()
self.critic_optimizer.step()
self.memory.clear()
```
该部分首先从memory中提取搜集到的轨迹信息然后计算gae即advantage接着使用随机梯度下降更新网络最后清除memory以便搜集下一条轨迹信息。
最后实现效果如下:
![在这里插入图片描述](assets/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0pvaG5KaW0w,size_16,color_FFFFFF,t_70-20210405110725113.png)

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{
"algo_name": "PPO",
"env_name": "CartPole-v0",
"continuous": false,
"train_eps": 200,
"test_eps": 20,
"gamma": 0.99,
"batch_size": 5,
"n_epochs": 4,
"actor_lr": 0.0003,
"critic_lr": 0.0003,
"gae_lambda": 0.95,
"policy_clip": 0.2,
"update_fre": 20,
"hidden_dim": 256,
"device": "cpu",
"result_path": "C:\\Users\\24438\\Desktop\\rl-tutorials\\codes\\PPO/outputs/CartPole-v0/20220731-233512/results/",
"model_path": "C:\\Users\\24438\\Desktop\\rl-tutorials\\codes\\PPO/outputs/CartPole-v0/20220731-233512/models/",
"save_fig": true
}

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#!/usr/bin/env python
# coding=utf-8
'''
Author: John
Email: johnjim0816@gmail.com
Date: 2021-03-23 15:17:42
LastEditor: John
LastEditTime: 2021-12-31 19:38:33
Discription:
Environment:
'''
import os
import numpy as np
import torch
import torch.optim as optim
import torch.nn as nn
from torch.distributions.categorical import Categorical
class PPOMemory:
def __init__(self, batch_size):
self.states = []
self.probs = []
self.vals = []
self.actions = []
self.rewards = []
self.dones = []
self.batch_size = batch_size
def sample(self):
batch_step = np.arange(0, len(self.states), self.batch_size)
indices = np.arange(len(self.states), dtype=np.int64)
np.random.shuffle(indices)
batches = [indices[i:i+self.batch_size] for i in batch_step]
return np.array(self.states),np.array(self.actions),np.array(self.probs),\
np.array(self.vals),np.array(self.rewards),np.array(self.dones),batches
def push(self, state, action, probs, vals, reward, done):
self.states.append(state)
self.actions.append(action)
self.probs.append(probs)
self.vals.append(vals)
self.rewards.append(reward)
self.dones.append(done)
def clear(self):
self.states = []
self.probs = []
self.actions = []
self.rewards = []
self.dones = []
self.vals = []
class Actor(nn.Module):
def __init__(self,n_states, n_actions,
hidden_dim):
super(Actor, self).__init__()
self.actor = nn.Sequential(
nn.Linear(n_states, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, n_actions),
nn.Softmax(dim=-1)
)
def forward(self, state):
dist = self.actor(state)
dist = Categorical(dist)
return dist
class Critic(nn.Module):
def __init__(self, n_states,hidden_dim):
super(Critic, self).__init__()
self.critic = nn.Sequential(
nn.Linear(n_states, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, hidden_dim),
nn.ReLU(),
nn.Linear(hidden_dim, 1)
)
def forward(self, state):
value = self.critic(state)
return value
class PPO:
def __init__(self, n_states, n_actions,cfg):
self.gamma = cfg.gamma
self.continuous = cfg.continuous
self.policy_clip = cfg.policy_clip
self.n_epochs = cfg.n_epochs
self.gae_lambda = cfg.gae_lambda
self.device = cfg.device
self.actor = Actor(n_states, n_actions,cfg.hidden_dim).to(self.device)
self.critic = Critic(n_states,cfg.hidden_dim).to(self.device)
self.actor_optimizer = optim.Adam(self.actor.parameters(), lr=cfg.actor_lr)
self.critic_optimizer = optim.Adam(self.critic.parameters(), lr=cfg.critic_lr)
self.memory = PPOMemory(cfg.batch_size)
self.loss = 0
def choose_action(self, state):
state = np.array([state]) # 先转成数组再转tensor更高效
state = torch.tensor(state, dtype=torch.float).to(self.device)
dist = self.actor(state)
value = self.critic(state)
action = dist.sample()
probs = torch.squeeze(dist.log_prob(action)).item()
if self.continuous:
action = torch.tanh(action)
else:
action = torch.squeeze(action).item()
value = torch.squeeze(value).item()
return action, probs, value
def update(self):
for _ in range(self.n_epochs):
state_arr, action_arr, old_prob_arr, vals_arr,reward_arr, dones_arr, batches = self.memory.sample()
values = vals_arr[:]
### compute advantage ###
advantage = np.zeros(len(reward_arr), dtype=np.float32)
for t in range(len(reward_arr)-1):
discount = 1
a_t = 0
for k in range(t, len(reward_arr)-1):
a_t += discount*(reward_arr[k] + self.gamma*values[k+1]*\
(1-int(dones_arr[k])) - values[k])
discount *= self.gamma*self.gae_lambda
advantage[t] = a_t
advantage = torch.tensor(advantage).to(self.device)
### SGD ###
values = torch.tensor(values).to(self.device)
for batch in batches:
states = torch.tensor(state_arr[batch], dtype=torch.float).to(self.device)
old_probs = torch.tensor(old_prob_arr[batch]).to(self.device)
actions = torch.tensor(action_arr[batch]).to(self.device)
dist = self.actor(states)
critic_value = self.critic(states)
critic_value = torch.squeeze(critic_value)
new_probs = dist.log_prob(actions)
prob_ratio = new_probs.exp() / old_probs.exp()
weighted_probs = advantage[batch] * prob_ratio
weighted_clipped_probs = torch.clamp(prob_ratio, 1-self.policy_clip,
1+self.policy_clip)*advantage[batch]
actor_loss = -torch.min(weighted_probs, weighted_clipped_probs).mean()
returns = advantage[batch] + values[batch]
critic_loss = (returns-critic_value)**2
critic_loss = critic_loss.mean()
total_loss = actor_loss + 0.5*critic_loss
self.loss = total_loss
self.actor_optimizer.zero_grad()
self.critic_optimizer.zero_grad()
total_loss.backward()
self.actor_optimizer.step()
self.critic_optimizer.step()
self.memory.clear()
def save(self,path):
actor_checkpoint = os.path.join(path, 'ppo_actor.pt')
critic_checkpoint= os.path.join(path, 'ppo_critic.pt')
torch.save(self.actor.state_dict(), actor_checkpoint)
torch.save(self.critic.state_dict(), critic_checkpoint)
def load(self,path):
actor_checkpoint = os.path.join(path, 'ppo_actor.pt')
critic_checkpoint= os.path.join(path, 'ppo_critic.pt')
self.actor.load_state_dict(torch.load(actor_checkpoint))
self.critic.load_state_dict(torch.load(critic_checkpoint))

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import sys,os
curr_path = os.path.dirname(os.path.abspath(__file__)) # 当前文件所在绝对路径
parent_path = os.path.dirname(curr_path) # 父路径
sys.path.append(parent_path) # 添加路径到系统路径
import gym
import torch
import numpy as np
import datetime
import argparse
from common.utils import plot_rewards,save_args,save_results,make_dir
from ppo2 import PPO
def get_args():
""" Hyperparameters
"""
curr_time = datetime.datetime.now().strftime("%Y%m%d-%H%M%S") # 获取当前时间
parser = argparse.ArgumentParser(description="hyperparameters")
parser.add_argument('--algo_name',default='PPO',type=str,help="name of algorithm")
parser.add_argument('--env_name',default='CartPole-v0',type=str,help="name of environment")
parser.add_argument('--continuous',default=False,type=bool,help="if PPO is continous") # PPO既可适用于连续动作空间也可以适用于离散动作空间
parser.add_argument('--train_eps',default=200,type=int,help="episodes of training")
parser.add_argument('--test_eps',default=20,type=int,help="episodes of testing")
parser.add_argument('--gamma',default=0.99,type=float,help="discounted factor")
parser.add_argument('--batch_size',default=5,type=int) # mini-batch SGD中的批量大小
parser.add_argument('--n_epochs',default=4,type=int)
parser.add_argument('--actor_lr',default=0.0003,type=float,help="learning rate of actor net")
parser.add_argument('--critic_lr',default=0.0003,type=float,help="learning rate of critic net")
parser.add_argument('--gae_lambda',default=0.95,type=float)
parser.add_argument('--policy_clip',default=0.2,type=float) # PPO-clip中的clip参数一般是0.1~0.2左右
parser.add_argument('--update_fre',default=20,type=int)
parser.add_argument('--hidden_dim',default=256,type=int)
parser.add_argument('--device',default='cpu',type=str,help="cpu or cuda")
parser.add_argument('--result_path',default=curr_path + "/outputs/" + parser.parse_args().env_name + \
'/' + curr_time + '/results/' )
parser.add_argument('--model_path',default=curr_path + "/outputs/" + parser.parse_args().env_name + \
'/' + curr_time + '/models/' ) # path to save models
parser.add_argument('--save_fig',default=True,type=bool,help="if save figure or not")
args = parser.parse_args()
return args
def env_agent_config(cfg,seed = 1):
''' 创建环境和智能体
'''
env = gym.make(cfg.env_name) # 创建环境
n_states = env.observation_space.shape[0] # 状态维度
if cfg.continuous:
n_actions = env.action_space.shape[0] # 动作维度
else:
n_actions = env.action_space.n # 动作维度
agent = PPO(n_states, n_actions, cfg) # 创建智能体
if seed !=0: # 设置随机种子
torch.manual_seed(seed)
env.seed(seed)
np.random.seed(seed)
return env, agent
def train(cfg,env,agent):
print('开始训练!')
print(f'环境:{cfg.env_name}, 算法:{cfg.algo_name}, 设备:{cfg.device}')
rewards = [] # 记录所有回合的奖励
ma_rewards = [] # 记录所有回合的滑动平均奖励
steps = 0
for i_ep in range(cfg.train_eps):
state = env.reset()
done = False
ep_reward = 0
while not done:
action, prob, val = agent.choose_action(state)
state_, reward, done, _ = env.step(action)
steps += 1
ep_reward += reward
agent.memory.push(state, action, prob, val, reward, done)
if steps % cfg.update_fre == 0:
agent.update()
state = state_
rewards.append(ep_reward)
if ma_rewards:
ma_rewards.append(0.9*ma_rewards[-1]+0.1*ep_reward)
else:
ma_rewards.append(ep_reward)
if (i_ep+1)%10 == 0:
print(f"回合:{i_ep+1}/{cfg.train_eps},奖励:{ep_reward:.2f}")
print('完成训练!')
env.close()
res_dic = {'rewards':rewards,'ma_rewards':ma_rewards}
return res_dic
def test(cfg,env,agent):
print('开始测试!')
print(f'环境:{cfg.env_name}, 算法:{cfg.algo_name}, 设备:{cfg.device}')
rewards = [] # 记录所有回合的奖励
ma_rewards = [] # 记录所有回合的滑动平均奖励
for i_ep in range(cfg.test_eps):
state = env.reset()
done = False
ep_reward = 0
while not done:
action, prob, val = agent.choose_action(state)
state_, reward, done, _ = env.step(action)
ep_reward += reward
state = state_
rewards.append(ep_reward)
if ma_rewards:
ma_rewards.append(
0.9*ma_rewards[-1]+0.1*ep_reward)
else:
ma_rewards.append(ep_reward)
print('回合:{}/{}, 奖励:{}'.format(i_ep+1, cfg.test_eps, ep_reward))
print('完成训练!')
env.close()
res_dic = {'rewards':rewards,'ma_rewards':ma_rewards}
return res_dic
if __name__ == "__main__":
cfg = get_args()
# 训练
env, agent = env_agent_config(cfg)
res_dic = train(cfg, env, agent)
make_dir(cfg.result_path, cfg.model_path)
save_args(cfg) # 保存参数
agent.save(path=cfg.model_path) # save model
save_results(res_dic, tag='train',
path=cfg.result_path)
plot_rewards(res_dic['rewards'], res_dic['ma_rewards'], cfg, tag="train")
# 测试
env, agent = env_agent_config(cfg)
agent.load(path=cfg.model_path) # 导入模型
res_dic = test(cfg, env, agent)
save_results(res_dic, tag='test',
path=cfg.result_path) # 保存结果
plot_rewards(res_dic['rewards'], res_dic['ma_rewards'],cfg, tag="test") # 画出结果

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import sys,os
curr_path = os.path.dirname(os.path.abspath(__file__)) # 当前文件所在绝对路径
parent_path = os.path.dirname(curr_path) # 父路径
sys.path.append(parent_path) # 添加路径到系统路径
import gym
import torch
import datetime
from common.utils import plot_rewards
from common.utils import save_results,make_dir
from ppo2 import PPO
curr_time = datetime.datetime.now().strftime("%Y%m%d-%H%M%S") # 获取当前时间
class PPOConfig:
def __init__(self) -> None:
self.algo = "PPO" # 算法名称
self.env_name = 'Pendulum-v1' # 环境名称
self.continuous = True # 环境是否为连续动作
self.device = torch.device("cuda" if torch.cuda.is_available() else "cpu") # 检测GPU
self.train_eps = 200 # 训练的回合数
self.test_eps = 20 # 测试的回合数
self.batch_size = 5
self.gamma=0.99
self.n_epochs = 4
self.actor_lr = 0.0003
self.critic_lr = 0.0003
self.gae_lambda=0.95
self.policy_clip=0.2
self.hidden_dim = 256
self.update_fre = 20 # frequency of agent update
class PlotConfig:
def __init__(self) -> None:
self.algo = "PPO" # 算法名称
self.env_name = 'Pendulum-v1' # 环境名称
self.device = torch.device("cuda" if torch.cuda.is_available() else "cpu") # 检测GPU
self.result_path = curr_path+"/outputs/" + self.env_name + \
'/'+curr_time+'/results/' # 保存结果的路径
self.model_path = curr_path+"/outputs/" + self.env_name + \
'/'+curr_time+'/models/' # 保存模型的路径
self.save = True # 是否保存图片
def env_agent_config(cfg,seed=1):
env = gym.make(cfg.env_name)
env.seed(seed)
n_states = env.observation_space.shape[0]
n_actions = env.action_space.shape[0]
agent = PPO(n_states,n_actions,cfg)
return env,agent
cfg = PPOConfig()
plot_cfg = PlotConfig()
# 训练
env,agent = env_agent_config(cfg,seed=1)
rewards, ma_rewards = train(cfg, env, agent)
make_dir(plot_cfg.result_path, plot_cfg.model_path) # 创建保存结果和模型路径的文件夹
agent.save(path=plot_cfg.model_path)
save_results(rewards, ma_rewards, tag='train', path=plot_cfg.result_path)
plot_rewards(rewards, ma_rewards, plot_cfg, tag="train")
# 测试
env,agent = env_agent_config(cfg,seed=10)
agent.load(path=plot_cfg.model_path)
rewards,ma_rewards = eval(cfg,env,agent)
save_results(rewards,ma_rewards,tag='eval',path=plot_cfg.result_path)
plot_rewards(rewards,ma_rewards,plot_cfg,tag="eval")