108 lines
5.1 KiB
Python
108 lines
5.1 KiB
Python
import random
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import math
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import torch
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import torch.optim as optim
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import torch.nn.functional as F
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from memory import ReplayBuffer
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from model import CNN
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class DQN:
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def __init__(self, screen_height=0, screen_width=0, n_actions=0, gamma=0.999, epsilon_start=0.9, epsilon_end=0.05, epsilon_decay=200, memory_capacity=10000, batch_size=128, device="cpu"):
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self.actions_count = 0
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self.n_actions = n_actions
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self.device = device
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self.gamma = gamma
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self.epsilon = 0
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self.epsilon_start = epsilon_start
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self.epsilon_end = epsilon_end
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self.epsilon_decay = epsilon_decay
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self.batch_size = batch_size
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self.policy_net = CNN(screen_height, screen_width,
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n_actions).to(self.device)
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self.target_net = CNN(screen_height, screen_width,
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n_actions).to(self.device)
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self.target_net.load_state_dict(self.policy_net.state_dict())
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self.target_net.eval() # 不启用 BatchNormalization 和 Dropout
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self.optimizer = optim.RMSprop(self.policy_net.parameters())
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self.loss = 0
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self.memory = ReplayBuffer(memory_capacity)
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def select_action(self, state):
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'''choose_action [summary]
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Args:
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state [torch tensor]: [description]
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Returns:
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actions [torch tensor]: [description]
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'''
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sample = random.random()
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self.epsilon = self.epsilon_end + (self.epsilon_start - self.epsilon_end) * \
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math.exp(-1. * self.actions_count / self.epsilon_decay)
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self.actions_count += 1
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if sample > self.epsilon:
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with torch.no_grad():
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# t.max(1) will return largest column value of each row.
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# second column on max result is index of where max element was
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# found, so we pick action with the larger expected reward.
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q_value = self.policy_net(state) # q_value比如tensor([[-0.2522, 0.3887]])
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action = q_value.max(1)[1].view(1, 1) # q_value最大对应的下标，注意该action是个张量，如tensor([1])
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return action
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else:
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return torch.tensor([[random.randrange(self.n_actions)]], device=self.device, dtype=torch.long)
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def update(self):
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if len(self.memory) < self.batch_size:
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return
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transitions = self.memory.sample(self.batch_size)
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# Transpose the batch (see https://stackoverflow.com/a/19343/3343043 for
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# detailed explanation). This converts batch-array of Transitions
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# to Transition of batch-arrays.
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batch = self.memory.Transition(*zip(*transitions))
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# Compute a mask of non-final states and concatenate the batch elements
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# (a final state would've been the one after which simulation ended)
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non_final_mask = torch.tensor(tuple(map(lambda s: s is not None,
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batch.next_state)), device=self.device, dtype=torch.bool)
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non_final_next_states = torch.cat([s for s in batch.next_state
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if s is not None])
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state_batch = torch.cat(batch.state)
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action_batch = torch.cat(batch.action)
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reward_batch = torch.cat(batch.reward) # tensor([1., 1.,...,])
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# Compute Q(s_t, a) - the model computes Q(s_t), then we select the
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# columns of actions taken. These are the actions which would've been taken
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# for each batch state according to policy_net
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state_action_values = self.policy_net(
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state_batch).gather(1, action_batch) #tensor([[ 1.1217],...,[ 0.8314]])
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# Compute V(s_{t+1}) for all next states.
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# Expected values of actions for non_final_next_states are computed based
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# on the "older" target_net; selecting their best reward with max(1)[0].
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# This is merged based on the mask, such that we'll have either the expected
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# state value or 0 in case the state was final.
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next_state_values = torch.zeros(self.batch_size, device=self.device)
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next_state_values[non_final_mask] = self.target_net(
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non_final_next_states).max(1)[0].detach()
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# Compute the expected Q values
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expected_state_action_values = (next_state_values * self.gamma) + reward_batch # tensor([0.9685, 0.9683,...,])
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# Compute Huber loss
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self.loss = F.smooth_l1_loss(
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state_action_values, expected_state_action_values.unsqueeze(1)) # .unsqueeze增加一个维度
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# Optimize the model
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self.optimizer.zero_grad() # zero_grad clears old gradients from the last step (otherwise you’d just accumulate the gradients from all loss.backward() calls).
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self.loss.backward() # loss.backward() computes the derivative of the loss w.r.t. the parameters (or anything requiring gradients) using backpropagation.
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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() # causes the optimizer to take a step based on the gradients of the parameters.
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if __name__ == "__main__":
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dqn = DQN()
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