class PPO(Agent):
"""
An agent learned with PPO using Advantage Actor-Critic framework
- Actor takes state as input
- Critic takes both state and action as input
- agent interact with environment to collect experience
- agent training with experience to update policy
- adam seems better than rmsprop for ppo
"""
def __init__(self,
env,
state_dim,
action_dim,
memory_capacity=10000,
max_steps=None,
roll_out_n_steps=1,
target_tau=1.,
target_update_steps=5,
clip_param=0.2,
reward_gamma=0.99,
reward_scale=1.,
done_penalty=None,
actor_hidden_size=32,
critic_hidden_size=32,
actor_output_act=nn.functional.log_softmax,
critic_loss="mse",
actor_lr=0.001,
critic_lr=0.001,
optimizer_type="adam",
entropy_reg=0.01,
max_grad_norm=0.5,
batch_size=100,
episodes_before_train=100,
epsilon_start=0.9,
epsilon_end=0.01,
epsilon_decay=200,
use_cuda=True):
super(PPO,
self).__init__(env, state_dim, action_dim, memory_capacity,
max_steps, reward_gamma, reward_scale,
done_penalty, actor_hidden_size,
critic_hidden_size, actor_output_act, critic_loss,
actor_lr, critic_lr, optimizer_type, entropy_reg,
max_grad_norm, batch_size, episodes_before_train,
epsilon_start, epsilon_end, epsilon_decay,
use_cuda)
self.roll_out_n_steps = roll_out_n_steps
self.target_tau = target_tau
self.target_update_steps = target_update_steps
self.clip_param = clip_param
self.actor = ActorNetwork(self.state_dim, self.actor_hidden_size,
self.action_dim, self.actor_output_act)
self.critic = CriticNetwork(self.state_dim, self.action_dim,
self.critic_hidden_size, 1)
# to ensure target network and learning network has the same weights
self.actor_target = deepcopy(self.actor)
self.critic_target = deepcopy(self.critic)
if self.optimizer_type == "adam":
self.actor_optimizer = Adam(self.actor.parameters(),
lr=self.actor_lr)
self.critic_optimizer = Adam(self.critic.parameters(),
lr=self.critic_lr)
elif self.optimizer_type == "rmsprop":
self.actor_optimizer = RMSprop(self.actor.parameters(),
lr=self.actor_lr)
self.critic_optimizer = RMSprop(self.critic.parameters(),
lr=self.critic_lr)
if self.use_cuda:
self.actor.cuda()
self.critic.cuda()
self.actor_target.cuda()
self.critic_target.cuda()
# agent interact with the environment to collect experience
def interact(self):
super(PPO, self)._take_n_steps()
# train on a roll out batch
def train(self):
if self.n_episodes <= self.episodes_before_train:
pass
batch = self.memory.sample(self.batch_size)
states_var = to_tensor_var(batch.states,
self.use_cuda).view(-1, self.state_dim)
one_hot_actions = index_to_one_hot(batch.actions, self.action_dim)
actions_var = to_tensor_var(one_hot_actions,
self.use_cuda).view(-1, self.action_dim)
rewards_var = to_tensor_var(batch.rewards, self.use_cuda).view(-1, 1)
# update actor network
self.actor_optimizer.zero_grad()
values = self.critic_target(states_var, actions_var).detach()
advantages = rewards_var - values
# # normalizing advantages seems not working correctly here
# advantages = (advantages - advantages.mean()) / (advantages.std() + 1e-5)
action_log_probs = self.actor(states_var)
action_log_probs = th.sum(action_log_probs * actions_var, 1)
old_action_log_probs = self.actor_target(states_var).detach()
old_action_log_probs = th.sum(old_action_log_probs * actions_var, 1)
ratio = th.exp(action_log_probs - old_action_log_probs)
surr1 = ratio * advantages
surr2 = th.clamp(ratio, 1.0 - self.clip_param,
1.0 + self.clip_param) * advantages
# PPO's pessimistic surrogate (L^CLIP)
actor_loss = -th.mean(th.min(surr1, surr2))
actor_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.actor.parameters(),
self.max_grad_norm)
self.actor_optimizer.step()
# update critic network
self.critic_optimizer.zero_grad()
target_values = rewards_var
values = self.critic(states_var, actions_var)
if self.critic_loss == "huber":
critic_loss = nn.functional.smooth_l1_loss(values, target_values)
else:
critic_loss = nn.MSELoss()(values, target_values)
critic_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.critic.parameters(),
self.max_grad_norm)
self.critic_optimizer.step()
# update actor target network and critic target network
if self.n_steps % self.target_update_steps == 0 and self.n_steps > 0:
super(PPO, self)._soft_update_target(self.actor_target, self.actor)
super(PPO, self)._soft_update_target(self.critic_target,
self.critic)
# predict softmax action based on state
def _softmax_action(self, state):
state_var = to_tensor_var([state], self.use_cuda)
softmax_action_var = th.exp(self.actor(state_var))
if self.use_cuda:
softmax_action = softmax_action_var.data.cpu().numpy()[0]
else:
softmax_action = softmax_action_var.data.numpy()[0]
return softmax_action
# choose an action based on state with random noise added for exploration in training
def exploration_action(self, state):
softmax_action = self._softmax_action(state)
epsilon = self.epsilon_end + (self.epsilon_start - self.epsilon_end) * \
np.exp(-1. * self.n_steps / self.epsilon_decay)
if np.random.rand() < epsilon:
action = np.random.choice(self.action_dim)
else:
action = np.argmax(softmax_action)
return action
# choose an action based on state for execution
def action(self, state):
softmax_action = self._softmax_action(state)
action = np.argmax(softmax_action)
return action
# evaluate value for a state-action pair
def value(self, state, action):
state_var = to_tensor_var([state], self.use_cuda)
action = index_to_one_hot(action, self.action_dim)
action_var = to_tensor_var([action], self.use_cuda)
value_var = self.critic(state_var, action_var)
if self.use_cuda:
value = value_var.data.cpu().numpy()[0]
else:
value = value_var.data.numpy()[0]
return value
class A2C(Agent):
"""
An agent learned with Advantage Actor-Critic
- Actor takes state as input
- Critic takes both state and action as input
- agent interact with environment to collect experience
- agent training with experience to update policy
"""
def __init__(self,
env,
state_dim,
action_dim,
memory_capacity=10000,
max_steps=None,
roll_out_n_steps=10,
reward_gamma=0.99,
reward_scale=1.,
done_penalty=None,
actor_hidden_size=32,
critic_hidden_size=32,
actor_output_act=nn.functional.log_softmax,
critic_loss="mse",
actor_lr=0.001,
critic_lr=0.001,
optimizer_type="rmsprop",
entropy_reg=0.01,
max_grad_norm=0.5,
batch_size=100,
episodes_before_train=100,
epsilon_start=0.9,
epsilon_end=0.01,
epsilon_decay=200,
use_cuda=True):
super(A2C,
self).__init__(env, state_dim, action_dim, memory_capacity,
max_steps, reward_gamma, reward_scale,
done_penalty, actor_hidden_size,
critic_hidden_size, actor_output_act, critic_loss,
actor_lr, critic_lr, optimizer_type, entropy_reg,
max_grad_norm, batch_size, episodes_before_train,
epsilon_start, epsilon_end, epsilon_decay,
use_cuda)
self.roll_out_n_steps = roll_out_n_steps
self.actor = ActorNetwork(self.state_dim, self.actor_hidden_size,
self.action_dim, self.actor_output_act)
self.critic = CriticNetwork(self.state_dim, self.action_dim,
self.critic_hidden_size, 1)
if self.optimizer_type == "adam":
self.actor_optimizer = Adam(self.actor.parameters(),
lr=self.actor_lr)
self.critic_optimizer = Adam(self.critic.parameters(),
lr=self.critic_lr)
elif self.optimizer_type == "rmsprop":
self.actor_optimizer = RMSprop(self.actor.parameters(),
lr=self.actor_lr)
self.critic_optimizer = RMSprop(self.critic.parameters(),
lr=self.critic_lr)
if self.use_cuda:
self.actor.cuda()
self.critic.cuda()
# agent interact with the environment to collect experience
def interact(self):
super(A2C, self)._take_n_steps()
# train on a roll out batch
def train(self):
if self.n_episodes <= self.episodes_before_train:
pass
batch = self.memory.sample(self.batch_size)
states_var = to_tensor_var(batch.states,
self.use_cuda).view(-1, self.state_dim)
one_hot_actions = index_to_one_hot(batch.actions, self.action_dim)
actions_var = to_tensor_var(one_hot_actions,
self.use_cuda).view(-1, self.action_dim)
rewards_var = to_tensor_var(batch.rewards, self.use_cuda).view(-1, 1)
# update actor network
self.actor_optimizer.zero_grad()
action_log_probs = self.actor(states_var)
entropy_loss = th.mean(entropy(th.exp(action_log_probs)))
action_log_probs = th.sum(action_log_probs * actions_var, 1)
values = self.critic(states_var, actions_var)
advantages = rewards_var - values.detach()
pg_loss = -th.mean(action_log_probs * advantages)
actor_loss = pg_loss - entropy_loss * self.entropy_reg
actor_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.actor.parameters(),
self.max_grad_norm)
self.actor_optimizer.step()
# update critic network
self.critic_optimizer.zero_grad()
target_values = rewards_var
if self.critic_loss == "huber":
critic_loss = nn.functional.smooth_l1_loss(values, target_values)
else:
critic_loss = nn.MSELoss()(values, target_values)
critic_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.critic.parameters(),
self.max_grad_norm)
self.critic_optimizer.step()
# predict softmax action based on state
def _softmax_action(self, state):
state_var = to_tensor_var([state], self.use_cuda)
softmax_action_var = th.exp(self.actor(state_var))
if self.use_cuda:
softmax_action = softmax_action_var.data.cpu().numpy()[0]
else:
softmax_action = softmax_action_var.data.numpy()[0]
return softmax_action
# choose an action based on state with random noise added for exploration in training
def exploration_action(self, state):
softmax_action = self._softmax_action(state)
epsilon = self.epsilon_end + (self.epsilon_start - self.epsilon_end) * \
np.exp(-1. * self.n_steps / self.epsilon_decay)
if np.random.rand() < epsilon:
action = np.random.choice(self.action_dim)
else:
action = np.argmax(softmax_action)
return action
# choose an action based on state for execution
def action(self, state):
softmax_action = self._softmax_action(state)
action = np.argmax(softmax_action)
return action
# evaluate value for a state-action pair
def value(self, state, action):
state_var = to_tensor_var([state], self.use_cuda)
action = index_to_one_hot(action, self.action_dim)
action_var = to_tensor_var([action], self.use_cuda)
value_var = self.critic(state_var, action_var)
if self.use_cuda:
value = value_var.data.cpu().numpy()[0]
else:
value = value_var.data.numpy()[0]
return value
class DDPG(Agent):
"""
An agent learned with Deep Deterministic Policy Gradient using Actor-Critic framework
- Actor takes state as input
- Critic takes both state and action as input
- Critic uses gradient temporal-difference learning
"""
def __init__(self,
env,
state_dim,
action_dim,
memory_capacity=10000,
max_steps=None,
target_tau=0.01,
target_update_steps=5,
reward_gamma=0.99,
reward_scale=1.,
done_penalty=None,
actor_hidden_size=32,
critic_hidden_size=32,
actor_output_act=nn.functional.tanh,
critic_loss="mse",
actor_lr=0.001,
critic_lr=0.001,
optimizer_type="adam",
entropy_reg=0.01,
max_grad_norm=0.5,
batch_size=100,
episodes_before_train=100,
epsilon_start=0.9,
epsilon_end=0.01,
epsilon_decay=200,
use_cuda=True):
super(DDPG,
self).__init__(env, state_dim, action_dim, memory_capacity,
max_steps, reward_gamma, reward_scale,
done_penalty, actor_hidden_size,
critic_hidden_size, actor_output_act, critic_loss,
actor_lr, critic_lr, optimizer_type, entropy_reg,
max_grad_norm, batch_size, episodes_before_train,
epsilon_start, epsilon_end, epsilon_decay,
use_cuda)
self.target_tau = target_tau
self.target_update_steps = target_update_steps
self.actor = ActorNetwork(self.state_dim, self.actor_hidden_size,
self.action_dim, self.actor_output_act)
self.critic = CriticNetwork(self.state_dim, self.action_dim,
self.critic_hidden_size, 1)
# to ensure target network and learning network has the same weights
self.actor_target = deepcopy(self.actor)
self.critic_target = deepcopy(self.critic)
if self.optimizer_type == "adam":
self.actor_optimizer = Adam(self.actor.parameters(),
lr=self.actor_lr)
self.critic_optimizer = Adam(self.critic.parameters(),
lr=self.critic_lr)
elif self.optimizer_type == "rmsprop":
self.actor_optimizer = RMSprop(self.actor.parameters(),
lr=self.actor_lr)
self.critic_optimizer = RMSprop(self.critic.parameters(),
lr=self.critic_lr)
if self.use_cuda:
self.actor.cuda()
self.critic.cuda()
self.actor_target.cuda()
self.critic_target.cuda()
# agent interact with the environment to collect experience
def interact(self):
super(DDPG, self)._take_one_step()
# train on a sample batch
def train(self):
# do not train until exploration is enough
if self.n_episodes <= self.episodes_before_train:
pass
batch = self.memory.sample(self.batch_size)
state_var = to_tensor_var(batch.states,
self.use_cuda).view(-1, self.state_dim)
action_var = to_tensor_var(batch.actions,
self.use_cuda).view(-1, self.action_dim)
reward_var = to_tensor_var(batch.rewards, self.use_cuda).view(-1, 1)
next_state_var = to_tensor_var(batch.next_states,
self.use_cuda).view(-1, self.state_dim)
done_var = to_tensor_var(batch.dones, self.use_cuda).view(-1, 1)
# estimate the target q with actor_target network and critic_target network
next_action_var = self.actor_target(next_state_var)
next_q = self.critic_target(next_state_var, next_action_var).detach()
target_q = self.reward_scale * reward_var + self.reward_gamma * next_q * (
1. - done_var)
# update critic network
self.critic_optimizer.zero_grad()
# current Q values
current_q = self.critic(state_var, action_var)
# rewards is target Q values
if self.critic_loss == "huber":
critic_loss = nn.functional.smooth_l1_loss(current_q, target_q)
else:
critic_loss = nn.MSELoss()(current_q, target_q)
critic_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.critic.parameters(),
self.max_grad_norm)
self.critic_optimizer.step()
# update actor network
self.actor_optimizer.zero_grad()
# the accurate action prediction
action = self.actor(state_var)
# actor_loss is used to maximize the Q value for the predicted action
actor_loss = -self.critic(state_var, action)
actor_loss = actor_loss.mean()
actor_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.actor.parameters(),
self.max_grad_norm)
self.actor_optimizer.step()
# update actor target network and critic target network
if self.n_steps % self.target_update_steps == 0 and self.n_steps > 0:
super(DDPG, self)._soft_update_target(self.critic_target,
self.critic)
super(DDPG, self)._soft_update_target(self.actor_target,
self.actor)
# choose an action based on state with random noise added for exploration in training
def exploration_action(self, state):
action = self.action(state)
epsilon = self.epsilon_end + (self.epsilon_start - self.epsilon_end) * \
np.exp(-1. * self.n_steps / self.epsilon_decay)
# add noise
noise = np.random.randn(self.action_dim) * epsilon
action += noise
return action
# choose an action based on state for execution
def action(self, state):
action_var = self.actor(to_tensor_var([state], self.use_cuda))
if self.use_cuda:
action = action_var.data.cpu().numpy()[0]
else:
action = action_var.data.numpy()[0]
return action
class A2C(Agent):
"""
An agent learned with Advantage Actor-Critic
- Actor takes state as input
- Critic takes both state and action as input
- agent interact with environment to collect experience
- agent training with experience to update policy
"""
def __init__(self, env, state_dim, action_dim,
memory_capacity=10000, max_steps=None,
roll_out_n_steps=10,
reward_gamma=0.99, reward_scale=1., done_penalty=None,
actor_hidden_size=32, critic_hidden_size=32,
actor_output_act=nn.functional.log_softmax, critic_loss="mse",
actor_lr=0.001, critic_lr=0.001,
optimizer_type="rmsprop", entropy_reg=0.01,
max_grad_norm=0.5, batch_size=100, episodes_before_train=100,
epsilon_start=0.9, epsilon_end=0.01, epsilon_decay=200,
use_cuda=True):
super(A2C, self).__init__(env, state_dim, action_dim,
memory_capacity, max_steps,
reward_gamma, reward_scale, done_penalty,
actor_hidden_size, critic_hidden_size,
actor_output_act, critic_loss,
actor_lr, critic_lr,
optimizer_type, entropy_reg,
max_grad_norm, batch_size, episodes_before_train,
epsilon_start, epsilon_end, epsilon_decay,
use_cuda)
self.roll_out_n_steps = roll_out_n_steps
self.actor = ActorNetwork(self.state_dim, self.actor_hidden_size,
self.action_dim, self.actor_output_act)
self.critic = CriticNetwork(self.state_dim, self.action_dim,
self.critic_hidden_size, 1)
if self.optimizer_type == "adam":
self.actor_optimizer = Adam(self.actor.parameters(), lr=self.actor_lr)
self.critic_optimizer = Adam(self.critic.parameters(), lr=self.critic_lr)
elif self.optimizer_type == "rmsprop":
self.actor_optimizer = RMSprop(self.actor.parameters(), lr=self.actor_lr)
self.critic_optimizer = RMSprop(self.critic.parameters(), lr=self.critic_lr)
if self.use_cuda:
self.actor.cuda()
self.critic.cuda()
# agent interact with the environment to collect experience
def interact(self):
super(A2C, self)._take_n_steps()
def get_loss(self):
if self.n_episodes <= self.episodes_before_train:
pass
batch = self.memory.sample(self.batch_size)
states_var = to_tensor_var(
batch.states, self.use_cuda).view(-1, self.state_dim)
one_hot_actions = index_to_one_hot(batch.actions, self.action_dim)
actions_var = to_tensor_var(
one_hot_actions, self.use_cuda).view(-1, self.action_dim)
rewards_var = to_tensor_var(batch.rewards, self.use_cuda).view(-1, 1)
# Get the actor network loss
self.actor_optimizer.zero_grad()
action_log_probs = self.actor(states_var)
entropy_loss = th.mean(entropy(th.exp(action_log_probs)))
action_log_probs = th.sum(action_log_probs * actions_var, 1)
values = self.critic(states_var, actions_var)
advantages = rewards_var - values.detach()
pg_loss = -th.mean(action_log_probs * advantages)
actor_loss = pg_loss - entropy_loss * self.entropy_reg
# Get the critic network loss
self.critic_optimizer.zero_grad()
target_values = rewards_var
if self.critic_loss == "huber":
critic_loss = nn.functional.smooth_l1_loss(values, target_values)
else:
critic_loss = nn.MSELoss()(values, target_values)
combined_loss = {'actor_loss': actor_loss,
'critic_loss': critic_loss}
return combined_loss
def update_net(self, combined_loss):
actor_loss = combined_loss['actor_loss']
critic_loss = combined_loss['critic_loss']
# Update the actor network
actor_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(
self.actor.parameters(), self.max_grad_norm)
self.actor_optimizer.step()
# Update the critic network
critic_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(
self.critic.parameters(), self.max_grad_norm)
self.critic_optimizer.step()
# train on a roll out batch
def train(self):
if self.n_episodes <= self.episodes_before_train:
pass
batch = self.memory.sample(self.batch_size)
states_var = to_tensor_var(batch.states, self.use_cuda).view(-1, self.state_dim)
one_hot_actions = index_to_one_hot(batch.actions, self.action_dim)
actions_var = to_tensor_var(one_hot_actions, self.use_cuda).view(-1, self.action_dim)
rewards_var = to_tensor_var(batch.rewards, self.use_cuda).view(-1, 1)
# update actor network
self.actor_optimizer.zero_grad()
action_log_probs = self.actor(states_var)
entropy_loss = th.mean(entropy(th.exp(action_log_probs)))
action_log_probs = th.sum(action_log_probs * actions_var, 1)
values = self.critic(states_var, actions_var)
advantages = rewards_var - values.detach()
pg_loss = -th.mean(action_log_probs * advantages)
actor_loss = pg_loss - entropy_loss * self.entropy_reg
actor_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.actor.parameters(), self.max_grad_norm)
self.actor_optimizer.step()
# update critic network
self.critic_optimizer.zero_grad()
target_values = rewards_var
if self.critic_loss == "huber":
critic_loss = nn.functional.smooth_l1_loss(values, target_values)
else:
critic_loss = nn.MSELoss()(values, target_values)
critic_loss.backward()
if self.max_grad_norm is not None:
nn.utils.clip_grad_norm(self.critic.parameters(), self.max_grad_norm)
self.critic_optimizer.step()
# predict softmax action based on state
def _softmax_action(self, state):
state_var = to_tensor_var([state], self.use_cuda)
softmax_action_var = th.exp(self.actor(state_var))
if self.use_cuda:
softmax_action = softmax_action_var.data.cpu().numpy()[0]
else:
softmax_action = softmax_action_var.data.numpy()[0]
return softmax_action
# choose an action based on state with random noise added for exploration in training
def exploration_action(self, state):
softmax_action = self._softmax_action(state)
epsilon = self.epsilon_end + (self.epsilon_start - self.epsilon_end) * \
np.exp(-1. * self.n_steps / self.epsilon_decay)
if np.random.rand() < epsilon:
action = np.random.choice(self.action_dim)
else:
action = np.argmax(softmax_action)
return action
# choose an action based on state for execution
def action(self, state):
softmax_action = self._softmax_action(state)
action = np.argmax(softmax_action)
return action
# evaluate value for a state-action pair
def value(self, state, action):
state_var = to_tensor_var([state], self.use_cuda)
action = index_to_one_hot(action, self.action_dim)
action_var = to_tensor_var([action], self.use_cuda)
value_var = self.critic(state_var, action_var)
if self.use_cuda:
value = value_var.data.cpu().numpy()[0]
else:
value = value_var.data.numpy()[0]
return value
def get_weights(self):
state_actor = {'id': id,
'state_dict': self.actor.state_dict(),
'optimizer': self.actor_optimizer.state_dict()}
state_critic = {'id': id,
'state_dict': self.critic.state_dict(),
'optimizer': self.critic_optimizer.state_dict()}
state_dicts = {'state_actor': state_actor,
'state_critic': state_critic}
return state_dicts
def set_weights(self, state_dicts):
actor_checkpoint = state_dicts['state_actor']
critic_checkpoint = state_dicts['state_critic']
self.actor.load_state_dict(actor_checkpoint['state_dict'])
self.critic.load_state_dict(critic_checkpoint['state_dict'])
self.actor_optimizer.load_state_dict(actor_checkpoint['optimizer'])
self.critic_optimizer.load_state_dict(critic_checkpoint['optimizer'])
def save_weights(self, env_name, id):
state_actor = {'id': id,
'state_dict': self.actor.state_dict(),
'optimizer': self.actor_optimizer.state_dict()}
state_critic = {'id': id,
'state_dict': self.critic.state_dict(),
'optimizer': self.critic_optimizer.state_dict()}
base_path = os.path.join(env_name, 'a2c_weights')
if not os.path.exists(base_path):
os.makedirs(base_path)
file_name_actor = os.path.join(base_path, 'actor_' + str(id) + '.pth.tar')
file_name_critic = os.path.join(
base_path, 'critic_' + str(id) + '.pth.tar')
th.save(state_actor, file_name_actor)
th.save(state_critic, file_name_critic)
def load_weights(self, actor_weight_file, critic_weight_file):
print("=> loading checkpoint '{}, {}'".format(
actor_weight_file, critic_weight_file))
actor_checkpoint = th.load(actor_weight_file)
critic_checkpoint = th.load(critic_weight_file)
self.actor.load_state_dict(actor_checkpoint['state_dict'])
self.critic.load_state_dict(critic_checkpoint['state_dict'])
self.actor_optimizer.load_state_dict(actor_checkpoint['optimizer'])
self.critic_optimizer.load_state_dict(critic_checkpoint['optimizer'])
print("=> loaded checkpoint '{}, {}'".format(
actor_weight_file, critic_weight_file))