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from typing import Dict, cast
import attr
from mlagents.torch_utils import torch, default_device
from mlagents.trainers.buffer import AgentBuffer, BufferKey, RewardSignalUtil
from mlagents_envs.timers import timed
from mlagents.trainers.policy.torch_policy import TorchPolicy
from mlagents.trainers.optimizer.torch_optimizer import TorchOptimizer
from mlagents.trainers.settings import (
TrainerSettings,
OnPolicyHyperparamSettings,
ScheduleType,
)
from mlagents.trainers.torch_entities.networks import ValueNetwork
from mlagents.trainers.torch_entities.agent_action import AgentAction
from mlagents.trainers.torch_entities.action_log_probs import ActionLogProbs
from mlagents.trainers.torch_entities.utils import ModelUtils
from mlagents.trainers.trajectory import ObsUtil
@attr.s(auto_attribs=True)
class PPOSettings(OnPolicyHyperparamSettings):
beta: float = 5.0e-3
epsilon: float = 0.2
lambd: float = 0.95
num_epoch: int = 3
shared_critic: bool = False
learning_rate_schedule: ScheduleType = ScheduleType.LINEAR
beta_schedule: ScheduleType = ScheduleType.LINEAR
epsilon_schedule: ScheduleType = ScheduleType.LINEAR
class TorchPPOOptimizer(TorchOptimizer):
def __init__(self, policy: TorchPolicy, trainer_settings: TrainerSettings):
"""
Takes a Policy and a Dict of trainer parameters and creates an Optimizer around the policy.
The PPO optimizer has a value estimator and a loss function.
:param policy: A TorchPolicy object that will be updated by this PPO Optimizer.
:param trainer_params: Trainer parameters dictionary that specifies the
properties of the trainer.
"""
# Create the graph here to give more granular control of the TF graph to the Optimizer.
super().__init__(policy, trainer_settings)
reward_signal_configs = trainer_settings.reward_signals
reward_signal_names = [key.value for key, _ in reward_signal_configs.items()]
self.hyperparameters: PPOSettings = cast(
PPOSettings, trainer_settings.hyperparameters
)
params = list(self.policy.actor.parameters())
if self.hyperparameters.shared_critic:
self._critic = policy.actor
else:
self._critic = ValueNetwork(
reward_signal_names,
policy.behavior_spec.observation_specs,
network_settings=trainer_settings.network_settings,
)
self._critic.to(default_device())
params += list(self._critic.parameters())
self.decay_learning_rate = ModelUtils.DecayedValue(
self.hyperparameters.learning_rate_schedule,
self.hyperparameters.learning_rate,
1e-10,
self.trainer_settings.max_steps,
)
self.decay_epsilon = ModelUtils.DecayedValue(
self.hyperparameters.epsilon_schedule,
self.hyperparameters.epsilon,
0.1,
self.trainer_settings.max_steps,
)
self.decay_beta = ModelUtils.DecayedValue(
self.hyperparameters.beta_schedule,
self.hyperparameters.beta,
1e-5,
self.trainer_settings.max_steps,
)
self.optimizer = torch.optim.Adam(
params, lr=self.trainer_settings.hyperparameters.learning_rate
)
self.stats_name_to_update_name = {
"Losses/Value Loss": "value_loss",
"Losses/Policy Loss": "policy_loss",
}
self.stream_names = list(self.reward_signals.keys())
@property
def critic(self):
return self._critic
@timed
def update(self, batch: AgentBuffer, num_sequences: int) -> Dict[str, float]:
"""
Performs update on model.
:param batch: Batch of experiences.
:param num_sequences: Number of sequences to process.
:return: Results of update.
"""
# Get decayed parameters
decay_lr = self.decay_learning_rate.get_value(self.policy.get_current_step())
decay_eps = self.decay_epsilon.get_value(self.policy.get_current_step())
decay_bet = self.decay_beta.get_value(self.policy.get_current_step())
returns = {}
old_values = {}
for name in self.reward_signals:
old_values[name] = ModelUtils.list_to_tensor(
batch[RewardSignalUtil.value_estimates_key(name)]
)
returns[name] = ModelUtils.list_to_tensor(
batch[RewardSignalUtil.returns_key(name)]
)
n_obs = len(self.policy.behavior_spec.observation_specs)
current_obs = ObsUtil.from_buffer(batch, n_obs)
# Convert to tensors
current_obs = [ModelUtils.list_to_tensor(obs) for obs in current_obs]
act_masks = ModelUtils.list_to_tensor(batch[BufferKey.ACTION_MASK])
actions = AgentAction.from_buffer(batch)
memories = [
ModelUtils.list_to_tensor(batch[BufferKey.MEMORY][i])
for i in range(0, len(batch[BufferKey.MEMORY]), self.policy.sequence_length)
]
if len(memories) > 0:
memories = torch.stack(memories).unsqueeze(0)
# Get value memories
value_memories = [
ModelUtils.list_to_tensor(batch[BufferKey.CRITIC_MEMORY][i])
for i in range(
0, len(batch[BufferKey.CRITIC_MEMORY]), self.policy.sequence_length
)
]
if len(value_memories) > 0:
value_memories = torch.stack(value_memories).unsqueeze(0)
run_out = self.policy.actor.get_stats(
current_obs,
actions,
masks=act_masks,
memories=memories,
sequence_length=self.policy.sequence_length,
)
log_probs = run_out["log_probs"]
entropy = run_out["entropy"]
values, _ = self.critic.critic_pass(
current_obs,
memories=value_memories,
sequence_length=self.policy.sequence_length,
)
old_log_probs = ActionLogProbs.from_buffer(batch).flatten()
log_probs = log_probs.flatten()
loss_masks = ModelUtils.list_to_tensor(batch[BufferKey.MASKS], dtype=torch.bool)
value_loss = ModelUtils.trust_region_value_loss(
values, old_values, returns, decay_eps, loss_masks
)
policy_loss = ModelUtils.trust_region_policy_loss(
ModelUtils.list_to_tensor(batch[BufferKey.ADVANTAGES]),
log_probs,
old_log_probs,
loss_masks,
decay_eps,
)
loss = (
policy_loss
+ 0.5 * value_loss
- decay_bet * ModelUtils.masked_mean(entropy, loss_masks)
)
# Set optimizer learning rate
ModelUtils.update_learning_rate(self.optimizer, decay_lr)
self.optimizer.zero_grad()
loss.backward()
self.optimizer.step()
update_stats = {
# NOTE: abs() is not technically correct, but matches the behavior in TensorFlow.
# TODO: After PyTorch is default, change to something more correct.
"Losses/Policy Loss": torch.abs(policy_loss).item(),
"Losses/Value Loss": value_loss.item(),
"Policy/Learning Rate": decay_lr,
"Policy/Epsilon": decay_eps,
"Policy/Beta": decay_bet,
}
return update_stats
# TODO move module update into TorchOptimizer for reward_provider
def get_modules(self):
modules = {
"Optimizer:value_optimizer": self.optimizer,
"Optimizer:critic": self._critic,
}
for reward_provider in self.reward_signals.values():
modules.update(reward_provider.get_modules())
return modules
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