Source code for torchrl.trainers.algorithms.ppo
# Copyright (c) Meta Platforms, Inc. and affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
from __future__ import annotations
import pathlib
import warnings
from collections.abc import Callable
from functools import partial
from tensordict import TensorDict, TensorDictBase
from torch import optim
from torchrl.collectors import DataCollectorBase
from torchrl.data.replay_buffers.replay_buffers import ReplayBuffer
from torchrl.data.replay_buffers.samplers import SamplerWithoutReplacement
from torchrl.objectives.common import LossModule
from torchrl.objectives.value.advantages import GAE
from torchrl.record.loggers import Logger
from torchrl.trainers.trainers import (
LogScalar,
ReplayBufferTrainer,
Trainer,
UpdateWeights,
)
try:
pass
_has_tqdm = True
except ImportError:
_has_tqdm = False
try:
pass
_has_ts = True
except ImportError:
_has_ts = False
[docs]class PPOTrainer(Trainer):
"""PPO (Proximal Policy Optimization) trainer implementation.
.. warning::
This is an experimental/prototype feature. The API may change in future versions.
Please report any issues or feedback to help improve this implementation.
This trainer implements the PPO algorithm for training reinforcement learning agents.
It extends the base Trainer class with PPO-specific functionality including
policy optimization, value function learning, and entropy regularization.
PPO typically uses multiple epochs of optimization on the same batch of data.
This trainer defaults to 4 epochs, which is a common choice for PPO implementations.
The trainer includes comprehensive logging capabilities for monitoring training progress:
- Training rewards (mean, std, max, total)
- Action statistics (norms)
- Episode completion rates
- Observation statistics (optional)
Logging can be configured via constructor parameters to enable/disable specific metrics.
Examples:
>>> # Basic usage with manual configuration
>>> from torchrl.trainers.algorithms.ppo import PPOTrainer
>>> from torchrl.trainers.algorithms.configs import PPOTrainerConfig
>>> from hydra import instantiate
>>> config = PPOTrainerConfig(...) # Configure with required parameters
>>> trainer = instantiate(config)
>>> trainer.train()
.. note::
This trainer requires a configurable environment setup. See the
:class:`~torchrl.trainers.algorithms.configs` module for configuration options.
.. warning::
This is an experimental feature. The API may change in future versions.
We welcome feedback and contributions to help improve this implementation!
"""
def __init__(
self,
*,
collector: DataCollectorBase,
total_frames: int,
frame_skip: int,
optim_steps_per_batch: int,
loss_module: LossModule | Callable[[TensorDictBase], TensorDictBase],
optimizer: optim.Optimizer | None = None,
logger: Logger | None = None,
clip_grad_norm: bool = True,
clip_norm: float | None = None,
progress_bar: bool = True,
seed: int | None = None,
save_trainer_interval: int = 10000,
log_interval: int = 10000,
save_trainer_file: str | pathlib.Path | None = None,
num_epochs: int = 4,
replay_buffer: ReplayBuffer | None = None,
batch_size: int | None = None,
gamma: float = 0.9,
lmbda: float = 0.99,
enable_logging: bool = True,
log_rewards: bool = True,
log_actions: bool = True,
log_observations: bool = False,
) -> None:
warnings.warn(
"PPOTrainer is an experimental/prototype feature. The API may change in future versions. "
"Please report any issues or feedback to help improve this implementation.",
UserWarning,
stacklevel=2,
)
super().__init__(
collector=collector,
total_frames=total_frames,
frame_skip=frame_skip,
optim_steps_per_batch=optim_steps_per_batch,
loss_module=loss_module,
optimizer=optimizer,
logger=logger,
clip_grad_norm=clip_grad_norm,
clip_norm=clip_norm,
progress_bar=progress_bar,
seed=seed,
save_trainer_interval=save_trainer_interval,
log_interval=log_interval,
save_trainer_file=save_trainer_file,
num_epochs=num_epochs,
)
self.replay_buffer = replay_buffer
gae = GAE(
gamma=gamma,
lmbda=lmbda,
value_network=self.loss_module.critic_network,
average_gae=True,
)
self.register_op("pre_epoch", gae)
if replay_buffer is not None and not isinstance(
replay_buffer.sampler, SamplerWithoutReplacement
):
warnings.warn(
"Sampler is not a SamplerWithoutReplacement, which is required for PPO."
)
if replay_buffer is not None:
rb_trainer = ReplayBufferTrainer(
replay_buffer,
batch_size=None,
flatten_tensordicts=True,
memmap=False,
device=getattr(replay_buffer.storage, "device", "cpu"),
iterate=True,
)
self.register_op("pre_epoch", rb_trainer.extend)
self.register_op("process_optim_batch", rb_trainer.sample)
self.register_op("post_loss", rb_trainer.update_priority)
policy_weights_getter = partial(
TensorDict.from_module, self.loss_module.actor_network
)
update_weights = UpdateWeights(
self.collector, 1, policy_weights_getter=policy_weights_getter
)
self.register_op("post_steps", update_weights)
# Store logging configuration
self.enable_logging = enable_logging
self.log_rewards = log_rewards
self.log_actions = log_actions
self.log_observations = log_observations
# Set up comprehensive logging for PPO training
if self.enable_logging:
self._setup_ppo_logging()
def _setup_ppo_logging(self):
"""Set up logging hooks for PPO-specific metrics.
This method configures logging for common PPO metrics including:
- Training rewards (mean and std)
- Action statistics (norms, entropy)
- Episode completion rates
- Value function statistics
- Advantage statistics
"""
# Always log done states as percentage (episode completion rate)
log_done_percentage = LogScalar(
key=("next", "done"),
logname="done_percentage",
log_pbar=True,
include_std=False, # No std for binary values
reduction="mean",
)
self.register_op("pre_steps_log", log_done_percentage)
# Log rewards if enabled
if self.log_rewards:
# 1. Log training rewards (most important metric for PPO)
log_rewards = LogScalar(
key=("next", "reward"),
logname="r_training",
log_pbar=True, # Show in progress bar
include_std=True,
reduction="mean",
)
self.register_op("pre_steps_log", log_rewards)
# 2. Log maximum reward in batch (for monitoring best performance)
log_max_reward = LogScalar(
key=("next", "reward"),
logname="r_max",
log_pbar=False,
include_std=False,
reduction="max",
)
self.register_op("pre_steps_log", log_max_reward)
# 3. Log total reward in batch (for monitoring cumulative performance)
log_total_reward = LogScalar(
key=("next", "reward"),
logname="r_total",
log_pbar=False,
include_std=False,
reduction="sum",
)
self.register_op("pre_steps_log", log_total_reward)
# Log actions if enabled
if self.log_actions:
# 4. Log action norms (useful for monitoring policy behavior)
log_action_norm = LogScalar(
key="action",
logname="action_norm",
log_pbar=False,
include_std=True,
reduction="mean",
)
self.register_op("pre_steps_log", log_action_norm)
# Log observations if enabled
if self.log_observations:
# 5. Log observation statistics (for monitoring state distributions)
log_obs_norm = LogScalar(
key="observation",
logname="obs_norm",
log_pbar=False,
include_std=True,
reduction="mean",
)
self.register_op("pre_steps_log", log_obs_norm)
