import warnings
from copy import deepcopy
from typing import Any, Dict, Optional, Tuple, Union
import numpy as np
import torch
from tianshou.data import Batch, ReplayBuffer
from tianshou.exploration import BaseNoise, GaussianNoise
from tianshou.policy import BasePolicy
[docs]class DDPGPolicy(BasePolicy):
"""Implementation of Deep Deterministic Policy Gradient. arXiv:1509.02971.
:param torch.nn.Module actor: the actor network following the rules in
:class:`~tianshou.policy.BasePolicy`. (s -> logits)
:param torch.optim.Optimizer actor_optim: the optimizer for actor network.
:param torch.nn.Module critic: the critic network. (s, a -> Q(s, a))
:param torch.optim.Optimizer critic_optim: the optimizer for critic network.
:param float tau: param for soft update of the target network. Default to 0.005.
:param float gamma: discount factor, in [0, 1]. Default to 0.99.
:param BaseNoise exploration_noise: the exploration noise,
add to the action. Default to ``GaussianNoise(sigma=0.1)``.
:param bool reward_normalization: normalize the reward to Normal(0, 1),
Default to False.
:param int estimation_step: the number of steps to look ahead. Default to 1.
:param bool action_scaling: whether to map actions from range [-1, 1] to range
[action_spaces.low, action_spaces.high]. Default to True.
:param str action_bound_method: method to bound action to range [-1, 1], can be
either "clip" (for simply clipping the action) or empty string for no bounding.
Default to "clip".
:param Optional[gym.Space] action_space: env's action space, mandatory if you want
to use option "action_scaling" or "action_bound_method". Default to None.
.. seealso::
Please refer to :class:`~tianshou.policy.BasePolicy` for more detailed
explanation.
"""
def __init__(
self,
actor: Optional[torch.nn.Module],
actor_optim: Optional[torch.optim.Optimizer],
critic: Optional[torch.nn.Module],
critic_optim: Optional[torch.optim.Optimizer],
tau: float = 0.005,
gamma: float = 0.99,
exploration_noise: Optional[BaseNoise] = GaussianNoise(sigma=0.1),
reward_normalization: bool = False,
estimation_step: int = 1,
action_scaling: bool = True,
action_bound_method: str = "clip",
**kwargs: Any,
) -> None:
super().__init__(
action_scaling=action_scaling,
action_bound_method=action_bound_method,
**kwargs
)
assert action_bound_method != "tanh", "tanh mapping is not supported" \
"in policies where action is used as input of critic , because" \
"raw action in range (-inf, inf) will cause instability in training"
if actor is not None and actor_optim is not None:
self.actor: torch.nn.Module = actor
self.actor_old = deepcopy(actor)
self.actor_old.eval()
self.actor_optim: torch.optim.Optimizer = actor_optim
if critic is not None and critic_optim is not None:
self.critic: torch.nn.Module = critic
self.critic_old = deepcopy(critic)
self.critic_old.eval()
self.critic_optim: torch.optim.Optimizer = critic_optim
assert 0.0 <= tau <= 1.0, "tau should be in [0, 1]"
self.tau = tau
assert 0.0 <= gamma <= 1.0, "gamma should be in [0, 1]"
self._gamma = gamma
self._noise = exploration_noise
# it is only a little difference to use GaussianNoise
# self.noise = OUNoise()
self._rew_norm = reward_normalization
self._n_step = estimation_step
[docs] def set_exp_noise(self, noise: Optional[BaseNoise]) -> None:
"""Set the exploration noise."""
self._noise = noise
[docs] def train(self, mode: bool = True) -> "DDPGPolicy":
"""Set the module in training mode, except for the target network."""
self.training = mode
self.actor.train(mode)
self.critic.train(mode)
return self
[docs] def sync_weight(self) -> None:
"""Soft-update the weight for the target network."""
self.soft_update(self.actor_old, self.actor, self.tau)
self.soft_update(self.critic_old, self.critic, self.tau)
def _target_q(self, buffer: ReplayBuffer, indices: np.ndarray) -> torch.Tensor:
batch = buffer[indices] # batch.obs_next: s_{t+n}
target_q = self.critic_old(
batch.obs_next,
self(batch, model='actor_old', input='obs_next').act
)
return target_q
[docs] def process_fn(
self, batch: Batch, buffer: ReplayBuffer, indices: np.ndarray
) -> Batch:
batch = self.compute_nstep_return(
batch, buffer, indices, self._target_q, self._gamma, self._n_step,
self._rew_norm
)
return batch
[docs] def forward(
self,
batch: Batch,
state: Optional[Union[dict, Batch, np.ndarray]] = None,
model: str = "actor",
input: str = "obs",
**kwargs: Any,
) -> Batch:
"""Compute action over the given batch data.
:return: A :class:`~tianshou.data.Batch` which has 2 keys:
* ``act`` the action.
* ``state`` the hidden state.
.. seealso::
Please refer to :meth:`~tianshou.policy.BasePolicy.forward` for
more detailed explanation.
"""
model = getattr(self, model)
obs = batch[input]
actions, hidden = model(obs, state=state, info=batch.info)
return Batch(act=actions, state=hidden)
@staticmethod
def _mse_optimizer(
batch: Batch, critic: torch.nn.Module, optimizer: torch.optim.Optimizer
) -> Tuple[torch.Tensor, torch.Tensor]:
"""A simple wrapper script for updating critic network."""
weight = getattr(batch, "weight", 1.0)
current_q = critic(batch.obs, batch.act).flatten()
target_q = batch.returns.flatten()
td = current_q - target_q
# critic_loss = F.mse_loss(current_q1, target_q)
critic_loss = (td.pow(2) * weight).mean()
optimizer.zero_grad()
critic_loss.backward()
optimizer.step()
return td, critic_loss
[docs] def learn(self, batch: Batch, **kwargs: Any) -> Dict[str, float]:
# critic
td, critic_loss = self._mse_optimizer(batch, self.critic, self.critic_optim)
batch.weight = td # prio-buffer
# actor
actor_loss = -self.critic(batch.obs, self(batch).act).mean()
self.actor_optim.zero_grad()
actor_loss.backward()
self.actor_optim.step()
self.sync_weight()
return {
"loss/actor": actor_loss.item(),
"loss/critic": critic_loss.item(),
}
[docs] def exploration_noise(self, act: Union[np.ndarray, Batch],
batch: Batch) -> Union[np.ndarray, Batch]:
if self._noise is None:
return act
if isinstance(act, np.ndarray):
return act + self._noise(act.shape)
warnings.warn("Cannot add exploration noise to non-numpy_array action.")
return act