from typing import Any, Dict, Optional
import torch
import torch.nn.functional as F
from tianshou.data import Batch, to_torch_as
from tianshou.exploration import BaseNoise, GaussianNoise
from tianshou.policy import TD3Policy
[docs]class TD3BCPolicy(TD3Policy):
"""Implementation of TD3+BC. arXiv:2106.06860.
: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 critic1: the first critic network. (s, a -> Q(s, a))
:param torch.optim.Optimizer critic1_optim: the optimizer for the first
critic network.
:param torch.nn.Module critic2: the second critic network. (s, a -> Q(s, a))
:param torch.optim.Optimizer critic2_optim: the optimizer for the second
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 float exploration_noise: the exploration noise, add to the action.
Default to ``GaussianNoise(sigma=0.1)``
:param float policy_noise: the noise used in updating policy network.
Default to 0.2.
:param int update_actor_freq: the update frequency of actor network.
Default to 2.
:param float noise_clip: the clipping range used in updating policy network.
Default to 0.5.
:param float alpha: the value of alpha, which controls the weight for TD3 learning
relative to behavior cloning.
:param bool reward_normalization: normalize the reward to Normal(0, 1).
Default to False.
: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.
:param lr_scheduler: a learning rate scheduler that adjusts the learning rate in
optimizer in each policy.update(). Default to None (no lr_scheduler).
.. seealso::
Please refer to :class:`~tianshou.policy.BasePolicy` for more detailed
explanation.
"""
def __init__(
self,
actor: torch.nn.Module,
actor_optim: torch.optim.Optimizer,
critic1: torch.nn.Module,
critic1_optim: torch.optim.Optimizer,
critic2: torch.nn.Module,
critic2_optim: torch.optim.Optimizer,
tau: float = 0.005,
gamma: float = 0.99,
exploration_noise: Optional[BaseNoise] = GaussianNoise(sigma=0.1),
policy_noise: float = 0.2,
update_actor_freq: int = 2,
noise_clip: float = 0.5,
alpha: float = 2.5,
reward_normalization: bool = False,
estimation_step: int = 1,
**kwargs: Any,
) -> None:
super().__init__(
actor, actor_optim, critic1, critic1_optim, critic2, critic2_optim, tau,
gamma, exploration_noise, policy_noise, update_actor_freq, noise_clip,
reward_normalization, estimation_step, **kwargs
)
self._alpha = alpha
[docs] def learn(self, batch: Batch, **kwargs: Any) -> Dict[str, float]:
# critic 1&2
td1, critic1_loss = self._mse_optimizer(
batch, self.critic1, self.critic1_optim
)
td2, critic2_loss = self._mse_optimizer(
batch, self.critic2, self.critic2_optim
)
batch.weight = (td1 + td2) / 2.0 # prio-buffer
# actor
if self._cnt % self._freq == 0:
act = self(batch, eps=0.0).act
q_value = self.critic1(batch.obs, act)
lmbda = self._alpha / q_value.abs().mean().detach()
actor_loss = -lmbda * q_value.mean() + F.mse_loss(
act, to_torch_as(batch.act, act)
)
self.actor_optim.zero_grad()
actor_loss.backward()
self._last = actor_loss.item()
self.actor_optim.step()
self.sync_weight()
self._cnt += 1
return {
"loss/actor": self._last,
"loss/critic1": critic1_loss.item(),
"loss/critic2": critic2_loss.item(),
}