class ImitationPolicy(*, actor: Module, optim: Optimizer, action_space: Space, observation_space: Space | None = None, action_scaling: bool = False, action_bound_method: Literal['clip', 'tanh'] | None = 'clip', lr_scheduler: LRScheduler | MultipleLRSchedulers | None = None)[source]#

Implementation of vanilla imitation learning.

  • actor – a model following the rules in BasePolicy. (s -> a)

  • optim – for optimizing the model.

  • action_space – Env’s action_space.

  • observation_space – Env’s observation space.

  • action_scaling – if True, scale the action from [-1, 1] to the range of action_space. Only used if the action_space is continuous.

  • action_bound_method – method to bound action to range [-1, 1]. Only used if the action_space is continuous.

  • lr_scheduler – if not None, will be called in policy.update().

See also

Please refer to BasePolicy for more detailed explanation.

forward(batch: ObsBatchProtocol, state: dict | BatchProtocol | ndarray | None = None, **kwargs: Any) ModelOutputBatchProtocol[source]#

Compute action over the given batch data.


A Batch which MUST have the following keys:

  • act an numpy.ndarray or a torch.Tensor, the action over given batch data.

  • state a dict, an numpy.ndarray or a torch.Tensor, the internal state of the policy, None as default.

Other keys are user-defined. It depends on the algorithm. For example,

# some code
return Batch(logits=..., act=..., state=None, dist=...)

The keyword policy is reserved and the corresponding data will be stored into the replay buffer. For instance,

# some code
return Batch(..., policy=Batch(log_prob=dist.log_prob(act)))
# and in the sampled data batch, you can directly use
# batch.policy.log_prob to get your data.


In continuous action space, you should do another step “map_action” to get the real action:

act = policy(batch).act  # doesn't map to the target action range
act = policy.map_action(act, batch)
learn(batch: RolloutBatchProtocol, *ags: Any, **kwargs: Any) TImitationTrainingStats[source]#

Update policy with a given batch of data.


A dataclass object, including the data needed to be logged (e.g., loss).


In order to distinguish the collecting state, updating state and testing state, you can check the policy state by and self.updating. Please refer to States for policy for more detailed explanation.


If you use torch.distributions.Normal and torch.distributions.Categorical to calculate the log_prob, please be careful about the shape: Categorical distribution gives “[batch_size]” shape while Normal distribution gives “[batch_size, 1]” shape. The auto-broadcasting of numerical operation with torch tensors will amplify this error.

class ImitationTrainingStats(*, train_time: float = 0.0, smoothed_loss: dict = <factory>, loss: float = 0.0)[source]#
loss: float = 0.0#