DeviceCastTransform

class torchrl.envs.transforms.DeviceCastTransform(device, orig_device=None, *, in_keys=None, out_keys=None, in_keys_inv=None, out_keys_inv=None)

Moves data from one device to another.

Parameters:

• device (torch.device or equivalent) – the destination device.

• orig_device (torch.device or equivalent) – the origin device. If not specified and a parent environment exists, it it retrieved from it. In all other cases, it remains unspecified.

Keyword Arguments:

• in_keys (list of NestedKey) – the list of entries to map to a different device. Defaults to None.

• out_keys (list of NestedKey) – the output names of the entries mapped onto a device. Defaults to the values of in_keys.

• in_keys_inv (list of NestedKey) – the list of entries to map to a different device. in_keys_inv are the names expected by the base environment. Defaults to None.

• out_keys_inv (list of NestedKey) – the output names of the entries mapped onto a device. out_keys_inv are the names of the keys as seen from outside the transformed env. Defaults to the values of in_keys_inv.

Examples

>>> td = TensorDict(
...     {'obs': torch.ones(1, dtype=torch.double),
... }, [], device="cpu:0")
>>> transform = DeviceCastTransform(device=torch.device("cpu:2"))
>>> td = transform(td)
>>> print(td.device)
cpu:2

forward(tensordict: TensorDictBase = None) → TensorDictBase

Reads the input tensordict, and for the selected keys, applies the transform.

By default, this method:

• calls directly _apply_transform().

• does not call _step() or _call().

This method is not called within env.step at any point. However, is is called within sample().

Note

forward also works with regular keyword arguments using dispatch to cast the args names to the keys.

Examples

>>> class TransformThatMeasuresBytes(Transform):
...     '''Measures the number of bytes in the tensordict, and writes it under `"bytes"`.'''
...     def __init__(self):
...         super().__init__(in_keys=[], out_keys=["bytes"])
...
...     def forward(self, tensordict: TensorDictBase) -> TensorDictBase:
...         bytes_in_td = tensordict.bytes()
...         tensordict["bytes"] = bytes
...         return tensordict
>>> t = TransformThatMeasuresBytes()
>>> env = env.append_transform(t) # works within envs
>>> t(TensorDict(a=0))  # Works offline too.

transform_action_spec(full_action_spec: Composite) → Composite

Transforms the action spec such that the resulting spec matches transform mapping.

Parameters:

action_spec (TensorSpec) – spec before the transform

Returns:

expected spec after the transform

transform_done_spec(full_done_spec: Composite) → Composite

Transforms the done spec such that the resulting spec matches transform mapping.

Parameters:

done_spec (TensorSpec) – spec before the transform

Returns:

expected spec after the transform

transform_env_device(device)

Transforms the device of the parent env.

transform_input_spec(input_spec: Composite) → Composite

Transforms the input spec such that the resulting spec matches transform mapping.

Parameters:

input_spec (TensorSpec) – spec before the transform

Returns:

expected spec after the transform

transform_observation_spec(observation_spec: Composite) → Composite

Transforms the observation spec such that the resulting spec matches transform mapping.

Parameters:

observation_spec (TensorSpec) – spec before the transform

Returns:

expected spec after the transform

transform_output_spec(output_spec: Composite) → Composite

Transforms the output spec such that the resulting spec matches transform mapping.

This method should generally be left untouched. Changes should be implemented using transform_observation_spec(), transform_reward_spec() and transform_full_done_spec(). :param output_spec: spec before the transform :type output_spec: TensorSpec

Returns:

expected spec after the transform

transform_reward_spec(full_reward_spec: Composite) → Composite

Transforms the reward spec such that the resulting spec matches transform mapping.

Parameters:

reward_spec (TensorSpec) – spec before the transform

Returns:

expected spec after the transform

transform_state_spec(full_state_spec: Composite) → Composite

Transforms the state spec such that the resulting spec matches transform mapping.

Parameters:

state_spec (TensorSpec) – spec before the transform

Returns:

expected spec after the transform