LazyStackedTensorSpec

class torchrl.data.LazyStackedTensorSpec(*specs: tuple[T, ...], dim: int)

A lazy representation of a stack of tensor specs.

Stacks tensor-specs together along one dimension. When random samples are drawn, a stack of samples is returned if possible. If not, an error is thrown.

Indexing is allowed but only along the stack dimension.

This class is aimed to be used in multi-task and multi-agent settings, where heterogeneous specs may occur (same semantic but different shape).

assert_is_in(value: Tensor) → None

Asserts whether a tensor belongs to the box, and raises an exception otherwise.

Parameters:

value (torch.Tensor) – value to be checked.

clear_device_()

Clears the device of the CompositeSpec.

contains(item)

Returns whether a sample is contained within the space defined by the TensorSpec.

See is_in() for more information.

encode(val: Union[ndarray, Tensor], *, ignore_device=False) → Tensor

Encodes a value given the specified spec, and return the corresponding tensor.

Parameters:

val (np.ndarray or torch.Tensor) – value to be encoded as tensor.

Keyword Arguments:

ignore_device (bool, optional) – if True, the spec device will be ignored. This is used to group tensor casting within a call to TensorDict(..., device="cuda") which is faster.

Returns:

torch.Tensor matching the required tensor specs.

expand(*shape)

Returns a new Spec with the extended shape.

Parameters:

*shape (tuple or iterable of int) – the new shape of the Spec. Must comply with the current shape: its length must be at least as long as the current shape length, and its last values must be complient too; ie they can only differ from it if the current dimension is a singleton.

flatten(start_dim, end_dim)

Flattens a tensorspec.

Check flatten() for more information on this method.

classmethod implements_for_spec(torch_function: Callable) → Callable

Register a torch function override for TensorSpec.

abstract index(index: Union[int, Tensor, ndarray, slice, List], tensor_to_index: Tensor) → Tensor

Indexes the input tensor.

Parameters:

• index (int, torch.Tensor, slice or list) – index of the tensor

• tensor_to_index – tensor to be indexed

Returns:

indexed tensor

is_in(value) → bool

If the value val is in the box defined by the TensorSpec, returns True, otherwise False.

Parameters:

val (torch.Tensor) – value to be checked

Returns:

boolean indicating if values belongs to the TensorSpec box

project(val: Tensor) → Tensor

If the input tensor is not in the TensorSpec box, it maps it back to it given some heuristic.

Parameters:

val (torch.Tensor) – tensor to be mapped to the box.

Returns:

a torch.Tensor belonging to the TensorSpec box.

rand(shape=None) → TensorDictBase

Returns a random tensor in the space defined by the spec. The sampling will be uniform unless the box is unbounded.

Parameters:

shape (torch.Size) – shape of the random tensor

Returns:

a random tensor sampled in the TensorSpec box.

reshape(*shape)

Reshapes a tensorspec.

Check reshape() for more information on this method.

property sample

Returns a random tensor in the space defined by the spec.

See rand() for details.

squeeze(dim: Optional[int] = None)

Returns a new Spec with all the dimensions of size 1 removed.

When dim is given, a squeeze operation is done only in that dimension.

Parameters:

dim (int or None) – the dimension to apply the squeeze operation to

to_numpy(val: Tensor, safe: Optional[bool] = None) → dict

Returns the np.ndarray correspondent of an input tensor.

Parameters:

• val (torch.Tensor) – tensor to be transformed_in to numpy.

• safe (bool) – boolean value indicating whether a check should be performed on the value against the domain of the spec. Defaults to the value of the CHECK_SPEC_ENCODE environment variable.

Returns:

a np.ndarray

type_check(value: torch.Tensor, key: NestedKey | None = None) → None

Checks the input value dtype against the TensorSpec dtype and raises an exception if they don’t match.

Parameters:

• value (torch.Tensor) – tensor whose dtype has to be checked

• key (str, optional) – if the TensorSpec has keys, the value dtype will be checked against the spec pointed by the indicated key.

unflatten(dim, sizes)

Unflattens a tensorspec.

Check unflatten() for more information on this method.

view(*shape)

Reshapes a tensorspec.

Check reshape() for more information on this method.

zero(shape=None) → TensorDictBase

Returns a zero-filled tensor in the box.

Parameters:

shape (torch.Size) – shape of the zero-tensor

Returns:

a zero-filled tensor sampled in the TensorSpec box.