TensorDictPrimer

class torchrl.envs.transforms.TensorDictPrimer(primers: dict | CompositeSpec = None, random: bool | None = None, default_value: float | Callable | Dict[NestedKey, float] | Dict[NestedKey, Callable] = None, reset_key: NestedKey | None = None, **kwargs)

A primer for TensorDict initialization at reset time.

This transform will populate the tensordict at reset with values drawn from the relative tensorspecs provided at initialization. If the transform is used out of the env context (e.g. as an nn.Module or appended to a replay buffer), a call to forward will also populate the tensordict with the desired features.

Parameters:

• primers (dict or CompositeSpec, optional) – a dictionary containing key-spec pairs which will be used to populate the input tensordict. CompositeSpec instances are supported too.

• random (bool, optional) – if True, the values will be drawn randomly from the TensorSpec domain (or a unit Gaussian if unbounded). Otherwise a fixed value will be assumed. Defaults to False.

• default_value (float, Callable, Dict[NestedKey, float], Dict[NestedKey, Callable], optional) – If non-random filling is chosen, default_value will be used to populate the tensors. If default_value is a float, all elements of the tensors will be set to that value. If it is a callable, this callable is expected to return a tensor fitting the specs, and it will be used to generate the tensors. Finally, if default_value is a dictionary of tensors or a dictionary of callables with keys matching those of the specs, these will be used to generate the corresponding tensors. Defaults to 0.0.

• reset_key (NestedKey, optional) – the reset key to be used as partial reset indicator. Must be unique. If not provided, defaults to the only reset key of the parent environment (if it has only one) and raises an exception otherwise.

• **kwargs – each keyword argument corresponds to a key in the tensordict. The corresponding value has to be a TensorSpec instance indicating what the value must be.

When used in a TransfomedEnv, the spec shapes must match the envs shape if the parent env is batch-locked (env.batch_locked=True). If the env is not batch-locked (e.g. model-based envs), it is assumed that the batch is given by the input tensordict instead.

Examples

>>> from torchrl.envs.libs.gym import GymEnv
>>> from torchrl.envs import SerialEnv
>>> base_env = SerialEnv(2, lambda: GymEnv("Pendulum-v1"))
>>> env = TransformedEnv(base_env)
>>> # the env is batch-locked, so the leading dims of the spec must match those of the env
>>> env.append_transform(TensorDictPrimer(mykey=UnboundedContinuousTensorSpec([2, 3])))
>>> td = env.reset()
>>> print(td)
TensorDict(
    fields={
        done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        mykey: Tensor(shape=torch.Size([2, 3]), device=cpu, dtype=torch.float32, is_shared=False),
        observation: Tensor(shape=torch.Size([2, 3]), device=cpu, dtype=torch.float32, is_shared=False)},
    batch_size=torch.Size([2]),
    device=cpu,
    is_shared=False)
>>> # the entry is populated with 0s
>>> print(td.get("mykey"))
tensor([[0., 0., 0.],
        [0., 0., 0.]])

When calling env.step(), the current value of the key will be carried in the "next" tensordict __unless it already exists__.

Examples

>>> td = env.rand_step(td)
>>> print(td.get(("next", "mykey")))
tensor([[0., 0., 0.],
        [0., 0., 0.]])
>>> # with another value for "mykey", the previous value is not carried on
>>> td = env.reset()
>>> td = td.set(("next", "mykey"), torch.ones(2, 3))
>>> td = env.rand_step(td)
>>> print(td.get(("next", "mykey")))
tensor([[1., 1., 1.],
        [1., 1., 1.]])

Note

Some TorchRL modules rely on specific keys being present in the environment TensorDicts, like LSTM or GRU. To facilitate this process, the method get_primers_from_module() automatically checks for required primer transforms in a module and its submodules and generates them.

forward(tensordict: TensorDictBase) → TensorDictBase

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

to(*args, **kwargs)

Move and/or cast the parameters and buffers.

This can be called as

to(device=None, dtype=None, non_blocking=False)

to(dtype, non_blocking=False)

to(tensor, non_blocking=False)

to(memory_format=torch.channels_last)

Its signature is similar to torch.Tensor.to(), but only accepts floating point or complex dtypes. In addition, this method will only cast the floating point or complex parameters and buffers to dtype (if given). The integral parameters and buffers will be moved device, if that is given, but with dtypes unchanged. When non_blocking is set, it tries to convert/move asynchronously with respect to the host if possible, e.g., moving CPU Tensors with pinned memory to CUDA devices.

See below for examples.

Note

This method modifies the module in-place.

Parameters:

• device (torch.device) – the desired device of the parameters and buffers in this module

• dtype (torch.dtype) – the desired floating point or complex dtype of the parameters and buffers in this module

• tensor (torch.Tensor) – Tensor whose dtype and device are the desired dtype and device for all parameters and buffers in this module

• memory_format (torch.memory_format) – the desired memory format for 4D parameters and buffers in this module (keyword only argument)

Returns:

self

Return type:

Module

Examples:

>>> # xdoctest: +IGNORE_WANT("non-deterministic")
>>> linear = nn.Linear(2, 2)
>>> linear.weight
Parameter containing:
tensor([[ 0.1913, -0.3420],
        [-0.5113, -0.2325]])
>>> linear.to(torch.double)
Linear(in_features=2, out_features=2, bias=True)
>>> linear.weight
Parameter containing:
tensor([[ 0.1913, -0.3420],
        [-0.5113, -0.2325]], dtype=torch.float64)
>>> # xdoctest: +REQUIRES(env:TORCH_DOCTEST_CUDA1)
>>> gpu1 = torch.device("cuda:1")
>>> linear.to(gpu1, dtype=torch.half, non_blocking=True)
Linear(in_features=2, out_features=2, bias=True)
>>> linear.weight
Parameter containing:
tensor([[ 0.1914, -0.3420],
        [-0.5112, -0.2324]], dtype=torch.float16, device='cuda:1')
>>> cpu = torch.device("cpu")
>>> linear.to(cpu)
Linear(in_features=2, out_features=2, bias=True)
>>> linear.weight
Parameter containing:
tensor([[ 0.1914, -0.3420],
        [-0.5112, -0.2324]], dtype=torch.float16)

>>> linear = nn.Linear(2, 2, bias=None).to(torch.cdouble)
>>> linear.weight
Parameter containing:
tensor([[ 0.3741+0.j,  0.2382+0.j],
        [ 0.5593+0.j, -0.4443+0.j]], dtype=torch.complex128)
>>> linear(torch.ones(3, 2, dtype=torch.cdouble))
tensor([[0.6122+0.j, 0.1150+0.j],
        [0.6122+0.j, 0.1150+0.j],
        [0.6122+0.j, 0.1150+0.j]], dtype=torch.complex128)

transform_input_spec(input_spec: TensorSpec) → TensorSpec

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: CompositeSpec) → CompositeSpec

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