Task-specific policy in multi-task environments¶

This tutorial details how multi-task policies and batched environments can be used.

At the end of this tutorial, you will be capable of writing policies that can compute actions in diverse settings using a distinct set of weights. You will also be able to execute diverse environments in parallel.

from tensordict.nn import TensorDictModule, TensorDictSequential
from torch import nn

from torchrl.envs import CatTensors, Compose, DoubleToFloat, ParallelEnv, TransformedEnv
from torchrl.envs.libs.dm_control import DMControlEnv
from torchrl.modules import MLP

We design two environments, one humanoid that must complete the stand task and another that must learn to walk.

env1 = DMControlEnv("humanoid", "stand")
env1_obs_keys = list(env1.observation_spec.keys())
env1 = TransformedEnv(
    env1,
    Compose(
        CatTensors(env1_obs_keys, "observation_stand", del_keys=False),
        CatTensors(env1_obs_keys, "observation"),
        DoubleToFloat(
            in_keys=["observation_stand", "observation"],
            in_keys_inv=["action"],
        ),
    ),
)
env2 = DMControlEnv("humanoid", "walk")
env2_obs_keys = list(env2.observation_spec.keys())
env2 = TransformedEnv(
    env2,
    Compose(
        CatTensors(env2_obs_keys, "observation_walk", del_keys=False),
        CatTensors(env2_obs_keys, "observation"),
        DoubleToFloat(
            in_keys=["observation_walk", "observation"],
            in_keys_inv=["action"],
        ),
    ),
)

tdreset1 = env1.reset()
tdreset2 = env2.reset()

# With LazyStackedTensorDict, stacking is done in a lazy manner: the original tensordicts
# can still be recovered by indexing the main tensordict
tdreset = LazyStackedTensorDict.lazy_stack([tdreset1, tdreset2], 0)
assert tdreset[0] is tdreset1

print(tdreset[0])

TensorDict(
    fields={
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)

Policy¶

We will design a policy where a backbone reads the “observation” key. Then specific sub-components will ready the “observation_stand” and “observation_walk” keys of the stacked tensordicts, if they are present, and pass them through the dedicated sub-network.

action_dim = env1.action_spec.shape[-1]

policy_common = TensorDictModule(
    nn.Linear(67, 64), in_keys=["observation"], out_keys=["hidden"]
)
policy_stand = TensorDictModule(
    MLP(67 + 64, action_dim, depth=2),
    in_keys=["observation_stand", "hidden"],
    out_keys=["action"],
)
policy_walk = TensorDictModule(
    MLP(67 + 64, action_dim, depth=2),
    in_keys=["observation_walk", "hidden"],
    out_keys=["action"],
)
seq = TensorDictSequential(
    policy_common, policy_stand, policy_walk, partial_tolerant=True
)

Let’s check that our sequence outputs actions for a single env (stand).

seq(env1.reset())

TensorDict(
    fields={
        action: Tensor(shape=torch.Size([21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([64]), device=cpu, dtype=torch.float32, is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)

Let’s check that our sequence outputs actions for a single env (walk).

seq(env2.reset())

TensorDict(
    fields={
        action: Tensor(shape=torch.Size([21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([64]), device=cpu, dtype=torch.float32, is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)

This also works with the stack: now the stand and walk keys have disappeared, because they’re not shared by all tensordicts. But the TensorDictSequential still performed the operations. Note that the backbone was executed in a vectorized way - not in a loop - which is more efficient.

seq(tdreset)

LazyStackedTensorDict(
    fields={
        action: Tensor(shape=torch.Size([2, 21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([2, 64]), device=cpu, dtype=torch.float32, is_shared=False),
        observation: Tensor(shape=torch.Size([2, 67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False)},
    exclusive_fields={
        0 ->
            observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        1 ->
            observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False)},
    batch_size=torch.Size([2]),
    device=None,
    is_shared=False,
    stack_dim=0)

Executing diverse tasks in parallel¶

We can parallelize the operations if the common keys-value pairs share the same specs (in particular their shape and dtype must match: you can’t do the following if the observation shapes are different but are pointed to by the same key).

If ParallelEnv receives a single env making function, it will assume that a single task has to be performed. If a list of functions is provided, then it will assume that we are in a multi-task setting.

def env1_maker():
    return TransformedEnv(
        DMControlEnv("humanoid", "stand"),
        Compose(
            CatTensors(env1_obs_keys, "observation_stand", del_keys=False),
            CatTensors(env1_obs_keys, "observation"),
            DoubleToFloat(
                in_keys=["observation_stand", "observation"],
                in_keys_inv=["action"],
            ),
        ),
    )


def env2_maker():
    return TransformedEnv(
        DMControlEnv("humanoid", "walk"),
        Compose(
            CatTensors(env2_obs_keys, "observation_walk", del_keys=False),
            CatTensors(env2_obs_keys, "observation"),
            DoubleToFloat(
                in_keys=["observation_walk", "observation"],
                in_keys_inv=["action"],
            ),
        ),
    )


env = ParallelEnv(2, [env1_maker, env2_maker])
assert not env._single_task

tdreset = env.reset()
print(tdreset)
print(tdreset[0])
print(tdreset[1])  # should be different

LazyStackedTensorDict(
    fields={
        done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        observation: Tensor(shape=torch.Size([2, 67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False)},
    exclusive_fields={
        0 ->
            observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        1 ->
            observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False)},
    batch_size=torch.Size([2]),
    device=None,
    is_shared=False,
    stack_dim=0)
TensorDict(
    fields={
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)
TensorDict(
    fields={
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)

Let’s pass the output through our network.

tdreset = seq(tdreset)
print(tdreset)
print(tdreset[0])
print(tdreset[1])  # should be different but all have an "action" key


env.step(tdreset)  # computes actions and execute steps in parallel
print(tdreset)
print(tdreset[0])
print(tdreset[1])  # next_observation has now been written

LazyStackedTensorDict(
    fields={
        action: Tensor(shape=torch.Size([2, 21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([2, 64]), device=cpu, dtype=torch.float32, is_shared=False),
        observation: Tensor(shape=torch.Size([2, 67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False)},
    exclusive_fields={
        0 ->
            observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        1 ->
            observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False)},
    batch_size=torch.Size([2]),
    device=None,
    is_shared=False,
    stack_dim=0)
TensorDict(
    fields={
        action: Tensor(shape=torch.Size([21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([64]), device=cpu, dtype=torch.float32, is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)
TensorDict(
    fields={
        action: Tensor(shape=torch.Size([21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([64]), device=cpu, dtype=torch.float32, is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)
LazyStackedTensorDict(
    fields={
        action: Tensor(shape=torch.Size([2, 21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([2, 64]), device=cpu, dtype=torch.float32, is_shared=False),
        next: LazyStackedTensorDict(
            fields={
                done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
                observation: Tensor(shape=torch.Size([2, 67]), device=cpu, dtype=torch.float32, is_shared=False),
                reward: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.float64, is_shared=False),
                terminated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
                truncated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False)},
            exclusive_fields={
                0 ->
                    observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
                1 ->
                    observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False)},
            batch_size=torch.Size([2]),
            device=None,
            is_shared=False,
            stack_dim=0),
        observation: Tensor(shape=torch.Size([2, 67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False)},
    exclusive_fields={
        0 ->
            observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        1 ->
            observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False)},
    batch_size=torch.Size([2]),
    device=None,
    is_shared=False,
    stack_dim=0)
TensorDict(
    fields={
        action: Tensor(shape=torch.Size([21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([64]), device=cpu, dtype=torch.float32, is_shared=False),
        next: TensorDict(
            fields={
                done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
                observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
                observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
                reward: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.float64, is_shared=False),
                terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
                truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
            batch_size=torch.Size([]),
            device=None,
            is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)
TensorDict(
    fields={
        action: Tensor(shape=torch.Size([21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([64]), device=cpu, dtype=torch.float32, is_shared=False),
        next: TensorDict(
            fields={
                done: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
                observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
                observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
                reward: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.float64, is_shared=False),
                terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
                truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
            batch_size=torch.Size([]),
            device=None,
            is_shared=False),
        observation: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([1]), device=cpu, dtype=torch.bool, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)

Rollout¶

td_rollout = env.rollout(100, policy=seq, return_contiguous=False)

td_rollout[:, 0]  # tensordict of the first step: only the common keys are shown

LazyStackedTensorDict(
    fields={
        action: Tensor(shape=torch.Size([2, 21]), device=cpu, dtype=torch.float32, is_shared=False),
        done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        hidden: Tensor(shape=torch.Size([2, 64]), device=cpu, dtype=torch.float32, is_shared=False),
        next: LazyStackedTensorDict(
            fields={
                done: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
                observation: Tensor(shape=torch.Size([2, 67]), device=cpu, dtype=torch.float32, is_shared=False),
                reward: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.float64, is_shared=False),
                terminated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
                truncated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False)},
            exclusive_fields={
                0 ->
                    observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
                1 ->
                    observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False)},
            batch_size=torch.Size([2]),
            device=None,
            is_shared=False,
            stack_dim=0),
        observation: Tensor(shape=torch.Size([2, 67]), device=cpu, dtype=torch.float32, is_shared=False),
        terminated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False),
        truncated: Tensor(shape=torch.Size([2, 1]), device=cpu, dtype=torch.bool, is_shared=False)},
    exclusive_fields={
        0 ->
            observation_stand: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False),
        1 ->
            observation_walk: Tensor(shape=torch.Size([67]), device=cpu, dtype=torch.float32, is_shared=False)},
    batch_size=torch.Size([2]),
    device=None,
    is_shared=False,
    stack_dim=0)

td_rollout[0]  # tensordict of the first env: the stand obs is present

env.close()
del env

Total running time of the script: (0 minutes 49.699 seconds)

Estimated memory usage: 318 MB

Gallery generated by Sphinx-Gallery

Task-specific policy in multi-task environments¶

Policy¶

Executing diverse tasks in parallel¶

Rollout¶

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