CQLLoss

class torchrl.objectives.CQLLoss(*args, **kwargs)

TorchRL implementation of the continuous CQL loss.

Presented in “Conservative Q-Learning for Offline Reinforcement Learning” https://arxiv.org/abs/2006.04779

Parameters:

• actor_network (ProbabilisticActor) – stochastic actor

• qvalue_network (TensorDictModule or list of TensorDictModule) –

  Q(s, a) parametric model. This module typically outputs a "state_action_value" entry. If a single instance of qvalue_network is provided, it will be duplicated N times (where N=2 for this loss). If a list of modules is passed, their parameters will be stacked unless they share the same identity (in which case the original parameter will be expanded).

  Warning

  When a list of parameters if passed, it will __not__ be compared against the policy parameters and all the parameters will be considered as untied.

Keyword Arguments:

• loss_function (str, optional) – loss function to be used with the value function loss. Default is “smooth_l1”.

• alpha_init (float, optional) – initial entropy multiplier. Default is 1.0.

• min_alpha (float, optional) – min value of alpha. Default is None (no minimum value).

• max_alpha (float, optional) – max value of alpha. Default is None (no maximum value).

• action_spec (TensorSpec, optional) – the action tensor spec. If not provided and the target entropy is "auto", it will be retrieved from the actor.

• fixed_alpha (bool, optional) – if True, alpha will be fixed to its initial value. Otherwise, alpha will be optimized to match the ‘target_entropy’ value. Default is False.

• target_entropy (float or str, optional) – Target entropy for the stochastic policy. Default is “auto”, where target entropy is computed as -prod(n_actions).

• delay_actor (bool, optional) – Whether to separate the target actor networks from the actor networks used for data collection. Default is False.

• delay_qvalue (bool, optional) – Whether to separate the target Q value networks from the Q value networks used for data collection. Default is True.

• gamma (float, optional) – Discount factor. Default is None.

• temperature (float, optional) – CQL temperature. Default is 1.0.

• min_q_weight (float, optional) – Minimum Q weight. Default is 1.0.

• max_q_backup (bool, optional) – Whether to use the max-min Q backup. Default is False.

• deterministic_backup (bool, optional) – Whether to use the deterministic. Default is True.

• num_random (int, optional) – Number of random actions to sample for the CQL loss. Default is 10.

• with_lagrange (bool, optional) – Whether to use the Lagrange multiplier. Default is False.

• lagrange_thresh (float, optional) – Lagrange threshold. Default is 0.0.

• reduction (str, optional) – Specifies the reduction to apply to the output: "none" | "mean" | "sum". "none": no reduction will be applied, "mean": the sum of the output will be divided by the number of elements in the output, "sum": the output will be summed. Default: "mean".

Examples

>>> import torch
>>> from torch import nn
>>> from torchrl.data import BoundedTensorSpec
>>> from torchrl.modules.distributions import NormalParamExtractor, TanhNormal
>>> from torchrl.modules.tensordict_module.actors import ProbabilisticActor, ValueOperator
>>> from torchrl.modules.tensordict_module.common import SafeModule
>>> from torchrl.objectives.cql import CQLLoss
>>> from tensordict import TensorDict
>>> n_act, n_obs = 4, 3
>>> spec = BoundedTensorSpec(-torch.ones(n_act), torch.ones(n_act), (n_act,))
>>> net = nn.Sequential(nn.Linear(n_obs, 2 * n_act), NormalParamExtractor())
>>> module = SafeModule(net, in_keys=["observation"], out_keys=["loc", "scale"])
>>> actor = ProbabilisticActor(
...     module=module,
...     in_keys=["loc", "scale"],
...     spec=spec,
...     distribution_class=TanhNormal)
>>> class ValueClass(nn.Module):
...     def __init__(self):
...         super().__init__()
...         self.linear = nn.Linear(n_obs + n_act, 1)
...     def forward(self, obs, act):
...         return self.linear(torch.cat([obs, act], -1))
>>> module = ValueClass()
>>> qvalue = ValueOperator(
...     module=module,
...     in_keys=['observation', 'action'])
>>> loss = CQLLoss(actor, qvalue)
>>> batch = [2, ]
>>> action = spec.rand(batch)
>>> data = TensorDict({
...         "observation": torch.randn(*batch, n_obs),
...         "action": action,
...         ("next", "done"): torch.zeros(*batch, 1, dtype=torch.bool),
...         ("next", "terminated"): torch.zeros(*batch, 1, dtype=torch.bool),
...         ("next", "reward"): torch.randn(*batch, 1),
...         ("next", "observation"): torch.randn(*batch, n_obs),
...     }, batch)
>>> loss(data)
TensorDict(
    fields={
        alpha: Tensor(shape=torch.Size([]), device=cpu, dtype=torch.float32, is_shared=False),
        entropy: Tensor(shape=torch.Size([]), device=cpu, dtype=torch.float32, is_shared=False),
        loss_actor: Tensor(shape=torch.Size([]), device=cpu, dtype=torch.float32, is_shared=False),
        loss_actor_bc: Tensor(shape=torch.Size([]), device=cpu, dtype=torch.float32, is_shared=False),
        loss_alpha: Tensor(shape=torch.Size([]), device=cpu, dtype=torch.float32, is_shared=False),
        loss_cql: Tensor(shape=torch.Size([]), device=cpu, dtype=torch.float32, is_shared=False),
        loss_qvalue: Tensor(shape=torch.Size([]), device=cpu, dtype=torch.float32, is_shared=False)},
    batch_size=torch.Size([]),
    device=None,
    is_shared=False)

This class is compatible with non-tensordict based modules too and can be used without recurring to any tensordict-related primitive. In this case, the expected keyword arguments are: ["action", "next_reward", "next_done", "next_terminated"] + in_keys of the actor, value, and qvalue network. The return value is a tuple of tensors in the following order: ["loss_actor", "loss_qvalue", "loss_alpha", "loss_alpha_prime", "alpha", "entropy"].

Examples

>>> import torch
>>> from torch import nn
>>> from torchrl.data import BoundedTensorSpec
>>> from torchrl.modules.distributions import NormalParamExtractor, TanhNormal
>>> from torchrl.modules.tensordict_module.actors import ProbabilisticActor, ValueOperator
>>> from torchrl.modules.tensordict_module.common import SafeModule
>>> from torchrl.objectives.cql import CQLLoss
>>> _ = torch.manual_seed(42)
>>> n_act, n_obs = 4, 3
>>> spec = BoundedTensorSpec(-torch.ones(n_act), torch.ones(n_act), (n_act,))
>>> net = nn.Sequential(nn.Linear(n_obs, 2 * n_act), NormalParamExtractor())
>>> module = SafeModule(net, in_keys=["observation"], out_keys=["loc", "scale"])
>>> actor = ProbabilisticActor(
...     module=module,
...     in_keys=["loc", "scale"],
...     spec=spec,
...     distribution_class=TanhNormal)
>>> class ValueClass(nn.Module):
...     def __init__(self):
...         super().__init__()
...         self.linear = nn.Linear(n_obs + n_act, 1)
...     def forward(self, obs, act):
...         return self.linear(torch.cat([obs, act], -1))
>>> module = ValueClass()
>>> qvalue = ValueOperator(
...     module=module,
...     in_keys=['observation', 'action'])
>>> loss = CQLLoss(actor, qvalue)
>>> batch = [2, ]
>>> action = spec.rand(batch)
>>> loss_actor, loss_actor_bc, loss_qvalue, loss_cql, *_ = loss(
...     observation=torch.randn(*batch, n_obs),
...     action=action,
...     next_done=torch.zeros(*batch, 1, dtype=torch.bool),
...     next_terminated=torch.zeros(*batch, 1, dtype=torch.bool),
...     next_observation=torch.zeros(*batch, n_obs),
...     next_reward=torch.randn(*batch, 1))
>>> loss_actor.backward()

The output keys can also be filtered using the CQLLoss.select_out_keys() method.

Examples

>>> _ = loss.select_out_keys('loss_actor', 'loss_qvalue')
>>> loss_actor, loss_qvalue = loss(
...     observation=torch.randn(*batch, n_obs),
...     action=action,
...     next_done=torch.zeros(*batch, 1, dtype=torch.bool),
...     next_terminated=torch.zeros(*batch, 1, dtype=torch.bool),
...     next_observation=torch.zeros(*batch, n_obs),
...     next_reward=torch.randn(*batch, 1))
>>> loss_actor.backward()

forward(tensordict: TensorDictBase) → TensorDictBase

It is designed to read an input TensorDict and return another tensordict with loss keys named “loss*”.

Splitting the loss in its component can then be used by the trainer to log the various loss values throughout training. Other scalars present in the output tensordict will be logged too.

Parameters:

tensordict – an input tensordict with the values required to compute the loss.

Returns:

A new tensordict with no batch dimension containing various loss scalars which will be named “loss*”. It is essential that the losses are returned with this name as they will be read by the trainer before backpropagation.

make_value_estimator(value_type: Optional[ValueEstimators] = None, **hyperparams)

Value-function constructor.

If the non-default value function is wanted, it must be built using this method.

Parameters:

• value_type (ValueEstimators) – A ValueEstimators enum type indicating the value function to use. If none is provided, the default stored in the default_value_estimator attribute will be used. The resulting value estimator class will be registered in self.value_type, allowing future refinements.

• **hyperparams – hyperparameters to use for the value function. If not provided, the value indicated by default_value_kwargs() will be used.

Examples

>>> from torchrl.objectives import DQNLoss
>>> # initialize the DQN loss
>>> actor = torch.nn.Linear(3, 4)
>>> dqn_loss = DQNLoss(actor, action_space="one-hot")
>>> # updating the parameters of the default value estimator
>>> dqn_loss.make_value_estimator(gamma=0.9)
>>> dqn_loss.make_value_estimator(
...     ValueEstimators.TD1,
...     gamma=0.9)
>>> # if we want to change the gamma value
>>> dqn_loss.make_value_estimator(dqn_loss.value_type, gamma=0.9)