stable_learning_control.algos.pytorch.policies.soft_actor_critic

This module contains a Pytorch implementation of the Soft Actor Critic policy of Haarnoja et al. 2019.

Module Contents

Classes

SoftActorCritic

Soft Actor-Critic network.

Attributes

HIDDEN_SIZES_DEFAULT
ACTIVATION_DEFAULT
OUTPUT_ACTIVATION_DEFAULT

stable_learning_control.algos.pytorch.policies.soft_actor_critic.HIDDEN_SIZES_DEFAULT

stable_learning_control.algos.pytorch.policies.soft_actor_critic.ACTIVATION_DEFAULT

stable_learning_control.algos.pytorch.policies.soft_actor_critic.OUTPUT_ACTIVATION_DEFAULT

class stable_learning_control.algos.pytorch.policies.soft_actor_critic.SoftActorCritic(observation_space, action_space, hidden_sizes=HIDDEN_SIZES_DEFAULT, activation=ACTIVATION_DEFAULT, output_activation=OUTPUT_ACTIVATION_DEFAULT)

Bases: torch.nn.Module

Soft Actor-Critic network.

self.pi

The squashed gaussian policy network (actor).

Type:

SquashedGaussianActor

self.Q1

The first soft Q-network (critic).

Type:

QCritic

self.Q1

The second soft Q-network (critic).

Type:

QCritic

Initialise the SoftActorCritic object.

Parameters:

• observation_space (gym.space.box.Box) – A gymnasium observation space.

• action_space (gym.space.box.Box) – A gymnasium action space.

• hidden_sizes (Union[dict, tuple, list], optional) – Sizes of the hidden layers for the actor. Defaults to (256, 256).

• activation (Union[dict, torch.nn.modules.activation], optional) – The (actor and critic) hidden layers activation function. Defaults to torch.nn.ReLU.

• output_activation (Union[dict, torch.nn.modules.activation], optional) – The (actor and critic) output activation function. Defaults to torch.nn.ReLU for the actor and nn.Identity for the critic.

forward(obs, act, deterministic=False, with_logprob=True)

Performs a forward pass through all the networks (Actor, Q critic 1 and Q critic 2).

Parameters:

• obs (torch.Tensor) – The tensor of observations.

• act (torch.Tensor) – The tensor of actions.

• deterministic (bool, optional) – Whether we want to use a deterministic policy (used at test time). When true the mean action of the stochastic policy is returned. If false the action is sampled from the stochastic policy. Defaults to False.

• with_logprob (bool, optional) – Whether we want to return the log probability of an action. Defaults to True.

Returns:

tuple containing:

• pi_action (torch.Tensor): The actions given by the policy.

• logp_pi (torch.Tensor): The log probabilities of each of these actions.

• Q1(torch.Tensor): Q-values of the first critic.

• Q2(torch.Tensor): Q-values of the second critic.

Return type:

(tuple)

Note

Useful for when you want to print out the full network graph using TensorBoard.

act(obs, deterministic=False)

Returns the action from the current state given the current policy.

Parameters:

• obs (torch.Tensor) – The current observation (state).

• deterministic (bool, optional) – Whether we want to use a deterministic policy (used at test time). When true the mean action of the stochastic policy is returned. If False the action is sampled from the stochastic policy. Defaults to False.

Returns:

The action from the current state given the current policy.

Return type:

numpy.ndarray