ray.rllib.algorithms.algorithm.Algorithm

class ray.rllib.algorithms.algorithm.Algorithm(config: AlgorithmConfig | None = None, env=None, logger_creator: Callable[[], Logger] | None = None, **kwargs)

Bases: Trainable, AlgorithmBase

An RLlib algorithm responsible for optimizing one or more Policies.

Algorithms contain a WorkerSet under self.workers. A WorkerSet is normally composed of a single local worker (self.workers.local_worker()), used to compute and apply learning updates, and optionally one or more remote workers used to generate environment samples in parallel. WorkerSet is fault tolerant and elastic. It tracks health states for all the managed remote worker actors. As a result, Algorithm should never access the underlying actor handles directly. Instead, always access them via all the foreach APIs with assigned IDs of the underlying workers.

Each worker (remotes or local) contains a PolicyMap, which itself may contain either one policy for single-agent training or one or more policies for multi-agent training. Policies are synchronized automatically from time to time using ray.remote calls. The exact synchronization logic depends on the specific algorithm used, but this usually happens from local worker to all remote workers and after each training update.

You can write your own Algorithm classes by sub-classing from Algorithm or any of its built-in sub-classes. This allows you to override the training_step method to implement your own algorithm logic. You can find the different built-in algorithms’ training_step() methods in their respective main .py files, e.g. rllib.algorithms.dqn.dqn.py or rllib.algorithms.impala.impala.py.

The most important API methods a Algorithm exposes are train(), evaluate(), save() and restore().

Methods

__init__	Initializes an Algorithm instance.
add_module	Adds a new (single-agent) RLModule to this Algorithm's MARLModule.
add_policy	Adds a new policy to this Algorithm.
compute_actions	Computes an action for the specified policy on the local Worker.
compute_single_action	Computes an action for the specified policy on the local worker.
evaluate	Evaluates current policy under evaluation_config settings.
export_model	Exports model based on export_formats.
export_policy_checkpoint	Exports Policy checkpoint to a local directory and returns an AIR Checkpoint.
export_policy_model	Exports policy model with given policy_id to a local directory.
from_checkpoint	Creates a new algorithm instance from a given checkpoint.
from_state	Recovers an Algorithm from a state object.
get_config	Returns configuration passed in by Tune.
get_default_policy_class	Returns a default Policy class to use, given a config.
get_module	Returns the (single-agent) RLModule with model_id (None if ID not found).
get_policy	Return policy for the specified id, or None.
get_weights	Return a dictionary of policy ids to weights.
import_model	Imports a model from import_file.
merge_algorithm_configs	Merges a complete Algorithm config dict with a partial override dict.
remove_policy	Removes a new policy from this Algorithm.
reset	Resets trial for use with new config.
reset_config	Resets configuration without restarting the trial.
restore	Restores training state from a given model checkpoint.
restore_workers	Try syncing previously failed and restarted workers with local, if necessary.
save	Saves the current model state to a checkpoint.
save_checkpoint	Exports checkpoint to a local directory.
set_weights	Set policy weights by policy id.
step	Implements the main Algorithm.train() logic.
stop	Releases all resources used by this trainable.
train	Runs one logical iteration of training.
train_buffered	Runs multiple iterations of training.
training_step	Default single iteration logic of an algorithm.
validate_env	Env validator function for this Algorithm class.

Attributes

iteration	Current training iteration.
logdir	Directory of the results and checkpoints for this Trainable.
training_iteration	Current training iteration (same as self.iteration).
trial_id	Trial ID for the corresponding trial of this Trainable.
trial_name	Trial name for the corresponding trial of this Trainable.
trial_resources	Resources currently assigned to the trial of this Trainable.