# garage.sampler.sampler¶

Base sampler class.

class Sampler(algo, env)[source]

Bases: abc.ABC

Abstract base class of all samplers.

Implementations of this class should override construct, obtain_samples, and shutdown_worker. construct takes a WorkerFactory, which implements most of the RL-specific functionality a Sampler needs. Specifically, it specifies how to construct Workers, which know how to collect episodes and update both agents and environments.

Currently, __init__ is also part of the interface, but calling it is deprecated. start_worker is also deprecated, and does not need to be implemented.

classmethod from_worker_factory(cls, worker_factory, agents, envs)[source]

Construct this sampler.

Parameters
• worker_factory (WorkerFactory) – Pickleable factory for creating workers. Should be transmitted to other processes / nodes where work needs to be done, then workers should be constructed there.

• agents (Policy or List[Policy]) – Agent(s) to use to collect episodes. If a list is passed in, it must have length exactly worker_factory.n_workers, and will be spread across the workers.

• envs (Environment or List[Environment]) – Environment from which episodes are sampled. If a list is passed in, it must have length exactly worker_factory.n_workers, and will be spread across the workers.

Returns

An instance of cls.

Return type

Sampler

start_worker(self)[source]

Initialize the sampler.

i.e. launching parallel workers if necessary.

This method is deprecated, please launch workers in construct instead.

abstract obtain_samples(self, itr, num_samples, agent_update, env_update=None)[source]

Collect at least a given number transitions :class:TimeSteps.

Parameters
• itr (int) – The current iteration number. Using this argument is deprecated.

• num_samples (int) – Minimum number of :class:TimeSteps to sample.

• agent_update (object) – Value which will be passed into the agent_update_fn before sampling episodes. If a list is passed in, it must have length exactly factory.n_workers, and will be spread across the workers.

• env_update (object) – Value which will be passed into the env_update_fn before sampling episodes. If a list is passed in, it must have length exactly factory.n_workers, and will be spread across the workers.

Returns

The batch of collected episodes.

Return type

EpisodeBatch

abstract shutdown_worker(self)[source]

Terminate workers if necessary.

Because Python object destruction can be somewhat unpredictable, this method isn’t deprecated.