"""Base sampler class."""
import abc
import copy
[docs]class Sampler(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 `Worker`s,
which know how to perform rollouts 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.
"""
def __init__(self, algo, env):
"""Construct a Sampler from an Algorithm.
Args:
algo(garage.RLAlgorithm): The RL Algorithm controlling this
sampler.
env(gym.Env): The environment being sampled from.
Calling this method is deprecated.
"""
self.algo = algo
self.env = env
[docs] @classmethod
def from_worker_factory(cls, worker_factory, agents, envs):
"""Construct this sampler.
Args:
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(Agent or List[Agent]): Agent(s) to use to perform rollouts.
If a list is passed in, it must have length exactly
`worker_factory.n_workers`, and will be spread across the
workers.
envs(gym.Env or List[gym.Env]): Environment rollouts are performed
in. If a list is passed in, it must have length exactly
`worker_factory.n_workers`, and will be spread across the
workers.
Returns:
Sampler: An instance of `cls`.
"""
# This implementation works for most current implementations.
# Relying on this implementation is deprecated, but calling this method
# is not.
fake_algo = copy.copy(worker_factory)
fake_algo.policy = agents
return cls(fake_algo, envs)
[docs] def start_worker(self):
"""Initialize the sampler.
i.e. launching parallel workers if necessary.
This method is deprecated, please launch workers in construct instead.
"""
[docs] @abc.abstractmethod
def obtain_samples(self, itr, num_samples, agent_update, env_update=None):
"""Collect at least a given number transitions (timesteps).
Args:
itr(int): The current iteration number. Using this argument is
deprecated.
num_samples(int): Minimum number of transitions / timesteps to
sample.
agent_update(object): Value which will be passed into the
`agent_update_fn` before doing rollouts. 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 doing rollouts. If a list is passed in,
it must have length exactly `factory.n_workers`, and will be
spread across the workers.
Returns:
garage.TrajectoryBatch: The batch of collected trajectories.
"""
[docs] @abc.abstractmethod
def shutdown_worker(self):
"""Terminate workers if necessary.
Because Python object destruction can be somewhat unpredictable, this
method isn't deprecated.
"""