#
# Copyright (c) 2017 Intel Corporation
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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# http://www.apache.org/licenses/LICENSE-2.0
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from typing import Union
import numpy as np
import scipy.signal
from rl_coach.agents.policy_optimization_agent import PolicyOptimizationAgent, PolicyGradientRescaler
from rl_coach.architectures.embedder_parameters import InputEmbedderParameters
from rl_coach.architectures.head_parameters import PolicyHeadParameters, VHeadParameters
from rl_coach.architectures.middleware_parameters import FCMiddlewareParameters
from rl_coach.base_parameters import AlgorithmParameters, NetworkParameters, \
AgentParameters
from rl_coach.exploration_policies.categorical import CategoricalParameters
from rl_coach.exploration_policies.continuous_entropy import ContinuousEntropyParameters
from rl_coach.logger import screen
from rl_coach.memories.episodic.single_episode_buffer import SingleEpisodeBufferParameters
from rl_coach.spaces import DiscreteActionSpace, BoxActionSpace
from rl_coach.utils import last_sample
[docs]class ActorCriticAlgorithmParameters(AlgorithmParameters):
"""
:param policy_gradient_rescaler: (PolicyGradientRescaler)
The value that will be used to rescale the policy gradient
:param apply_gradients_every_x_episodes: (int)
The number of episodes to wait before applying the accumulated gradients to the network.
The training iterations only accumulate gradients without actually applying them.
:param beta_entropy: (float)
The weight that will be given to the entropy regularization which is used in order to improve exploration.
:param num_steps_between_gradient_updates: (int)
Every num_steps_between_gradient_updates transitions will be considered as a single batch and use for
accumulating gradients. This is also the number of steps used for bootstrapping according to the n-step formulation.
:param gae_lambda: (float)
If the policy gradient rescaler was defined as PolicyGradientRescaler.GAE, the generalized advantage estimation
scheme will be used, in which case the lambda value controls the decay for the different n-step lengths.
:param estimate_state_value_using_gae: (bool)
If set to True, the state value targets for the V head will be estimated using the GAE scheme.
"""
def __init__(self):
super().__init__()
self.policy_gradient_rescaler = PolicyGradientRescaler.A_VALUE
self.apply_gradients_every_x_episodes = 5
self.beta_entropy = 0
self.num_steps_between_gradient_updates = 5000 # this is called t_max in all the papers
self.gae_lambda = 0.96
self.estimate_state_value_using_gae = False
class ActorCriticNetworkParameters(NetworkParameters):
def __init__(self):
super().__init__()
self.input_embedders_parameters = {'observation': InputEmbedderParameters()}
self.middleware_parameters = FCMiddlewareParameters()
self.heads_parameters = [VHeadParameters(loss_weight=0.5), PolicyHeadParameters(loss_weight=1.0)]
self.optimizer_type = 'Adam'
self.clip_gradients = 40.0
self.async_training = True
class ActorCriticAgentParameters(AgentParameters):
def __init__(self):
super().__init__(algorithm=ActorCriticAlgorithmParameters(),
exploration={DiscreteActionSpace: CategoricalParameters(),
BoxActionSpace: ContinuousEntropyParameters()},
memory=SingleEpisodeBufferParameters(),
networks={"main": ActorCriticNetworkParameters()})
@property
def path(self):
return 'rl_coach.agents.actor_critic_agent:ActorCriticAgent'
# Actor Critic - https://arxiv.org/abs/1602.01783
class ActorCriticAgent(PolicyOptimizationAgent):
def __init__(self, agent_parameters, parent: Union['LevelManager', 'CompositeAgent']=None):
super().__init__(agent_parameters, parent)
self.last_gradient_update_step_idx = 0
self.action_advantages = self.register_signal('Advantages')
self.state_values = self.register_signal('Values')
self.value_loss = self.register_signal('Value Loss')
self.policy_loss = self.register_signal('Policy Loss')
# Discounting function used to calculate discounted returns.
def discount(self, x, gamma):
return scipy.signal.lfilter([1], [1, -gamma], x[::-1], axis=0)[::-1]
def get_general_advantage_estimation_values(self, rewards, values):
# values contain n+1 elements (t ... t+n+1), rewards contain n elements (t ... t + n)
bootstrap_extended_rewards = np.array(rewards.tolist() + [values[-1]])
# Approximation based calculation of GAE (mathematically correct only when Tmax = inf,
# although in practice works even in much smaller Tmax values, e.g. 20)
deltas = rewards + self.ap.algorithm.discount * values[1:] - values[:-1]
gae = self.discount(deltas, self.ap.algorithm.discount * self.ap.algorithm.gae_lambda)
if self.ap.algorithm.estimate_state_value_using_gae:
discounted_returns = np.expand_dims(gae + values[:-1], -1)
else:
discounted_returns = np.expand_dims(np.array(self.discount(bootstrap_extended_rewards,
self.ap.algorithm.discount)), 1)[:-1]
return gae, discounted_returns
def learn_from_batch(self, batch):
# batch contains a list of episodes to learn from
network_keys = self.ap.network_wrappers['main'].input_embedders_parameters.keys()
# get the values for the current states
result = self.networks['main'].online_network.predict(batch.states(network_keys))
current_state_values = result[0]
self.state_values.add_sample(current_state_values)
# the targets for the state value estimator
num_transitions = batch.size
state_value_head_targets = np.zeros((num_transitions, 1))
# estimate the advantage function
action_advantages = np.zeros((num_transitions, 1))
if self.policy_gradient_rescaler == PolicyGradientRescaler.A_VALUE:
if batch.game_overs()[-1]:
R = 0
else:
R = self.networks['main'].online_network.predict(last_sample(batch.next_states(network_keys)))[0]
for i in reversed(range(num_transitions)):
R = batch.rewards()[i] + self.ap.algorithm.discount * R
state_value_head_targets[i] = R
action_advantages[i] = R - current_state_values[i]
elif self.policy_gradient_rescaler == PolicyGradientRescaler.GAE:
# get bootstraps
bootstrapped_value = self.networks['main'].online_network.predict(last_sample(batch.next_states(network_keys)))[0]
values = np.append(current_state_values, bootstrapped_value)
if batch.game_overs()[-1]:
values[-1] = 0
# get general discounted returns table
gae_values, state_value_head_targets = self.get_general_advantage_estimation_values(batch.rewards(), values)
action_advantages = np.vstack(gae_values)
else:
screen.warning("WARNING: The requested policy gradient rescaler is not available")
action_advantages = action_advantages.squeeze(axis=-1)
actions = batch.actions()
if not isinstance(self.spaces.action, DiscreteActionSpace) and len(actions.shape) < 2:
actions = np.expand_dims(actions, -1)
# train
result = self.networks['main'].online_network.accumulate_gradients({**batch.states(network_keys),
'output_1_0': actions},
[state_value_head_targets, action_advantages])
# logging
total_loss, losses, unclipped_grads = result[:3]
self.action_advantages.add_sample(action_advantages)
self.unclipped_grads.add_sample(unclipped_grads)
self.value_loss.add_sample(losses[0])
self.policy_loss.add_sample(losses[1])
return total_loss, losses, unclipped_grads
def get_prediction(self, states):
tf_input_state = self.prepare_batch_for_inference(states, "main")
return self.networks['main'].online_network.predict(tf_input_state)[1:] # index 0 is the state value