Unity 机器学习代理工具包 (ML-Agents) 是一个开源项目,它使游戏和模拟能够作为训练智能代理的环境。
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# # Unity ML-Agents Toolkit
# ## ML-Agent Learning (PPO)
# Contains an implementation of PPO as described in: https://arxiv.org/abs/1707.06347
import logging
from collections import defaultdict
from typing import Dict
import numpy as np
from mlagents.envs.brain import BrainInfo
from mlagents.trainers.ppo.policy import PPOPolicy
from mlagents.trainers.ppo.multi_gpu_policy import MultiGpuPPOPolicy, get_devices
from mlagents.trainers.rl_trainer import RLTrainer, AllRewardsOutput
from mlagents.envs.action_info import ActionInfoOutputs
logger = logging.getLogger("mlagents.trainers")
class PPOTrainer(RLTrainer):
"""The PPOTrainer is an implementation of the PPO algorithm."""
def __init__(
self,
brain,
reward_buff_cap,
trainer_parameters,
training,
load,
seed,
run_id,
multi_gpu,
):
"""
Responsible for collecting experiences and training PPO model.
:param trainer_parameters: The parameters for the trainer (dictionary).
:param reward_buff_cap: Max reward history to track in the reward buffer
:param training: Whether the trainer is set for training.
:param load: Whether the model should be loaded.
:param seed: The seed the model will be initialized with
:param run_id: The identifier of the current run
"""
super(PPOTrainer, self).__init__(
brain, trainer_parameters, training, run_id, reward_buff_cap
)
self.param_keys = [
"batch_size",
"beta",
"buffer_size",
"epsilon",
"hidden_units",
"lambd",
"learning_rate",
"max_steps",
"normalize",
"num_epoch",
"num_layers",
"time_horizon",
"sequence_length",
"summary_freq",
"use_recurrent",
"summary_path",
"memory_size",
"model_path",
"reward_signals",
]
self.check_param_keys()
if multi_gpu and len(get_devices()) > 1:
self.policy = MultiGpuPPOPolicy(
seed, brain, trainer_parameters, self.is_training, load
)
else:
self.policy = PPOPolicy(
seed, brain, trainer_parameters, self.is_training, load
)
for _reward_signal in self.policy.reward_signals.keys():
self.collected_rewards[_reward_signal] = {}
def process_experiences(
self, current_info: BrainInfo, next_info: BrainInfo
) -> None:
"""
Checks agent histories for processing condition, and processes them as necessary.
Processing involves calculating value and advantage targets for model updating step.
:param current_info: current BrainInfo.
:param next_info: next BrainInfo.
"""
if self.is_training:
self.policy.update_normalization(next_info.vector_observations)
for l in range(len(next_info.agents)):
agent_actions = self.training_buffer[next_info.agents[l]]["actions"]
if (
next_info.local_done[l]
or len(agent_actions) > self.trainer_parameters["time_horizon"]
) and len(agent_actions) > 0:
agent_id = next_info.agents[l]
if next_info.max_reached[l]:
bootstrapping_info = self.training_buffer[agent_id].last_brain_info
idx = bootstrapping_info.agents.index(agent_id)
else:
bootstrapping_info = next_info
idx = l
value_next = self.policy.get_value_estimates(
bootstrapping_info,
idx,
next_info.local_done[l] and not next_info.max_reached[l],
)
tmp_advantages = []
tmp_returns = []
for name in self.policy.reward_signals:
bootstrap_value = value_next[name]
local_rewards = self.training_buffer[agent_id][
"{}_rewards".format(name)
].get_batch()
local_value_estimates = self.training_buffer[agent_id][
"{}_value_estimates".format(name)
].get_batch()
local_advantage = get_gae(
rewards=local_rewards,
value_estimates=local_value_estimates,
value_next=bootstrap_value,
gamma=self.policy.reward_signals[name].gamma,
lambd=self.trainer_parameters["lambd"],
)
local_return = local_advantage + local_value_estimates
# This is later use as target for the different value estimates
self.training_buffer[agent_id]["{}_returns".format(name)].set(
local_return
)
self.training_buffer[agent_id]["{}_advantage".format(name)].set(
local_advantage
)
tmp_advantages.append(local_advantage)
tmp_returns.append(local_return)
global_advantages = list(np.mean(np.array(tmp_advantages), axis=0))
global_returns = list(np.mean(np.array(tmp_returns), axis=0))
self.training_buffer[agent_id]["advantages"].set(global_advantages)
self.training_buffer[agent_id]["discounted_returns"].set(global_returns)
self.training_buffer.append_update_buffer(
agent_id,
batch_size=None,
training_length=self.policy.sequence_length,
)
self.training_buffer[agent_id].reset_agent()
if next_info.local_done[l]:
self.stats["Environment/Episode Length"].append(
self.episode_steps.get(agent_id, 0)
)
self.episode_steps[agent_id] = 0
for name, rewards in self.collected_rewards.items():
if name == "environment":
self.cumulative_returns_since_policy_update.append(
rewards.get(agent_id, 0)
)
self.stats["Environment/Cumulative Reward"].append(
rewards.get(agent_id, 0)
)
self.reward_buffer.appendleft(rewards.get(agent_id, 0))
rewards[agent_id] = 0
else:
self.stats[
self.policy.reward_signals[name].stat_name
].append(rewards.get(agent_id, 0))
rewards[agent_id] = 0
def add_policy_outputs(
self, take_action_outputs: ActionInfoOutputs, agent_id: str, agent_idx: int
) -> None:
"""
Takes the output of the last action and store it into the training buffer.
"""
actions = take_action_outputs["action"]
if self.policy.use_continuous_act:
actions_pre = take_action_outputs["pre_action"]
self.training_buffer[agent_id]["actions_pre"].append(actions_pre[agent_idx])
epsilons = take_action_outputs["random_normal_epsilon"]
self.training_buffer[agent_id]["random_normal_epsilon"].append(
epsilons[agent_idx]
)
a_dist = take_action_outputs["log_probs"]
# value is a dictionary from name of reward to value estimate of the value head
self.training_buffer[agent_id]["actions"].append(actions[agent_idx])
self.training_buffer[agent_id]["action_probs"].append(a_dist[agent_idx])
def add_rewards_outputs(
self,
rewards_out: AllRewardsOutput,
values: Dict[str, np.ndarray],
agent_id: str,
agent_idx: int,
agent_next_idx: int,
) -> None:
"""
Takes the value output of the last action and store it into the training buffer.
"""
for name, reward_result in rewards_out.reward_signals.items():
# 0 because we use the scaled reward to train the agent
self.training_buffer[agent_id]["{}_rewards".format(name)].append(
reward_result.scaled_reward[agent_next_idx]
)
self.training_buffer[agent_id]["{}_value_estimates".format(name)].append(
values[name][agent_idx][0]
)
def is_ready_update(self):
"""
Returns whether or not the trainer has enough elements to run update model
:return: A boolean corresponding to whether or not update_model() can be run
"""
size_of_buffer = len(self.training_buffer.update_buffer["actions"])
return size_of_buffer > self.trainer_parameters["buffer_size"]
def update_policy(self):
"""
Uses demonstration_buffer to update the policy.
The reward signal generators must be updated in this method at their own pace.
"""
buffer_length = len(self.training_buffer.update_buffer["actions"])
self.trainer_metrics.start_policy_update_timer(
number_experiences=buffer_length,
mean_return=float(np.mean(self.cumulative_returns_since_policy_update)),
)
self.cumulative_returns_since_policy_update.clear()
# Make sure batch_size is a multiple of sequence length. During training, we
# will need to reshape the data into a batch_size x sequence_length tensor.
batch_size = (
self.trainer_parameters["batch_size"]
- self.trainer_parameters["batch_size"] % self.policy.sequence_length
)
# Make sure there is at least one sequence
batch_size = max(batch_size, self.policy.sequence_length)
n_sequences = max(
int(self.trainer_parameters["batch_size"] / self.policy.sequence_length), 1
)
advantages = self.training_buffer.update_buffer["advantages"].get_batch()
self.training_buffer.update_buffer["advantages"].set(
(advantages - advantages.mean()) / (advantages.std() + 1e-10)
)
num_epoch = self.trainer_parameters["num_epoch"]
batch_update_stats = defaultdict(list)
for _ in range(num_epoch):
self.training_buffer.update_buffer.shuffle(
sequence_length=self.policy.sequence_length
)
buffer = self.training_buffer.update_buffer
max_num_batch = buffer_length // batch_size
for l in range(0, max_num_batch * batch_size, batch_size):
update_stats = self.policy.update(
buffer.make_mini_batch(l, l + batch_size), n_sequences
)
for stat_name, value in update_stats.items():
batch_update_stats[stat_name].append(value)
for stat, stat_list in batch_update_stats.items():
self.stats[stat].append(np.mean(stat_list))
if self.policy.bc_module:
update_stats = self.policy.bc_module.update()
for stat, val in update_stats.items():
self.stats[stat].append(val)
self.clear_update_buffer()
self.trainer_metrics.end_policy_update()
def discount_rewards(r, gamma=0.99, value_next=0.0):
"""
Computes discounted sum of future rewards for use in updating value estimate.
:param r: List of rewards.
:param gamma: Discount factor.
:param value_next: T+1 value estimate for returns calculation.
:return: discounted sum of future rewards as list.
"""
discounted_r = np.zeros_like(r)
running_add = value_next
for t in reversed(range(0, r.size)):
running_add = running_add * gamma + r[t]
discounted_r[t] = running_add
return discounted_r
def get_gae(rewards, value_estimates, value_next=0.0, gamma=0.99, lambd=0.95):
"""
Computes generalized advantage estimate for use in updating policy.
:param rewards: list of rewards for time-steps t to T.
:param value_next: Value estimate for time-step T+1.
:param value_estimates: list of value estimates for time-steps t to T.
:param gamma: Discount factor.
:param lambd: GAE weighing factor.
:return: list of advantage estimates for time-steps t to T.
"""
value_estimates = np.append(value_estimates, value_next)
delta_t = rewards + gamma * value_estimates[1:] - value_estimates[:-1]
advantage = discount_rewards(r=delta_t, gamma=gamma * lambd)
return advantage