ml-agents/ml-agents/mlagents/trainers/ppo/trainer.py

# # 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 List, Any, Dict

import numpy as np

from mlagents.envs import AllBrainInfo, BrainInfo
from mlagents.trainers.buffer import Buffer
from mlagents.trainers.ppo.policy import PPOPolicy
from mlagents.trainers.ppo.multi_gpu_policy import MultiGpuPPOPolicy, get_devices
from mlagents.trainers.trainer import UnityTrainerException
from mlagents.trainers.rl_trainer import RLTrainer
from mlagents.trainers.components.reward_signals import RewardSignalResult
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: AllBrainInfo, new_info: AllBrainInfo
    ) -> 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: Dictionary of all current brains and corresponding BrainInfo.
        :param new_info: Dictionary of all next brains and corresponding BrainInfo.
        """
        info = new_info[self.brain_name]
        for l in range(len(info.agents)):
            agent_actions = self.training_buffer[info.agents[l]]["actions"]
            if (
                info.local_done[l]
                or len(agent_actions) > self.trainer_parameters["time_horizon"]
            ) and len(agent_actions) > 0:
                agent_id = info.agents[l]
                if info.max_reached[l]:
                    bootstrapping_info = self.training_buffer[agent_id].last_brain_info
                    idx = bootstrapping_info.agents.index(agent_id)
                else:
                    bootstrapping_info = info
                    idx = l
                value_next = self.policy.get_value_estimates(
                    bootstrapping_info,
                    idx,
                    info.local_done[l] and not 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 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,
        value: Dict[str, Any],
        rewards_dict: Dict[str, RewardSignalResult],
        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_dict.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_idx]
            )
            self.training_buffer[agent_id]["{}_value_estimates".format(name)].append(
                value[name][agent_next_idx][0]
            )

    def end_episode(self):
        """
        A signal that the Episode has ended. The buffer must be reset.
        Get only called when the academy resets.
        """
        self.training_buffer.reset_local_buffers()
        for agent_id in self.episode_steps:
            self.episode_steps[agent_id] = 0
        for rewards in self.collected_rewards.values():
            for agent_id in rewards:
                rewards[agent_id] = 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.
        """
        self.trainer_metrics.start_policy_update_timer(
            number_experiences=len(self.training_buffer.update_buffer["actions"]),
            mean_return=float(np.mean(self.cumulative_returns_since_policy_update)),
        )
        self.cumulative_returns_since_policy_update = []
        batch_size = self.trainer_parameters["batch_size"]
        n_sequences = max(
            int(self.trainer_parameters["batch_size"] / self.policy.sequence_length), 1
        )
        value_total, policy_total = [], []
        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"]
        for _ in range(num_epoch):
            self.training_buffer.update_buffer.shuffle(
                sequence_length=self.policy.sequence_length
            )
            buffer = self.training_buffer.update_buffer
            for l in range(
                0, len(self.training_buffer.update_buffer["actions"]), batch_size
            ):
                run_out = self.policy.update(
                    buffer.make_mini_batch(l, l + batch_size), n_sequences
                )
                value_total.append(run_out["value_loss"])
                policy_total.append(np.abs(run_out["policy_loss"]))
        self.stats["Losses/Value Loss"].append(np.mean(value_total))
        self.stats["Losses/Policy Loss"].append(np.mean(policy_total))
        for _, reward_signal in self.policy.reward_signals.items():
            update_stats = reward_signal.update(
                self.training_buffer.update_buffer, n_sequences
            )
            for stat, val in update_stats.items():
                self.stats[stat].append(val)
        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.training_buffer.reset_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