from copy import deepcopy
from typing import Any, Dict
import torch
import torch.optim as opt
from genrl.agents import OffPolicyAgentAC
from genrl.core import ActionNoise
from genrl.utils import get_env_properties, get_model, safe_mean
[docs]class DDPG(OffPolicyAgentAC):
"""Deep Deterministic Policy Gradient Algorithm
Paper: https://arxiv.org/abs/1509.02971
Attributes:
network (str): The network type of the Q-value function.
Supported types: ["cnn", "mlp"]
env (Environment): The environment that the agent is supposed to act on
create_model (bool): Whether the model of the algo should be created when initialised
batch_size (int): Mini batch size for loading experiences
gamma (float): The discount factor for rewards
layers (:obj:`tuple` of :obj:`int`): Layers in the Neural Network
of the Q-value function
shared_layers(:obj:`tuple` of :obj:`int`): Sizes of shared layers in Actor Critic if using
lr_policy (float): Learning rate for the policy/actor
lr_value (float): Learning rate for the critic
replay_size (int): Capacity of the Replay Buffer
buffer_type (str): Choose the type of Buffer: ["push", "prioritized"]
polyak (float): Target model update parameter (1 for hard update)
noise (:obj:`ActionNoise`): Action Noise function added to aid in exploration
noise_std (float): Standard deviation of the action noise distribution
seed (int): Seed for randomness
render (bool): Should the env be rendered during training?
device (str): Hardware being used for training. Options:
["cuda" -> GPU, "cpu" -> CPU]
"""
def __init__(
self, *args, noise: ActionNoise = None, noise_std: float = 0.2, **kwargs
):
super(DDPG, self).__init__(*args, **kwargs)
self.noise = noise
self.noise_std = noise_std
self.empty_logs()
if self.create_model:
self._create_model()
def _create_model(self) -> None:
"""Function to initialize Actor-Critic architecture
This will create the Actor-Critic net for the agent and initialise the action noise
"""
state_dim, action_dim, discrete, _ = get_env_properties(self.env, self.network)
if discrete:
raise Exception(
"Discrete Environments not supported for {}.".format(__class__.__name__)
)
if self.noise is not None:
self.noise = self.noise(
torch.zeros(action_dim), self.noise_std * torch.ones(action_dim)
)
if isinstance(self.network, str):
arch_type = self.network
if self.shared_layers is not None:
arch_type += "s"
self.ac = get_model("ac", arch_type)(
state_dim,
action_dim,
self.shared_layers,
self.policy_layers,
self.value_layers,
"Qsa",
False,
).to(self.device)
else:
self.ac = self.network
actor_params, critic_params = self.ac.get_params()
self.ac_target = deepcopy(self.ac).to(self.device)
self.optimizer_policy = opt.Adam(actor_params, lr=self.lr_policy)
self.optimizer_value = opt.Adam(critic_params, lr=self.lr_value)
[docs] def update_params(self, update_interval: int) -> None:
"""Update parameters of the model
Args:
update_interval (int): Interval between successive updates of the target model
"""
for timestep in range(update_interval):
batch = self.sample_from_buffer()
value_loss = self.get_q_loss(batch)
self.logs["value_loss"].append(value_loss.item())
policy_loss = self.get_p_loss(batch.states)
self.logs["policy_loss"].append(policy_loss.item())
self.optimizer_policy.zero_grad()
policy_loss.backward()
self.optimizer_policy.step()
self.optimizer_value.zero_grad()
value_loss.backward()
self.optimizer_value.step()
self.update_target_model()
[docs] def get_hyperparams(self) -> Dict[str, Any]:
"""Get relevant hyperparameters to save
Returns:
hyperparams (:obj:`dict`): Hyperparameters to be saved
weights (:obj:`torch.Tensor`): Neural Network weights
"""
hyperparams = {
"network": self.network,
"gamma": self.gamma,
"batch_size": self.batch_size,
"replay_size": self.replay_size,
"polyak": self.polyak,
"noise_std": self.noise_std,
"lr_policy": self.lr_policy,
"lr_value": self.lr_value,
}
return hyperparams, self.ac.state_dict()
[docs] def get_logging_params(self) -> Dict[str, Any]:
"""Gets relevant parameters for logging
Returns:
logs (:obj:`dict`): Logging parameters for monitoring training
"""
logs = {
"policy_loss": safe_mean(self.logs["policy_loss"]),
"value_loss": safe_mean(self.logs["value_loss"]),
}
self.empty_logs()
return logs
[docs] def empty_logs(self):
"""Empties logs"""
self.logs = {}
self.logs["policy_loss"] = []
self.logs["value_loss"] = []