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import numpy as np
from typing import Dict, List, Mapping, cast, Tuple, Optional
from mlagents.torch_utils import torch, nn, default_device
from mlagents_envs.logging_util import get_logger
from mlagents_envs.base_env import ActionSpec
from mlagents.trainers.optimizer.torch_optimizer import TorchOptimizer
from mlagents.trainers.policy.torch_policy import TorchPolicy
from mlagents.trainers.settings import NetworkSettings
from mlagents.trainers.torch.networks import ValueNetwork
from mlagents.trainers.torch.utils import ModelUtils
from mlagents.trainers.buffer import AgentBuffer
from mlagents_envs.timers import timed
from mlagents.trainers.exception import UnityTrainerException
from mlagents.trainers.settings import TrainerSettings, SACSettings
from contextlib import ExitStack
EPSILON = 1e-6 # Small value to avoid divide by zero
logger = get_logger(__name__)
class TorchSACOptimizer(TorchOptimizer):
class PolicyValueNetwork(nn.Module):
def __init__(
self,
stream_names: List[str],
observation_shapes: List[Tuple[int, ...]],
network_settings: NetworkSettings,
action_spec: ActionSpec,
):
super().__init__()
self.action_spec = action_spec
if self.action_spec.is_continuous():
self.act_size = self.action_spec.continuous_size
num_value_outs = 1
num_action_ins = self.act_size
else:
self.act_size = self.action_spec.discrete_branches
num_value_outs = sum(self.act_size)
num_action_ins = 0
self.q1_network = ValueNetwork(
stream_names,
observation_shapes,
network_settings,
num_action_ins,
num_value_outs,
)
self.q2_network = ValueNetwork(
stream_names,
observation_shapes,
network_settings,
num_action_ins,
num_value_outs,
)
def forward(
self,
vec_inputs: List[torch.Tensor],
vis_inputs: List[torch.Tensor],
actions: Optional[torch.Tensor] = None,
memories: Optional[torch.Tensor] = None,
sequence_length: int = 1,
q1_grad: bool = True,
q2_grad: bool = True,
) -> Tuple[Dict[str, torch.Tensor], Dict[str, torch.Tensor]]:
"""
Performs a forward pass on the value network, which consists of a Q1 and Q2
network. Optionally does not evaluate gradients for either the Q1, Q2, or both.
:param vec_inputs: List of vector observation tensors.
:param vis_input: List of visual observation tensors.
:param actions: For a continuous Q function (has actions), tensor of actions.
Otherwise, None.
:param memories: Initial memories if using memory. Otherwise, None.
:param sequence_length: Sequence length if using memory.
:param q1_grad: Whether or not to compute gradients for the Q1 network.
:param q2_grad: Whether or not to compute gradients for the Q2 network.
:return: Tuple of two dictionaries, which both map {reward_signal: Q} for Q1 and Q2,
respectively.
"""
# ExitStack allows us to enter the torch.no_grad() context conditionally
with ExitStack() as stack:
if not q1_grad:
stack.enter_context(torch.no_grad())
q1_out, _ = self.q1_network(
vec_inputs,
vis_inputs,
actions=actions,
memories=memories,
sequence_length=sequence_length,
)
with ExitStack() as stack:
if not q2_grad:
stack.enter_context(torch.no_grad())
q2_out, _ = self.q2_network(
vec_inputs,
vis_inputs,
actions=actions,
memories=memories,
sequence_length=sequence_length,
)
return q1_out, q2_out
def __init__(self, policy: TorchPolicy, trainer_params: TrainerSettings):
super().__init__(policy, trainer_params)
hyperparameters: SACSettings = cast(SACSettings, trainer_params.hyperparameters)
self.tau = hyperparameters.tau
self.init_entcoef = hyperparameters.init_entcoef
self.policy = policy
self.act_size = policy.act_size
policy_network_settings = policy.network_settings
self.tau = hyperparameters.tau
self.burn_in_ratio = 0.0
# Non-exposed SAC parameters
self.discrete_target_entropy_scale = 0.2 # Roughly equal to e-greedy 0.05
self.continuous_target_entropy_scale = 1.0
self.stream_names = list(self.reward_signals.keys())
# Use to reduce "survivor bonus" when using Curiosity or GAIL.
self.gammas = [_val.gamma for _val in trainer_params.reward_signals.values()]
self.use_dones_in_backup = {
name: int(not self.reward_signals[name].ignore_done)
for name in self.stream_names
}
self.value_network = TorchSACOptimizer.PolicyValueNetwork(
self.stream_names,
self.policy.behavior_spec.observation_shapes,
policy_network_settings,
self.policy.behavior_spec.action_spec,
)
self.target_network = ValueNetwork(
self.stream_names,
self.policy.behavior_spec.observation_shapes,
policy_network_settings,
)
ModelUtils.soft_update(
self.policy.actor_critic.critic, self.target_network, 1.0
)
self._log_ent_coef = torch.nn.Parameter(
torch.log(torch.as_tensor([self.init_entcoef] * len(self.act_size))),
requires_grad=True,
)
if self.policy.use_continuous_act:
self.target_entropy = torch.as_tensor(
-1
* self.continuous_target_entropy_scale
* np.prod(self.act_size[0]).astype(np.float32)
)
else:
self.target_entropy = [
self.discrete_target_entropy_scale * np.log(i).astype(np.float32)
for i in self.act_size
]
policy_params = list(self.policy.actor_critic.network_body.parameters()) + list(
self.policy.actor_critic.distribution.parameters()
)
value_params = list(self.value_network.parameters()) + list(
self.policy.actor_critic.critic.parameters()
)
logger.debug("value_vars")
for param in value_params:
logger.debug(param.shape)
logger.debug("policy_vars")
for param in policy_params:
logger.debug(param.shape)
self.decay_learning_rate = ModelUtils.DecayedValue(
hyperparameters.learning_rate_schedule,
hyperparameters.learning_rate,
1e-10,
self.trainer_settings.max_steps,
)
self.policy_optimizer = torch.optim.Adam(
policy_params, lr=hyperparameters.learning_rate
)
self.value_optimizer = torch.optim.Adam(
value_params, lr=hyperparameters.learning_rate
)
self.entropy_optimizer = torch.optim.Adam(
[self._log_ent_coef], lr=hyperparameters.learning_rate
)
self._move_to_device(default_device())
def _move_to_device(self, device: torch.device) -> None:
self._log_ent_coef.to(device)
self.target_network.to(device)
self.value_network.to(device)
def sac_q_loss(
self,
q1_out: Dict[str, torch.Tensor],
q2_out: Dict[str, torch.Tensor],
target_values: Dict[str, torch.Tensor],
dones: torch.Tensor,
rewards: Dict[str, torch.Tensor],
loss_masks: torch.Tensor,
) -> Tuple[torch.Tensor, torch.Tensor]:
q1_losses = []
q2_losses = []
# Multiple q losses per stream
for i, name in enumerate(q1_out.keys()):
q1_stream = q1_out[name].squeeze()
q2_stream = q2_out[name].squeeze()
with torch.no_grad():
q_backup = rewards[name] + (
(1.0 - self.use_dones_in_backup[name] * dones)
* self.gammas[i]
* target_values[name]
)
_q1_loss = 0.5 * ModelUtils.masked_mean(
torch.nn.functional.mse_loss(q_backup, q1_stream), loss_masks
)
_q2_loss = 0.5 * ModelUtils.masked_mean(
torch.nn.functional.mse_loss(q_backup, q2_stream), loss_masks
)
q1_losses.append(_q1_loss)
q2_losses.append(_q2_loss)
q1_loss = torch.mean(torch.stack(q1_losses))
q2_loss = torch.mean(torch.stack(q2_losses))
return q1_loss, q2_loss
def sac_value_loss(
self,
log_probs: torch.Tensor,
values: Dict[str, torch.Tensor],
q1p_out: Dict[str, torch.Tensor],
q2p_out: Dict[str, torch.Tensor],
loss_masks: torch.Tensor,
discrete: bool,
) -> torch.Tensor:
min_policy_qs = {}
with torch.no_grad():
_ent_coef = torch.exp(self._log_ent_coef)
for name in values.keys():
if not discrete:
min_policy_qs[name] = torch.min(q1p_out[name], q2p_out[name])
else:
action_probs = log_probs.exp()
_branched_q1p = ModelUtils.break_into_branches(
q1p_out[name] * action_probs, self.act_size
)
_branched_q2p = ModelUtils.break_into_branches(
q2p_out[name] * action_probs, self.act_size
)
_q1p_mean = torch.mean(
torch.stack(
[
torch.sum(_br, dim=1, keepdim=True)
for _br in _branched_q1p
]
),
dim=0,
)
_q2p_mean = torch.mean(
torch.stack(
[
torch.sum(_br, dim=1, keepdim=True)
for _br in _branched_q2p
]
),
dim=0,
)
min_policy_qs[name] = torch.min(_q1p_mean, _q2p_mean)
value_losses = []
if not discrete:
for name in values.keys():
with torch.no_grad():
v_backup = min_policy_qs[name] - torch.sum(
_ent_coef * log_probs, dim=1
)
value_loss = 0.5 * ModelUtils.masked_mean(
torch.nn.functional.mse_loss(values[name], v_backup), loss_masks
)
value_losses.append(value_loss)
else:
branched_per_action_ent = ModelUtils.break_into_branches(
log_probs * log_probs.exp(), self.act_size
)
# We have to do entropy bonus per action branch
branched_ent_bonus = torch.stack(
[
torch.sum(_ent_coef[i] * _lp, dim=1, keepdim=True)
for i, _lp in enumerate(branched_per_action_ent)
]
)
for name in values.keys():
with torch.no_grad():
v_backup = min_policy_qs[name] - torch.mean(
branched_ent_bonus, axis=0
)
value_loss = 0.5 * ModelUtils.masked_mean(
torch.nn.functional.mse_loss(values[name], v_backup.squeeze()),
loss_masks,
)
value_losses.append(value_loss)
value_loss = torch.mean(torch.stack(value_losses))
if torch.isinf(value_loss).any() or torch.isnan(value_loss).any():
raise UnityTrainerException("Inf found")
return value_loss
def sac_policy_loss(
self,
log_probs: torch.Tensor,
q1p_outs: Dict[str, torch.Tensor],
loss_masks: torch.Tensor,
discrete: bool,
) -> torch.Tensor:
_ent_coef = torch.exp(self._log_ent_coef)
mean_q1 = torch.mean(torch.stack(list(q1p_outs.values())), axis=0)
if not discrete:
mean_q1 = mean_q1.unsqueeze(1)
batch_policy_loss = torch.mean(_ent_coef * log_probs - mean_q1, dim=1)
policy_loss = ModelUtils.masked_mean(batch_policy_loss, loss_masks)
else:
action_probs = log_probs.exp()
branched_per_action_ent = ModelUtils.break_into_branches(
log_probs * action_probs, self.act_size
)
branched_q_term = ModelUtils.break_into_branches(
mean_q1 * action_probs, self.act_size
)
branched_policy_loss = torch.stack(
[
torch.sum(_ent_coef[i] * _lp - _qt, dim=1, keepdim=True)
for i, (_lp, _qt) in enumerate(
zip(branched_per_action_ent, branched_q_term)
)
],
dim=1,
)
batch_policy_loss = torch.squeeze(branched_policy_loss)
policy_loss = ModelUtils.masked_mean(batch_policy_loss, loss_masks)
return policy_loss
def sac_entropy_loss(
self, log_probs: torch.Tensor, loss_masks: torch.Tensor, discrete: bool
) -> torch.Tensor:
if not discrete:
with torch.no_grad():
target_current_diff = torch.sum(log_probs + self.target_entropy, dim=1)
entropy_loss = -1 * ModelUtils.masked_mean(
self._log_ent_coef * target_current_diff, loss_masks
)
else:
with torch.no_grad():
branched_per_action_ent = ModelUtils.break_into_branches(
log_probs * log_probs.exp(), self.act_size
)
target_current_diff_branched = torch.stack(
[
torch.sum(_lp, axis=1, keepdim=True) + _te
for _lp, _te in zip(
branched_per_action_ent, self.target_entropy
)
],
axis=1,
)
target_current_diff = torch.squeeze(
target_current_diff_branched, axis=2
)
entropy_loss = -1 * ModelUtils.masked_mean(
torch.mean(self._log_ent_coef * target_current_diff, axis=1), loss_masks
)
return entropy_loss
def _condense_q_streams(
self, q_output: Dict[str, torch.Tensor], discrete_actions: torch.Tensor
) -> Dict[str, torch.Tensor]:
condensed_q_output = {}
onehot_actions = ModelUtils.actions_to_onehot(discrete_actions, self.act_size)
for key, item in q_output.items():
branched_q = ModelUtils.break_into_branches(item, self.act_size)
only_action_qs = torch.stack(
[
torch.sum(_act * _q, dim=1, keepdim=True)
for _act, _q in zip(onehot_actions, branched_q)
]
)
condensed_q_output[key] = torch.mean(only_action_qs, dim=0)
return condensed_q_output
@timed
def update(self, batch: AgentBuffer, num_sequences: int) -> Dict[str, float]:
"""
Updates model using buffer.
:param num_sequences: Number of trajectories in batch.
:param batch: Experience mini-batch.
:param update_target: Whether or not to update target value network
:param reward_signal_batches: Minibatches to use for updating the reward signals,
indexed by name. If none, don't update the reward signals.
:return: Output from update process.
"""
rewards = {}
for name in self.reward_signals:
rewards[name] = ModelUtils.list_to_tensor(batch[f"{name}_rewards"])
vec_obs = [ModelUtils.list_to_tensor(batch["vector_obs"])]
next_vec_obs = [ModelUtils.list_to_tensor(batch["next_vector_in"])]
act_masks = ModelUtils.list_to_tensor(batch["action_mask"])
if self.policy.use_continuous_act:
actions = ModelUtils.list_to_tensor(batch["actions"]).unsqueeze(-1)
else:
actions = ModelUtils.list_to_tensor(batch["actions"], dtype=torch.long)
memories_list = [
ModelUtils.list_to_tensor(batch["memory"][i])
for i in range(0, len(batch["memory"]), self.policy.sequence_length)
]
# LSTM shouldn't have sequence length <1, but stop it from going out of the index if true.
offset = 1 if self.policy.sequence_length > 1 else 0
next_memories_list = [
ModelUtils.list_to_tensor(
batch["memory"][i][self.policy.m_size // 2 :]
) # only pass value part of memory to target network
for i in range(offset, len(batch["memory"]), self.policy.sequence_length)
]
if len(memories_list) > 0:
memories = torch.stack(memories_list).unsqueeze(0)
next_memories = torch.stack(next_memories_list).unsqueeze(0)
else:
memories = None
next_memories = None
# Q network memories are 0'ed out, since we don't have them during inference.
q_memories = (
torch.zeros_like(next_memories) if next_memories is not None else None
)
vis_obs: List[torch.Tensor] = []
next_vis_obs: List[torch.Tensor] = []
if self.policy.use_vis_obs:
vis_obs = []
for idx, _ in enumerate(
self.policy.actor_critic.network_body.visual_processors
):
vis_ob = ModelUtils.list_to_tensor(batch["visual_obs%d" % idx])
vis_obs.append(vis_ob)
next_vis_ob = ModelUtils.list_to_tensor(
batch["next_visual_obs%d" % idx]
)
next_vis_obs.append(next_vis_ob)
# Copy normalizers from policy
self.value_network.q1_network.network_body.copy_normalization(
self.policy.actor_critic.network_body
)
self.value_network.q2_network.network_body.copy_normalization(
self.policy.actor_critic.network_body
)
self.target_network.network_body.copy_normalization(
self.policy.actor_critic.network_body
)
(sampled_actions, _, log_probs, _, _) = self.policy.sample_actions(
vec_obs,
vis_obs,
masks=act_masks,
memories=memories,
seq_len=self.policy.sequence_length,
all_log_probs=not self.policy.use_continuous_act,
)
value_estimates, _ = self.policy.actor_critic.critic_pass(
vec_obs, vis_obs, memories, sequence_length=self.policy.sequence_length
)
if self.policy.use_continuous_act:
squeezed_actions = actions.squeeze(-1)
# Only need grad for q1, as that is used for policy.
q1p_out, q2p_out = self.value_network(
vec_obs,
vis_obs,
sampled_actions,
memories=q_memories,
sequence_length=self.policy.sequence_length,
q2_grad=False,
)
q1_out, q2_out = self.value_network(
vec_obs,
vis_obs,
squeezed_actions,
memories=q_memories,
sequence_length=self.policy.sequence_length,
)
q1_stream, q2_stream = q1_out, q2_out
else:
# For discrete, you don't need to backprop through the Q for the policy
q1p_out, q2p_out = self.value_network(
vec_obs,
vis_obs,
memories=q_memories,
sequence_length=self.policy.sequence_length,
q1_grad=False,
q2_grad=False,
)
q1_out, q2_out = self.value_network(
vec_obs,
vis_obs,
memories=q_memories,
sequence_length=self.policy.sequence_length,
)
q1_stream = self._condense_q_streams(q1_out, actions)
q2_stream = self._condense_q_streams(q2_out, actions)
with torch.no_grad():
target_values, _ = self.target_network(
next_vec_obs,
next_vis_obs,
memories=next_memories,
sequence_length=self.policy.sequence_length,
)
masks = ModelUtils.list_to_tensor(batch["masks"], dtype=torch.bool)
use_discrete = not self.policy.use_continuous_act
dones = ModelUtils.list_to_tensor(batch["done"])
q1_loss, q2_loss = self.sac_q_loss(
q1_stream, q2_stream, target_values, dones, rewards, masks
)
value_loss = self.sac_value_loss(
log_probs, value_estimates, q1p_out, q2p_out, masks, use_discrete
)
policy_loss = self.sac_policy_loss(log_probs, q1p_out, masks, use_discrete)
entropy_loss = self.sac_entropy_loss(log_probs, masks, use_discrete)
total_value_loss = q1_loss + q2_loss + value_loss
decay_lr = self.decay_learning_rate.get_value(self.policy.get_current_step())
ModelUtils.update_learning_rate(self.policy_optimizer, decay_lr)
self.policy_optimizer.zero_grad()
policy_loss.backward()
self.policy_optimizer.step()
ModelUtils.update_learning_rate(self.value_optimizer, decay_lr)
self.value_optimizer.zero_grad()
total_value_loss.backward()
self.value_optimizer.step()
ModelUtils.update_learning_rate(self.entropy_optimizer, decay_lr)
self.entropy_optimizer.zero_grad()
entropy_loss.backward()
self.entropy_optimizer.step()
# Update target network
ModelUtils.soft_update(
self.policy.actor_critic.critic, self.target_network, self.tau
)
update_stats = {
"Losses/Policy Loss": policy_loss.item(),
"Losses/Value Loss": value_loss.item(),
"Losses/Q1 Loss": q1_loss.item(),
"Losses/Q2 Loss": q2_loss.item(),
"Policy/Entropy Coeff": torch.mean(torch.exp(self._log_ent_coef)).item(),
"Policy/Learning Rate": decay_lr,
}
return update_stats
def update_reward_signals(
self, reward_signal_minibatches: Mapping[str, AgentBuffer], num_sequences: int
) -> Dict[str, float]:
update_stats: Dict[str, float] = {}
for name, update_buffer in reward_signal_minibatches.items():
update_stats.update(self.reward_signals[name].update(update_buffer))
return update_stats
def get_modules(self):
modules = {
"Optimizer:value_network": self.value_network,
"Optimizer:target_network": self.target_network,
"Optimizer:policy_optimizer": self.policy_optimizer,
"Optimizer:value_optimizer": self.value_optimizer,
"Optimizer:entropy_optimizer": self.entropy_optimizer,
}
for reward_provider in self.reward_signals.values():
modules.update(reward_provider.get_modules())
return modules