ml-agents/ml-agents/mlagents/trainers/torch/agent_action.py

from typing import List, Optional, NamedTuple
import itertools
import numpy as np
from mlagents.torch_utils import torch

from mlagents.trainers.buffer import AgentBuffer, BufferKey, AgentBufferField
from mlagents.trainers.torch.utils import ModelUtils
from mlagents_envs.base_env import ActionTuple


class AgentAction(NamedTuple):
    """
    A NamedTuple containing the tensor for continuous actions and list of tensors for
    discrete actions. Utility functions provide numpy <=> tensor conversions to be
    sent as actions to the environment manager as well as used by the optimizers.
    :param continuous_tensor: Torch tensor corresponding to continuous actions
    :param discrete_list: List of Torch tensors each corresponding to discrete actions
    """

    continuous_tensor: torch.Tensor
    discrete_list: Optional[List[torch.Tensor]]

    @property
    def discrete_tensor(self):
        """
        Returns the discrete action list as a stacked tensor
        """
        return torch.stack(self.discrete_list, dim=-1)

    def to_action_tuple(self, clip: bool = False) -> ActionTuple:
        """
        Returns an ActionTuple
        """
        action_tuple = ActionTuple()
        if self.continuous_tensor is not None:
            _continuous_tensor = self.continuous_tensor
            if clip:
                _continuous_tensor = torch.clamp(_continuous_tensor, -3, 3) / 3
            continuous = ModelUtils.to_numpy(_continuous_tensor)
            action_tuple.add_continuous(continuous)
        if self.discrete_list is not None:
            discrete = ModelUtils.to_numpy(self.discrete_tensor[:, 0, :])
            action_tuple.add_discrete(discrete)
        return action_tuple

    @staticmethod
    def from_buffer(buff: AgentBuffer) -> "AgentAction":
        """
        A static method that accesses continuous and discrete action fields in an AgentBuffer
        and constructs the corresponding AgentAction from the retrieved np arrays.
        """
        continuous: torch.Tensor = None
        discrete: List[torch.Tensor] = None  # type: ignore
        if BufferKey.CONTINUOUS_ACTION in buff:
            continuous = ModelUtils.list_to_tensor(buff[BufferKey.CONTINUOUS_ACTION])
        if BufferKey.DISCRETE_ACTION in buff:
            discrete_tensor = ModelUtils.list_to_tensor(
                buff[BufferKey.DISCRETE_ACTION], dtype=torch.long
            )
            discrete = [
                discrete_tensor[..., i] for i in range(discrete_tensor.shape[-1])
            ]
        return AgentAction(continuous, discrete)

    @staticmethod
    def _padded_time_to_batch(
        agent_buffer_field: AgentBufferField, dtype: torch.dtype = torch.float32
    ) -> List[torch.Tensor]:
        """
        Pad actions and convert to tensor. Note that data is padded by 0's, not NaNs
        as the observations are.
        """
        action_shape = None
        for _action in agent_buffer_field:
            if _action:
                action_shape = _action[0].shape
                break
        # If there were no critic obs at all
        if action_shape is None:
            return []

        new_list = list(
            map(
                lambda x: ModelUtils.list_to_tensor(x, dtype=dtype),
                itertools.zip_longest(
                    *agent_buffer_field, fillvalue=np.full(action_shape, 0)
                ),
            )
        )
        return new_list

    @staticmethod
    def _group_from_buffer(
        buff: AgentBuffer, cont_action_key: BufferKey, disc_action_key: BufferKey
    ) -> List["AgentAction"]:
        continuous_tensors: List[torch.Tensor] = []
        discrete_tensors: List[torch.Tensor] = []  # type: ignore
        if cont_action_key in buff:
            continuous_tensors = AgentAction._padded_time_to_batch(
                buff[cont_action_key]
            )
        if disc_action_key in buff:
            discrete_tensors = AgentAction._padded_time_to_batch(
                buff[disc_action_key], dtype=torch.long
            )

        actions_list = []
        for _cont, _disc in itertools.zip_longest(
            continuous_tensors, discrete_tensors, fillvalue=None
        ):
            if _disc is not None:
                _disc = [_disc[..., i] for i in range(_disc.shape[-1])]
            actions_list.append(AgentAction(_cont, _disc))
        return actions_list

    @staticmethod
    def group_from_buffer(buff: AgentBuffer) -> List["AgentAction"]:
        """
        A static method that accesses continuous and discrete action fields in an AgentBuffer
        and constructs the corresponding AgentAction from the retrieved np arrays.
        """
        return AgentAction._group_from_buffer(
            buff, BufferKey.GROUP_CONTINUOUS_ACTION, BufferKey.GROUP_DISCRETE_ACTION
        )

    @staticmethod
    def group_from_buffer_next(buff: AgentBuffer) -> List["AgentAction"]:
        """
        A static method that accesses next continuous and discrete action fields in an AgentBuffer
        and constructs the corresponding AgentAction from the retrieved np arrays.
        """
        return AgentAction._group_from_buffer(
            buff, BufferKey.GROUP_NEXT_CONT_ACTION, BufferKey.GROUP_NEXT_DISC_ACTION
        )

    def to_flat(self, discrete_branches: List[int]) -> torch.Tensor:
        discrete_oh = ModelUtils.actions_to_onehot(
            self.discrete_tensor, discrete_branches
        )
        discrete_oh = torch.cat(discrete_oh, dim=1)
        return torch.cat([self.continuous_tensor, discrete_oh], dim=-1)