ray/rllib/models/torch/recurrent_net.py

import numpy as np

from ray.rllib.models.modelv2 import ModelV2
from ray.rllib.models.torch.misc import SlimFC
from ray.rllib.models.torch.torch_modelv2 import TorchModelV2
from ray.rllib.policy.rnn_sequencing import add_time_dimension
from ray.rllib.policy.sample_batch import SampleBatch
from ray.rllib.utils.annotations import override, DeveloperAPI
from ray.rllib.utils.framework import try_import_torch

torch, nn = try_import_torch()


@DeveloperAPI
class RecurrentNetwork(TorchModelV2):
    """Helper class to simplify implementing RNN models with TorchModelV2.

    Instead of implementing forward(), you can implement forward_rnn() which
    takes batches with the time dimension added already.

    Here is an example implementation for a subclass
    ``MyRNNClass(RecurrentNetwork, nn.Module)``::

        def __init__(self, obs_space, num_outputs):
            nn.Module.__init__(self)
            super().__init__(obs_space, action_space, num_outputs,
                             model_config, name)
            self.obs_size = _get_size(obs_space)
            self.rnn_hidden_dim = model_config["lstm_cell_size"]
            self.fc1 = nn.Linear(self.obs_size, self.rnn_hidden_dim)
            self.rnn = nn.GRUCell(self.rnn_hidden_dim, self.rnn_hidden_dim)
            self.fc2 = nn.Linear(self.rnn_hidden_dim, num_outputs)

            self.value_branch = nn.Linear(self.rnn_hidden_dim, 1)
            self._cur_value = None

        @override(ModelV2)
        def get_initial_state(self):
            # Place hidden states on same device as model.
            h = [self.fc1.weight.new(
                1, self.rnn_hidden_dim).zero_().squeeze(0)]
            return h

        @override(ModelV2)
        def value_function(self):
            assert self._cur_value is not None, "must call forward() first"
            return self._cur_value

        @override(RecurrentNetwork)
        def forward_rnn(self, input_dict, state, seq_lens):
            x = nn.functional.relu(self.fc1(input_dict["obs_flat"].float()))
            h_in = state[0].reshape(-1, self.rnn_hidden_dim)
            h = self.rnn(x, h_in)
            q = self.fc2(h)
            self._cur_value = self.value_branch(h).squeeze(1)
            return q, [h]
    """

    @override(ModelV2)
    def forward(self, input_dict, state, seq_lens):
        """Adds time dimension to batch before sending inputs to forward_rnn().

        You should implement forward_rnn() in your subclass."""
        if isinstance(seq_lens, np.ndarray):
            seq_lens = torch.Tensor(seq_lens).int()
        output, new_state = self.forward_rnn(
            add_time_dimension(
                input_dict["obs_flat"].float(), seq_lens, framework="torch"),
            state, seq_lens)
        return torch.reshape(output, [-1, self.num_outputs]), new_state

    def forward_rnn(self, inputs, state, seq_lens):
        """Call the model with the given input tensors and state.

        Args:
            inputs (dict): Observation tensor with shape [B, T, obs_size].
            state (list): List of state tensors, each with shape [B, size].
            seq_lens (Tensor): 1D tensor holding input sequence lengths.
                Note: len(seq_lens) == B.

        Returns:
            (outputs, new_state): The model output tensor of shape
                [B, T, num_outputs] and the list of new state tensors each with
                shape [B, size].

        Examples:
            def forward_rnn(self, inputs, state, seq_lens):
                model_out, h, c = self.rnn_model([inputs, seq_lens] + state)
                return model_out, [h, c]
        """
        raise NotImplementedError("You must implement this for an RNN model")


class LSTMWrapper(RecurrentNetwork, nn.Module):
    """An LSTM wrapper serving as an interface for ModelV2s that set use_lstm.
    """

    def __init__(self, obs_space, action_space, num_outputs, model_config,
                 name):

        nn.Module.__init__(self)
        super().__init__(obs_space, action_space, None, model_config, name)

        self.cell_size = model_config["lstm_cell_size"]
        self.use_prev_action_reward = model_config[
            "lstm_use_prev_action_reward"]
        self.action_dim = int(np.product(action_space.shape))
        # Add prev-action/reward nodes to input to LSTM.
        if self.use_prev_action_reward:
            self.num_outputs += 1 + self.action_dim
        self.lstm = nn.LSTM(self.num_outputs, self.cell_size, batch_first=True)

        self.num_outputs = num_outputs

        # Postprocess LSTM output with another hidden layer and compute values.
        self._logits_branch = SlimFC(
            in_size=self.cell_size,
            out_size=self.num_outputs,
            activation_fn=None,
            initializer=torch.nn.init.xavier_uniform_)
        self._value_branch = SlimFC(
            in_size=self.cell_size,
            out_size=1,
            activation_fn=None,
            initializer=torch.nn.init.xavier_uniform_)

    @override(RecurrentNetwork)
    def forward(self, input_dict, state, seq_lens):
        assert seq_lens is not None
        # Push obs through "unwrapped" net's `forward()` first.
        wrapped_out, _ = self._wrapped_forward(input_dict, [], None)

        # Concat. prev-action/reward if required.
        if self.model_config["lstm_use_prev_action_reward"]:
            wrapped_out = torch.cat(
                [
                    wrapped_out,
                    torch.reshape(input_dict[SampleBatch.PREV_ACTIONS].float(),
                                  [-1, self.action_dim]),
                    torch.reshape(input_dict[SampleBatch.PREV_REWARDS],
                                  [-1, 1]),
                ],
                dim=1)

        # Then through our LSTM.
        input_dict["obs_flat"] = wrapped_out
        return super().forward(input_dict, state, seq_lens)

    @override(RecurrentNetwork)
    def forward_rnn(self, inputs, state, seq_lens):
        self._features, [h, c] = self.lstm(
            inputs,
            [torch.unsqueeze(state[0], 0),
             torch.unsqueeze(state[1], 0)])
        model_out = self._logits_branch(self._features)
        return model_out, [torch.squeeze(h, 0), torch.squeeze(c, 0)]

    @override(ModelV2)
    def get_initial_state(self):
        # Place hidden states on same device as model.
        linear = next(self._logits_branch._model.children())
        h = [
            linear.weight.new(1, self.cell_size).zero_().squeeze(0),
            linear.weight.new(1, self.cell_size).zero_().squeeze(0)
        ]
        return h

    @override(ModelV2)
    def value_function(self):
        assert self._features is not None, "must call forward() first"
        return torch.reshape(self._value_branch(self._features), [-1])