PytorchSeq2SeqWrapper(self, module:torch.nn.modules.module.Module, stateful:bool=False) -> None

Pytorch's RNNs have two outputs: the hidden state for every time step, and the hidden state at the last time step for every layer. We just want the first one as a single output. This wrapper pulls out that output, and adds a :func:get_output_dim method, which is useful if you want to, e.g., define a linear + softmax layer on top of this to get some distribution over a set of labels. The linear layer needs to know its input dimension before it is called, and you can get that from get_output_dim.

In order to be wrapped with this wrapper, a class must have the following members:

- `self.input_size: int`
- `self.hidden_size: int`
- `def forward(inputs: PackedSequence, hidden_state: torch.Tensor) ->
  Tuple[PackedSequence, torch.Tensor]`.
- `self.bidirectional: bool` (optional)

This is what pytorch's RNN's look like - just make sure your class looks like those, and it should work.

Note that we require you to pass a binary mask of shape (batch_size, sequence_length) when you call this module, to avoid subtle bugs around masking. If you already have a PackedSequence you can pass None as the second parameter.

We support stateful RNNs where the final state from each batch is used as the initial state for the subsequent batch by passing stateful=True to the constructor.


PytorchSeq2SeqWrapper.get_input_dim(self) -> int

Returns the dimension of the vector input for each element in the sequence input to a Seq2SeqEncoder. This is not the shape of the input tensor, but the last element of that shape.


PytorchSeq2SeqWrapper.get_output_dim(self) -> int

Returns the dimension of each vector in the sequence output by this Seq2SeqEncoder. This is not the shape of the returned tensor, but the last element of that shape.


PytorchSeq2SeqWrapper.is_bidirectional(self) -> bool

Returns True if this encoder is bidirectional. If so, we assume the forward direction of the encoder is the first half of the final dimension, and the backward direction is the second half.


PytorchSeq2SeqWrapper.forward(self, inputs:torch.Tensor, mask:torch.Tensor, hidden_state:torch.Tensor=None) -> torch.Tensor

Defines the computation performed at every call.

Should be overridden by all subclasses.

.. note:: Although the recipe for forward pass needs to be defined within this function, one should call the :class:Module instance afterwards instead of this since the former takes care of running the registered hooks while the latter silently ignores them.