Bidirectional QRNN?

[wise-east]

When is the bidirectional QRNN going to be ready? It says it would be available in the near future, but I guess I underestimated the span of time represented by 'near'. I'm wondering if it is being developed at all.

[danFromTelAviv]

I wanted to PR this change but I need to sign some agreement to do this and I am not sure about the details there so I'll just post the changes since they are small: in qrnn.py add the following class:

class BiDirQRNNLayer(nn.Module):
    def __init__(self, input_size, hidden_size=None, save_prev_x=False, zoneout=0, window=1, output_gate=True,
                 use_cuda=True):
        super(BiDirQRNNLayer, self).__init__()

        assert window in [1,
                          2], "This QRNN implementation currently only handles convolutional window of size 1 or size 2"
        self.window = window
        self.input_size = input_size
        self.hidden_size = hidden_size if hidden_size else input_size
        self.zoneout = zoneout
        self.save_prev_x = save_prev_x
        self.prevX = None
        self.output_gate = output_gate
        self.use_cuda = use_cuda

        self.forward_qrnn = QRNNLayer(input_size, hidden_size=hidden_size, save_prev_x=save_prev_x, zoneout=zoneout, window=window,
                                      output_gate=output_gate, use_cuda=use_cuda)
        self.backward_qrnn = QRNNLayer(input_size, hidden_size=hidden_size, save_prev_x=save_prev_x, zoneout=zoneout, window=window,
                                       output_gate=output_gate, use_cuda=use_cuda)

    def forward(self, X, hidden=None):
        if not hidden is None:
            fwd, h_fwd = self.forward_qrnn(X, hidden=hidden)
            bwd, h_bwd = self.backward_qrnn(torch.flip(X, [0]), hidden=hidden)
        else:
            fwd, h_fwd = self.forward_qrnn(X)
            bwd, h_bwd = self.backward_qrnn(torch.flip(X, [0]))
        bwd = torch.flip(bwd, [0])
        return torch.cat([fwd, bwd], dim=-1), torch.cat([h_fwd, h_bwd], dim=-1)

in the same file in the "class QRNN(torch.nn.Module):" replace :

self.layers = torch.nn.ModuleList(
                layers if layers else [QRNNLayer(input_size if l == 0 else hidden_size, hidden_size, **kwargs) for l in
                                       range(num_layers)])

with :

        if bidirectional:
            self.layers = torch.nn.ModuleList(
                layers if layers else [BiDirQRNNLayer(input_size if l == 0 else hidden_size*2, hidden_size, **kwargs) for l in
                                       range(num_layers)])
        else:
            self.layers = torch.nn.ModuleList(
                layers if layers else [QRNNLayer(input_size if l == 0 else hidden_size, hidden_size, **kwargs) for l in
                                       range(num_layers)])

and remove the assert statement above that deals with bidirectional.:

assert bidirectional == False, 'Bidirectional QRNN is not yet supported'

[danFromTelAviv]

I didn't test super thoroughly but it works for me on a basic use case. If you need to fix something please post it here also :) @salesforce do feel free to incorporate this into your code. I don't think any paper work is needed for this.