Key Code Blocks of Pytorch RNN Dropout Implementation

locked_dropout.py

# https://github.com/salesforce/awd-lstm-lm/blob/dfd3cb0235d2caf2847a4d53e1cbd495b781b5d2/locked_dropout.py#L5
class LockedDropout(nn.Module):
    # ...
    def forward(self, x, dropout=0.5):
        if not self.training or not dropout:
            return x
        m = x.data.new(1, x.size(1), x.size(2)).bernoulli_(1 - dropout)
        mask = Variable(m, requires_grad=False) / (1 - dropout)
        mask = mask.expand_as(x)
        return mask * x