Training Error. Epoch 5. about loop HOT 3 CLOSED

        mask = self._sequence_mask(target[1]).unsqueeze(2)
        mask_ = mask.expand_as(input)

class MaskedMSE(nn.Module):
    def __init__(self):
        super(MaskedMSE, self).__init__()
        self.criterion = nn.MSELoss(size_average=False)

    # Taken from
    # https://github.com/spro/practical-pytorch/blob/master/seq2seq-translation
    @staticmethod
    def _sequence_mask(sequence_length, max_len):
        batch_size = sequence_length.size(0)
        seq_range = torch.arange(0, max_len).long()
        seq_range_expand = seq_range.unsqueeze(0).expand(batch_size, max_len)
        seq_range_expand = Variable(seq_range_expand)
        if sequence_length.is_cuda:
            seq_range_expand = seq_range_expand.cuda()
        seq_length_expand = sequence_length.unsqueeze(1) \
                                           .expand_as(seq_range_expand)
        return (seq_range_expand < seq_length_expand).t().float()

    def forward(self, input, target, lengths):
        max_len = input.size(0)
        mask = self._sequence_mask(lengths, max_len).unsqueeze(2)
        mask_ = mask.expand_as(input)
        self.loss = self.criterion(input*mask_, target*mask_)
        self.loss = self.loss / mask.sum()
        return self.loss