espnet2.legacy.nets.pytorch_backend.nets_utils.mask_by_length

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espnet2.legacy.nets.pytorch_backend.nets_utils.mask_by_length(xs, lengths, fill=0)

Mask tensor according to length.

• Parameters:
  • xs (Tensor) – Batch of input tensor (B, *).
  • lengths (LongTensor or List) – Batch of lengths (B,).
  • fill (int or float) – Value to fill masked part.
• Returns: Batch of masked input tensor (B, *).
• Return type: Tensor

Examples

>>> x = torch.arange(5).repeat(3, 1) + 1
>>> x
tensor([[1, 2, 3, 4, 5],
        [1, 2, 3, 4, 5],
        [1, 2, 3, 4, 5]])
>>> lengths = [5, 3, 2]
>>> mask_by_length(x, lengths)
tensor([[1, 2, 3, 4, 5],
        [1, 2, 3, 0, 0],
        [1, 2, 0, 0, 0]])