def collate_tokens(
    values,
    pad_idx,
    eos_idx=None,
    left_pad=False,
    move_eos_to_beginning=False,
    pad_to_length=None,
    pad_to_multiple=1,
    pad_to_bsz=None,
):
    """Convert a list of 1d tensors into a padded 2d tensor."""
    size = max(v.size(0) for v in values)
    size = size if pad_to_length is None else max(size, pad_to_length)
    if pad_to_multiple != 1 and size % pad_to_multiple != 0:
        size = int(((size - 0.1) // pad_to_multiple + 1) * pad_to_multiple)

    batch_size = len(values) if pad_to_bsz is None else max(len(values), pad_to_bsz)
    res = values[0].new(batch_size, size).fill_(pad_idx)

    def copy_tensor(src, dst):
        assert dst.numel() == src.numel()
        if move_eos_to_beginning:
            if eos_idx is None:
                # if no eos_idx is specified, then use the last token in src
                dst[0] = src[-1]
            else:
                dst[0] = eos_idx
            dst[1:] = src[:-1]
        else:
            dst.copy_(src)

    for i, v in enumerate(values):
        copy_tensor(v, res[i][size - len(v) :] if left_pad else res[i][: len(v)])
    return res
Convert a list of 1d tensors into a padded 2d tensor.
fairseq/data/data_utils.py