def make_positions(self, input):
      """Replace non-padding symbols with their position numbers."""
      if not hasattr(self, 'range_buf'):
          self.range_buf = input.new()
      seqlen = input.size(1)
      if self.range_buf.numel() < seqlen:
          # offset positions by the padding index
          torch.arange(self.padding_idx + 1, self.padding_idx + 1 + seqlen,
                       out=self.range_buf)
      mask = input.ne(self.padding_idx)
      positions = self.range_buf[:seqlen].expand_as(input)
      if self.left_pad:
          positions = positions - mask.size(1) + mask.long().sum(dim=1).unsqueeze(1)
      return input.clone().masked_scatter_(mask, positions[mask])


'''
import torch

a= torch.arange(0, 10)
tensor([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

inp = torch.tensor([-1, -1, -1, 1,2,3,4,5,6,7])
inp
tensor([-1, -1, -1,  1,  2,  3,  4,  5,  6,  7])

mask = inp.ne(-1)
mask
tensor([0, 0, 0, 1, 1, 1, 1, 1, 1, 1], dtype=torch.uint8)

a[mask]
tensor([3, 4, 5, 6, 7, 8, 9])

inp.clone().masked_scatter_(mask, a)
tensor([-1, -1, -1,  0,  1,  2,  3,  4,  5,  6])

inp.clone().masked_scatter_(mask, a[mask])
tensor([-1, -1, -1,  3,  4,  5,  6,  7,  8,  9])

mask.size(0)
10

a - mask.size(0) + mask.sum()
tensor([-3, -2, -1,  0,  1,  2,  3,  4,  5,  6])

b = a - mask.size(0) + mask.sum()
b
tensor([-3, -2, -1,  0,  1,  2,  3,  4,  5,  6])

inp.clone().masked_scatter_(mask, b[mask])
tensor([-1, -1, -1,  0,  1,  2,  3,  4,  5,  6])

    '''