torch.Tensor.scatter_add_
Tensor.scatter_add_(dim, index, src) -> Tensor
Adds all values from the tensor "src" into "self" at the indices
   specified in the "index" tensor in a similar fashion as
   "scatter_()". For each value in "src", it is added to an index in
   "self" which is specified by its index in "src" for "dimension !=
   dim" and by the corresponding value in "index" for "dimension =
   dim".
For a 3-D tensor, "self" is updated as:
  self[index[i][j][k]][j][k] += src[i][j][k]  # if dim == 0
  self[i][index[i][j][k]][k] += src[i][j][k]  # if dim == 1
  self[i][j][index[i][j][k]] += src[i][j][k]  # if dim == 2

"self", "index" and "src" should have same number of dimensions. It
   is also required that "index.size(d) <= src.size(d)" for all
   dimensions "d", and that "index.size(d) <= self.size(d)" for all
   dimensions "d != dim". Note that "index" and "src" do not
   broadcast.
Note: