How to use pytorch scatter_add

scatter.py

[nav] In [48]: table = torch.arange(12, dtype=torch.float32).reshape(4,3)

[ins] In [49]: new_table = torch.zeros(4, 3)

[ins] In [50]: index = torch.tensor([1,1,0,3])

[ins] In [51]: index2 = index.unsqueeze(1).expand(4,3)

[ins] In [52]: table
Out[52]:
tensor([[ 0.,  1.,  2.],
        [ 3.,  4.,  5.],
        [ 6.,  7.,  8.],
        [ 9., 10., 11.]])

[ins] In [53]: new_table
Out[53]:
tensor([[0., 0., 0.],
        [0., 0., 0.],
        [0., 0., 0.],
        [0., 0., 0.]])

[ins] In [54]: index2
Out[54]:
tensor([[1, 1, 1],
        [1, 1, 1],
        [0, 0, 0],
        [3, 3, 3]])

[ins] In [55]: new_table.scatter_add_(0, index2, table)
Out[55]:
tensor([[ 6.,  7.,  8.],
        [ 3.,  5.,  7.],
        [ 0.,  0.,  0.],
        [ 9., 10., 11.]])