pytorch更新tensor中指定index位置的值scatter_add_问题

import torch
a = torch.zeros((3, 4))
print(a)
"""
tensor([[0., 0., 0., 0.],
        [0., 0., 0., 0.],
        [0., 0., 0., 0.]])
"""
b = torch.rand((2, 4))
print(b)
"""
tensor([[0.6293, 0.3050, 0.9608, 0.5577],
        [0.3469, 0.1025, 0.8185, 0.5085]])
"""
# 将a中第0行和第2行的值修改为b
a = a.scatter_add_(0, torch.tensor([[0, 0, 0], [2, 2, 2]]), b)
print(a)
"""
tensor([[0.6293, 0.3050, 0.9608, 0.0000],
        [0.0000, 0.0000, 0.0000, 0.0000],
        [0.3469, 0.1025, 0.8185, 0.0000]])
"""

torch_scatter.scatter_add(src, index, dim=-1, out=None, dim_size=None, fill_value=0)

src = torch.tensor([10, 20, 30, 40, 1, 2, 2, 2, 9])
index = torch.tensor([2, 1, 1, 1, 1, 1, 1, 1, 0])
out=scatter_add(src, index)
print(out)

scatter_add_(self, dim, index, other):

For a 3-D tensor, :attr:`self` is updated as::
    self[index[i][j][k]][j][k] += other[i][j][k]  # if dim == 0
    self[i][index[i][j][k]][k] += other[i][j][k]  # if dim == 1
    self[i][j][index[i][j][k]] += other[i][j][k]  # if dim == 2

            >>> x = torch.rand(2, 5)
            >>> x
            tensor([[0.7404, 0.0427, 0.6480, 0.3806, 0.8328],
                    [0.7953, 0.2009, 0.9154, 0.6782, 0.9620]])
            >>> torch.ones(3, 5).scatter_add_(0, torch.tensor([[0, 1, 2, 0, 0], [2, 0, 0, 1, 2]]), x)
            tensor([[1.7404, 1.2009, 1.9154, 1.3806, 1.8328],
                    [1.0000, 1.0427, 1.0000, 1.6782, 1.0000],
                    [1.7953, 1.0000, 1.6480, 1.0000, 1.9620]])

index[0][0]=0  self[index[0][0]][0]=self[0][0] =self[0][0]+ x[0][0]=1 +0.7404=1.7404
index[0][1]=1  self[index[0][1]][1]=self[1][1] =self[1][1]+ x[0][1] =1 +0.0427 =1.0427

scatter_(self, dim, index, src)

>>> x = torch.rand(2, 5)
            >>> x
            tensor([[ 0.3992,  0.2908,  0.9044,  0.4850,  0.6004],
                    [ 0.5735,  0.9006,  0.6797,  0.4152,  0.1732]])
            >>> torch.zeros(3, 5).scatter_(0, torch.tensor([[0, 1, 2, 0, 0], [2, 0, 0, 1, 2]]), x)
            tensor([[ 0.3992,  0.9006,  0.6797,  0.4850,  0.6004],
                    [ 0.0000,  0.2908,  0.0000,  0.4152,  0.0000],
                    [ 0.5735,  0.0000,  0.9044,  0.0000,  0.1732]])
            >>> z = torch.zeros(2, 4).scatter_(1, torch.tensor([[2], [3]]), 1.23)
            >>> z
            tensor([[ 0.0000,  0.0000,  1.2300,  0.0000],
                    [ 0.0000,  0.0000,  0.0000,  1.2300]])