我对torch中的gather函数的一点理解

torch.gather(input,dim,index,out=None) → Tensor
torch.gather(input, dim, index, out=None) → Tensor
    Gathers values along an axis specified by dim.
    For a 3-D tensor the output is specified by:
    out[i][j][k] = input[index[i][j][k]][j][k]  # dim=0    out[i][j][k] = input[i][index[i][j][k]][k]  # dim=1    out[i][j][k] = input[i][j][index[i][j][k]]  # dim=2
    Parameters:
        input (Tensor) – The source tensor        dim (int) – The axis along which to index        index (LongTensor) – The indices of elements to gather        out (Tensor, optional) – Destination tensor
    Example:
    >>> t = torch.Tensor([[1,2],[3,4]])    >>> torch.gather(t, 1, torch.LongTensor([[0,0],[1,0]]))     1  1     4  3    [torch.FloatTensor of size 2x2]

import torch
a = torch.Tensor([[1,2],                 [3,4]])
b = torch.gather(a,1,torch.LongTensor([[0,0],[1,0]]))#1. 取各个元素行号：[(0,y)(0,y)][(1,y)(1,y)]#2. 取各个元素值做行号：[(0,0)(0,0)][(1,1)(1,0)]#3. 根据得到的索引在输入中取值#[1,1],[4,3]
c = torch.gather(a,0,torch.LongTensor([[0,0],[1,0]]))#1. 取各个元素列号：[(x,0)(x,1)][(x,0)(x,1)]#2. 取各个元素值做行号：[(0,0)(0,1)][(1,0)(0,1)]#3. 根据得到的索引在输入中取值#[1,2],[3,2]