torch 的 unsqueeze用法

import torch

a=torch.tensor([[3.0000, 3.0000],
        [3.0000, 4.0000],
        [3.6000, 3.0000],
        [3.5000, 3.0000]])

个人以为这个unsqueeze方法有点废话，完全可以用reshape 实现，鸡肋！

a.reshape([a.shape[0],1,a.shape[1]])==a.unsqueeze(1)

a.reshape([1,a.shape[0],1,a.shape[1]])==a.unsqueeze(0)

a.reshape([a.shape[0],a.shape[1] ,1])==a.unsqueeze(2)

a.reshape([a.shape[0],1,a.shape[1]])==a.unsqueeze(1)

'''
      0
m ,n------> 1,m,n

      1
m ,n------> m,1,n

      2
m ,n------> m,n,2

      k
m ,.....,n------> m,...,k,k+1,n
'''

print('a=',a)
print('a.shape=',a.shape)
print('-'*30+'分割线'+'-'*30)

print('a.unsqueeze(0).shape=',a.unsqueeze(0).shape)

print('a.unsqueeze(0)=',a.unsqueeze(0))


print('-'*30+'分割线'+'-'*30)

print('a.unsqueeze(1).shape=',a.unsqueeze(1).shape)

print('a.unsqueeze(1)=',a.unsqueeze(1))



print('-'*30+'分割线'+'-'*30)

print('a.unsqueeze(2).shape=',a.unsqueeze(2).shape)

print('a.unsqueeze(2)=',a.unsqueeze(2))

在这里是一个二位矩阵　可以在[0,1,2]三个维度上

a= tensor([[3.0000, 3.0000],
        [3.0000, 4.0000],
        [3.6000, 3.0000],
        [3.5000, 3.0000]])
a.shape= torch.Size([4, 2])
------------------------------分割线------------------------------
a.unsqueeze(0).shape= torch.Size([1, 4, 2])
a.unsqueeze(0)= tensor([[[3.0000, 3.0000],
         [3.0000, 4.0000],
         [3.6000, 3.0000],
         [3.5000, 3.0000]]])
------------------------------分割线------------------------------
a.unsqueeze(1).shape= torch.Size([4, 1, 2])
a.unsqueeze(1)= tensor([[[3.0000, 3.0000]],

        [[3.0000, 4.0000]],

        [[3.6000, 3.0000]],

        [[3.5000, 3.0000]]])
------------------------------分割线------------------------------
a.unsqueeze(2).shape= torch.Size([4, 2, 1])
a.unsqueeze(2)= tensor([[[3.0000],
         [3.0000]],

        [[3.0000],
         [4.0000]],

        [[3.6000],
         [3.0000]],

        [[3.5000],
         [3.0000]]])

一个是顺序，一个逆序，形成一个闭环

'''
-3 -2 -1 
0   1  2
'''
print('a.unsqueeze(-3)==a.unsqueeze(0)',a.unsqueeze(-3)==a.unsqueeze(0))

print('a.unsqueeze(-2)==a.unsqueeze(1)',a.unsqueeze(-2)==a.unsqueeze(1))

print('a.unsqueeze(-1)==a.unsqueeze(2)',a.unsqueeze(-1)==a.unsqueeze(2))

a.unsqueeze(-3)==a.unsqueeze(0) tensor([[[True, True],
         [True, True],
         [True, True],
         [True, True]]])
a.unsqueeze(-2)==a.unsqueeze(1) tensor([[[True, True]],

        [[True, True]],

        [[True, True]],

        [[True, True]]])
a.unsqueeze(-1)==a.unsqueeze(2) tensor([[[True],
         [True]],

        [[True],
         [True]],

        [[True],
         [True]],

        [[True],
         [True]]])