squeeze

torch.squeeze () of dimensional data compression, remove dimension is a dimension 1, a default is to delete all of the dimensions 1. 
                You can also dim the specified location, delete the specified location is the number of dimensions of a dimension. 

torch.unsqueeze () data dimensions

import torch

x = torch.zeros(3, 2, 4, 1, 2, 1)  # dimension of 3*2*4*1*2
print(x.size())  # torch.Size([3, 2, 4, 1, 2, 1])
print(x.shape) # torch.Size([3, 2, 4, 1, 2, 1])

y = torch.squeeze(x)  # Returns a tensor with all the dimensions of input of size 1 removed.
print(y.size())  # torch.Size([3, 2, 4, 2])
print(y.shape)

z = torch.unsqueeze(y, dim=0)  # Add a dimension of 1 in the 0th position
print(z.size())  # torch.Size([1, 3, 2, 4, 2])
print(z.shape)

z = torch.unsqueeze(y, dim=1)  # Add a dimension of 1 in the 1st position
print(z.size())  # torch.Size([3, 1, 2, 4, 2])
print(z.shape)

z = torch.unsqueeze(y, dim=2)  # Add a dimension of 1 in the 2nd position
print(z.size())  # torch.Size([3, 2, 1, 4, 2])
print(z.shape)

y = torch.squeeze(x, dim=0)  # remove the 0th position of 1 (no 1)
print('dim=0', y.size())  # torch.Size([3, 2, 4, 1, 2, 1])
print('dim=0', y.shape)

y = torch.squeeze(x, dim=1)  # remove the 1st position of 1 (no 1)
print('dim=1', y.size())  # torch.Size([3, 2, 4, 1, 2, 1])
print('dim=1', y.shape)

y = torch.squeeze(x, dim=2)  # remove the 2nd position of 1 (no 1)
print('dim=2', y.size())  # torch.Size([3, 2, 4, 1, 2])
print('dim=2', y.shape)

y = torch.squeeze(x, dim=3)  # remove the 3rd position of 1 (yes)
print('dim=3', y.size())  # torch.Size([3, 2, 4, 2, 1])
print('dim=3', y.shape)

y = torch.squeeze(x, dim=4)  # remove the 4th position of 1 (no 1)
print('dim=4', y.size())  # torch.Size([3, 2, 4, 1, 2, 1])
print('dim=4', y.shape)

y = torch.squeeze(x, dim=5)  # remove the 5th position of 1 (yes)
print('dim=5', y.size())  # torch.Size([3, 2, 4, 1, 2])
print('dim=5', y.shape)

y = torch.squeeze(x, dim=6)  # RuntimeError: Dimension out of range (expected to be in range of [-6, 5], but got 6)
print('dim=6', y.size())
print('dim=6', y.shape)

 

expansion. Need to dim the specified position to a specified position plus the dimension is a dimension.