浅析对torch.unsqueeze()函数理解
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torch.unsqueeze()函数起到升维的作用,dim等于几表示在第几维度加一,这篇文章主要介绍了对torch.unsqueeze()函数理解深度解析,感兴趣的朋友跟随小编一起看看吧
torch.unsqueeze()函数理解
torch.unsqueeze(input, dim) 使用时等同于 input.unsqueeze(dim)
torch.unsqueeze()函数起到升维的作用,dim等于几表示在第几维度加一,比如原来x的size=([4]),x.unsqueeze(0)之后就变成了size=([1, 4]),而x.unsqueeze(1)之后就变成了size=([4, 1]),注意dim∈[-input.dim() - 1, input.dim() + 1]
例如
输入一维张量,即input.dim()=1
# 输入: x = torch.tensor([1, 2, 3, 4]) # x.dim()=1 print(x) print(x.shape) y = x.unsqueeze(0) print(y) print(y.shape) # 此时y.dim()=2 z = x.unsqueeze(1) print(z) print(z.shape) # 此时z.dim()=2
# 输出: tensor([1, 2, 3, 4]) torch.Size([4]) tensor([[1, 2, 3, 4]]) torch.Size([1, 4]) tensor([[1], [2], [3], [4]]) torch.Size([4, 1])
输入二维张量,即input.dim()=2
# 输入: x = torch.tensor([[1, 2, 3], [4, 5, 6]]) # x.dim()=2 print(x) print(x.shape) y = x.unsqueeze(0) print(y) print(y.shape) # 此时y.dim()=3 z = x.unsqueeze(1) print(z) print(z.shape) # 此时z.dim()=3
# 输出: tensor([[1, 2, 3], [4, 5, 6]]) torch.Size([2, 3]) tensor([[[1, 2, 3], [4, 5, 6]]]) torch.Size([1, 2, 3]) tensor([[[1, 2, 3]], [[4, 5, 6]]]) torch.Size([2, 1, 3])
输入四维张量,即input.dim()=4
# 输入: x = torch.tensor([[[[1, 2, 3], [4, 5, 6]], [[0, 2, 1], [1, 5, 2]]], [[[1, 2, 3], [4, 5, 6]], [[0, 2, 1], [1, 5, 2]]]]) print(x) print(x.shape) y2 = x.unsqueeze(2) print(y2) print(y2.shape) y3 = x.unsqueeze(3) print(y3) print(y3.shape)
# 输出: tensor([[[[1, 2, 3], [4, 5, 6]], [[0, 2, 1], [1, 5, 2]]], [[[1, 2, 3], [4, 5, 6]], [[0, 2, 1], [1, 5, 2]]]]) torch.Size([2, 2, 2, 3]) tensor([[[[[1, 2, 3], [4, 5, 6]]], [[[0, 2, 1], [1, 5, 2]]]], [[[[1, 2, 3], [4, 5, 6]]], [[[0, 2, 1], [1, 5, 2]]]]]) torch.Size([2, 2, 1, 2, 3]) tensor([[[[[1, 2, 3]], [[4, 5, 6]]], [[[0, 2, 1]], [[1, 5, 2]]]], [[[[1, 2, 3]], [[4, 5, 6]]], [[[0, 2, 1]], [[1, 5, 2]]]]]) torch.Size([2, 2, 2, 1, 3])
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