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Super Kai (Kazuya Ito)
Super Kai (Kazuya Ito)

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Flatten in PyTorch

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*Memos:

Flatten() can remove zero or more dimensions by selecting dimensions from the 0D or more D tensor of zero or more elements, getting the 1D or more D tensor of zero or more elements as shown below:

*Memos:

  • The 1st argument for initialization is start_dim(Optional-Default:1-Type:int).
  • The 2nd argument for initialization is end_dim(Optional-Default:-1-Type:int).
  • The 1st argument is input(Required-Type:tensor of int, float, complex or bool).
  • Flatten() can change a 0D tensor to a 1D tensor.
  • Flatten() does nothing for a 1D tensor.
  • The difference between Flatten() and flatten() is:
    • The default value of start_dim for Flatten() is 1 while the default value of start_dim for flatten() is 0.
    • Basically, Flatten() is used to define a model while flatten() is not used to define a model.
import torch from torch import nn flatten = nn.Flatten() flatten # Flatten(start_dim=1, end_dim=-1)  flatten.start_dim # 1  flatten.end_dim # -1  my_tensor = torch.tensor(7) flatten = nn.Flatten(start_dim=0, end_dim=0) flatten = nn.Flatten(start_dim=0, end_dim=-1) flatten = nn.Flatten(start_dim=-1, end_dim=0) flatten = nn.Flatten(start_dim=-1, end_dim=-1) flatten(input=my_tensor) # tensor([7])  my_tensor = torch.tensor([7, 1, -8, 3, -6, 0]) flatten = nn.Flatten(start_dim=0, end_dim=0) flatten = nn.Flatten(start_dim=0, end_dim=-1) flatten = nn.Flatten(start_dim=-1, end_dim=0) flatten = nn.Flatten(start_dim=-1, end_dim=-1) flatten(input=my_tensor) # tensor([7, 1, -8, 3, -6, 0])  my_tensor = torch.tensor([[7, 1, -8], [3, -6, 0]]) flatten = nn.Flatten(start_dim=0, end_dim=1) flatten = nn.Flatten(start_dim=0, end_dim=-1) flatten = nn.Flatten(start_dim=-2, end_dim=1) flatten = nn.Flatten(start_dim=-2, end_dim=-1) flatten(input=my_tensor) # tensor([7, 1, -8, 3, -6, 0])  flatten = nn.Flatten() flatten = nn.Flatten(start_dim=0, end_dim=0) flatten = nn.Flatten(start_dim=-1, end_dim=-1) flatten = nn.Flatten(start_dim=0, end_dim=-2) flatten = nn.Flatten(start_dim=1, end_dim=1) flatten = nn.Flatten(start_dim=1, end_dim=-1) flatten = nn.Flatten(start_dim=-1, end_dim=1) flatten = nn.Flatten(start_dim=-1, end_dim=-1) flatten = nn.Flatten(start_dim=-2, end_dim=0) flatten = nn.Flatten(start_dim=-2, end_dim=-2) flatten(input=my_tensor) # tensor([[7, 1, -8], [3, -6, 0]])  my_tensor = torch.tensor([[[7], [1], [-8]], [[3], [-6], [0]]]) flatten = nn.Flatten(start_dim=0, end_dim=2) flatten = nn.Flatten(start_dim=0, end_dim=-1) flatten = nn.Flatten(start_dim=-3, end_dim=2) flatten = nn.Flatten(start_dim=-3, end_dim=-1) flatten(input=my_tensor) # tensor([7, 1, -8, 3, -6, 0])  flatten = nn.Flatten(start_dim=0, end_dim=0) flatten = nn.Flatten(start_dim=0, end_dim=-3) flatten = nn.Flatten(start_dim=1, end_dim=1) flatten = nn.Flatten(start_dim=1, end_dim=-2) flatten = nn.Flatten(start_dim=2, end_dim=2) flatten = nn.Flatten(start_dim=2, end_dim=-1) flatten = nn.Flatten(start_dim=-1, end_dim=2) flatten = nn.Flatten(start_dim=-1, end_dim=-1) flatten = nn.Flatten(start_dim=-2, end_dim=1) flatten = nn.Flatten(start_dim=-2, end_dim=-2) flatten = nn.Flatten(start_dim=-3, end_dim=0) flatten = nn.Flatten(start_dim=-3, end_dim=-3) flatten(input=my_tensor) # tensor([[[7], [1], [-8]], [[3], [-6], [0]]])  flatten = nn.Flatten(start_dim=0, end_dim=1) flatten = nn.Flatten(start_dim=0, end_dim=-2) flatten = nn.Flatten(start_dim=-3, end_dim=1) flatten = nn.Flatten(start_dim=-3, end_dim=-2) flatten(input=my_tensor) # tensor([[7], [1], [-8], [3], [-6], [0]])  flatten = nn.Flatten() flatten = nn.Flatten(start_dim=1, end_dim=2) flatten = nn.Flatten(start_dim=1, end_dim=-1) flatten = nn.Flatten(start_dim=-2, end_dim=2) flatten = nn.Flatten(start_dim=-2, end_dim=-1) flatten(input=my_tensor) # tensor([[7, 1, -8], [3, -6, 0]])  my_tensor = torch.tensor([[[7.], [1.], [-8.]], [[3.], [-6.], [0.]]]) flatten = nn.Flatten() flatten(input=my_tensor) # tensor([[7., 1., -8.], [3., -6., 0.]])  my_tensor = torch.tensor([[[7.+0.j], [1.+0.j], [-8.+0.j]], [[3.+0.j], [-6.+0.j], [0.+0.j]]]) flatten = nn.Flatten() flatten(input=my_tensor) # tensor([[7.+0.j, 1.+0.j, -8.+0.j], # [3.+0.j, -6.+0.j, 0.+0.j]])  my_tensor = torch.tensor([[[True], [False], [True]], [[False], [True], [False]]]) flatten = nn.Flatten() flatten(input=my_tensor) # tensor([[True, False, True], # [False, True, False]]) 
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