BCELoss() in PyTorch

#pytorch #bceloss #lossfunction #function

*Memos:

My post explains L1 Loss(MAE), L2 Loss(MSE), Huber Loss, BCE and Cross Entropy Loss.
My post explains L1Loss() and MSELoss().
My post explains HuberLoss().
My post explains CrossEntropyLoss().

BCELoss() can get the 0D or more D tensor of the zero or more values(float) computed by BCE Loss from the 0D or more D tensor of zero or more elements as shown below:

*Memos:

The 1st argument for initialization is weight(Optional-Default:None-Type:tensor of int, float or bool). If not given, it's 1.
There is reduction argument for initialization(Optional-Default:'mean'-Type:str). *'none', 'mean' or 'sum' can be selected.
There are size_average and reduce argument for initialization but they are deprecated.
The 1st argument is input(Required-Type:tensor of float). *It must be 0<=x<=1.
The 2nd argument is target(Required-Type:tensor of float). *It must be 0<=y<=1.
input and target must be the same size otherwise there is error.
The empty 1D or more D input and target tensor with reduction='mean' return nan.
The empty 1D or more D input and target tensor with reduction='sum' return 0..

import torch
from torch import nn

tensor1 = torch.tensor([0.4, 0.8, 0.6, 0.3, 0.0, 0.5])
tensor2 = torch.tensor([0.2, 0.9, 0.4, 0.1, 0.8, 0.5])
                   # -w(y*logx+(1-y)*log(1-x)))
                   # -1(0.2*log0.4+(1-0.2)*log(1-0.4))
                   # ↓↓↓↓↓↓
                   # 0.5919+0.3618+0.7541+0.4414+80.0+0.6931 = 82.8423
                   # 82.8423 / 6 = 13.8071
bceloss = nn.BCELoss()
bceloss(input=tensor1, target=tensor2)
# tensor(7.2500)

bceloss
# BCELoss()

print(bceloss.weight)
# None

bceloss.reduction
# 'mean'

bceloss = nn.BCELoss(weight=None, reduction='mean')
bceloss(input=tensor1, target=tensor2)
# tensor(13.8071)

bceloss = nn.BCELoss(reduction='sum')
bceloss(input=tensor1, target=tensor2)
# tensor(82.8423)

bceloss = nn.BCELoss(reduction='none')
bceloss(input=tensor1, target=tensor2)
# tensor([0.5919, 0.3618, 0.7541, 0.4414, 80.0000, 0.6931])

bceloss = nn.BCELoss(weight=torch.tensor([0., 1., 2., 3., 4., 5.]))
bceloss(input=tensor1, target=tensor2)
# tensor(54.4433)

bceloss = nn.BCELoss(weight=torch.tensor([0.]))
bceloss(input=tensor1, target=tensor2)
# tensor(0.)

bceloss = nn.BCELoss(weight=torch.tensor([0, 1, 2, 3, 4, 5]))
bceloss(input=tensor1, target=tensor2)
# tensor(54.4433)

bceloss = nn.BCELoss(weight=torch.tensor([0]))
bceloss(input=tensor1, target=tensor2)
# tensor(0.)

bceloss = nn.BCELoss(
              weight=torch.tensor([True, False, True, False, True, False])
          )
bceloss(input=tensor1, target=tensor2)
# tensor(13.5577)

bceloss = nn.BCELoss(weight=torch.tensor([False]))
bceloss(input=tensor1, target=tensor2)
# tensor(0.)

tensor1 = torch.tensor([[0.4, 0.8, 0.6], [0.3, 0.0, 0.5]])
tensor2 = torch.tensor([[0.2, 0.9, 0.4], [0.1, 0.8, 0.5]])

bceloss = nn.BCELoss()
bceloss(input=tensor1, target=tensor2)
# tensor(13.8071)

tensor1 = torch.tensor([[[0.4], [0.8], [0.6]], [[0.3], [0.0], [0.5]]])
tensor2 = torch.tensor([[[0.2], [0.9], [0.4]], [[0.1], [0.8], [0.5]]])

bceloss = nn.BCELoss()
bceloss(input=tensor1, target=tensor2)
# tensor(13.8071)

tensor1 = torch.tensor([])
tensor2 = torch.tensor([])

bceloss = nn.BCELoss(reduction='mean')
bceloss(input=tensor1, target=tensor2)
# tensor(nan)

bceloss = nn.BCELoss(reduction='sum')
bceloss(input=tensor1, target=tensor2)
# tensor(0.)

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BCELoss() in PyTorch

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