PyTorch??????????????

    
    
     
        
      
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?????????PyTorch?????????????????????????????????????????????
    
     
    
     
        
      
PyTorch??????
        
      
PyTorch??????TensorFlow?????????????????????????????nn.Module???????????Convolutional Neural Network (CNN)???
        
      
class Net(nn.Module):def __init__(self):    super().__init__()    self.conv1 = nn.Conv2d(1, 6, 5)    self.conv2 = nn.Conv2d(6, 16, 5)def forward(self, x):    x = F.max_pool2d(F.relu(self.conv1(x)), 2)    x = F.max_pool2d(F.relu(self.conv2(x)), 2)    return x
        
      
????????????????__init__???????forward??__init__????????????forward??????????????
    
     
    
     
        
      
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???????????????????????????????????????????PyTorch??????????????????????????
    
     
    
     
        
      
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????????????????????????????????????????????MSELoss???????CrossEntropyLoss?????????
        
      
compute_loss = nn.MSELoss()
     
    

loss = compute_loss(target, output)

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?????SGD?Adam?????????????????????????????????????????????
        
     
optimizer = optim.SGD(net.parameters(), lr=0.001, momentum=0.9)
    

optimizer.zero_grad()loss.backward()optimizer.step()