Question

嗨，我刚刚学习了通过udacity课程在pytorch中实现NN模型的方法，因此创建了一个带有几个CNN和FC层的简单模型。经过艰苦的努力，我使模型得以运作。但是，即使重复执行，它似乎也陷入了同样的损失。我不知道我要去哪里错了。必须是一些我看不到的逻辑错误。这是代码。

模型

class cifar_clasify(nn.Module):

    def __init__(self):

        super().__init__()

        self.conv1 = nn.Conv2d(3,16,3)
        self.BNorm1 = nn.BatchNorm2d(16)
        self.conv2 = nn.Conv2d(16,32,3)
        self.BNorm2 = nn.BatchNorm2d(32)
        self.fc1 = nn.Linear(32*6*6,256)
        self.fc2 = nn.Linear(256,512)
        self.fc3 = nn.Linear(512,10)

        self.drop = nn.Dropout(p =0.2)

    def forward(self,x):


        out = self.conv1(x)
        out = F.relu(out)
        #print(out.shape)
        out = F.max_pool2d(out,2)
        out = self.BNorm1(out)
        #print(out.shape)

        out = self.conv2(out)
        out = F.relu(out)
        #print(out.shape)
        out = F.max_pool2d(out,2)
        out = self.BNorm2(out)
        #print(out.shape)
        out = out.view(out.shape[0],-1)

        out = self.fc1(out)
        out = self.drop(F.relu(out))
        out = self.fc2(out)
        out = self.drop(F.relu(out))
        final = F.log_softmax(F.relu(self.fc3(out)) , dim = 1)

        return final

培训代码

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
print(device)

model = cifar_clasify()
criterion = nn.NLLLoss()
optimizer = optim.Adam(model.parameters(), lr =0.03)

epoch =2 
step = 2
running_loss = 0
accuracy = 0 
print_every = 5

model.to(device)


for e in range(epoch):

    for inputs,label_ in zip(train_X,train_labels):

        step +=1
        inputs = inputs.view((-1,3,32,32))
        inputs,label_ = inputs.to(device) , label_.to(device)

        #inputs.cuda()
        #label.cuda()

        optimizer.zero_grad()

        logps = model.forward(inputs)

        loss = criterion(logps , label_.reshape(1))

        loss.backward()

        optimizer.step()

        running_loss += loss.item()


        if step % print_every == 0:
            test_loss = 0 
            accuracy = 0
            model.eval()
            with torch.no_grad():
                for testx, lab in zip(test_X , test_labels):

                    testx = testx.view((-1,3,32,32))

                    testx,lab = testx.to(device) , lab.to(device)
                    lab = lab.reshape(1)
                    logps = model.forward(testx)
                    batch_loss = criterion(logps , lab)
                    #print(batch_loss.item())
                    test_loss += batch_loss.item()

                    ps = torch.exp(logps)

                    top_p , topclass = ps.topk(1,dim = 1)

                    equals = topclass == lab.view(*topclass.shape)

                    accuracy += torch.mean(torch.mean(equals.type(torch.FloatTensor))).item()
            print(f"Epoch {e+1}/{epoch}.. "
                  f"Train loss: {running_loss/print_every:.3f}.. "
                  f"Test loss: {test_loss/len(test_X):.3f}.. "
                  f"Test accuracy: {accuracy/len(test_X):.3f}")
            running_loss = 0
            model.train()

这是我不得不停止的结果，因为它没有改善：

Epoch 1/2.. Train loss: 1.396.. Test loss: 5.288.. Test accuracy: 0.104
step =  5
Epoch 1/2.. Train loss: 3.038.. Test loss: 2.303.. Test accuracy: 0.104
step =  10
Epoch 1/2.. Train loss: 2.303.. Test loss: 2.303.. Test accuracy: 0.104
step =  15
Epoch 1/2.. Train loss: 2.669.. Test loss: 2.318.. Test accuracy: 0.105
step =  20
Epoch 1/2.. Train loss: 3.652.. Test loss: 2.303.. Test accuracy: 0.104
step =  25
Epoch 1/2.. Train loss: 2.303.. Test loss: 2.303.. Test accuracy: 0.104
step =  30
Epoch 1/2.. Train loss: 2.303.. Test loss: 2.303.. Test accuracy: 0.104
step =  35
Epoch 1/2.. Train loss: 2.303.. Test loss: 2.303.. Test accuracy: 0.104
step =  40
Epoch 1/2.. Train loss: 2.303.. Test loss: 2.303.. Test accuracy: 0.104
step =  45
Epoch 1/2.. Train loss: 2.303.. Test loss: 2.303.. Test accuracy: 0.104
step =  50
Epoch 1/2.. Train loss: 2.303.. Test loss: 2.303.. Test accuracy: 0.104
step =  55

如果您需要其他任何信息，请参见以下代码：

Simple CNN for CIFAR 10 classification in google colab

Answer 1

由于批次大小为1，请使用较低的学习率（例如1e-4）或增加批次大小。

我建议将批次大小设置为16或更大。

编辑：要创建一批数据，您可以执行以下操作。

N = input.shape[0] #know the total size/samples in input
for i in range(n_epochs):
    # this is to shuffle data
    indices = torch.randperm(N)
    for idx in range(0, N, batch_size):
        batch_input = input[idx:idx+batch_size]   # this will get you input of size batch_size
        # do whatever you want with the batch_input
        # ....

使用CIFAR-10数据集STUCK的低精度的简单CNN模型训练

1 个答案: