I’m training a CNN model and got this error:

This is my code for training the model:

```
def train_cnn(log_interval, model, device, train_loader, optimizer, epoch):
model.train()
for batch_idx, (data, target) in enumerate(train_loader):
data, target = data.to(device), target.to(device)
# zero the parameter gradients
optimizer.zero_grad()
# forward + backward + optimize
output = model(data)
loss = F.cross_entropy(output, target)
# losses = []
# losses.append(loss)
loss.backward()
optimizer.step()
if batch_idx % log_interval == 0:
print('Train Epoch: {} [{}/{} ({:.0f}%)]\tLoss: {:.6f}'.format(
epoch, batch_idx * len(data), len(train_loader.dataset),
100. * batch_idx / len(train_loader), loss.item()))
```

This is my model

```
class Net(nn.Module):
def __init__(self):
super(Net, self).__init__()
# Define 2D convolution layers
# 3: input channels, 32: output channels, 5: kernel size, 1: stride
self.conv1 = nn.Conv2d(3, 32, 5, 1) # The size of input channel is 3 because all images are coloured
self.conv2 = nn.Conv2d(32, 64, 5, 1)
self.conv3 = nn.Conv2d(64, 128, 3, 1)
self.conv4 = nn.Conv2d(128, 256, 3, 1)
# It will 'filter' out some of the input by the probability(assign zero)
self.dropout1 = nn.Dropout2d(0.25)
self.dropout2 = nn.Dropout2d(0.5)
# Fully connected layer: input size, output size
self.fc1 = nn.Linear(692224, 128)
self.fc2 = nn.Linear(128, 10)
# forward() link all layers together,
def forward(self, x):
x = self.conv1(x)
x = F.relu(x)
x = self.conv2(x)
x = F.relu(x)
x = F.max_pool2d(x, 2)
x = self.dropout1(x)
x = self.conv3(x)
x = F.relu(x)
x = self.conv4(x)
x = F.relu(x)
x = F.max_pool2d(x, 2)
x = self.dropout1(x)
x = torch.flatten(x, 1)
x = self.fc1(x)
x = F.relu(x)
x = self.dropout2(x)
x = self.fc2(x)
output = F.log_softmax(x, dim=1)
return output
```

Any advice would be appreciated. Thanks in advance!