import torch import os import torch.nn as nn import torch.optim as optim import numpy as np import random class Net(nn.Module): def init(self): super(Net, self).init() self.conv1 = nn.Conv2d(1, 16, kernel_size=3,stride=1) self.pool = nn.MaxPool2d(kernel_size=2,stride=2) self.conv2 = nn.Conv2d(16, 32, kernel_size=3,stride=1) self.fc1 = nn.Linear(32 * 9 * 9, 120) self.fc2 = nn.Linear(120, 84) self.fc3 = nn.Linear(84, 2) def forward(self, x): x = self.pool(nn.functional.relu(self.conv1(x))) x = self.pool(nn.functional.relu(self.conv2(x))) x = x.view(-1, 32 * 9 * 9) x = nn.functional.relu(self.fc1(x)) x = nn.functional.relu(self.fc2(x)) x = self.fc3(x) return x net = Net() criterion = nn.CrossEntropyLoss() optimizer = optim.SGD(net.parameters(), lr=0.001, momentum=0.9) folder_path = 'random_matrices2' # 创建空的tensor x = torch.empty((40, 1, 42, 42)) # 遍历文件夹内的文件，将每个矩阵转化为tensor并存储 for j in range(40): for j in range(40): file_name = 'matrix_{}.npy'.format(j) file_path = os.path.join(folder_path, file_name) matrix = np.load(file_path) x[j] = torch.from_numpy(matrix).unsqueeze(0) #y = torch.cat((torch.zeros(20), torch.ones(20))) y = torch.cat((torch.zeros(20, dtype=torch.long), torch.ones(20, dtype=torch.long))) for epoch in range(10): running_loss = 0.0 for i in range(40): inputs = x[i] labels = y[i].unsqueeze(0) labels = nn.functional.one_hot(labels, num_classes=2) optimizer.zero_grad() outputs = net(inputs) #loss = criterion(outputs, labels) loss = criterion(outputs.unsqueeze(0), labels.float()) loss.backward() optimizer.step() running_loss += loss.item() print('[%d] loss: %.3f' % (epoch + 1, running_loss / 40)) print('Finished Training') 报错：RuntimeError: expected scalar type Long but found Float，怎么修改？

在代码中，我们使用 nn.CrossEntropyLoss() 作为损失函数，它的标签（即targets）应该是一个长整型 (Long) 的 Tensor。而在代码中，我们将标签先转换为了 one-hot 向量，然后再转换成了 float 类型，所以出现了上述错误。为了解决这个问题，我们只需要将标签 y 的类型修改为 Long 即可。可以将以下代码：

y = torch.cat((torch.zeros(20, dtype=torch.long), torch.ones(20, dtype=torch.long)))

修改为：

y = torch.cat((torch.zeros(20, dtype=torch.long), torch.ones(20, dtype=torch.long)), dim=0)

同时，我们也需要将以下代码：

labels = nn.functional.one_hot(labels, num_classes=2)

修改为：

labels = labels.long()

这样就可以解决上述问题了。