pytorch环境下CIfer-10图像分类 代码

下面是一个使用 PyTorch 进行 CIFAR-10 图像分类的示例代码：

import torch
import torch.nn as nn
import torch.optim as optim
import torchvision.datasets as datasets
import torchvision.transforms as transforms

# 定义超参数
batch_size = 64
learning_rate = 0.001
num_epochs = 10

# 加载数据集并进行预处理
transform = transforms.Compose([
    transforms.RandomHorizontalFlip(),  # 随机水平翻转
    transforms.RandomCrop(32, padding=4),  # 随机裁剪
    transforms.ToTensor(),  # 转换为张量
    transforms.Normalize(mean=[0.5, 0.5, 0.5], std=[0.5, 0.5, 0.5])  # 归一化
])
train_dataset = datasets.CIFAR10(root='./data', train=True, download=True, transform=transform)
train_loader = torch.utils.data.DataLoader(train_dataset, batch_size=batch_size, shuffle=True)
test_dataset = datasets.CIFAR10(root='./data', train=False, download=True, transform=transform)
test_loader = torch.utils.data.DataLoader(test_dataset, batch_size=batch_size, shuffle=False)

# 定义模型
class Net(nn.Module):
    def __init__(self):
        super(Net, self).__init__()
        self.conv1 = nn.Conv2d(3, 64, kernel_size=3, padding=1)
        self.bn1 = nn.BatchNorm2d(64)
        self.conv2 = nn.Conv2d(64, 128, kernel_size=3, padding=1)
        self.bn2 = nn.BatchNorm2d(128)
        self.conv3 = nn.Conv2d(128, 256, kernel_size=3, padding=1)
        self.bn3 = nn.BatchNorm2d(256)
        self.fc1 = nn.Linear(256 * 4 * 4, 1024)
        self.fc2 = nn.Linear(1024, 10)

    def forward(self, x):
        x = nn.functional.relu(self.bn1(self.conv1(x)))
        x = nn.functional.max_pool2d(x, 2)
        x = nn.functional.relu(self.bn2(self.conv2(x)))
        x = nn.functional.max_pool2d(x, 2)
        x = nn.functional.relu(self.bn3(self.conv3(x)))
        x = nn.functional.max_pool2d(x, 2)
        x = x.view(-1, 256 * 4 * 4)
        x = nn.functional.relu(self.fc1(x))
        x = self.fc2(x)
        return x

model = Net()

# 定义损失函数和优化器
criterion = nn.CrossEntropyLoss()
optimizer = optim.Adam(model.parameters(), lr=learning_rate)

# 训练模型
for epoch in range(num_epochs):
    for i, (images, labels) in enumerate(train_loader):
        # 前向传播
        outputs = model(images)
        loss = criterion(outputs, labels)

        # 反向传播和优化
        optimizer.zero_grad()
        loss.backward()
        optimizer.step()

        # 每100个batch打印一次日志
        if (i + 1) % 100 == 0:
            print('Epoch [{}/{}], Batch [{}/{}], Loss: {:.4f}'.format(epoch + 1, num_epochs, i + 1, len(train_loader), loss.item()))

    # 在测试集上测试模型
    correct = 0
    total = 0
    with torch.no_grad():
        for images, labels in test_loader:
            outputs = model(images)
            _, predicted = torch.max(outputs.data, 1)
            total += labels.size(0)
            correct += (predicted == labels).sum().item()

    print('Test Accuracy of the model on the 10000 test images: {} %'.format(100 * correct / total))

# 保存模型
torch.save(model.state_dict(), 'cifar10.ckpt')

这个示例代码包括了以下几个步骤：

1. 加载数据集并进行预处理。
2. 定义模型，并将其前向传播的过程实现在 `forward` 方法中。
3. 定义损失函数和优化器。
4. 训练模型，并在测试集上测试模型。
5. 保存模型。

其中，数据集预处理的过程包括了随机水平翻转、随机裁剪、归一化等操作，模型的定义采用了卷积神经网络。你可以根据自己的需求对这个示例代码进行修改和扩展。