在nn.Sequential中可以定义分支结构吗

在nn.Sequential中不能定义分支结构。因为nn.Sequential是一种线性结构，只能按照顺序依次添加网络层，无法实现分支结构。如果需要定义分支结构，可以使用Functional API或者ModuleList等其他方式来构建模型。

以下是使用Functional API实现分支结构的示例代码：

import torch
import torch.nn as nn

class BranchNet(nn.Module):
    def __init__(self):
        super(BranchNet, self).__init__()
        self.conv1 = nn.Conv2d(3, 16, kernel_size=3, stride=1, padding=1)
        self.bn1 = nn.BatchNorm2d(16)
        self.relu1 = nn.ReLU(inplace=True)
        self.conv2 = nn.Conv2d(16, 32, kernel_size=3, stride=1, padding=1)
        self.bn2 = nn.BatchNorm2d(32)
        self.relu2 = nn.ReLU(inplace=True)

    def forward(self, x):
        x = self.conv1(x)
        x = self.bn1(x)
        x = self.relu1(x)
        x = self.conv2(x)
        x = self.bn2(x)
        x = self.relu2(x)
        return x

class MyNet(nn.Module):
    def __init__(self):
        super(MyNet, self).__init__()
        self.branch1 = BranchNet()
        self.branch2 = BranchNet()
        self.fc = nn.Linear(32*8*8, 10)

    def forward(self, x):
        x1 = self.branch1(x)
        x2 = self.branch2(x)
        x = torch.cat([x1, x2], dim=1)
        x = x.view(x.size(0), -1)
        x = self.fc(x)
        return x

net = MyNet()
print(net)