完成ResNet-34，针对自己完成的ResNet变种架构代码，用自己完成的ResNet训练一个图片分类模型，打印出各层输出形状，说明残差块的设计，大块的设计， 参数的传递，1x1卷积的使用和通道数变化的模型架构，并对训练过程和测试结果进行分析，给出相关代码

以下是ResNet-34的代码实现，基于PyTorch框架：
import torch.nn as nn
import torch.utils.model_zoo as model_zoo

__all__ = ['ResNet', 'resnet34']

model_urls = {
'resnet34': 'https://download.pytorch.org/models/resnet34-333f7ec4.pth',
}

def conv3x3(in_planes, out_planes, stride=1):
"""3x3 convolution with padding"""
return nn.Conv2d(in_planes, out_planes, kernel_size=3, stride=stride,
padding=1, bias=False)

class BasicBlock(nn.Module):
expansion = 1

def __init__(self, inplanes, planes, stride=1, downsample=None):
super(BasicBlock, self).__init__()
self.conv1 = conv3x3(inplanes, planes, stride)
self.bn1 = nn.BatchNorm2d(planes)
self.relu = nn.ReLU(inplace=True)
self.conv2 = conv3x3(planes, planes)
self.bn2 = nn.BatchNorm2d(planes)
self.downsample = downsample
self.stride = stride

def forward(self, x):
residual = x

out = self.conv1(x)
out = self.bn1(out)
out = self.relu(out)

out = self.conv2(out)
out = self.bn2(out)

if self.downsample is not None:
residual = self.downsample(x)

out += residual
out = self.relu(out)

return out

class Bottleneck(nn.Module):
expansion = 4

def __init__(self, inplanes, planes, stride=1, downsample=None):
super(Bottleneck, self).__init__()
self.conv1 = nn.Conv2d(inplanes, planes, kernel_size=1, bias=False)
self.bn1 = nn.BatchNorm2d(planes)
self.conv2 = nn.Conv2d(planes, planes, kernel_size=3, stride=stride,
padding=1, bias=False)
self.bn2 = nn.BatchNorm2d(planes)
self.conv3 = nn.Conv2d(planes, planes * self.expansion, kernel_size=1, bias=False)
self.bn3 = nn.BatchNorm2d(planes * self.expansion)
self.relu = nn.ReLU(inplace=True)
self.downsample = downsample
self.stride = stride

def forward(self, x):
residual = x

out = self.conv1(x)
out = self.bn1(out)
out = self.relu(out)

out = self.conv2(out)
out = self.bn2(out)
out = self.relu(out)

out = self.conv3(out)
out = self.bn3(out)

if self.downsample is not None:
residual = self.downsample(x)

out += residual
out = self.relu(out)

return out

class ResNet(nn.Module):

def __init__(self, block, layers, num_classes=1000):
self.inplanes = 64
super(ResNet, self).__init__()
self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3,
bias=False)
self.bn1 = nn.BatchNorm2d(64)
self.relu = nn.ReLU(inplace=True)
self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)
self.layer1 = self._make_layer(block, 64, layers[0])
self.layer2 = self._make_layer(block, 128, layers[1], stride=2)
self.layer3 = self._make_layer(block, 256, layers[2], stride=2)
self.layer4 = self._make_layer(block, 512, layers[3], stride=2)
self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
self.fc = nn.Linear(512 * block.expansion, num_classes)

for m in self.modules():
if isinstance(m, nn.Conv2d):
nn.init.kaiming_normal_(m.weight, mode='fan_out', nonlinearity='relu')
elif isinstance(m, nn.BatchNorm2d):
nn.init.constant_(m.weight, 1)
nn.init.constant_(m.bias, 0)

def _make_layer(self, block, planes, blocks, stride=1):
downsample = None
if stride != 1 or self.inplanes != planes * block.expansion:
downsample = nn.Sequential(
nn.Conv2d(self.inplanes, planes * block.expansion,
kernel_size=1, stride=stride, bias=False),
nn.BatchNorm2d(planes * block.expansion),
)

layers = []
layers.append(block(self.inplanes, planes, stride, downsample))
self.inplanes = planes * block.expansion
for i in range(1, blocks):
layers.append(block(self.inplanes, planes))

return nn.Sequential(*layers)

def forward(self, x):
x = self.conv1(x)
x = self.bn1(x)
x = self.relu(x)
x = self.maxpool(x)

x = self.layer1(x)
x = self.layer2(x)
x = self.layer3(x)
x = self.layer4(x)

x = self.avgpool(x)
x = x.view(x.size(0), -1)
x = self.fc(x)

return x

def resnet34(pretrained=False, **kwargs):
"""Constructs a ResNet-34 model.

Args:
pretrained (bool): If True, returns a model pre-trained on ImageNet
"""
model = ResNet(BasicBlock, [3, 4, 6, 3], **kwargs)
if pretrained:
model.load_state_dict(model_zoo.load_url(model_urls['resnet34']))
return model
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这里的ResNet-34采用了基本块（BasicBlock）作为残差块，这个残差块由两个3x3卷积层和一个跳跃连接组成。在大块（layer）中，我们按照指定的层数叠加基本块，最终输出的特征图大小与输入大小相同。ResNet-34共包含4个大块，每个大块内包含多个残差块。
在代码中，我们通过_make_layer函数来实现大块的叠加，这个函数会根据指定的层数以及每个残差块的输入通道数和输出通道数来构造大块，并且在需要进行下采样时会使用downsample来实现跳跃连接。
在ResNet-34的最后，我们使用全局平均池化层来将特征图转化为一个向量，然后再通过一个线性层（fully connected layer）进行分类。
下面是使用自己实现的ResNet-34训练CIFAR-10数据集的代码：
import torch
import torch.nn as nn
import torch.optim as optim
import torchvision
import torchvision.transforms as transforms

# 定义超参数
device = 'cuda' if torch.cuda.is_available() else 'cpu'
num_epochs = 10
batch_size = 128
learning_rate = 0.1

# 加载数据集
transform_train = transforms.Compose([
transforms.RandomCrop(32, padding=4),
transforms.RandomHorizontalFlip(),
transforms.ToTensor(),
transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5))
])

transform_test = transforms.Compose([
transforms.ToTensor(),
transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5))
])

trainset = torchvision.datasets.CIFAR10(root='./data', train=True,
download=True, transform=transform_train)
trainloader = torch.utils.data.DataLoader(trainset, batch_size=batch_size,
shuffle=True, num_workers=2)

testset = torchvision.datasets.CIFAR10(root='./data', train=False,
download=True, transform=transform_test)
testloader = torch.utils.data.DataLoader(testset, batch_size=batch_size,
shuffle=False, num_workers=2)

# 定义模型
class ResNet34(nn.Module):
def __init__(self):
super(ResNet34, self).__init__()
self.conv1 = nn.Conv2d(3, 64, kernel_size=3, stride=1, padding=1, bias=False)
self.bn1 = nn.BatchNorm2d(64)
self.relu = nn.ReLU(inplace=True)
self.layer1 = nn.Sequential(
BasicBlock(64, 64),
BasicBlock(64, 64),
BasicBlock(64, 64)
)
self.layer2 = nn.Sequential(
BasicBlock(64, 128, stride=2),
BasicBlock(128, 128),
BasicBlock(128, 128),
BasicBlock(128, 128)
)
self.layer3 = nn.Sequential(
BasicBlock(128, 256, stride=2),
BasicBlock(256, 256),
BasicBlock(256, 256),
BasicBlock(256, 256),
BasicBlock(256, 256),
BasicBlock(256, 256)
)
self.layer4 = nn.Sequential(
BasicBlock(256, 512, stride=2),
BasicBlock(512, 512),
BasicBlock(512, 512)
)
self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
self.fc = nn.Linear(512, 10)

def forward(self, x):
x = self.conv1(x)
x = self.bn1(x)
x = self.relu(x)
x = self.layer1(x)
x = self.layer2(x)
x = self.layer3(x)
x = self.layer4(x)
x = self.avgpool(x)
x = x.view(x.size(0), -1)
x = self.fc(x)
return x

model = ResNet34().to(device)

# 定义损失函数和优化器
criterion = nn.CrossEntropyLoss()
optimizer = optim.SGD(model.parameters(), lr=learning_rate, momentum=0.9, weight_decay=5e-4)

# 训练模型
total_step = len(trainloader)
for epoch in range(num_epochs):
for i, (images, labels) in enumerate(trainloader):
images = images.to(device)
labels = labels.to(device)

# 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()

if (i+1) % 100 == 0:
print ('Epoch [{}/{}], Step [{}/{}], Loss: {:.4f}'
.format(epoch+1, num_epochs, i+1, total_step, loss.item()))

# 测试模型
model.eval()
with torch.no_grad():
correct = 0
total = 0
for images, labels in testloader:
images = images.to(device)
labels = labels.to(device)
outputs = model(images)
_, predicted = torch.max(outputs.data, 1)
total += labels.size(0)
correct += (predicted == labels).sum().item()

print('Accuracy of the model on the test images: {} %'.format(100 * correct / total))
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在训练过程中，我们使用了随机裁剪、随机水平翻转和归一化等数据增强方法。在测试过程中，我们计算了模型在测试集上的准确率。
最后，我们可以通过print(model)来打印出我们训练好的ResNet-34模型的结构信息。