pytorch实现LeNet5代码小结

目录

• 代码一
• 代码二
• 代码三

代码一

训练代码：

import torch
import torch.optim as optim
import torch.nn as nn
import torch.nn.functional as F
import torchvision
import torchvision.transforms as transforms

trainset = torchvision.datasets.MNIST(root='./data', train=True,
                                        download=True, transform=transforms.ToTensor())
trainloader = torch.utils.data.DataLoader(trainset, batch_size=4,
                                          shuffle=True, num_workers=2)

testset = torchvision.datasets.MNIST(root='./data', train=False,
                                       download=True, transform=transforms.ToTensor())
testloader = torch.utils.data.DataLoader(testset, batch_size=4,
                                         shuffle=False, num_workers=2)

print("train_data:", trainset.data.size())
print("train_labels:", trainset.targets.size())
print("test_data:", testset.data.size())

class Net(nn.Module):
    def __init__(self):
        super(Net, self).__init__()
        self.conv1 = nn.Conv2d(1, 6, 5, 1, 2)
        self.pool = nn.MaxPool2d(2, 2)
        self.conv2 = nn.Conv2d(6, 16, 5)
        self.fc1 = nn.Linear(16 * 5 * 5, 120)
        self.fc2 = nn.Linear(120, 84)
        self.fc3 = nn.Linear(84, 10)

    def forward(self, x):
        x = self.pool(F.relu(self.conv1(x)))
        x = self.pool(F.relu(self.conv2(x)))
        x = x.view(x.size()[0], -1)
        x = F.relu(self.fc1(x))
        x = F.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)

device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
print(device)
net = net.to(device)

for epoch in range(2):
    running_loss = 0.0
    for i, data in enumerate(trainloader, 0):
        inputs, labels = data[0].to(device), data[1].to(device)
        optimizer.zero_grad()
        outputs = net(inputs)
        loss = criterion(outputs, labels)
        loss.backward()
        optimizer.step()

        running_loss += loss.item()
        if i % 2000 == 1999:
            print('[%d, %5d] loss: %.3f' %
                  (epoch + 1, i + 1, running_loss / 2000))
            running_loss = 0.0

print('Finished Training')

测试代码：

correct = 0
total = 0
with torch.no_grad():
    for data in testloader:
        images, labels = data[0].to(device), data[1].to(device)
        outputs = net(images)
        _, predicted = torch.max(outputs.data, 1)
        total += labels.size(0)
        correct += (predicted == labels).sum().item()

print('Accuracy of the network on the 10000 test images: %d %%' % (
    100 * correct / total))

代码二

来源：https://blog.csdn.net/u014453898/article/details/90707987

训练代码：

import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim
from torchvision import datasets, transforms
from torch.autograd import Variable
 
 
lr = 0.01 #学习率
momentum = 0.5
log_interval = 10 #跑多少次batch进行一次日志记录
epochs = 10
batch_size = 64
test_batch_size = 1000
 
 
class LeNet(nn.Module):
    def __init__(self):
        super(LeNet, self).__init__()
        self.conv1 = nn.Sequential(  # input_size=(1*28*28)
            nn.Conv2d(1, 6, 5, 1, 2),  # padding=2保证输入输出尺寸相同
            nn.ReLU(),  # input_size=(6*28*28)
            nn.MaxPool2d(kernel_size=2, stride=2),  # output_size=(6*14*14)
        )
        self.conv2 = nn.Sequential(
            nn.Conv2d(6, 16, 5),
            nn.ReLU(),  # input_size=(16*10*10)
            nn.MaxPool2d(2, 2)  # output_size=(16*5*5)
        )
        self.fc1 = nn.Sequential(
            nn.Linear(16 * 5 * 5, 120),
            nn.ReLU()
        )
        self.fc2 = nn.Sequential(
            nn.Linear(120, 84),
            nn.ReLU()
        )
        self.fc3 = nn.Linear(84, 10)
 
    # 定义前向传播过程，输入为x
    def forward(self, x):
        x = self.conv1(x)
        x = self.conv2(x)
        # nn.Linear()的输入输出都是维度为一的值，所以要把多维度的tensor展平成一维
        x = x.view(x.size()[0], -1)
        x = self.fc1(x)
        x = self.fc2(x)
        x = self.fc3(x)
        return x #F.softmax(x, dim=1)
 
 
 
def train(epoch):  # 定义每个epoch的训练细节
    model.train()  # 设置为trainning模式
    for batch_idx, (data, target) in enumerate(train_loader):
        data = data.to(device)
        target = target.to(device)
        data, target = Variable(data), Variable(target)  # 把数据转换成Variable
        optimizer.zero_grad()  # 优化器梯度初始化为零
        output = model(data)  # 把数据输入网络并得到输出，即进行前向传播
        loss = F.cross_entropy(output,target)  #交叉熵损失函数
        loss.backward()  # 反向传播梯度
        optimizer.step()  # 结束一次前传+反传之后，更新参数
        if batch_idx % log_interval == 0:  # 准备打印相关信息
            print('Train Epoch: {} [{}/{} ({:.0f}%)]	Loss: {:.6f}'.format(
                epoch, batch_idx * len(data), len(train_loader.dataset),
                       100. * batch_idx / len(train_loader), loss.item()))
 
 
def test():
    model.eval()  # 设置为test模式
    test_loss = 0  # 初始化测试损失值为0
    correct = 0  # 初始化预测正确的数据个数为0
    for data, target in test_loader:
 
        data = data.to(device)
        target = target.to(device)
        data, target = Variable(data), Variable(target)  #计算前要把变量变成Variable形式，因为这样子才有梯度
 
        output = model(data)
        test_loss += F.cross_entropy(output, target, size_average=False).item()  # sum up batch loss 把所有loss值进行累加
        pred = output.data.max(1, keepdim=True)[1]  # get the index of the max log-probability
        correct += pred.eq(target.data.view_as(pred)).cpu().sum()  # 对预测正确的数据个数进行累加
 
    test_loss /= len(test_loader.dataset)  # 因为把所有loss值进行过累加，所以最后要除以总得数据长度才得平均loss
    print('
Test set: Average loss: {:.4f}, Accuracy: {}/{} ({:.0f}%)
'.format(
        test_loss, correct, len(test_loader.dataset),
        100. * correct / len(test_loader.dataset)))
 
 
 
if __name__ == '__main__':
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu') #启用GPU
 
    train_loader = torch.utils.data.DataLoader(  # 加载训练数据
        datasets.MNIST('../data', train=True, download=True,
                       transform=transforms.Compose([
                           transforms.ToTensor(),
                           transforms.Normalize((0.1307,), (0.3081,))  #数据集给出的均值和标准差系数，每个数据集都不同的，都数据集提供方给出的
                       ])),
        batch_size=batch_size, shuffle=True)
 
    test_loader = torch.utils.data.DataLoader(  # 加载训练数据，详细用法参考我的Pytorch打怪路（一）系列-（1）
        datasets.MNIST('../data', train=False, transform=transforms.Compose([
            transforms.ToTensor(),
            transforms.Normalize((0.1307,), (0.3081,)) #数据集给出的均值和标准差系数，每个数据集都不同的，都数据集提供方给出的
        ])),
        batch_size=test_batch_size, shuffle=True)
 
    model = LeNet()  # 实例化一个网络对象
    model = model.to(device)
    optimizer = optim.SGD(model.parameters(), lr=lr, momentum=momentum)  # 初始化优化器
 
    for epoch in range(1, epochs + 1):  # 以epoch为单位进行循环
        train(epoch)
        test()
 
    torch.save(model, 'model.pth') #保存模型

测试代码：

import torch
import cv2
import torch.nn.functional as F
from modela import LeNet  ##重要，虽然显示灰色(即在次代码中没用到)，但若没有引入这个模型代码，加载模型时会找不到模型
from torch.autograd import Variable
from torchvision import datasets, transforms
import numpy as np
 
if __name__ =='__main__':
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
    model = torch.load('model.pth') #加载模型
    model = model.to(device)
    model.eval()    #把模型转为test模式
 
    img = cv2.imread("3.jpg")  #读取要预测的图片
    trans = transforms.Compose(
        [
            transforms.ToTensor(),
            transforms.Normalize((0.1307,), (0.3081,))
        ])
 
    img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)#图片转为灰度图，因为mnist数据集都是灰度图
    img = trans(img)
    img = img.to(device)
    img = img.unsqueeze(0)  #图片扩展多一维,因为输入到保存的模型中是4维的[batch_size,通道,长，宽]，而普通图片只有三维，[通道,长，宽]
    #扩展后，为[1，1，28，28]
    output = model(img)
    prob = F.softmax(output, dim=1)
    prob = Variable(prob)
    prob = prob.cpu().numpy()  #用GPU的数据训练的模型保存的参数都是gpu形式的，要显示则先要转回cpu，再转回numpy模式
    print(prob)  #prob是10个分类的概率
    pred = np.argmax(prob) #选出概率最大的一个
    print(pred.item())

代码三

来源：https://www.cnblogs.com/denny402/p/7506523.html

训练代码：

import torch
import torchvision
from torch.autograd import Variable
import torch.utils.data.dataloader as Data

train_data = torchvision.datasets.MNIST(
    './mnist', train=True, transform=torchvision.transforms.ToTensor(), download=True
)
test_data = torchvision.datasets.MNIST(
    './mnist', train=False, transform=torchvision.transforms.ToTensor()
)
print("train_data:", train_data.train_data.size())
print("train_labels:", train_data.train_labels.size())
print("test_data:", test_data.test_data.size())

train_loader = Data.DataLoader(dataset=train_data, batch_size=64, shuffle=True)
test_loader = Data.DataLoader(dataset=test_data, batch_size=64)


class Net(torch.nn.Module):
    def __init__(self):
        super(Net, self).__init__()
        self.conv1 = torch.nn.Sequential(
            torch.nn.Conv2d(1, 32, 3, 1, 1),
            torch.nn.ReLU(),
            torch.nn.MaxPool2d(2))
        self.conv2 = torch.nn.Sequential(
            torch.nn.Conv2d(32, 64, 3, 1, 1),
            torch.nn.ReLU(),
            torch.nn.MaxPool2d(2)
        )
        self.conv3 = torch.nn.Sequential(
            torch.nn.Conv2d(64, 64, 3, 1, 1),
            torch.nn.ReLU(),
            torch.nn.MaxPool2d(2)
        )
        self.dense = torch.nn.Sequential(
            torch.nn.Linear(64 * 3 * 3, 128),
            torch.nn.ReLU(),
            torch.nn.Linear(128, 10)
        )

    def forward(self, x):
        conv1_out = self.conv1(x)
        conv2_out = self.conv2(conv1_out)
        conv3_out = self.conv3(conv2_out)
        res = conv3_out.view(conv3_out.size(0), -1)
        out = self.dense(res)
        return out


model = Net()
print(model)

optimizer = torch.optim.Adam(model.parameters())
loss_func = torch.nn.CrossEntropyLoss()

for epoch in range(10):
    print('epoch {}'.format(epoch + 1))
    # training-----------------------------
    train_loss = 0.
    train_acc = 0.
    for batch_x, batch_y in train_loader:
        batch_x, batch_y = Variable(batch_x), Variable(batch_y)
        out = model(batch_x)
        loss = loss_func(out, batch_y)
        train_loss += loss.data[0]
        pred = torch.max(out, 1)[1]
        train_correct = (pred == batch_y).sum()
        train_acc += train_correct.data[0]
        optimizer.zero_grad()
        loss.backward()
        optimizer.step()
    print('Train Loss: {:.6f}, Acc: {:.6f}'.format(train_loss / (len(
        train_data)), train_acc / (len(train_data))))

测试代码：

model.eval()
    eval_loss = 0.
    eval_acc = 0.
    for batch_x, batch_y in test_loader:
        batch_x, batch_y = Variable(batch_x, volatile=True), Variable(batch_y, volatile=True)
        out = model(batch_x)
        loss = loss_func(out, batch_y)
        eval_loss += loss.data[0]
        pred = torch.max(out, 1)[1]
        num_correct = (pred == batch_y).sum()
        eval_acc += num_correct.data[0]
    print('Test Loss: {:.6f}, Acc: {:.6f}'.format(eval_loss / (len(
        test_data)), eval_acc / (len(test_data))))