深层神经网络——Pytorch实现MNIST手写数据集识别

拼搏现实的明天。 2023-05-28 06:43 39阅读 0赞

# Pytorch实现MNIST手写数据集识别 #

## pytorch从入门到实战学习笔记 ##

本文搭建简单的深层神经网络模型，对MNIST手写数据集进行识别。该神经网络由784个输入神经元，100个隐层神经元和10个输出神经元构成。待读者通过这个例子掌握深层神经网络特征，便可自行设计。

import torch
    import torch.nn as nn
    from torch.autograd import  Variable
    import torch.utils.data as Data
    import torchvision
    import matplotlib.pyplot as plt
    
    # Hypwe parameters
    EPOCH = 10
    BATCH_SIZE = 100                        #批处理大小
    LR = 0.001                              #learning rate
    DOWNLOAD_MNIST = False                   #在这里，我已经下载了MNIST数据集了，就不用再下载了，否则为True
    
    # MNIST Dataest
    train_data = torchvision.datasets.MNIST(           #下载MNIST数据
        root='./mnist/',
        train=True,
        transform=torchvision.transforms.ToTensor(), #下载的数据改成Tensor的数据 图片数据（0,255），转换为（0,1）的totensor数据
        download=DOWNLOAD_MNIST
    )                                          #设置训练集
    test_data = torchvision.datasets.MNIST(root='./data',train=False,transform=torchvision.transforms.ToTensor(),download=True)                      #设置测试集
    train_loader = Data.DataLoader(dataset=train_data,batch_size=BATCH_SIZE,shuffle=True)    #训练集中，shuffle必须为True 打乱次序
    test_loader = Data.DataLoader(dataset=test_data,batch_size=BATCH_SIZE,shuffle=False)
    
    # Neural Network Model
    class Net(torch.nn.Module):                                    # 设置DNN模型
        def __init__(self,n_feature,n_hidden,n_output):                      
            super(Net,self).__init__()
            self.hidden = torch.nn.Linear(n_feature,n_hidden)         #设置 输入层到隐含层
            self.relu = nn.ReLU()                                   #激活函数
            self.predict = torch.nn.Linear(n_hidden,n_output)       #隐含层到输出层
    
        def forward(self, x):                       
            out = self.hidden(x)
            out = self.relu(out)
            out = self.predict(out)
            return out
    
    net = Net(784,100,10)                                         
    print(net)
    
    # Loss and Optimizer
    optimizer = torch.optim.SGD(net.parameters(),lr=LR)
    loss_func = nn.CrossEntropyLoss()
    
    
    Loss_list = []                      #创建一个list，以便后续可视化
    Accuracy_list = []
    
    
    #Train the Model
    for epoch in range(EPOCH):
        running_loss = 0
        running_acc = 0
        for i, (images, labels) in enumerate(train_loader):  #批处理
            images = Variable(images.view(-1, 28*28))
            labels = Variable(labels)  #Convert torch tensor to Variable 将数据用Variable包起来输入模型中
    
    
    
            outputs = net(images)                     #前向传播，将包好的数据输入net
            loss = loss_func(outputs, labels)           #损失函数
            running_loss += loss.item()*labels.size(0)    #由于loss是batch取均值的，所以把要把batch size乘回去
            _,pred = torch.max(outputs,1)               #预测结果
            num_correct = (pred == labels).sum()          
            running_acc += num_correct.item()              #正确结果的总数
            optimizer.zero_grad()       #梯度清零 以免影响其他batch
            loss.backward()             #反向传播
            optimizer.step()            #梯度更新
    
    
        print('Train{} epoch, Loss: {:.6f},Acc: {:.6f}'.format(epoch + 1, running_loss / (len(train_data)),running_acc / (len(train_data)))) 输出每个epoch的 loss 和 acc
              
        Loss_list.append(running_loss / (len(train_data)))         
        Accuracy_list.append(running_acc / (len(train_data)))
     # 我这里迭代了10次，所以x的取值范围为(0，10)，然后再将每次相对应的准确率以及损失率附在x上
        x1 = range(0, 10)
        x2 = range(0, 10)
        y1 = Accuracy_list
        y2 = Loss_list
    plt.subplot(2, 1, 1)
    plt.plot(x1, y1, 'o-')
    plt.title('Test accuracy vs. epoches')
    plt.ylabel('Test accuracy')
    plt.subplot(2, 1, 2)
    plt.plot(x2, y2, '.-')
    plt.xlabel('epoches')
    plt.ylabel('Test loss')                     #将精确率可视化的过程
    
    
    #Test the model
    correct = 0
    total = 0
    for images, labels in test_loader:
        images = Variable(images.view(-1,28*28))
        outputs = net(images)
        _,predicted = torch.max(outputs.data,1)
        total +=labels.size(0)
        correct += (predicted == labels).sum()
    print('Accuracy of the network on the 10000 test images: %d %%' % (100*correct /total))

具体可视化过程参照：

> https://blog.csdn.net/tequilaro/article/details/81841748

结果  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODQzMjk2OA_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODQzMjk2OA_size_16_color_FFFFFF_t_70 1]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODQzMjk2OA_size_16_color_FFFFFF_t_70]: /images/20230528/a28cfbaa772c498593a23fc9f0c6c841.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zODQzMjk2OA_size_16_color_FFFFFF_t_70 1]: /images/20230528/b9f500c8f5094173b5bc3d281064f914.png