0026-pytorch入门-图片二分类在VGG16基础上finetune

Bertha 。 2023-01-10 13:24 99阅读 0赞

# -*- coding: utf-8 -*-
    """
    Created on ${DATE} ${TIME}
    @author: Johnson
    Email:593956670@qq.com
    """
    import torch
    import torchvision
    
    #prepare
    model1_vgg16 = torchvision.models.vgg16(pretrained=True)
    
    
    #设置网络参数
    #读取输入特征的维度
    num_fc = model1_vgg16.classifier[6].in_features
    #修改最后一层的输出维度，即分类数
    model1_vgg16.classifier[6] = torch.nn.Linear(num_fc,2)
    
    #固定权值参数
    #对于模型的每个权重，使其不进行反向传播，即固定参数
    for param in model1_vgg16.parameters():
        param.requires_grad = False
    #但是参数全部固定了，也没法进行学习，所以我们不固定最后一层，即全连接层
    for param in model1_vgg16.classifier[6].parameters():
        param.requires_grad = True
    
    #训练模型
    import numpy as np
    from torchvision import transforms,utils
    from torch.utils.data import DataLoader
    from torch.autograd import Variable
    
    #加载图片
    ##这种读取图片的方式用的是Torch自带的ImageFloder,读取的文件夹必须在一个大的子文件下，按类别归好类
    
    
    #train data
    train_data = torchvision.datasets.ImageFolder("C:/datafolder/hymenoptera_data/train",transform=transforms.Compose(
        [
            transforms.Resize(256),
            transforms.CenterCrop(224),
            transforms.ToTensor()
        ]))
    
    train_loader = DataLoader(train_data,batch_size=20,shuffle=True)
    
    #test data
    test_data = torchvision.datasets.ImageFolder("C:/datafolder/hymenoptera_data/val",transform=transforms.Compose(
        [
            transforms.Resize(256),
            transforms.CenterCrop(224),
            transforms.ToTensor()
        ]))
    
    test_loader = DataLoader(test_data,batch_size=20,shuffle=True)
    
    #训练
    ## 定义自己的优化器
    criterion = torch.nn.CrossEntropyLoss()
    optimizer = torch.optim.Adam(model1_vgg16.parameters(),lr=0.001)
    
    
    #训练模型
    EPOCH = 20
    for epoch in range(EPOCH):
        train_loss = 0.
        train_acc = 0.
        for step, data in enumerate(train_loader):
            batch_x, batch_y = data
            batch_x, batch_y = Variable(batch_x), Variable(batch_y)
            # batch_y not one hot
            # out is the probability of eatch class
            # such as one sample[-1.1009  0.1411  0.0320],need to calculate the max index
            # out shape is batch_size * class
            out = model1_vgg16(batch_x)
            loss = criterion(out, batch_y)
            train_loss += loss.item()
            # pred is the expect class
            # batch_y is the true label
            pred = torch.max(out, 1)[1]
            train_correct = (pred == batch_y).sum()
            train_acc += train_correct.item()
            optimizer.zero_grad()
            loss.backward()
            optimizer.step()
            if step % 100 == 0:
                print('Epoch: ', epoch, 'Step', step,
                      'Train_loss: ', train_loss / ((step + 1) * 20), 'Train acc: ', train_acc / ((step + 1) * 20))
    
        print('Epoch: ', epoch, 'Train_loss: ', train_loss / len(train_data), 'Train acc: ', train_acc / len(train_data))
    
    
    #测试
    model1_vgg16.eval()
    eval_loss = 0
    eval_acc = 0
    for step,data in enumerate(test_loader):
        batch_x,batch_y = data
        batch_x,batch_y = Variable(batch_x),Variable(batch_y)
        out = model1_vgg16(batch_x)
        loss = criterion(out,batch_y)
        eval_loss+=loss.item()
        #pred is the expect class
        #batch_y is the true label
        pred = torch.max(out,1)[1]
        test_correct = (pred==batch_y).sum()
        eval_acc += test_correct.item()
    print('Test_loss: ', eval_loss / len(test_data), 'Test acc: ', eval_acc / len(test_data))