0014-pytorch入门-二分类迁移学习实战

浅浅的花香味﹌ 2023-01-07 10:29 145阅读 0赞

import torch
    import torch.nn as nn
    import torch.optim as optim
    from torch.optim import lr_scheduler
    from torch.utils.data import DataLoader
    import torchvision
    from torchvision.transforms import transforms
    from torchvision import models
    from torchvision.models import ResNet
    import numpy as np
    import matplotlib.pyplot as plt
    import os
    
    data_dir = "/hymenoptera_data/"
    
    train_dataset = torchvision.datasets.ImageFolder(root=os.path.join(data_dir, 'train'),
                                                     transform=transforms.Compose(
                                                         [
                                                             transforms.RandomResizedCrop(224),
                                                             transforms.RandomHorizontalFlip(),
                                                             transforms.ToTensor(),
                                                             transforms.Normalize(
                                                                 mean=(0.485, 0.456, 0.406),
                                                                 std=(0.229, 0.224, 0.225))
                                                         ]))
    
    val_dataset = torchvision.datasets.ImageFolder(root=os.path.join(data_dir, 'val'),
                                                   transform=transforms.Compose(
                                                         [
                                                             transforms.RandomResizedCrop(224),
                                                             transforms.RandomHorizontalFlip(),
                                                             transforms.ToTensor(),
                                                             transforms.Normalize(
                                                                 mean=(0.485, 0.456, 0.406),
                                                                 std=(0.229, 0.224, 0.225))
                                                         ]))
    
    
    train_dataloader = DataLoader(dataset=train_dataset,batch_size=4,shuffle=4)
    val_dataloder = DataLoader(dataset=val_dataset,batch_size=4,shuffle=4)
    
    #类别名称
    class_names = train_dataloader.classes
    print('class_names:{}'.format(class_names))
    
    #训练设备 cpu/GPU
    device = torch.device('cuda:0' if torch.cuda.is_available() else "cpu")
    print('train_device:{}'.format(device.type))
    
    #随机显示一个batch
    plt.figure()
    torchvision.utils.make_grid(next(iter(train_dataloader)))
    plt.imshow()
    
    # -------------------------模型选择，优化方法， 学习率策略----------------------
    model = models.resnet18(pretrained=True)
    
    #全联接层的输入通道in_channels个数
    num_fc_in = model.fc.in_features
    
    #改变全联接层，2分类问题，out_features = 2
    model.fc = nn.Linear(num_fc_in,2)
    
    #模型迁移到cpu/GPU
    model = model.to(device)
    
    #定义损失函数
    loss_fc = nn.CrossEntropyLoss()
    
    #选择优化方法
    optimizer = optim.SGD(model.parameters(),lr=0.0001,momentum=0.9)
    
    #学习率调整策略
    #每个7个epoch调整一次
    exp_lr_scheduler = lr_scheduler.StepLR(optimizer==optimizer,step_size=10,gamma=0.5) #step_size
    
    #train
    num_epochs = 50
    for epoch in range(num_epochs):
        running_loss = 0.0
        exp_lr_scheduler.step()
    
        for i,sample_batch in enumerate(train_dataloader):
            inputs = sample_batch[0]
            labels = sample_batch[1]
    
            model.train()
    
            #GPU /CPU
            inputs = inputs.to(device)
            labels = labels.to(device)
    
            optimizer.zero_grad()
    
            #forward
            outputs = model(inputs)
    
            #loss
            loss = loss_fc(outputs,labels)
    
            #loss求导，反向
            loss.backward()
    
            optimizer.step()
    
            running_loss += loss.item()
    
            #test
            if i%20==19:
                correct = 0
                total = 0
                model.eval()
                for images_test,labels_test in val_dataloder:
                    images_test = images_test.to(device)
                    labels_test = labels_test.to(device)
    
                    outputs_test = model(images_test)
                    _, prediction = torch.max(outputs_test, 1)
                    correct += (torch.sum((prediction == labels_test))).item()
                    # print(prediction, labels_test, correct)
                    total += labels_test.size(0)
                print('[{}, {}] running_loss = {:.5f} accurcay = {:.5f}'.format(epoch + 1, i + 1, running_loss / 20,
                                                                                correct / total))
                running_loss = 0.0
    
            # if i % 10 == 9:
            #     print('[{}, {}] loss={:.5f}'.format(epoch+1, i+1, running_loss / 10))
            #     running_loss = 0.0
    
        print('training finish !')
        # torch.save(model.state_dict(), './model/model_2.pth')