卷积神经网络--猫狗系列【VGG16】

数据集：【文末】

数据集预处理

定义读取数据辅助类（继承torch.utils.data.Dataset）

import osimport PILimport torchimport torchvisionimport matplotlib.pyplot as pltimport torch.utils.dataimport PIL.Image
# 数据集路径train_path = './train'test_path = './test'device = torch.device("cuda" if torch.cuda.is_available() else "cpu")class MyDataset(torch.utils.data.Dataset):    def __init__(self, data_path: str, train=True, transform=None):        self.data_path = data_path        self.train_flag = train        if transform is None:            self.transform = torchvision.transforms.Compose(                [                    torchvision.transforms.Resize(size=(224, 224)),  # 尺寸规范                    torchvision.transforms.ToTensor(),  # 转化为tensor                    torchvision.transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)),  # 归一化                ])        else:            self.transform = transform        self.path_list = os.listdir(data_path)  # 列出所有图片命名    def __getitem__(self, idx: int):        img_path = self.path_list[idx]        if self.train_flag is True:            # 例如 img_path 值 cat.10844.jpg -> label = 0            if img_path.split('.')[0] == 'dog':                label = 1            else:                label = 0        else:            label = int(img_path.split('.')[0])  # 获取test数据的编号        label = torch.tensor(label, dtype=torch.int64)  # 把标签转换成int64        img_path = os.path.join(self.data_path, img_path)  # 合成图片路径        img = PIL.Image.open(img_path)  # 读取图片        img = self.transform(img)  # 把图片转换成tensor        return img, label    def __len__(self) -> int:        return len(self.path_list)  # 返回图片数量train_datas = MyDataset(train_path)test_datas = MyDataset(test_path, train=False)

（原本数据有25000张，由于设备的原因，训练完之后我删掉了很多图片，训练集+测试集只有2000张）

查看读取的数据

# 展示读取的图片数据，因为做了归一化，所有图片显示不正常。Img_PIL_Tensor = train_datas[20][0]new_img_PIL = torchvision.transforms.ToPILImage()(Img_PIL_Tensor).convert('RGB')plt.imshow(new_img_PIL)plt.show(block=True)

训练集和测试集分组，数据分batch

（根据自己的设备来，好的就设32，不好就4吧）

# 70%训练集  30%测试集train_size = int(0.7 * len(train_datas))validate_size = len(train_datas) - train_sizetrain_datas,validate_datas = torch.utils.data.random_split(train_datas,[train_size, validate_size])# 数据分批# batch_size=32 每一个batch大小为32# shuffle=True 打乱分组# pin_memory=True 锁页内存，数据不会因内存不足，交换到虚拟内存中，能加快数据读入到GPU显存中.# num_workers 线程数。num_worker设置越大，加载batch就会很快，训练迭代结束可能下一轮batch已经加载好# win10 设置会多线程可能会出现问题，一般设置0.train_loader = torch.utils.data.DataLoader(train_datas, batch_size=4,                                            shuffle=True, pin_memory=True, num_workers=0)validate_loader = torch.utils.data.DataLoader(validate_datas, batch_size=4,                                            shuffle=True, pin_memory=True, num_workers=0)test_loader = torch.utils.data.DataLoader(test_datas, batch_size=4,                                            shuffle=False, pin_memory=True, num_workers=0)

VGG网络：

def vgg_block(num_convs, in_channels, out_channels):    layers = []    for _ in range(num_convs):        layers.append(torch.nn.Conv2d(in_channels, out_channels, kernel_size=3, padding=1))        layers.append(torch.nn.ReLU())        in_channels = out_channels    # ceil_mode=False 输入的形状不是kernel_size的倍数，直接不要。    # ceil_mode=True 输入的形状不是kernel_size的倍数，单独计算。    layers.append(torch.nn.MaxPool2d(kernel_size=2, stride=2, ceil_mode=False))    return torch.nn.Sequential(*layers)def vgg(conv_arch):    conv_blks = []    # 数据输入是几个通道    in_channels = 3    # 卷积层部分    for (num_convs, out_channels) in conv_arch:        conv_blks.append(vgg_block(num_convs, in_channels, out_channels))        in_channels = out_channels    return torch.nn.Sequential(        *conv_blks, torch.nn.Flatten(),        torch.nn.Linear(out_channels * 7 * 7, 4096), torch.nn.ReLU(), torch.nn.Dropout(0.5),        torch.nn.Linear(4096, 4096), torch.nn.ReLU(), torch.nn.Dropout(0.5),        torch.nn.Linear(4096, 2))

VGG神经网络定义和参数初始化

# VGG11，VGG13，VGG16，VGG19 可自行更换。conv_arch = ((2, 64), (2, 128), (3, 256), (3, 512), (3, 512))  # vgg16#conv_arch = ((1, 64), (1, 128), (2, 256), (2, 512), (2, 512))  # vgg11#conv_arch = ((2, 64), (2, 128), (2 , 256), (2, 512), (2, 512))  # vgg13#conv_arch = ((2, 64), (2, 128), (4, 256), (4, 512), (4, 512))  # vgg19net = vgg(conv_arch)   # 定义网络net = net.to(device)   # 把网络加载到GPU上# Xavier方法 初始化网络参数，最开始没有初始化一直训练不起来。def init_normal(m):    if type(m) == torch.nn.Linear:        # Xavier初始化        torch.nn.init.xavier_uniform_(m.weight)        torch.nn.init.zeros_(m.bias)    if type(m) == torch.nn.Conv2d:        # Xavier初始化        torch.nn.init.xavier_uniform_(m.weight)        torch.nn.init.zeros_(m.bias)net.apply(init_normal)learn_rate = 1e-5#momentum = 0.9#optimizer = torch.optim.SGD(net.parameters(), learn_rate, momentum = momentum) #定义梯度优化算法optimizer = torch.optim.Adam(net.parameters(), learn_rate) #开始使用SGD没有训练起来，才更换的Adamcost = torch.nn.CrossEntropyLoss(reduction='sum')     # 定义损失函数，返回batch的loss和。print(net)    # 打印模型架构

训练VGG神经网络

epoch = 10  # 迭代10次def train_model(net, train_loader, validate_loader, cost, optimezer):    net.train()  # 训练模式    now_loss = 1e9  # flag 计算当前最优loss    train_ls = []  # 记录在训练集上每个epoch的loss的变化情况    train_acc = []  # 记录在训练集上每个epoch的准确率的变化情况    for i in range(epoch):        loss_epoch = 0.  # 保存当前epoch的loss和        correct_epoch = 0  # 保存当前epoch的正确个数和        for j, (data, label) in enumerate(train_loader):            data, label = data.to(device), label.to(device)            pre = net(data)            # 计算当前batch预测正确个数            correct_epoch += torch.sum(pre.argmax(dim=1).view(-1) == label.view(-1)).item()            loss = cost(pre, label)            loss_epoch += loss.item()            optimezer.zero_grad()            loss.backward()            optimezer.step()            if j % 100 == 0:                print(                    f'batch_loss:{loss.item()}, batch_acc:{torch.sum(pre.argmax(dim=1).view(-1) == label.view(-1)).item() / len(label)}%')        train_ls.append(loss_epoch / train_size)        train_acc.append(correct_epoch / train_size)        # 每一个epoch结束后，在验证集上验证实验结果。        with torch.no_grad():            loss_validate = 0.            correct_validate = 0            for j, (data, label) in enumerate(validate_loader):                data, label = data.to(device), label.to(device)                pre = net(data)                correct_validate += torch.sum(pre.argmax(dim=1).view(-1) == label.view(-1)).item()                loss = cost(pre, label)                loss_validate += loss.item()            # print(f'validate_sum:{loss_validate},  validate_Acc:{correct_validate}')            print(f'validate_Loss:{loss_validate / validate_size},  validate_Acc:{correct_validate / validate_size}%')            # 保存当前最优模型参数            if now_loss > loss_validate:                now_loss = loss_validate                print("保存模型参数。。。。。。。。。。。")                torch.save(net.state_dict(), 'model.params')    # 画图    plt.plot(range(epoch), train_ls, color='b', label='loss')    plt.plot(range(epoch), train_acc, color='g', label='acc')    plt.legend()    plt.show(block=True)  # 显示 labletrain_model(net, train_loader, validate_loader, cost, optimizer)