P5 运动鞋识别(动态学习率)(小白入门)

一、前期准备

1.设置GPU

import torch
import torch.nn as nn
import torchvision.transforms as transforms
import torchvision
from torchvision import transforms, datasets
import os,PIL,pathlib

device = torch.device("cuda" if torch.cuda.is_available else "cpu")
device

device(type=‘cuda’)

2.导入数据

import os,PIL,random,pathlib

data_dir = r"D:\z_temp\data\46-data"
data_dir = pathlib.Path(data_dir)

data_paths = list(data_dir.glob("*"))

classNames = [str(path).split("\\")[4]for path in data_paths]
classNames

[‘test’, ‘train’]

train_transforms = transforms.Compose([
    transforms.Resize([224,224]),
    transforms.ToTensor(),
    transforms.Normalize(
        mean=[0.485,0.456,0.406],
        std=[0.229,0.224,0.225]
    )
])
test_transforms = transforms.Compose([
    transforms.Resize([224,224]),
    transforms.ToTensor(),
    transforms.Normalize(
        mean=[0.485,0.456,0.406],
        std=[0.229,0.224,0.225]
    )
])
train_dataset = datasets.ImageFolder(r'D:/z_temp/data/46-data/train/' , transform = train_transforms)
test_dataset = datasets.ImageFolder(r'D:/z_temp/data/46-data/test/' , transform = test_transforms)
train_dataset.class_to_idx

{‘adidas’: 0, ‘nike’: 1}

batch_size = 32

train_dl = torch.utils.data.DataLoader(train_dataset,
                                      batch_size = batch_size,
                                      shuffle = True,
                                      num_workers = 1)
test_dl = torch.utils.data.DataLoader(test_dataset,
                                      batch_size = batch_size,
                                      shuffle = True,
                                      num_workers = 1)
for X,y in test_dl:
    print("shape of x [N,C,H,W]:",X.shape)
    print("shape of y:",y.shape,y.dtype)
    break

shape of x [N,C,H,W]: torch.Size([32, 3, 224, 224])
shape of y: torch.Size([32]) torch.int64

二、构建CNN网络

import torch.nn.functional as F

class Model(nn.Module):
    def __init__(self):
        super(Model,self).__init__()
        self.conv1 = nn.Sequential(
            nn.Conv2d(3,12,kernel_size = 5,padding = 0),
            nn.BatchNorm2d(12),
            nn.ReLU())#12*220*220
        self.conv2 = nn.Sequential(
            nn.Conv2d(12,12,kernel_size = 5,padding = 0),
            nn.BatchNorm2d(12),
            nn.ReLU())#12*216*216
        self.pool3 = nn.Sequential(
            nn.MaxPool2d(2))#12*108*108
        self.conv4 = nn.Sequential(
            nn.Conv2d(12,24,kernel_size = 5, padding = 0),
            nn.BatchNorm2d(24),
            nn.ReLU())#24*104*104
        self.conv5 = nn.Sequential(
            nn.Conv2d(24,24,kernel_size = 5, padding = 0),
            nn.BatchNorm2d(24),
            nn.ReLU())#24*100*100
        self.pool6 = nn.Sequential(
            nn.MaxPool2d(2))#24*50*50
        
        self.dropout = nn.Sequential(
            nn.Dropout(0.2))
        self.fc = nn.Sequential(
            nn.Linear(24*50*50,len(classNames)))
        
    def forward(self,x):
        batch_size = x.size(0)#?
        x = self.conv1(x)
        x = self.conv2(x)
        x = self.pool3(x)
        x = self.conv4(x)
        x = self.conv5(x)
        x = self.pool6(x)
        x = self.dropout(x)
        x = x.view(batch_size,-1)
        x = self.fc(x)
        
        return x

device = "cuda" if torch.cuda.is_available else "cpu"
print("Using {} device".format(device))

model = Model().to(device)
model

Model(
(conv1): Sequential(
(0): Conv2d(3, 12, kernel_size=(5, 5), stride=(1, 1))
(1): BatchNorm2d(12, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(2): ReLU()
)
(conv2): Sequential(
(0): Conv2d(12, 12, kernel_size=(5, 5), stride=(1, 1))
(1): BatchNorm2d(12, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(2): ReLU()
)
(pool3): Sequential(
(0): MaxPool2d(kernel_size=2, stride=2, padding=0, dilation=1, ceil_mode=False)
)
(conv4): Sequential(
(0): Conv2d(12, 24, kernel_size=(5, 5), stride=(1, 1))
(1): BatchNorm2d(24, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(2): ReLU()
)
(conv5): Sequential(
(0): Conv2d(24, 24, kernel_size=(5, 5), stride=(1, 1))
(1): BatchNorm2d(24, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
(2): ReLU()
)
(pool6): Sequential(
(0): MaxPool2d(kernel_size=2, stride=2, padding=0, dilation=1, ceil_mode=False)
)
(dropout): Sequential(
(0): Dropout(p=0.2, inplace=False)
)
(fc): Sequential(
(0): Linear(in_features=60000, out_features=2, bias=True)
)
)

三、训练模型

1.编写训练函数

# 训练循环
def train(dataloader, model, loss_fn, optimizer):
    size = len(dataloader.dataset)  # 训练集的大小
    num_batches = len(dataloader)   # 批次数目, (size/batch_size,向上取整)

    train_loss, train_acc = 0, 0  # 初始化训练损失和正确率
    
    for X, y in dataloader:  # 获取图片及其标签
        X, y = X.to(device), y.to(device)
        
        # 计算预测误差
        pred = model(X)          # 网络输出
        loss = loss_fn(pred, y)  # 计算网络输出和真实值之间的差距,targets为真实值,计算二者差值即为损失
        
        # 反向传播
        optimizer.zero_grad()  # grad属性归零
        loss.backward()        # 反向传播
        optimizer.step()       # 每一步自动更新
        
        # 记录acc与loss
        train_acc  += (pred.argmax(1) == y).type(torch.float).sum().item()
        train_loss += loss.item()
            
    train_acc  /= size
    train_loss /= num_batches

    return train_acc, train_loss

2.编写测试函数

def test (dataloader, model, loss_fn):
    size        = len(dataloader.dataset)  # 测试集的大小
    num_batches = len(dataloader)          # 批次数目, (size/batch_size,向上取整)
    test_loss, test_acc = 0, 0
    
    # 当不进行训练时,停止梯度更新,节省计算内存消耗
    with torch.no_grad():
        for imgs, target in dataloader:
            imgs, target = imgs.to(device), target.to(device)
            
            # 计算loss
            target_pred = model(imgs)
            loss        = loss_fn(target_pred, target)
            
            test_loss += loss.item()
            test_acc  += (target_pred.argmax(1) == target).type(torch.float).sum().item()

    test_acc  /= size
    test_loss /= num_batches

    return test_acc, test_loss

3.设置动态学习率

为什么要调整学习率?
前期(epoch 小):较大学习率 → 快速收敛
后期(epoch 大):较小学习率 → 更稳定,不跳过最优点

指数衰减 (Exponential Decay):是一种常见的学习率调节策略,保证模型在收敛前不会震荡太大。

这个策略相比 固定学习率 能更好地提高准确率,并减少训练震荡。

def adjust_learning_rate(optimizer, epoch, start_lr):
    # 每 2 个epoch衰减到原来的 0.92
    lr = start_lr * (0.92 ** (epoch // 2))
    for param_group in optimizer.param_groups:
        param_group['lr'] = lr

learn_rate = 1e-4 # 初始学习率
optimizer  = torch.optim.SGD(model.parameters(), lr=learn_rate)

4.正式训练

loss_fn    = nn.CrossEntropyLoss() # 创建损失函数
epochs     = 40

train_loss = []
train_acc  = []
test_loss  = []
test_acc   = []

for epoch in range(epochs):
    # 更新学习率(使用自定义学习率时使用)
    adjust_learning_rate(optimizer, epoch, learn_rate)
    
    model.train()
    epoch_train_acc, epoch_train_loss = train(train_dl, model, loss_fn, optimizer)
    # scheduler.step() # 更新学习率(调用官方动态学习率接口时使用)
    
    model.eval()
    epoch_test_acc, epoch_test_loss = test(test_dl, model, loss_fn)
    
    train_acc.append(epoch_train_acc)
    train_loss.append(epoch_train_loss)
    test_acc.append(epoch_test_acc)
    test_loss.append(epoch_test_loss)
    
    # 获取当前的学习率
    lr = optimizer.state_dict()['param_groups'][0]['lr']
    
    template = ('Epoch:{:2d}, Train_acc:{:.1f}%, Train_loss:{:.3f}, Test_acc:{:.1f}%, Test_loss:{:.3f}, Lr:{:.2E}')
    print(template.format(epoch+1, epoch_train_acc*100, epoch_train_loss, 
                          epoch_test_acc*100, epoch_test_loss, lr))
print('Done')

Epoch: 1, Train_acc:57.0%, Train_loss:0.746, Test_acc:50.0%, Test_loss:0.722, Lr:1.00E-04
Epoch: 2, Train_acc:60.2%, Train_loss:0.702, Test_acc:65.8%, Test_loss:0.635, Lr:1.00E-04
Epoch: 3, Train_acc:69.1%, Train_loss:0.598, Test_acc:67.1%, Test_loss:0.566, Lr:9.20E-05
Epoch: 4, Train_acc:71.9%, Train_loss:0.580, Test_acc:67.1%, Test_loss:0.615, Lr:9.20E-05
Epoch: 5, Train_acc:74.3%, Train_loss:0.532, Test_acc:68.4%, Test_loss:0.553, Lr:8.46E-05
Epoch: 6, Train_acc:74.3%, Train_loss:0.512, Test_acc:68.4%, Test_loss:0.547, Lr:8.46E-05
Epoch: 7, Train_acc:78.1%, Train_loss:0.488, Test_acc:69.7%, Test_loss:0.540, Lr:7.79E-05
Epoch: 8, Train_acc:80.3%, Train_loss:0.461, Test_acc:72.4%, Test_loss:0.551, Lr:7.79E-05
Epoch: 9, Train_acc:83.3%, Train_loss:0.448, Test_acc:67.1%, Test_loss:0.521, Lr:7.16E-05
Epoch:10, Train_acc:85.7%, Train_loss:0.416, Test_acc:72.4%, Test_loss:0.531, Lr:7.16E-05
Epoch:11, Train_acc:81.5%, Train_loss:0.432, Test_acc:75.0%, Test_loss:0.483, Lr:6.59E-05
Epoch:12, Train_acc:86.9%, Train_loss:0.394, Test_acc:73.7%, Test_loss:0.540, Lr:6.59E-05
Epoch:13, Train_acc:86.1%, Train_loss:0.390, Test_acc:78.9%, Test_loss:0.489, Lr:6.06E-05
Epoch:14, Train_acc:86.7%, Train_loss:0.378, Test_acc:77.6%, Test_loss:0.521, Lr:6.06E-05
Epoch:15, Train_acc:86.9%, Train_loss:0.366, Test_acc:73.7%, Test_loss:0.489, Lr:5.58E-05
Epoch:16, Train_acc:88.4%, Train_loss:0.357, Test_acc:76.3%, Test_loss:0.477, Lr:5.58E-05
Epoch:17, Train_acc:88.4%, Train_loss:0.355, Test_acc:76.3%, Test_loss:0.539, Lr:5.13E-05
Epoch:18, Train_acc:89.8%, Train_loss:0.350, Test_acc:75.0%, Test_loss:0.496, Lr:5.13E-05
Epoch:19, Train_acc:90.8%, Train_loss:0.339, Test_acc:77.6%, Test_loss:0.499, Lr:4.72E-05
Epoch:20, Train_acc:90.4%, Train_loss:0.330, Test_acc:76.3%, Test_loss:0.454, Lr:4.72E-05
Epoch:21, Train_acc:91.0%, Train_loss:0.320, Test_acc:75.0%, Test_loss:0.448, Lr:4.34E-05
Epoch:22, Train_acc:92.4%, Train_loss:0.318, Test_acc:78.9%, Test_loss:0.473, Lr:4.34E-05
Epoch:23, Train_acc:91.4%, Train_loss:0.315, Test_acc:76.3%, Test_loss:0.442, Lr:4.00E-05
Epoch:24, Train_acc:93.2%, Train_loss:0.305, Test_acc:77.6%, Test_loss:0.475, Lr:4.00E-05
Epoch:25, Train_acc:90.4%, Train_loss:0.317, Test_acc:76.3%, Test_loss:0.466, Lr:3.68E-05
Epoch:26, Train_acc:91.0%, Train_loss:0.313, Test_acc:77.6%, Test_loss:0.422, Lr:3.68E-05
Epoch:27, Train_acc:91.6%, Train_loss:0.299, Test_acc:78.9%, Test_loss:0.475, Lr:3.38E-05
Epoch:28, Train_acc:91.4%, Train_loss:0.296, Test_acc:77.6%, Test_loss:0.425, Lr:3.38E-05
Epoch:29, Train_acc:93.0%, Train_loss:0.292, Test_acc:80.3%, Test_loss:0.425, Lr:3.11E-05
Epoch:30, Train_acc:93.0%, Train_loss:0.282, Test_acc:78.9%, Test_loss:0.431, Lr:3.11E-05
Epoch:31, Train_acc:93.2%, Train_loss:0.287, Test_acc:77.6%, Test_loss:0.415, Lr:2.86E-05
Epoch:32, Train_acc:93.8%, Train_loss:0.285, Test_acc:76.3%, Test_loss:0.481, Lr:2.86E-05
Epoch:33, Train_acc:92.4%, Train_loss:0.289, Test_acc:78.9%, Test_loss:0.461, Lr:2.63E-05
Epoch:34, Train_acc:92.8%, Train_loss:0.276, Test_acc:77.6%, Test_loss:0.433, Lr:2.63E-05
Epoch:35, Train_acc:93.8%, Train_loss:0.286, Test_acc:78.9%, Test_loss:0.436, Lr:2.42E-05
Epoch:36, Train_acc:93.2%, Train_loss:0.269, Test_acc:77.6%, Test_loss:0.463, Lr:2.42E-05
Epoch:37, Train_acc:94.2%, Train_loss:0.278, Test_acc:77.6%, Test_loss:0.459, Lr:2.23E-05
Epoch:38, Train_acc:94.2%, Train_loss:0.272, Test_acc:78.9%, Test_loss:0.399, Lr:2.23E-05
Epoch:39, Train_acc:94.2%, Train_loss:0.268, Test_acc:78.9%, Test_loss:0.449, Lr:2.05E-05
Epoch:40, Train_acc:94.0%, Train_loss:0.272, Test_acc:78.9%, Test_loss:0.448, Lr:2.05E-05
Done

四、结果可视化

1.lcc和acc图

import matplotlib.pyplot as plt
#隐藏警告
import warnings
warnings.filterwarnings("ignore")               #忽略警告信息
plt.rcParams['font.sans-serif']    = ['SimHei'] # 用来正常显示中文标签
plt.rcParams['axes.unicode_minus'] = False      # 用来正常显示负号
plt.rcParams['figure.dpi']         = 100        #分辨率

from datetime import datetime
current_time = datetime.now() # 获取当前时间

epochs_range = range(epochs)

plt.figure(figsize=(12, 3))
plt.subplot(1, 2, 1)

plt.plot(epochs_range, train_acc, label='Training Accuracy')
plt.plot(epochs_range, test_acc, label='Test Accuracy')
plt.legend(loc='lower right')
plt.title('Training and Validation Accuracy')
plt.xlabel(current_time) # 打卡请带上时间戳,否则代码截图无效

plt.subplot(1, 2, 2)
plt.plot(epochs_range, train_loss, label='Training Loss')
plt.plot(epochs_range, test_loss, label='Test Loss')
plt.legend(loc='upper right')
plt.title('Training and Validation Loss')
plt.show()

请添加图片描述

2.指定图片预测

from PIL import Image 

classes = list(train_dataset.class_to_idx)

def predict_one_image(image_path, model, transform, classes):
    
    test_img = Image.open(image_path).convert('RGB')
    # plt.imshow(test_img)  # 展示预测的图片

    test_img = transform(test_img)
    img = test_img.to(device).unsqueeze(0)
    
    model.eval()
    output = model(img)

    _,pred = torch.max(output,1)
    pred_class = classes[pred]
    print(f'预测结果是:{pred_class}')
# 预测训练集中的某张照片
predict_one_image(image_path=r'D:/z_temp/data/46-data/test/adidas/1.jpg', 
                  model=model, 
                  transform=train_transforms, 
                  classes=classes)

预测结果是:adidas

五、优化

def adjust_learning_rate(optimizer, epoch, start_lr):
    # 每 4 个epoch衰减到原来的 0.92
    lr = start_lr * (0.92 ** (epoch // 4))
    for param_group in optimizer.param_groups:
        param_group['lr'] = lr

learn_rate = 1e-4 # 初始学习率
optimizer  = torch.optim.SGD(model.parameters(), lr=learn_rate)

Epoch: 1, Train_acc:49.2%, Train_loss:0.777, Test_acc:56.6%, Test_loss:0.681, Lr:1.00E-04
Epoch: 2, Train_acc:58.0%, Train_loss:0.678, Test_acc:69.7%, Test_loss:0.624, Lr:1.00E-04
Epoch: 3, Train_acc:67.5%, Train_loss:0.613, Test_acc:71.1%, Test_loss:0.604, Lr:1.00E-04
Epoch: 4, Train_acc:69.7%, Train_loss:0.577, Test_acc:68.4%, Test_loss:0.568, Lr:1.00E-04
Epoch: 5, Train_acc:73.5%, Train_loss:0.526, Test_acc:72.4%, Test_loss:0.526, Lr:9.20E-05
Epoch: 6, Train_acc:75.5%, Train_loss:0.507, Test_acc:75.0%, Test_loss:0.512, Lr:9.20E-05
Epoch: 7, Train_acc:81.5%, Train_loss:0.456, Test_acc:76.3%, Test_loss:0.508, Lr:9.20E-05
Epoch: 8, Train_acc:79.9%, Train_loss:0.450, Test_acc:78.9%, Test_loss:0.504, Lr:9.20E-05
Epoch: 9, Train_acc:81.3%, Train_loss:0.431, Test_acc:77.6%, Test_loss:0.456, Lr:8.46E-05
Epoch:10, Train_acc:83.1%, Train_loss:0.409, Test_acc:76.3%, Test_loss:0.502, Lr:8.46E-05
Epoch:11, Train_acc:87.1%, Train_loss:0.392, Test_acc:73.7%, Test_loss:0.471, Lr:8.46E-05
Epoch:12, Train_acc:86.1%, Train_loss:0.383, Test_acc:78.9%, Test_loss:0.442, Lr:8.46E-05
Epoch:13, Train_acc:87.5%, Train_loss:0.371, Test_acc:78.9%, Test_loss:0.450, Lr:7.79E-05
Epoch:14, Train_acc:87.8%, Train_loss:0.359, Test_acc:78.9%, Test_loss:0.436, Lr:7.79E-05
Epoch:15, Train_acc:90.2%, Train_loss:0.338, Test_acc:80.3%, Test_loss:0.461, Lr:7.79E-05
Epoch:16, Train_acc:89.8%, Train_loss:0.335, Test_acc:82.9%, Test_loss:0.437, Lr:7.79E-05
Epoch:17, Train_acc:90.4%, Train_loss:0.335, Test_acc:82.9%, Test_loss:0.466, Lr:7.16E-05
Epoch:18, Train_acc:91.8%, Train_loss:0.316, Test_acc:75.0%, Test_loss:0.452, Lr:7.16E-05
Epoch:19, Train_acc:90.2%, Train_loss:0.323, Test_acc:81.6%, Test_loss:0.438, Lr:7.16E-05
Epoch:20, Train_acc:92.4%, Train_loss:0.305, Test_acc:82.9%, Test_loss:0.417, Lr:7.16E-05
Epoch:21, Train_acc:94.2%, Train_loss:0.284, Test_acc:82.9%, Test_loss:0.461, Lr:6.59E-05
Epoch:22, Train_acc:93.4%, Train_loss:0.285, Test_acc:82.9%, Test_loss:0.440, Lr:6.59E-05
Epoch:23, Train_acc:92.4%, Train_loss:0.280, Test_acc:82.9%, Test_loss:0.411, Lr:6.59E-05
Epoch:24, Train_acc:93.4%, Train_loss:0.282, Test_acc:82.9%, Test_loss:0.390, Lr:6.59E-05
Epoch:25, Train_acc:94.0%, Train_loss:0.270, Test_acc:84.2%, Test_loss:0.384, Lr:6.06E-05
Epoch:26, Train_acc:93.6%, Train_loss:0.266, Test_acc:81.6%, Test_loss:0.461, Lr:6.06E-05
Epoch:27, Train_acc:93.2%, Train_loss:0.270, Test_acc:84.2%, Test_loss:0.452, Lr:6.06E-05
Epoch:28, Train_acc:94.2%, Train_loss:0.258, Test_acc:82.9%, Test_loss:0.398, Lr:6.06E-05
Epoch:29, Train_acc:94.4%, Train_loss:0.249, Test_acc:85.5%, Test_loss:0.422, Lr:5.58E-05
Epoch:30, Train_acc:95.4%, Train_loss:0.246, Test_acc:81.6%, Test_loss:0.408, Lr:5.58E-05
Epoch:31, Train_acc:94.4%, Train_loss:0.243, Test_acc:86.8%, Test_loss:0.409, Lr:5.58E-05
Epoch:32, Train_acc:96.8%, Train_loss:0.237, Test_acc:82.9%, Test_loss:0.399, Lr:5.58E-05
Epoch:33, Train_acc:95.2%, Train_loss:0.237, Test_acc:82.9%, Test_loss:0.416, Lr:5.13E-05
Epoch:34, Train_acc:95.6%, Train_loss:0.244, Test_acc:81.6%, Test_loss:0.411, Lr:5.13E-05
Epoch:35, Train_acc:95.0%, Train_loss:0.229, Test_acc:85.5%, Test_loss:0.442, Lr:5.13E-05
Epoch:36, Train_acc:96.0%, Train_loss:0.227, Test_acc:81.6%, Test_loss:0.377, Lr:5.13E-05
Epoch:37, Train_acc:96.4%, Train_loss:0.224, Test_acc:81.6%, Test_loss:0.370, Lr:4.72E-05
Epoch:38, Train_acc:97.0%, Train_loss:0.221, Test_acc:82.9%, Test_loss:0.446, Lr:4.72E-05
Epoch:39, Train_acc:96.4%, Train_loss:0.214, Test_acc:81.6%, Test_loss:0.391, Lr:4.72E-05
Epoch:40, Train_acc:96.8%, Train_loss:0.216, Test_acc:84.2%, Test_loss:0.396, Lr:4.72E-05
Done
请添加图片描述

前期(epoch 小):较大学习率 → 快速收敛
后期(epoch 大):较小学习率 → 更稳定
能看到简单地将每2个epoch衰减,修改为将每4个epoch衰减,让前期保持学习率较大,提高收敛速度,acc就有了一些提高。

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