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知识点回顾：

1.过拟合的判断：测试集和训练集同步打印指标

2.模型的保存和加载 a.仅保存权重 b.保存权重和模型 c.保存全部信息checkpoint，还包含训练状态

3.早停策略

作业：对信贷数据集训练后保存权重，加载权重后继续训练50轮，并采取早停策略

首先对信贷数据集进行训练后保存权重

import torch
import pandas as pd
import torch.nn as nn
import torch.optim as optim
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import MinMaxScaler
import time
import matplotlib.pyplot as plt# 替换import numpy as np     #用于数值计算，提供了高效的数组操作。
import matplotlib.pyplot as plt    #用于绘制各种类型的图表
import seaborn as sns   #基于matplotlib的高级绘图库，能绘制更美观的统计图形。
from tqdm import tqdm # 设置GPU设备
device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
print(f"使用设备: {device}")# 设置中文字体（解决中文显示问题）
plt.rcParams['font.sans-serif'] = ['SimHei']  # Windows系统常用黑体字体
plt.rcParams['axes.unicode_minus'] = False    # 正常显示负号
data = pd.read_csv(r'C:\Users\许兰\Desktop\打卡文件\python60-days-challenge-master\data.csv')    #读取数据# 先筛选字符串变量 
discrete_features = data.select_dtypes(include=['object']).columns.tolist()
# Home Ownership 标签编码
home_ownership_mapping = {'Own Home': 1,'Rent': 2,'Have Mortgage': 3,'Home Mortgage': 4
}
data['Home Ownership'] = data['Home Ownership'].map(home_ownership_mapping)# Years in current job 标签编码
years_in_job_mapping = {'< 1 year': 1,'1 year': 2,'2 years': 3,'3 years': 4,'4 years': 5,'5 years': 6,'6 years': 7,'7 years': 8,'8 years': 9,'9 years': 10,'10+ years': 11
}
data['Years in current job'] = data['Years in current job'].map(years_in_job_mapping)# Purpose 独热编码，记得需要将bool类型转换为数值
data = pd.get_dummies(data, columns=['Purpose'])
data2 = pd.read_csv(r'C:\Users\许兰\Desktop\打卡文件\python60-days-challenge-master\data.csv') # 重新读取数据，用来做列名对比
list_final = [] # 新建一个空列表，用于存放独热编码后新增的特征名
for i in data.columns:if i not in data2.columns:list_final.append(i) # 这里打印出来的就是独热编码后的特征名
for i in list_final:data[i] = data[i].astype(int) # 这里的i就是独热编码后的特征名# Term 0 - 1 映射
term_mapping = {'Short Term': 0,'Long Term': 1
}
data['Term'] = data['Term'].map(term_mapping)
data.rename(columns={'Term': 'Long Term'}, inplace=True) # 重命名列
continuous_features = data.select_dtypes(include=['int64', 'float64']).columns.tolist()  #把筛选出来的列名转换成列表# 连续特征用中位数补全
for feature in continuous_features:     mode_value = data[feature].mode()[0]            #获取该列的众数。data[feature].fillna(mode_value, inplace=True)          #用众数填充该列的缺失值，inplace=True表示直接在原数据上# 划分训练集、验证集和测试集，因为需要考2次
# 这里演示一下如何2次划分数据集，因为这个函数只能划分一次，所以需要调用两次才能划分出训练集、验证集和测试集。
from sklearn.model_selection import train_test_split
X = data.drop(['Credit Default'], axis=1)  # 特征，axis=1表示按列删除
y = data['Credit Default']  # 标签
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)  # 80%训练集，20%临时集# 归一化数据
scaler = MinMaxScaler()
X_train = scaler.fit_transform(X_train)
X_test = scaler.transform(X_test)X_train = torch.FloatTensor(X_train).to(device)
y_train = torch.LongTensor(y_train.to_numpy()).to(device)
X_test = torch.FloatTensor(X_test).to(device)
y_test = torch.LongTensor(y_test).to(device)class MLP(nn.Module):def __init__(self):super(MLP, self).__init__()self.fc1 = nn.Linear(31, 18)  # 输入层到隐藏层self.relu = nn.ReLU()self.fc2 = nn.Linear(18, 2)  # 隐藏层到输出层def forward(self, x):out = self.fc1(x)out = self.relu(out)out = self.fc2(out)return out# 实例化模型并移至GPU
model = MLP()# 分类问题使用交叉熵损失函数
criterion = nn.CrossEntropyLoss()# 使用随机梯度下降优化器
optimizer = optim.SGD(model.parameters(), lr=0.01)# 训练模型
num_epochs = 20000  # 训练的轮数# 用于存储每100个epoch的损失值和对应的epoch数
train_losses = []
test_losses = []
epochs = []# ===== 新增早停相关参数 =====
best_test_loss = float('inf')  # 记录最佳测试集损失
best_epoch = 0                 # 记录最佳epoch
patience = 50                # 早停耐心值（连续多少轮测试集损失未改善时停止训练）
counter = 0                    # 早停计数器
early_stopped = False      
start_time = time.time()  # 记录开始时间# 创建tqdm进度条
with tqdm(total=num_epochs, desc="训练进度", unit="epoch") as pbar:# 训练模型for epoch in range(num_epochs):# 前向传播outputs = model(X_train)  # 隐式调用forward函数train_loss = criterion(outputs, y_train)# 反向传播和优化optimizer.zero_grad()train_loss.backward()optimizer.step()# 记录损失值并更新进度条if (epoch + 1) % 200 == 0:model.eval()with torch.no_grad():test_outputs = model(X_test)test_loss = criterion(test_outputs, y_test)model.train()train_losses.append(train_loss.item())test_losses.append(test_loss.item())epochs.append(epoch + 1)# 更新进度条的描述信息pbar.set_postfix({'Train Loss': f'{train_loss.item():.4f}', 'Test Loss': f'{test_loss.item():.4f}'})# ===== 新增早停逻辑 =====if test_loss.item() < best_test_loss: # 如果当前测试集损失小于最佳损失best_test_loss = test_loss.item() # 更新最佳损失best_epoch = epoch + 1 # 更新最佳epochcounter = 0 # 重置计数器# 保存最佳模型torch.save(model.state_dict(), 'best_model.pth')else:counter += 1if counter >= patience:print(f"早停触发！在第{epoch+1}轮，测试集损失已有{patience}轮未改善。")print(f"最佳测试集损失出现在第{best_epoch}轮，损失值为{best_test_loss:.4f}")early_stopped = Truebreak  # 终止训练循环# ======================# 每1000个epoch更新一次进度条if (epoch + 1) % 1000 == 0:pbar.update(1000)  # 更新进度条# 确保进度条达到100%if pbar.n < num_epochs:pbar.update(num_epochs - pbar.n)  # 计算剩余的进度并更新time_all = time.time() - start_time  # 计算训练时间
print(f'Training time: {time_all:.2f} seconds')# ===== 新增：加载最佳模型用于最终评估 =====
if early_stopped:print(f"加载第{best_epoch}轮的最佳模型进行最终评估...")model.load_state_dict(torch.load('best_model.pth'))
# 可视化损失曲线
plt.figure(figsize=(10, 6))
plt.plot(epochs, train_losses, label='Train Loss') # 原始代码已有
plt.plot(epochs, test_losses, label='Test Loss')  # 新增：测试集损失曲线
plt.xlabel('Epoch')
plt.ylabel('Loss')
plt.title('Training and Test Loss over Epochs')
plt.legend() # 新增：显示图例
plt.grid(True)
plt.show()model.eval() # 设置模型为评估模式
with torch.no_grad(): # torch.no_grad()的作用是禁用梯度计算，可以提高模型推理速度outputs = model(X_test)  # 对测试数据进行前向传播，获得预测结果_, predicted = torch.max(outputs, 1) # torch.max(outputs, 1)返回每行的最大值和对应的索引correct = (predicted == y_test).sum().item() # 计算预测正确的样本数accuracy = correct / y_test.size(0)print(f'测试集准确率: {accuracy * 100:.2f}%')
torch.save(model.state_dict(), "model_weights.pth")

 保存权重后的模型损失曲线

测试集准确率

 

采取早停策略后

 

 

并没有触发早停策略

@浙大疏锦行