DAY 53 对抗生成网络

知识点回顾：

1. 对抗生成网络的思想：关注损失从何而来
2. 生成器、判别器
3. nn.sequential容器：适合于按顺序运算的情况，简化前向传播写法
4. leakyReLU介绍：避免relu的神经元失活现象

ps；如果你学有余力，对于gan的损失函数的理解，建议去找找视频看看，如果只是用，没必要学

**作业：**对于心脏病数据集，对于病人这个不平衡的样本用GAN来学习并生成病人样本，观察不用GAN和用GAN的F1分数差异。

import numpy as np
import pandas as pd
import torch
import torch.nn as nn
import torch.optim as optim
from torch.utils.data import DataLoader, TensorDataset
from sklearn.preprocessing import StandardScaler
from sklearn.model_selection import train_test_split
from sklearn.metrics import f1_score
from sklearn.ensemble import RandomForestClassifier
import matplotlib.pyplot as plt

# 加载数据
def load_data():
    # 这里需要替换为实际的心脏病数据集路径
    # df = pd.read_csv('heart_disease.csv')
    # 为了示例，我们创建一个模拟数据集
    np.random.seed(42)
    n_samples = 1000
    n_features = 13
    
    # 生成健康人群特征 (标签0)
    healthy_features = np.random.randn(800, n_features) * 0.5 + 2
    
    # 生成病人特征 (标签1) - 数量较少，导致类别不平衡
    patient_features = np.random.randn(200, n_features) * 0.5 + 3
    
    # 合并特征和标签
    features = np.vstack([healthy_features, patient_features])
    labels = np.hstack([np.zeros(800), np.ones(200)])
    
    # 创建DataFrame
    columns = [f'feature_{i}' for i in range(n_features)]
    df = pd.DataFrame(features, columns=columns)
    df['target'] = labels
    
    return df

# 构建生成器网络
class Generator(nn.Module):
    def __init__(self, input_dim, output_dim):
        super(Generator, self).__init__()
        self.model = nn.Sequential(
            nn.Linear(input_dim, 64),
            nn.LeakyReLU(0.2),
            nn.Linear(64, 128),
            nn.LeakyReLU(0.2),
            nn.Linear(128, 64),
            nn.LeakyReLU(0.2),
            nn.Linear(64, output_dim),
            nn.Tanh()  # 输出范围限制在[-1, 1]之间
        )
        
    def forward(self, z):
        return self.model(z)

# 构建判别器网络
class Discriminator(nn.Module):
    def __init__(self, input_dim):
        super(Discriminator, self).__init__()
        self.model = nn.Sequential(
            nn.Linear(input_dim, 64),
            nn.LeakyReLU(0.2),
            nn.Dropout(0.3),
            nn.Linear(64, 32),
            nn.LeakyReLU(0.2),
            nn.Dropout(0.3),
            nn.Linear(32, 1),
            nn.Sigmoid()  # 输出为概率值
        )
        
    def forward(self, x):
        return self.model(x)

# 训练GAN
def train_gan(generator, discriminator, dataloader, n_epochs, latent_dim, device):
    # 优化器
    g_optimizer = optim.Adam(generator.parameters(), lr=0.0002, betas=(0.5, 0.999))
    d_optimizer = optim.Adam(discriminator.parameters(), lr=0.0002, betas=(0.5, 0.999))
    
    # 损失函数
    criterion = nn.BCELoss()
    
    # 训练记录
    g_losses = []
    d_losses = []
    
    for epoch in range(n_epochs):
        epoch_g_loss = 0
        epoch_d_loss = 0
        
        for i, (real_samples, _) in enumerate(dataloader):
            batch_size = real_samples.size(0)
            
            # 真实样本标签为1，生成样本标签为0
            real_labels = torch.ones(batch_size, 1).to(device)
            fake_labels = torch.zeros(batch_size, 1).to(device)
            
            # 训练判别器
            d_optimizer.zero_grad()
            
            # 真实样本的损失
            real_outputs = discriminator(real_samples)
            d_loss_real = criterion(real_outputs, real_labels)
            
            # 生成样本
            z = torch.randn(batch_size, latent_dim).to(device)
            fake_samples = generator(z)
            
            # 生成样本的损失
            fake_outputs = discriminator(fake_samples.detach())
            d_loss_fake = criterion(fake_outputs, fake_labels)
            
            # 总判别器损失
            d_loss = d_loss_real + d_loss_fake
            d_loss.backward()
            d_optimizer.step()
            
            # 训练生成器
            g_optimizer.zero_grad()
            
            # 生成样本的损失 - 希望判别器将生成样本识别为真实样本
            fake_outputs = discriminator(fake_samples)
            g_loss = criterion(fake_outputs, real_labels)
            g_loss.backward()
            g_optimizer.step()
            
            # 累加损失
            epoch_d_loss += d_loss.item()
            epoch_g_loss += g_loss.item()
        
        # 计算平均损失
        epoch_d_loss /= len(dataloader)
        epoch_g_loss /= len(dataloader)
        
        g_losses.append(epoch_g_loss)
        d_losses.append(epoch_d_loss)
        
        if (epoch + 1) % 10 == 0:
            print(f'Epoch [{epoch+1}/{n_epochs}], D Loss: {epoch_d_loss:.4f}, G Loss: {epoch_g_loss:.4f}')
    
    # 绘制损失曲线
    plt.figure(figsize=(10, 5))
    plt.plot(g_losses, label='Generator Loss')
    plt.plot(d_losses, label='Discriminator Loss')
    plt.xlabel('Epochs')
    plt.ylabel('Loss')
    plt.legend()
    plt.title('GAN Training Loss')
    plt.savefig('gan_loss.png')
    plt.close()
    
    return generator

# 使用GAN生成样本
def generate_samples(generator, n_samples, latent_dim, scaler, device):
    # 生成随机噪声
    z = torch.randn(n_samples, latent_dim).to(device)
    
    # 生成样本
    generator.eval()
    with torch.no_grad():
        generated_samples = generator(z).cpu().numpy()
    
    # 反标准化
    generated_samples = scaler.inverse_transform(generated_samples)
    
    return generated_samples

# 评估模型性能
def evaluate_model(X_train, y_train, X_test, y_test):
    # 使用随机森林分类器
    clf = RandomForestClassifier(random_state=42)
    clf.fit(X_train, y_train)
    
    # 预测
    y_pred = clf.predict(X_test)
    
    # 计算F1分数
    f1 = f1_score(y_test, y_pred)
    
    return f1

# 主函数
def main():
    # 设置设备
    device = torch.device('cuda' if torch.cuda.is_available() else 'cpu')
    print(f'Using device: {device}')
    
    # 加载数据
    df = load_data()
    print(f"数据形状: {df.shape}")
    print(f"类别分布:\n{df['target'].value_counts()}")
    
    # 准备特征和标签
    X = df.drop('target', axis=1).values
    y = df['target'].values
    
    # 划分训练集和测试集
    X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=42)
    
    # 标准化特征
    scaler = StandardScaler()
    X_train_scaled = scaler.fit_transform(X_train)
    X_test_scaled = scaler.transform(X_test)
    
    # 分离病人和健康人的样本
    patient_indices = np.where(y_train == 1)[0]
    healthy_indices = np.where(y_train == 0)[0]
    
    X_patients = X_train_scaled[patient_indices]
    X_healthy = X_train_scaled[healthy_indices]
    
    # 计算需要生成的病人样本数量，使类别平衡
    n_healthy = len(healthy_indices)
    n_patients = len(patient_indices)
    n_samples_to_generate = n_healthy - n_patients
    
    print(f"健康样本数量: {n_healthy}")
    print(f"病人样本数量: {n_patients}")
    print(f"需要生成的病人样本数量: {n_samples_to_generate}")
    
    # 如果有必要生成样本
    if n_samples_to_generate > 0:
        # 准备GAN训练数据
        patient_dataset = TensorDataset(torch.FloatTensor(X_patients))
        patient_dataloader = DataLoader(patient_dataset, batch_size=32, shuffle=True)
        
        # 初始化模型
        input_dim = X_patients.shape[1]
        latent_dim = 10
        generator = Generator(latent_dim, input_dim).to(device)
        discriminator = Discriminator(input_dim).to(device)
        
        # 训练GAN
        print("开始训练GAN...")
        trained_generator = train_gan(generator, discriminator, patient_dataloader, 
                                     n_epochs=100, latent_dim=latent_dim, device=device)
        
        # 生成新的病人样本
        print("生成新的病人样本...")
        generated_patients = generate_samples(trained_generator, n_samples_to_generate, 
                                             latent_dim, scaler, device)
        
        # 创建生成样本的标签
        generated_labels = np.ones(n_samples_to_generate)
        
        # 将生成的样本与原始训练数据合并
        X_train_augmented = np.vstack([X_train, generated_patients])
        y_train_augmented = np.hstack([y_train, generated_labels])
        
        print(f"增强后的训练数据形状: {X_train_augmented.shape}")
        print(f"增强后的类别分布: {np.bincount(y_train_augmented.astype(int))}")
        
        # 评估原始数据上的模型性能
        f1_original = evaluate_model(X_train, y_train, X_test, y_test)
        print(f"原始数据上的F1分数: {f1_original:.4f}")
        
        # 评估增强数据上的模型性能
        f1_augmented = evaluate_model(X_train_augmented, y_train_augmented, X_test, y_test)
        print(f"增强数据上的F1分数: {f1_augmented:.4f}")
        
        # 打印结果比较
        print(f"\nF1分数提升: {f1_augmented - f1_original:.4f}")
        print(f"提升百分比: {(f1_augmented - f1_original) / f1_original * 100:.2f}%")
    else:
        print("数据已经平衡，不需要生成额外样本")

if __name__ == "__main__":
    main()