thread_local 线程局部存储

thread_local int threadCounter = 0;  // 每个线程独立计数

void worker() {
    ++threadCounter;  // 无锁操作当前线程自己的变量
    std::cout << "本线程计数: " << threadCounter << std::endl;
}

#include <iostream>
#include <thread>
#include <random>
#include <vector>
#include <string>
#include <chrono>

// 每个线程独立的随机数引擎——无需加锁
thread_local std::mt19937 engine(
    static_cast<unsigned>(
        std::chrono::steady_clock::now().time_since_epoch().count()
        ^ std::hash<std::thread::id>{}(std::this_thread::get_id())
    )
);

// 每个线程的生产计数器
thread_local int itemsProcessed = 0;

void processBatch(const std::string& workerName, int batchSize) {
    std::uniform_int_distribution<int> dist(50, 200);  // 模拟处理耗时 50-200ms

    for (int i = 0; i < batchSize; ++i) {
        int delay = dist(engine);  // 无锁使用线程专属引擎
        std::this_thread::sleep_for(std::chrono::milliseconds(delay / 20));  // 加速演示
        ++itemsProcessed;
    }

    // 输出时加锁避免交错（仅为输出美观）
    static std::mutex coutMutex;
    {
        std::lock_guard<std::mutex> lock(coutMutex);
        std::cout << workerName << " 完成 " << itemsProcessed
                  << " 个任务" << std::endl;
    }
}

int main() {
    std::cout << "===== 飞翔科技并行任务处理 =====" << std::endl;

    std::vector<std::thread> workers;

    // 启动 4 个线程，各处理不同数量的任务
    workers.emplace_back(processBatch, "李眉-日志分析", 30);
    workers.emplace_back(processBatch, "白歌-数据清洗", 40);
    workers.emplace_back(processBatch, "小崔-报表计算", 25);
    workers.emplace_back(processBatch, "黄俪-UI渲染",   35);

    for (auto& t : workers) t.join();

    std::cout << "\n所有线程完成！" << std::endl;

    // 验证：主线程中的 itemsProcessed 不受影响
    std::cout << "主线程 itemsProcessed = " << itemsProcessed
              << " (未参与工作线程的统计)" << std::endl;

    return 0;
}

#include <iostream>
#include <thread>
#include <vector>
#include <string>
#include <sstream>
#include <mutex>

// 每个线程独立的日志缓冲区
thread_local std::ostringstream logBuffer;

// 全局日志收集器（仅在 flush 时加锁）
std::vector<std::string> globalLogs;
std::mutex globalLogMutex;

void log(const std::string& message) {
    logBuffer << "  [" << std::this_thread::get_id() << "] "
              << message << "\n";
}

void flushLog(const std::string& threadName) {
    // 只在最后汇总时加锁一次——而非每次 log 都加锁
    std::lock_guard<std::mutex> lock(globalLogMutex);
    globalLogs.push_back(threadName + " 的日志:\n" + logBuffer.str());
}

void workerTask(const std::string& name, int steps) {
    log("开始执行任务");

    for (int i = 1; i <= steps; ++i) {
        log("步骤 " + std::to_string(i) + "/" + std::to_string(steps) + " 完成");
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }

    log("任务结束");

    // 一次性提交本线程所有日志
    flushLog(name);
}

int main() {
    std::cout << "===== 飞翔科技线程专属日志 =====" << std::endl;

    std::vector<std::thread> workers;
    workers.emplace_back(workerTask, "孔蓝-产品上线", 3);
    workers.emplace_back(workerTask, "赵鸣-活动发布", 5);
    workers.emplace_back(workerTask, "孙鹤-数据分析", 2);

    for (auto& t : workers) t.join();

    // 最终汇总输出
    std::cout << "\n===== 汇总日志 =====" << std::endl;
    for (const auto& logEntry : globalLogs) {
        std::cout << logEntry;
    }

    return 0;
}

#include <iostream>
#include <thread>
#include <mutex>

// 全局 thread_local：所有线程可访问，但地址不同
thread_local int tlsValue = 0;

// 带动态初始化的 thread_local
thread_local int tlsDynamic = []() -> int {
    // 这个 lambda 在每个线程首次访问 tlsDynamic 时执行一次
    auto id = std::this_thread::get_id();
    std::ostringstream oss;
    oss << id;
    int hash = std::hash<std::string>{}(oss.str());
    std::cout << "  [初始化] 线程 " << id
              << " 的 tlsDynamic = " << (hash % 100) << std::endl;
    return hash % 100;
}();

std::mutex coutMutex;

void threadFunc(const std::string& name, int value) {
    // 每个线程设置自己的 tlsValue
    tlsValue = value;

    {
        std::lock_guard<std::mutex> lock(coutMutex);
        std::cout << name << ":" << std::endl;
        std::cout << "  tlsValue   = " << tlsValue
                  << " (地址: " << &tlsValue << ")" << std::endl;
        std::cout << "  tlsDynamic = " << tlsDynamic
                  << " (地址: " << &tlsDynamic << ")" << std::endl;
    }
}

int main() {
    std::cout << "===== thread_local 地址验证 =====" << std::endl;

    // 主线程的设置
    tlsValue = 999;

    std::cout << "\n主线程:" << std::endl;
    std::cout << "  tlsValue   = " << tlsValue
              << " (地址: " << &tlsValue << ")" << std::endl;
    std::cout << "  tlsDynamic = " << tlsDynamic
              << " (地址: " << &tlsDynamic << ")" << std::endl;

    std::cout << "\n工作线程:" << std::endl;

    std::thread t1(threadFunc, "线程A", 111);
    std::thread t2(threadFunc, "线程B", 222);

    t1.join();
    t2.join();

    // 验证主线程的值未被影响
    std::cout << "\n验证 — 主线程的值未被修改:" << std::endl;
    std::cout << "  主线程 tlsValue = " << tlsValue
              << " (仍是 " << 999 << ")" << std::endl;

    return 0;
}