#include <random>  

std::random_device rd;                         // A function object for generating seeds
  std::mt19937 gen(rd());
  std::uniform_int_distribution<> dis(1, 6000);//取值 1-6000

使用：
dis(gen)

執行緒延遲隨機多少秒內啟動：

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include 
 
<string.h>
#include <thread>
#include <random>

using namespace std;
using std::cout;

class HelloWorld {
public:
    HelloWorld(string url)
    {
        std::random_device rd;                         // A function object for generating seeds
        std::mt19937 gen(rd());
        std::uniform_int_distribution
 
<> dis(1, 6000);//

        const int len = 100;
        std::thread threads[len];
        std::cout << "Spawning 5 threads...\n";
        for (int i = 0; i < len; i++) {
            threads[i] = std::thread(&HelloWorld::thread_task, this, url, dis(gen));
        }

        std::cout << "
 
Done spawning threads! Now wait for them to join\n";
        for (auto& t : threads) {
            t.join();
        }
        std::cout << "All threads joined.\n";
    }

    void thread_task(string url, int time) {
        std::this_thread::sleep_for(std::chrono::milliseconds(time));
        std::cout << "hello thread "
            << std::this_thread::get_id()
            << " paused " << time << " milliseconds" << std::endl;
    }
};

int main() {
 
    HelloWorld hw("url");

    return EXIT_SUCCESS;
}