类似线程池，demo如下：

#include <boost/thread.hpp>
#include <boost/bind.hpp>
#include <iostream>
void fun(int i) {
    std::cout << "fun:" << i << std::endl;
}
int main() {
    boost::thread_group threads;
    for (auto i = 0;i < 10;i++) {
        threads.create_thread(boost::bind(fun, i));
    }
    threads.join_all();
 
    return 0;
}