#include <algorithm>
#include <functional>
#include <thread>
#include <vector>

void
do_work(unsigned id)
{
}

void
f()
{
  std::vector<std::thread> threads;
  for (unsigned i = 0; i < 20; ++i) {
    threads.push_back(std::thread(do_work, i));
  }
  std::for_each(
      threads.begin(), threads.end(), std::mem_fn(&std::thread::join));
}

int
main()
{
  f();
}