How to run multiple threads created by loop simultaneous using boost.thread?

I'm using learning the basic of boost.thread. So far, I can create each thread one by on开发者_运维知识库e manually to let them run at the same time. However, when creating by loop, it runs sequentially not concurrency anymore.

#include <iostream>
#include <boost/thread.hpp>
void workerFunc()
{
  boost::posix_time::seconds workTime(3);
  std::cout << "Worker: Running" << '\n';
  boost::this_thread::sleep(workTime);
  std::cout<< "Worker: Finished" << '\n';
}

int main()
{
  std::cout << "main: startup" << '\n';
  boost::thread workerThread(workerFunc);
  std::cout << "main: waiting for thread" << '\n';
  //these are ok
  boost::thread t(workerFunc), t2(workerFunc), t3(workerFunc), t4(workerFunc);     
  t.join();
  t2.join();
  t3.join();
  t4.join();
  //these are not
  for (int i = 0; i < 2; ++i)
    {
      boost::thread z(workerFunc);
      z.join();
    }
  std::cout << "main:done" << '\n';
  return 0;
}

  for (int i = 0; i < 2; ++i)
    {
      boost::thread z(workerFunc);
      z.join();
    }

You are starting your thread and then immediately waiting for it to complete!

EDIT

One of several alternative hacks besides thread groups.

  std::vector<boost::thread *> z;

  for (int i = 0; i < 2; ++i)
    z.push_back(new boost::thread(workerFunc));

  for (int i = 0; i < 2; ++i)
  {
      z[i]->join();
      delete z[i];
  }

Ok I found the answer through the problem of someone else, as well as learn their problem:

How to make boost::thread_group execute a fixed number of parallel threads

Use shared_ptr

#include <iostream>
#include <boost/thread.hpp>

void workerFunc()
{
    boost::posix_time::seconds workTime(3);
    std::cout << "Worker: Running" << '\n';
    boost::this_thread::sleep(workTime);
    std::cout << "Worker: Finished" << '\n';
}

int main()
{
    std::cout << "main: startup" << '\n';
    std::vector<std::shared_ptr<boost::thread>> z;

    for (int i = 0; i < 2; ++i) {
        z.push_back(std::make_shared<boost::thread>(workerFunc));
    }

    for (auto t : z) {
        t->join();
    }

    std::cout << "main:done" << '\n';
    return 0;
}

Execute it

# g++ e.cpp -lboost_thread && ./a.out
main: startup
Worker: Running
Worker: Running
Worker: Finished
Worker: Finished
main:done