boost multithreading and shared mutex example: multiple reader, multiple writer

Here is a simple example of boost multithreading and shared mutex. Hope it helps. The code is quite simple and self explanatory:

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

boost::shared_mutex g_mutex;

using namespace std;

void reader(string id)
{
    cout << id << ": running" << endl;

    boost::shared_lock<boost::shared_mutex> lock(g_mutex);
    if (!lock.owns_lock())
        cout << id << ": Writer has the lock" << endl;
    else
        cout << id << ": Got the lock" << endl;

    // pretend doing something
    boost::this_thread::sleep(boost::posix_time::seconds(3));

    cout << id << ": finished" << endl;
}

void writer(string id)
{
    cout << id << ": running" << endl;

    boost::upgrade_lock<boost::shared_mutex> lock(g_mutex);
    boost::upgrade_to_unique_lock<boost::shared_mutex>  unique_lock(lock);

    cout << id << ": Got the lock" << endl;

    // pretend doing something
    boost::this_thread::sleep(boost::posix_time::seconds(3));

    cout << id << ": finished" << endl;
    boost::this_thread::sleep(boost::posix_time::seconds(1));
}

int main(int argc, char* argv[])
{
    const int writerthreadcount = 2;
    const int readerthreadcount = 2;

    vector writerthread;
    vector readerthread;

    for(int i=0; i<writerthreadcount; i++){
        ostringstream id;  id << "writer" << i+1;
        writerthread.push_back(new boost::thread(writer, id.str()));
    }
    for(int i=0; i<readerthreadcount; i++){
        ostringstream id;  id << "reader" << i+1;
        readerthread.push_back(new boost::thread(reader, id.str()));
    }

//    boost::this_thread::sleep(boost::posix_time::seconds(1));

    cout << "main: waiting for thread" << endl;

    for(int i=0; i<writerthreadcount; i++){         writerthread[i]->join(); delete writerthread[i];
    }
    for(int i=0; i<readerthreadcount; i++){         readerthread[i]->join(); delete readerthread[i];
    }

    cout << "main: done" << endl;

    return 0;
}