Now that we know how to start threads of execution, we want to have access to some common resources from different threads:

#include <cassert> 
#include <cstddef> 
#include <iostream>
 
// In previous recipe we included 
// <boost/thread.hpp>, which includes all 
// the classes of Boost.Thread.
// Following header includes only boost::thread. 
#include <boost/thread/thread.hpp> 
 
int shared_i = 0;

void do_inc() {
    for (std::size_t i = 0; i < 30000; ++i) {
        const int i_snapshot = ++shared_i;
        // Do some work with i_snapshot.
        // ...
    }
}

void do_dec() {
    for (std::size_t i = 0; i < 30000; ++i) {
        const int i_snapshot = --shared_i;
        // Do some work with i_snapshot.
        // ...
    }
}

void run() {
    boost::thread t1(&do_inc);
    boost::thread t2(&do_dec);

    t1.join();
    t2.join...