[boost] Granulity of boost_thread?

From: awite2_at_[hidden]
Date: 2003-04-15 16:47:23

Dear Readers,

Is this a general problem with threads or is the reason in the boost_thread
library?
==> I expected that both threads are executed evenly (see example below),
but one is executed more often.

Problem:
Having a program with 5 to 10 threads, I experienced that 1 thread was never
activated, if I set certain boost::sleep() values to each  thread.

Therefore I tried the following short program (now with
boost::sleep(boost::xtime) instead of ::sleep(), and a recursive_timed_mutex
instead of a recursive_mutex).

But the result is similar:
The "fast" thread is run about 700 times, the "slow" thread is run 1 time,
and the main loop isn't executed much, as otherwise the "fast" thread would
not have reached 700. If I run it much longer, than the "slow" thread
becomes faster at some point than the "fast".

(I used linux 2.4.10, pthreads).

////////// Start of Example

#include <iostream.h>
#include <stdlib.h>
#include <pthread.h>
#include <boost/thread.hpp>

boost::recursive_mutex M;
int iFast = 0;
int iSlow = 0;

void FastThread()
{
 while(1)
 {
 iFast ++;
 cout << "Enter Fast " << iFast<< " : " << iSlow << endl;
         {
         boost::recursive_mutex::scoped_lock L(M);
          }
 cout << "Leave Fast" << endl;
 }
}

void SlowThread()
{
 while(1)
 {

 iSlow++;
 cout << "Enter Slow " << iFast<< " : " << iSlow << endl;
         {
         boost::recursive_mutex::scoped_lock L(M);
          }
 }
}

int main(int argc, char *argv[])
{
  cout << "Start" << endl;
  boost::thread_group thrds;
         thrds.create_thread(&FastThread);
         thrds.create_thread(&SlowThread);
         while((iFast < 10) && (iSlow < 10))
                 {
                 cout << "MAIN: Fast : Slow = "<< iFast<< " : " << iSlow  << endl;
                 }
   cout << "End" << endl;

  return EXIT_SUCCESS;
}

/////////End of Example

Greetings,
Ernst

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