Newsgroups: comp.programming.threads,comp.parallel.mpi
From: Alexandre Carissimi <Alexandre.Carissimi@imag.fr>
Subject: BUG on Threads IRIX6.4??
Organization: LMC-Laboratoire de Modelisation et Calcul
Date: Sat, 21 Feb 1998 11:11:36 +0100
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Message-ID: <34EEA858.7FDB@imag.fr>

Hi;

	I'm using IRIX6.4 threads and MPI-SGI but I'm having
strange problems. To analyse and even debug my program I begun
to write some "similar behaviors" programs very simples, and I
detected a strange thing. Anybody can says me if I doing a
mistake or if was a problem with IRIX 6.4 systems.

	The problems is: WHEN I CHANGE THE THREAD PRIORITY
THE THREAD ID IS ALSO CHANGED. As you can imagine I have a
lot of problems when I try joining them.

	- If I use only threads call, I commented MPI calls,
the program works fine even if I link with mpi library.
The program changes the main thread priority, and after,
it creates 10 threads with other priorities. Threads Id
are sequential.

	- If I use threads and MPI call (only MPI_Init,
Comm_size, Comm_rank and Finalize) the SAME program does
a change on main thread id after prioriry changing.

	- Another thing: in the first case, on my execution,
thread id begun with id=10000 and the other are sequential
after 10000. In the second case, thread id begun with 10000
and after priority change it assumes id=30000.

	ANYBODY can explain me? TIA.

THE CODE IS:


#include        <pthread.h>
#include        <stdio.h>
#include        <mpi.h>
#include        <sched.h>

pthread_attr_t attr;
pthread_mutex_t mutex;
pthread_cond_t cond;
int xcond=0;
int size,rank;

void *Slaves(void *arg)
{
    int i,j;

    pthread_mutex_lock(&mutex);
    while(xcond==0)
       pthread_cond_wait(&cond,&mutex);
                         
    pthread_mutex_unlock(&mutex);
    printf("Size: %d Rank: %d    Thread Id %x\n", size, rank,
pthread_self());
    fflush(stdout);
}

int main (int argc, char **argv)
{
    int i,k=10,r;
    pthread_t *ThreadId;  
    struct sched_param params;
    int sched;

    printf("THREAD MAIN BEFORE MPI INIT %x\n", pthread_self());
/*   
 *  This lines are commented to see if MPI calls influence over
 *  system behavior.
 
    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    printf("THREAD MAIN AFTER MPI INIT %x\n", pthread_self());

 */

/*
 * If I called MPI the main thread id will be changed after
 * this lines. When I just left MPI initialisation main thread
 * has the same ID that it had before, the problem arrives
 * from this point
 */

    params.sched_priority=20;
    pthread_setschedparam(pthread_self(), SCHED_RR, &params);

    printf("THREAD MAIN AFTER  PRIO CHG %x\n", pthread_self());


    
    if (argc==2)
       k=atoi(argv[1]);

    ThreadId= (pthread_t *) malloc(k*sizeof(pthread_t));

    pthread_attr_init(&attr);
    pthread_mutex_init(&mutex, NULL);
    pthread_cond_init(&cond, NULL);

    printf("\n Creating %d threads - Main thread is %x  \n", k,
pthread_self());

    for(i=0; i<k; i++) {
        pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED); 
        params.sched_priority=21;
        pthread_attr_setschedparam(&attr, &params);
        r=pthread_create(&ThreadId[i], &attr, Slaves, NULL);
        if (r!=0) {
           printf("Error on thread creation! \n");
           exit(0);
        }
    }

    xcond=1;
    pthread_cond_broadcast(&cond);

/*
 * It was to force threads execution, but this is not necessary
  
    for(;;) sched_yield(); 
 */

    for(i=0; i<k; i++) {
        r=pthread_join(ThreadId[i], NULL);
        if (r!=0) {
           printf("Error on joining threads...\n");
           exit(0);
         }
    }
    printf(" Thead MAIN with id %x terminating...\n", pthread_self());
/*
    MPI_Finalize();
*/
}



__________________________________________________________________
CARISSIMI, Alexandre                  Alexandre.Carissimi@imag.fr
Laboratoire de Modelisation et Calcul - LMC
Institut National Polytechnique de Grenoble - INPG
100, Rue des Mathematiques               Fone: (33) 04.76.51.46.03
38041 - Grenoble - Cedex 9  FRANCE       Fax : (33) 04.76.51.48.46
                            (International calls removes 0 from 04)

"Le seul moteur pour gagner c'est innover" Renault (F1 - 1996)
________________________________________________________________