On Sun, Jul 5, 2009 at 7:10 AM, Jeff Squyres<jsquyres_at_[hidden]> wrote:
> How did you determine that both processes are staying on a single core?
I was using this very simple mpi code in C. It prints only the same
cpu but twice. On "correctly running" machines it loops over all cpus.
##################################
#include "stdio.h"
#include <stdlib.h>
#include <mpi.h>
int main(int argc, char *argv[])
{
int tid,nthreads;
char *cpu_name, fn[512];
FILE *fid;
/* add in MPI startup routines */
/* 1st: launch the MPI processes on each node */
MPI_Init(&argc,&argv);
/* 2nd: request a thread id, sometimes called a "rank" from
the MPI master process, which has rank or tid == 0
*/
MPI_Comm_rank(MPI_COMM_WORLD, &tid);
/* 3rd: this is often useful, get the number of threads
or processes launched by MPI, this should be NCPUs-1
*/
MPI_Comm_size(MPI_COMM_WORLD, &nthreads);
/* on EVERY process, allocate space for the machine name */
cpu_name = (char *)calloc(80,sizeof(char));
/* get the machine name of this particular host ... well
at least the first 80 characters of it ... */
gethostname(cpu_name,80);
sprintf(fn, "%s.log", argv[0]);
fid = fopen(fn, "w");
if(fid==NULL)
{ exit(1);
}
fprintf(stdout, "hello MPI user: from process = %i on machine=%s, of
NCPU=%i processors\n",
tid, cpu_name, nthreads);
MPI_Finalize();
return(0);
###############################################################################
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