hello_mpi.c

#include "stdio.h"
#include <stdlib.h>

#include <mpi.h>

// http://www.linux-mag.com/id/5759/#install-openmpi, 18/09/2016
int main(int argc, char *argv[])
{
	int tid,nthreads;
	char *cpu_name;

	/* 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);

	printf("hello MPI user: from process = %i on machine=%s, of NCPU=%i processes\n",
			tid, cpu_name, nthreads);
	MPI_Finalize();
	return(0);
}