Hello world in MPI.

hello.c

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


int main(int argc, char *argv[])
{
  int rank, size;

  MPI_Init(&argc, &argv);

  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &size);

  printf("Hello world! I am %d of %d\n", rank, size);

  MPI_Finalize();

  return 0;
}