MPI and OpenMP

//MPI and processes

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include "mpi.h"

int main( int argc, char *argv[] )
{
    int rank;
    int size;
    int x=5;
    printf( "Hello world from process %d x=%d\n", getpid(),x);
/*   MPI_Comm_rank(MPI_COMM_WORLD, &rank); Error 1 */
    MPI_Init( NULL, NULL );
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &size);
    x=rank;
    printf( "Hello world from process %d x=%d\n", getpid(),x);
    MPI_Finalize();
  /* MPI_Comm_rank(MPI_COMM_WORLD, &rank); Error 2 */
    printf( "Hello world from process %d x=%d\n", getpid(),x);
    return 0;
}

Error 1

Error 2

//Just Hello

#include <stdio.h>
#include <unistd.h> /* getpid() */
/*#include "mpi.h"*/

int main( int argc, char *argv[] )
{
printf( "Hello from process %d.\n",getpid());
return 0;
}

//OpenMPI and threads

#include <stdio.h>
#include <omp.h>
#include <sys/types.h>
#include <unistd.h>
int main(int argc, char* argv[]){
   printf("Hello-Before from thread %d of process %d\n",omp_get_thread_num(),getpid());
   {
#pragma omp parallel num_threads(4)
    printf("Hello-During from thread %d of process %d\n",omp_get_thread_num(),getpid());
   }
   printf("Hello-After from thread %d of process %d\n",omp_get_thread_num(),getpid());
   return 0;
}