5.5.1. Current Practice #1

Example #1a:

main(int argc, char **argv) 
   { 
     int me, size; 
     ... 
     MPI_Init ( &argc, &argv ); 
     MPI_Comm_rank (MPI_COMM_WORLD, &me); 
     MPI_Comm_size (MPI_COMM_WORLD, &size); 
 
(void)printf ("Process %d size %d\n", me, size); 
     ... 
     MPI_Finalize(); 
   } 

Example #1b (supposing that size is even):

main(int argc, char **argv) 
    { 
       int me, size; 
       int SOME_TAG = 0; 
       ... 
       MPI_Init(&argc, &argv); 
 
MPI_Comm_rank(MPI_COMM_WORLD, &me);   /* local */ 
       MPI_Comm_size(MPI_COMM_WORLD, &size); /* local */ 
 
if((me % 2) == 0) 
       { 
          /* send unless highest-numbered process */ 
          if((me + 1) < size) 
             MPI_Send(..., me + 1, SOME_TAG, MPI_COMM_WORLD); 
       } 
       else 
          MPI_Recv(..., me - 1, SOME_TAG, MPI_COMM_WORLD); 
 
... 
       MPI_Finalize(); 
    }