Critical section in MPI?

Question

I have some code to print a 2D array to the standard output. The problem is that when I run it, every process writes to the output and the data overlaps, rendering it unusable.

How can i build a critical section in MPI so that only one process at a time enters the section where I display the output?

I'm using OpenMPI.

Answer 1

Separate it out by using MPI_Barriers.

rank = 0;
while (rank < total_processes) {
   if (myrank == rank) {
       printf ("Array printed by rank: %d\n", myrank);
       print_array();
       fflush (stdout);
   }
   rank ++;
   MPI_Barrier ();
}