Description Greg Watson 2008-04-13 12:00:24 EDT

Running the barrier synchronization on the following code shows no errors:

#include <mpi.h>

void test()
{
	int i;
	int rank, size;
	int a = 0, b = 0;

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

	for (i = 0; i < size; ++i) {
		if (i == rank) {
			if (a > 0 || b > 0) {
				printf("hi\n");
			}
		}
		MPI_Barrier(MPI_COMM_WORLD);
	}
}

However, running the barrier synchronization on the same code with the MPI_Comm_size and MPI_Comm_rank statements swapped results in an incorrect error indication "Loop (dynamic number of barriers)" at the for loop. 

i.e.

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