mpi_ex4.c

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

int main(int argc, char *argv[]) {
	MPI_Init(&argc, &argv);
	MPI_Comm comm = MPI_COMM_WORLD;
	MPI_Comm newcomm;
	int rank, size;
	MPI_Comm_rank(comm ,&rank);
	MPI_Comm_size(comm ,&size);
	int A[size];
	int B;
	int root = size -1;
	//int root = size/2;
	for (int i=0; i<size; i++) A[i] = i;
	// printf("KEY[%d] = %d\n", rank, (rank < size/2) ? rank:size-rank);
	MPI_Comm_split (comm , 0, ((rank <size /2) ? rank : size -rank), &newcomm);
	MPI_Scatter(A,1,MPI_INT ,&B,1,MPI_INT ,root ,newcomm );
	printf ("B[%d]=%d\n",rank ,B);
	MPI_Finalize();
	return 0;
}