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

int main( int argc, char *argv[])
{
    int n, myid, numprocs, done;
    int  namelen;
    char processor_name[MPI_MAX_PROCESSOR_NAME];
    MPI_Status status;

    MPI_Init(&argc,&argv);
    MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD,&myid);

    if (myid == 0)
	n = 12345;
    else
	n = 0;

    // MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);

    /* Algorithm 1 */
#if 0
    if (myid == 0) {
	int i;
	for (i = 1; i < numprocs; i++)
	    MPI_Send(&n, 1, MPI_INT, i, i, MPI_COMM_WORLD);
    }
    else {
	MPI_Recv(&n, 1, MPI_INT, 0, myid, MPI_COMM_WORLD, &status);
    }
#endif

    /* Algorithm 2 (binary tree) */
    done = 1;
    while (done < numprocs) {
	if (myid < done) {
	    if (myid + done < numprocs)
	        MPI_Send(&n, 1, MPI_INT, myid + done, 1, MPI_COMM_WORLD);
	}
	else if (myid < done + done)
	    MPI_Recv(&n, 1, MPI_INT, myid - done, 1, MPI_COMM_WORLD, &status);
	done += done;
    }

    MPI_Get_processor_name(processor_name,&namelen);
    fprintf(stderr,"Process %d on %s, n=%d\n",
	    myid, processor_name, n);

    MPI_Finalize();

    return 0;
}