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

int main(int argc, char* argv[]){
    MPI_Init(&argc, &argv);
    int id, np;
    MPI_Comm_size(MPI_COMM_WORLD, &np);
    MPI_Comm_rank(MPI_COMM_WORLD, &id);
    double a = np / 10.;
    double sum;
    MPI_Reduce(&a,&sum,1,MPI_DOUBLE,MPI_SUM,np-1,MPI_COMM_WORLD);
    printf("id = %d, a = %f\n", id, a);
    if(id == np-1){
        printf("id = %d, sum = %f\n", id, sum);
    }
    MPI_Finalize();
    return 0;
}