MPI.c

#include <mpi.h>
#include <stdio.h>
#define MCW MPI_COMM_WORLD

int main(int argc, char* argv[]){
    MPI_Init(&argc, &argv);
    int id, np;
    MPI_Comm_size(MCW, &np);
    MPI_Comm_rank(MCW, &id);

    float a, sum = 0;
    a = np/10.;
    MPI_Reduce(&a, &sum, 1, MPI_FLOAT, MPI_SUM, np-1, MCW);
    printf("id=%d, a=%f\n", id, a);
    if(id == np-1){
        printf("id=%d, np=%d, s=%f\n", id, np, sum);
    }

    MPI_Finalize();
    return 0;
}