4 int main (int argc, char **argv) {
13 MPI_Init(&argc, &argv);
14 MPI_Comm_size(MPI_COMM_WORLD, &size);
15 MPI_Comm_rank(MPI_COMM_WORLD, &rank);
17 start_timer = MPI_Wtime();
19 printf("rank %d has value %d\n", rank, value);
20 MPI_Reduce(&value, &sum, 1, MPI_INT, MPI_SUM, root, MPI_COMM_WORLD);
22 printf("On root: sum=%d\n",sum);
23 printf("Elapsed time=%lf s\n", MPI_Wtime()-start_timer);