9. Write a MPI Program to demonstration of MPI_Reduce and MPI_Allreduce (MPI_MAX, MPI_MIN, MPI_SUM, MPI_PROD).
COMMAND:
- Create:
gedit prg9.c - Compile:
mpicc prg9.c -o prg9 - Run:
mpirun -np 4 ./prg9
PROGRAM:
#include <mpi.h>
#include <stdio.h>
int main(int argc, char *argv[]) {
int rank, size;
int value, sum, prod, max, min;
int all_sum, all_prod, all_max, all_min;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
value = rank + 1;
MPI_Reduce(&value, &sum, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);
MPI_Reduce(&value, &prod, 1, MPI_INT, MPI_PROD, 0, MPI_COMM_WORLD);
MPI_Reduce(&value, &max, 1, MPI_INT, MPI_MAX, 0, MPI_COMM_WORLD);
MPI_Reduce(&value, &min, 1, MPI_INT, MPI_MIN, 0, MPI_COMM_WORLD);
MPI_Allreduce(&value, &all_sum, 1, MPI_INT, MPI_SUM, MPI_COMM_WORLD);
MPI_Allreduce(&value, &all_prod, 1, MPI_INT, MPI_PROD, MPI_COMM_WORLD);
MPI_Allreduce(&value, &all_max, 1, MPI_INT, MPI_MAX, MPI_COMM_WORLD);
MPI_Allreduce(&value, &all_min, 1, MPI_INT, MPI_MIN, MPI_COMM_WORLD);
if (rank == 0) {
printf("--- Results using MPI_Reduce (only root prints) ---\n");
printf("Sum = %d\n", sum);
printf("Product = %d\n", prod);
printf("Max = %d\n", max);
printf("Min = %d\n", min);
}
printf("Process %d has value %d\n", rank, value);
printf("Process %d sees (MPI_Allreduce): Sum=%d, Prod=%d, Max=%d, Min=%d\n",
rank, all_sum, all_prod, all_max, all_min);
MPI_Finalize();
return 0;
}OUTPUT:
