/* 
Jonathan Hauenstein - University of Notre Dame
Center for Applied Mathematics Minicourse on Parallel Computing
April 24, May 1, May 8, 2008
Sample programs are designed for educational use 
*/

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

int main(int argc, char **argv)
{ 
  int my_id, num_proc, my_value[2] = {0, 0}, max_value[2] = {0, 0}, root = 0;

  // initialize MPI
  MPI_Init(&argc, &argv);

  // find unique id
  MPI_Comm_rank(MPI_COMM_WORLD, &my_id);

  // find the number of processes running
  MPI_Comm_size(MPI_COMM_WORLD, &num_proc);

  // setup my_value
  my_value[0] = (my_id + 1) * num_proc;
  my_value[1] = - (my_id + 1) * num_proc;

  // print original values
  printf("id: %d num: %d values: %d & %d\n", my_id, num_proc, my_value[0], my_value[1]);
  
  // find the maximum
  MPI_Reduce(my_value, max_value, 2, MPI_INT, MPI_MAX, root, MPI_COMM_WORLD);

  // print maximum values
  printf("id: %d num: %d max values: %d & %d\n", my_id, num_proc, max_value[0], max_value[1]);

  // finalize MPI
  MPI_Finalize();

  return 0;
}