/* 
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 "trapezoid.h"
#include <mpi.h>

int main(int argc, char **argv)
{
  int i, my_id, num_proc, totalTrap = 0;
  MPI_Status status;
  double my_ans = 0, total = 0;
  trapInfo my_info;

  // 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);

  if (my_id == 0)
  { // find the number of trapezoids the user wants to use
    printf("Please enter the number of trapezoids to use: ");
    scanf("%d", &totalTrap);

    // quick error checking
    if (totalTrap <= 0)
    {
      printf("The number of trapezoids was not read in properly.  This program will terminate!\n\n");
      MPI_Abort(MPI_COMM_WORLD, 1);
    }

    // determine my_info
    setup_my_info(&my_info, -1, 1, totalTrap, my_id, num_proc);
  }
  else
  { // recv my_info
    setup_my_info(&my_info, 0, 0, 0, my_id, num_proc);
  }

  // compute the trapezoid integral locally
  my_ans = composite_trapApprox(&my_info);

  // collect the sum on id 0
  MPI_Reduce(&my_ans, &total, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);

  if (my_id == 0)
  { // find 2*total and print ans
    total *= 2;
    printf("Using %d trapezoids, the approximation to pi is %.15f.\n\n", totalTrap, total);
  }

  // finalize MPI
  MPI_Finalize();

  return 0;
}