//
// Open Systems Laboratory
// http://www.lam-mpi.org/tutorials/
// Indiana University
//
// MPI Tutorial
// Homework: Manager/worker (calculate an average in parallel)
//
// Mail questions regarding tutorial material to lam at lam dash mpi dot org
//

#include <iostream>
#include <mpi.h>

using namespace std;


int
main(int argc, char *argv[])
{
  int source, dest;
  int total, workers;
  double avg;
  int *data, *sum, mysum;
  int rank, size;
  int i, len = 100, tag = 200;
  MPI::Request *request;

  MPI::Init(argc, argv);
  rank = MPI::COMM_WORLD.Get_rank();
  size = MPI::COMM_WORLD.Get_size();

  if (rank == 0) {

    // Allocate and initialize the data

    workers = size - 1;
    data = new int[workers * len];
    sum = new int[workers];
    request = new MPI::Request[workers];

    for (i = 0; i < workers * len; ++i)
      data[i] = i;
    
    // Send the data to each of the other processes

    for (i = 0; i< workers; ++i) {
      int dest = i + 1;

      // Send the data to worker dest, use a non-blocking send and use
      // request[i]
    }

    // Wait for all of the sends to complete */
    
    // Receive the results

    for (i = 0; i < workers; ++i) {
      int source = i + 1;

      // Do a non-blocking receive from source, placing the
      // incoming number in the sum array, again use request[i]

    }

    // Wait for all of the receives to complete

    total = 0;
    for (i = 0; i < workers; ++i)
      total += sum[i];

    avg = total / (len * workers);
    cout << "The average is " << avg << endl;

    delete[] data;
    delete[] sum;
    delete[] request;
  } 

  // Workers

  else {
    data = new int[100];
    mysum = 0;

    // Receive the data from the manager

    for (i = 0; i < len; ++i)
      mysum += data[i];
    
    // Send my sum back to the manager

    delete[] data;
  }

  MPI::Finalize();
  return 0;
}