// array2MPI.c
// Run this with multiple processors.  Processor 0 creates an array of 'count'
// numbers 1 to 'count.  In this example 'count' is 100.
// Processor n (n is not the root process) receives a portion of this array
// from processor 0.

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

const int MAXNUMS = 100;

int main(int argc, char **argv)
{
  int rank, size;
  MPI_Status status;
  int data[MAXNUMS];
  int i, count, local_start, local_finish;
  int sum=0, total;

  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &size);

  count = MAXNUMS;
  if (rank == 0) {
    srand(7);
    for (i=0;i<MAXNUMS; i++)
      data[i] = i+1; //rand() % 20;
    for(i = 1; i < size; i++) {
      local_start = i*(MAXNUMS/size);
      local_finish = local_start + (MAXNUMS/size);
      printf("Process 0 send array to process %d, start=%d, finish=%d\n",
             i, local_start,local_finish);
      MPI_Send(data, MAXNUMS, MPI_INT, i, 10, MPI_COMM_WORLD);
      MPI_Send(&local_start, 1, MPI_INT, i, 20, MPI_COMM_WORLD);
      MPI_Send(&local_finish, 1, MPI_INT, i, 30, MPI_COMM_WORLD);
    }
    for(i=0; i<(MAXNUMS/size); i++)
      sum = sum+ data[i];
  }
  else {
    MPI_Recv(data, MAXNUMS, MPI_INT, 0, 10, MPI_COMM_WORLD, &status);
    MPI_Recv(&local_start, 1, MPI_INT, 0, 20, MPI_COMM_WORLD, &status);
    MPI_Recv(&local_finish, 1, MPI_INT, 0, 30, MPI_COMM_WORLD, &status);
    printf("Data received from process 0, start=%d, finish=%d\n",
           local_start, local_finish);
    for (i = local_start; i < local_finish; i++) {
      printf("%7d", data[i]);
      sum = sum + data[i];
      if (i % 10 == 9) printf("\n");
    }
    printf("\n");
  }
  MPI_Reduce(&sum,&total,1,MPI_INT, MPI_SUM, 0,MPI_COMM_WORLD);
  if (rank == 0)
    printf("Total sum = %d\n", total);
  MPI_Finalize();
  return 0;
}