/* FEVS: A Functional Equivalence Verification Suite for High-Performance
 * Scientific Computing
 *
 * Copyright (C) 2010, Stephen F. Siegel, Timothy K. Zirkel,
 * University of Delaware
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */

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

#ifdef _CIVL
#include<civlc.cvh>
$input int NB;
$output double __sum;
#endif
double sum;
double localSum = 0.0;
int PID;
int NPROCS;

double computeGlobalSum() {
  double result = localSum;
  double buffer;
  int i;
  MPI_Status status;

  for (i=1; i<NPROCS; i++) {
    MPI_Recv(&buffer, 1, MPI_DOUBLE, i, 0, MPI_COMM_WORLD, &status);
    result += buffer;
  }
  return result;
}
    
int main(int argc, char *argv[]) {
  int n, first, afterLast, i;
  FILE *fp = fopen("data","r");

  MPI_Init(&argc, &argv);
  MPI_Comm_size(MPI_COMM_WORLD, &NPROCS);
  MPI_Comm_rank(MPI_COMM_WORLD, &PID);
#ifdef _CIVL
  $assume(1 < argc);
#endif
  n = atoi(argv[1]);
#ifdef _CIVL
  $assume(0 < n && n <= NB);
#endif

  double a[n];  

  first = n*PID/NPROCS;
  afterLast = n*(PID+1)/NPROCS;
  for (i=0; i<n; i++) fscanf(fp, "%lf", &a[i]);
  for (i=first; i<afterLast; i++) localSum += a[i];
  if (PID == 0) {
    sum = computeGlobalSum(); 
    printf("%lf", sum);
#ifdef _CIVL
    __sum = sum;
#endif
  } else {
    MPI_Send(&localSum, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD);
  }
  fclose(fp);
  MPI_Finalize();
  return 0;
}