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

#define MAXSIZE 1000

int add(int *A, int low, int high)
{
	int res, i;

	for(i=low; i<high; i++)
		res += A[i];

	return(res);
}

void main(argc,argv)
int argc;
char *argv[];
{
    int done = 0, n, myid, numprocs;
    int data[MAXSIZE], i, low, high, myres, res;
    char fn[255];
    char *fp;

    MPI_Init(&argc,&argv);
    MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD,&myid);

    n = 0;
    while (!done)
    {
        if (myid == 0)
        {
	    if (n==0) n=100; else n=0;

	    strcpy(fn,getenv("HOME"));
	    strcat(fn,"/MPI/rand_data.txt");

	    /* Open Input File and Initialize Data */
	    if ((fp = fopen(fn,"r")) == NULL)
	    {
		printf("Can't open the input file: %s\n\n", fn);
		exit(1);
	    }

	    for(i=0; i<MAXSIZE; i++)
		fscanf(fp,"%d", &data[i]);
       }

        MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
        MPI_Bcast(data, MAXSIZE, MPI_INT, 0, MPI_COMM_WORLD);
        if (n == 0)
            done = 1;
        else
        {
	low = myid * 100;
	high = low + 100;

	myres = add(data, low, high);
	printf("I got %d from %d\n", myres, myid);
        MPI_Reduce(&myres, &res, 1, MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);
 if (myid == 0)
printf("The sum is %d.\n", res);
}
}
  MPI_Finalize(); 
  }