/* data output samle program
 * file: sample.c
 * make: cc -64 sample.c out.o -lmpi
 * run: mpirun -np 4 ./a.out
 * check: cat out.txt

 * function ffopen(I)
     1. open a file 'out.txt' with append mode.
     2. put the current wallclock time in the file, then flush.
     3. if a file open error happens, return 1.
 * function ffput(int* A, int n)
     1. put the whole contents of an array 'A' in the file, then flush.
        the size of A is n.
     2. if the address of A is NULL, then return 1.
 * function ffclose()
     1. put the current wallclock time in the file, then flush.
     2. close the file.
     3. if a file close error happens, return 1.
  
 * M.Yuko@SuperCon2003(7.25)
 */

#include <mpi.h>     
#include <stdio.h>
#define N 5

int ffopen();
int ffput(int*, int);
int ffclose();

main(int argc, char *argv[])
{
  int num_procs;
  int my_proc;
  int a[N];
  int i, j;
  int root=0;

  MPI_Init(&argc, &argv);
  MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
  MPI_Comm_rank(MPI_COMM_WORLD, &my_proc);

  if(my_proc == root) ffopen();     /* called after MPI intialization */

  for(i = 0; i < N; i++) a[i] = -11; 

  if(my_proc == root) ffput(a, N);  /* called anytime */

  if (my_proc == root) {
    for(i=0;i<N;i++)
      a[i] = -20;
  }
  
  if(my_proc == root) ffput(a, N);   /* called anytime */

  MPI_Bcast ((void *) a, N, MPI_INT, root, MPI_COMM_WORLD);

  printf("rank=%d: ", my_proc);
  for (j = 0; j < N; j++)  printf("%d ",a[j]);
  printf("\n");

  if(my_proc == root) ffclose();   /* called before MPI finalized */

  MPI_Finalize();

}