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

int main(int argc, char **argv)
{

	MPI_File fh;
	MPI_Status status;
	MPI_Offset offset;
	int length, nprocs, rank, i;
	char buffer[1024];

	for(i=0; i<1024; i++) buffer[i] = i;

	MPI_Init(&argc, &argv);

	MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
	/*
	     e.g. P0 ( off_0 = 0,            len_0 > 2 )
             P1 ( off_1 < len_0 - 1,    len_1 = 0 )
             P2 ( off_2 < len_0 - 1,    len_2 = 0 )
             P3 ( off_3 < len_0 - 1,    len_3 = 0 )
                  .......               ........
	*/

	if (rank == 0) 
		length=nprocs;
	else
		length=0;
		

	offset = rank;


	MPI_File_open(MPI_COMM_WORLD, argv[1], MPI_MODE_CREATE|MPI_MODE_RDWR, 
			MPI_INFO_NULL, &fh);

	MPI_File_write_at_all(fh, offset, buffer, length, MPI_BYTE, &status);
	MPI_File_close(&fh);
	MPI_Finalize();

	return 0;
}