#include <stdio.h>
#include <mpi.h>
#define DIM_BUF 10

int main(int argc, char **argv){
int myrank, nproc;
int buf[DIM_BUF];
int i, offset, intsize;
MPI_File fh;
MPI_Status status;
MPI_Offset file_size;
MPI_Datatype filetype;

MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &nproc);
MPI_Comm_rank(MPI_COMM_WORLD, &myrank);

for(i=0;i<DIM_BUF;i++) buf[i] = myrank*DIM_BUF+i;

/* Open the file and write by using individual file pointers:
 * - use MPI_File_open to access the file "output.dat"; which access mode?
 * - use MPI_File_write for storing data, but first call function MPI_File_seek
 * -    to define 'offset'; on what values is it depending on?
 * - Hint: the function MPI_Type_size may be used to get the data type size
 * - do not forget of calling MPI_File_close at the end
 */
	---

/* Re-open the file and read by using explicit offset:
 * - use MPI_File_open to access "output.dat" for reading; which access mode?
 */
	---

/* - use the function MPI_File_get_size to obtain 'file_size' */
	---
offset = file_size/nproc*myrank;
printf("myid %d, filesize %lld, offset %d\n", myrank,file_size,offset);
/* - use the function MPI_File_read_at for reading
 * - do not forget to close the file at the end */
	---
	
printf("myid %d, buffer after read:",myrank);
for(i=0;i<DIM_BUF; i++)printf("%d ",buf[i]);
printf("\n\n");

/* Write the new file using the mpi_type_vector. Use the fileview:
 * - now every process has a copy of 'buf'
 * - use MPI_File_open to access "output_mod.dat" with the proper access mode 
 * - and use the right function for defining the new data type handle 'filetype'
 */
	---

/* - the function MPI_File_write_all could be used to store data appropriately,
 * - but the function MPI_File_set_view must first be called to use 'filetype'
 * - How will 'offset' be defined ?
 * - the function MPI_File_get_size may be useed to obtain file_size 
 */
	---
printf("myid %d, filesize of the second file written %lld, offset %d\n", myrank,file_size,offset);

MPI_Type_free(&filetype);
MPI_File_close(&fh);
MPI_Finalize();
return 0;
}