#include 
int MPI_File_open(MPI_Comm comm, const char *filename,
    int amode, MPI_Info info,
    MPI_File *fh)
 //MPI_File_open opens the file identified by the filename filename on all
  //processes in the comm communicator group. 
  //MPI_File_open is a collective routine; 
  //all processes must provide the same value for amode, 
  //and all processes must provide filenames that reference the same file 
  //which are textually identical