mp_file_open Subroutine

   SUBROUTINE mp_file_open(groupid, fh, filepath, amode_status, info)
      !! Opens a file
      !!
      !! MPI-I/O mapping  mpi_file_open
      !!
      !! STREAM-I/O mapping  OPEN

      INTEGER, INTENT(IN)                      :: groupid
         !! message passing environment identifier
      INTEGER, INTENT(OUT)                     :: fh
         !! file handle (file storage unit)
      CHARACTER(LEN=*), INTENT(IN)             :: filepath
         !! path to the file
      INTEGER, INTENT(IN)                      :: amode_status
         !! access mode
      INTEGER, INTENT(IN), OPTIONAL            :: info
         !! info object

      INTEGER                                  :: ierr, istat
#if defined(__parallel)
      INTEGER                                  :: my_info
#else
      CHARACTER(LEN=10)                        :: fstatus, fposition
      INTEGER                                  :: amode
      LOGICAL                                  :: exists, is_open
#endif

      ierr = 0
      istat = 0
#if defined(__parallel)
      my_info = mpi_info_null
      IF (PRESENT(info)) my_info = info
      CALL mpi_file_open(groupid, filepath, amode_status, my_info, fh, ierr)
      CALL mpi_file_set_errhandler(fh, MPI_ERRORS_RETURN, ierr)
      IF (ierr .NE. 0) CALL mp_stop(ierr, "mpi_file_set_errhandler @ mp_file_open")
#else
      MARK_USED(groupid)
      MARK_USED(info)
      amode = amode_status
      IF (amode .GT. file_amode_append) THEN
         fposition = "APPEND"
         amode = amode - file_amode_append
      ELSE
         fposition = "REWIND"
      END IF
      IF ((amode .EQ. file_amode_create) .OR. &
          (amode .EQ. file_amode_create + file_amode_wronly) .OR. &
          (amode .EQ. file_amode_create + file_amode_wronly + file_amode_excl)) THEN
         fstatus = "UNKNOWN"
      ELSE
         fstatus = "OLD"
      END IF
      ! Get a new unit number
      DO fh = 1, 999
         INQUIRE (UNIT=fh, EXIST=exists, OPENED=is_open, IOSTAT=istat)
         IF (exists .AND. (.NOT. is_open) .AND. (istat == 0)) EXIT
      END DO
      OPEN (UNIT=fh, FILE=filepath, STATUS=fstatus, ACCESS="STREAM", POSITION=fposition)
#endif
   END SUBROUTINE mp_file_open