18.2.139. MPI_File_seek_shared

MPI_File_seek_shared - Updates the global shared file pointer (collective). SYNTAX C Syntax

#include <mpi.h>

int MPI_File_seek_shared(MPI_File fh, MPI_Offset offset,
     int whence) Fortran Syntax (see FORTRAN 77 NOTES)

! or the older form: INCLUDE 'mpif.h'

USE mpi_f08
MPI_File_seek_shared(fh, offset, whence, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     INTEGER, INTENT(IN) :: whence

  • fh: File handle (handle).

  • offset: File offset (integer).

  • whence: Update mode (integer). OUTPUT PARAMETER

  • IERROR: Fortran only: Error status (integer). DESCRIPTION

MPI_File_seek_shared updates the shared file pointer according to whence, which could have the following possible values:

o MPI_SEEK_SET - The pointer is set to offset.

o MPI_SEEK_CUR - The pointer is set to the current pointer position plus offset.

o MPI_SEEK_END - The pointer is set to the end of the file plus offset.

MPI_File_seek_shared is collective; all the processes in the communicator group associated with the file handle fh must call MPI_File_seek_shared with the same offset and whence. All processes in the communicator group are synchronized before the shared file pointer is updated.

The offset can be negative, which allows seeking backwards. It is erroneous to seek to a negative position in the view. The end of the view is defined to be the position of the next elementary data item, relative to the current view, following the last whole elementary data item accessible. FORTRAN 77 NOTES

The MPI standard prescribes portable Fortran syntax for the OFFSET argument only for Fortran 90. FORTRAN 77 users may use the non-portable syntax


where MPI_OFFSET_KIND is a constant defined in mpif.h and gives the length of the declared integer in bytes. ERRORS

Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_INIT / MPI_INIT_THREAD, after MPI_FINALIZE, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_COMM_SET_ERRHANDLER on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_COMM_SPAWN[_MULTIPLE]. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

In the sessions model, the error handler can be set during MPI_Session_init.

Open MPI includes three predefined error handlers that can be used:

MPI_ERRORS_ARE_FATAL: Causes the program to abort all connected MPI processes.
MPI_ERRORS_ABORT:     An error handler that can be invoked on a communicator,
                      window, file, or session. When called on a communicator, it
                      acts as if MPI_ABORT was called on that communicator. If
                      called on a window or file, acts as if MPI_ABORT was called
                      on a communicator containing the group of processes in the
                      corresponding window or file. If called on a session,
                      aborts only the local process.
MPI_ERRORS_RETURN:    Returns an error code to the application.

MPI applications can also implement their own error handlers.

Custom MPI error handlers can be created by calling: MPI_Comm_create_errhandler(3) MPI_File_create_errhandler(3) MPI_Session_create_errhandler(3) MPI_Win_create_errhandler(3)

Predefined and custom error handlers can be set by calling: MPI_Comm_set_errhandler(3) MPI_File_set_errhandler(3) MPI_Session_set_errhandler(3) MPI_Win_set_errhandler(3)

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3 standard for more information.