MPI_SESSION_CREATE_ERRHANDLER(3)

💖 MPI_SESSION_CREATE_ERRHANDLER 💖

okay bestie, so this is a page from the Open MPI manual, section 3 (that's the library-calls girlies 🫶)

✨ NAME ✨

MPI_Session_create_errhandler — creates an error handler that can be attached to sessions 🌸

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✨ SYNTAX ✨

C Syntax

#include <mpi.h>

int MPI_Session_create_errhandler(MPI_Session_errhandler_function *function,
    MPI_Errhandler *errhandler)

Fortran Syntax

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

MPI_SESSION_CREATE_ERRHANDLER(FUNCTION, ERRHANDLER, IERROR)
    EXTERNAL    FUNCTION
    INTEGER ERRHANDLER, IERROR

Fortran 2008 Syntax

USE mpi_f08

MPI_Session_create_errhandler(session_errhandler_fn, errhandler, ierror)
    PROCEDURE(MPI_Session_errhandler_function) :: session_errhandler_fn
    TYPE(MPI_Errhandler), INTENT(OUT) :: errhandler
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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✨ INPUT PARAMETER ✨

• function — the user-defined error handling procedure you bring to the party (it's a function). your custom lil handler 💅

✨ OUTPUT PARAMETERS ✨

• errhandler — MPI error handler (a handle). this is the shiny new thing you get back ✨
• ierror — Fortran only: error status (integer). classic Fortran behavior, it hands you back an int 🎀

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✨ DESCRIPTION ✨

So MPI_Session_create_errhandler creates an error handler that can be attached to sessions. It is identical to MPI_Errhandler_create, except the use of that one is deprecated — like, do not use it, it's giving legacy 🙈

In C, your user routine should be a function of type MPI_Session_errhandler_function, which is defined as

typedef void MPI_Session_errhandler_function(MPI_Session *, int *, ...);

The first argument is the session in use. The second is the error code to be returned by the MPI routine that raised the error. This typedef replaces MPI_Handler_function — and yes, the use of that one is also deprecated, we don't do that anymore 💀

In Fortran, the user routine should be of this form:

SUBROUTINE SESSION_ERRHANDLER_FUNCTION(SESSION, ERROR_CODE, ...)
   INTEGER SESSION, ERROR_CODE

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✨ 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. iykyk 😌

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. That 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 the info key to MPI_Comm_spawn / 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. fr fr, that's the whole chain 🦋

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

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. like, everybody goes down 😭
• 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, it 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, it aborts only the local process. ✨
• MPI_ERRORS_RETURN — returns an error code to the application. the chill one, it just tells you what went wrong 💜

MPI applications can also implement their own error handlers by calling:

• MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
• MPI_File_create_errhandler then MPI_File_set_errhandler
• MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
• MPI_Win_create_errhandler then MPI_Win_set_errhandler

⚠️ note that MPI does not guarantee that an MPI program can continue past an error. lowkey scary but that's just how it is 💀

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

See the Error Handling section of the MPI-3.1 standard for more information.

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✨ Copyright ✨

2003-2026, The Open MPI Community

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and that's a wrap bestie!! 🎀 this icon of a page dropped Sep 10, 2026 and it's from your fave, MPI_SESSION_CREATE_ERRHANDLER(3) in the Open MPI collection — 2003-2026, The Open MPI Community stays iconic 👑✨💖