MPI_WIN_CREATE_ERRHANDLER(3)

💅 MPI_Win_create_errhandler — the Open MPI manual page, but make it make sense

okay so bestie, you're in the Open MPI docs, and this one's about MPI_Win_create_errhandler — it literally creates an error handler for a window 🪟✨ Think of it as making a little custom "if this goes wrong, do THIS" routine and handing it to your window. Iconic, honestly.

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✨ SYNTAX ✨

🌸 C Syntax

#include <mpi.h>

int MPI_Win_create_errhandler(MPI_Win_errhandler_function *function,
     MPI_Errhandler *errhandler)

🎀 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_WIN_CREATE_ERRHANDLER(FUNCTION, ERRHANDLER, IERROR)
     EXTERNAL FUNCTION
     INTEGER ERRHANDLER, IERROR

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Win_create_errhandler(win_errhandler_fn, errhandler, ierror)
     PROCEDURE(MPI_Win_errhandler_function) :: win_errhandler_fn
     TYPE(MPI_Errhandler), INTENT(OUT) :: errhandler
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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💀 DEPRECATED TYPE NAME NOTE 💀

ngl this is the part where the docs are like "we changed our mind." MPI-2.2 deprecated the MPI_Win_errhandler_fn type and said bestie use MPI_Win_errhandler_function instead. And Open MPI? It supports both names (fr fr — the _fn names are typedefs to the _function names, so nobody gets left behind 🫶).

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🌈 INPUT PARAMETER 🌈

• function — your user-defined error-handling procedure (a function, obviously 💅).

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⭐ OUTPUT PARAMETERS ⭐

• errhandler — the MPI error handler (a handle 🔥).
• ierror — Fortran only: the error status (an integer).

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💖 DESCRIPTION 💖

So MPI_Win_create_errhandler should be — in C — a function of type MPI_Win_errhandler_function, which is defined as:

typedef void MPI_Win_errhandler_function(MPI Win *, int *, ...);

The first argument is the window in use, and the second is the error code to be returned. That's it, that's the whole vibe ✨

In Fortran, your user routine should look like this:

SUBROUTINE WIN_ERRHANDLER_FUNCTION(WIN, ERROR_CODE, ...)
    INTEGER WIN, ERROR_CODE

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😭 ERRORS 😭

Okay, deep breath, this section is a whole saga but it's important:

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) gets called. If no communication object is associated with the MPI call, then the call counts as 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 you're using the Sessions Model exclusively), the error raises the initial error handler. You can change that initial error handler by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or via the mpi_initial_errhandler CLI argument to mpiexec, or the info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. And if no other appropriate error handler has been set, then MPI_ERRORS_RETURN gets called for MPI I/O functions and MPI_ERRORS_ABORT gets called for all other MPI functions 💀

Open MPI ships three predefined error handlers you can use:

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. yeah. everybody. gone. 💀
• MPI_ERRORS_ABORT — an error handler that can be invoked on a communicator, window, file, or session. When it's called on a communicator, it acts as if MPI_Abort was called on that communicator. If it's 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 it's called on a session, it aborts only the local process.
• MPI_ERRORS_RETURN — returns an error code to the application. polite king behavior 👑.

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

⚠️ heads up bestie: note that MPI does not guarantee that an MPI program can continue past an error. Like, do not bet your whole app on it. 🙈

See the MPI man page for a full list of MPI error codes. And see the Error Handling section of the MPI-3.1 standard for more information, iykyk 💜

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🎀 COPYRIGHT 🎀

2003-2026, The Open MPI Community

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okay that's the whole page, mwah 💋 this was MPI_WIN_CREATE_ERRHANDLER(3) from Open MPI, dated Sep 11, 2026 — go forth and handle your errors, bestie 🦋💖✨