MPI_OP_FREE(3)

💅 MPI_OP_FREE(3) 💅

okay so this is from the Open MPI manual, bestie, and it's literally about freeing a user-defined combination function handle. yes, that's a whole thing. sit down, we're learning 🫶

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✨ NAME ✨

MPI_Op_free — frees a user-defined combination function handle. bye bye, handle 💖

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🌸 SYNTAX 🌸

🎀 C Syntax

#include <mpi.h>

int MPI_Op_free(MPI_Op *op)

🎀 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_OP_FREE(OP, IERROR)
     INTEGER OP, IERROR

🎀 Fortran 2008 Syntax

USE mpi_f08
MPI_Op_free(op, ierror)
     TYPE(MPI_Op), INTENT(INOUT) :: op
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🔥 INPUT/OUTPUT PARAMETER 🔥

• op — the operation, aka a handle. it goes in and it comes out (that's the in/out part, iykyk) 👑

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💫 OUTPUT PARAMETER 💫

• ierror — Fortran only, bestie: the error status, and it's an integer 💜

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🦋 DESCRIPTION 🦋

so what this does is it marks a user-defined reduction operation for deallocation (not me evicting it from the group chat 😭) and then sets op to MPI_OP_NULL. periodt. that's the whole vibe.

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⭐ ERRORS ⭐

almost all MPI routines return an error value, okay? C routines give it to you as the return result of the function, and Fortran routines put it in the last argument. no cap.

before that error value gets 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/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. slay, but also scary 💀

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, everyone. all of them. 😭
• 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. main character energy but make it fatal ✨
• MPI_ERRORS_RETURN — returns an error code to the application. the chill one 🫶

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. like, it might just be over. 🙈

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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👑 SEE ALSO 👑

• MPI_Op_create
• MPI_Reduce
• MPI_Allreduce
• MPI_Reduce_scatter
• MPI_Scan

all of these are besties, go read them 💅

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🌈 COPYRIGHT 🌈

2003-2026, The Open MPI Community

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and that's the whole page, bestie! 🎀 this version was brought to you by Sep 11, 2026 and the MPI_OP_FREE(3) page from the Open MPI manual — go free those handles responsibly, mwah 💖🧚‍♀️