MPI_TYPE_COMMIT(3)

💅 MPI_TYPE_COMMIT(3) — Open MPI

okay bestie, welcome to the Open MPI manual, this one's all about MPI_Type_commit and honestly? it's a glow-up ritual for your data types. let's get into it 🎀

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✨ NAME ✨

MPI_Type_commit — commits a data type. yes that's it. it's the "make it official" button. 💖

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🌸 SYNTAX 🌸

💻 C Syntax

#include <mpi.h>

int MPI_Type_commit(MPI_Datatype *datatype)

🧚 Fortran Syntax

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

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Type_commit(datatype, ierror)
     TYPE(MPI_Datatype), INTENT(INOUT) :: datatype
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🍓 INPUT PARAMETER 🍓

• datatype — the data type handle. it's the thing you're committing, bestie. one job, and it does it. ✨

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💜 OUTPUT PARAMETER 💜

• ierror — Fortran only: the error status (an integer). C girlies get their error as the return value instead, iykyk.

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👑 DESCRIPTION 👑

so here's the tea: the commit operation commits the data type. and because this is a manual and we're being thorough — a data type is the formal description of a communication buffer, not the content of that buffer. read that again. it's describing the shape, not the stuff inside. 🫶

after a data type has been committed, you can reuse it over and over again to communicate the changing content of a buffer — or, honestly, the content of totally different buffers, with different starting addresses. it's giving versatility, it's giving main character energy. 🔥

Example: here's a Fortran code fragment showing examples of using MPI_Type_commit.

INTEGER :: type1, type2
CALL MPI_TYPE_CONTIGUOUS(5, MPI_REAL, type1, ierr)
              ! new type object created
CALL MPI_TYPE_COMMIT(type1, ierr)
              ! now type1 can be used for communication

and if the data type specified in datatype is already committed? it's equivalent to a no-op. no drama, nothing happens, we move on. 💀

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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. noted. 💅

before that error value gets returned, the current MPI error handler associated with the communication object (like, a communicator, window, or file) gets called. if there's no communication object associated with the MPI call, then the call counts as attached to MPI_COMM_SELF and it'll call the associated MPI error handler. and when MPI_COMM_SELF is not initialized — meaning 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. that initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or with 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 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. phew. 😮💨

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. 🔥
• 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. chill of it honestly.

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. no cap. once it's over, it's 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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🎀 Copyright 🎀

2003-2026, The Open MPI Community

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and that's the whole thing bestie, you ate that. this was MPI_TYPE_COMMIT(3) from Open MPI, dated Sep 10, 2026, brought to you by 2003-2026, The Open MPI Community. now go commit that datatype, periodt. 💅✨🦋