MPI_TYPE_EXTENT(3)

💅 MPI_TYPE_EXTENT(3) — Open MPI

okay bestie, so this one's an Open MPI man page, and the function is MPI_Type_extent — it Returns the extent of a data type 🦋 — but listen, the headline here is that this routine is deprecated in favor of MPI_Type_get_extent. Like, it still works and all, but it's giving "senior who's technically retired but still shows up to every meeting." Use the new one, mwah 💋

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✨ SYNTAX ✨

🌸 C Syntax

#include <mpi.h>

int MPI_Type_extent(MPI_Datatype datatype, MPI_Aint *extent)

💜 Fortran Syntax

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

MPI_TYPE_EXTENT(DATATYPE, EXTENT, IERROR)
     INTEGER DATATYPE, EXTENT, IERROR

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🎀 INPUT PARAMETER

• datatype — Datatype (handle). The type whose extent we're about to measure, no big deal 💅

🫶 OUTPUT PARAMETERS

• extent — Datatype extent (integer). This is the number you came for ✨
• ierror — Fortran only: Error status (integer).

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🔥 DESCRIPTION 🔥

okay so first thing, and I need you to hear me on this: use of this routine is deprecated as of MPI-2. Please use MPI_Type_get_extent instead. Not me being dramatic, that's just the facts 💀

So MPI_Type_extent returns the extent of a data type — literally just the difference between the upper and lower bounds of the data type. That's it. That's the whole vibe.

In general, if

Typemap = {(type(0), disp(0)), ..., (type(n-1), disp(n-1))}

then the lower bound of Typemap is defined to be

                ( min(j) disp(j)                         if no entry has
    lb(Typemap)=(                                        basic type lb
                (min(j) {disp(j) such that type(j) = lb} otherwise

Similarly, the upper bound of Typemap is defined to be

                (max(j) disp(j) + sizeof(type(j)) + e    if no entry has
    ub(Typemap)=(                                        basic type ub
                (max(j) {disp(j) such that type(j) = ub} otherwise

Then — and this is the iconique part 👑

extent(Typemap) = ub(Typemap) - lb(Typemap)

and one more thing, don't skip it: if type(i) requires alignment to a byte address that is a multiple of k(i), then e is the least nonnegative increment needed to round extent(Typemap) to the next multiple of max(i) k(i). Like, e is the little padding goblin making everything line up 🧚

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💀 ERRORS 💀

okay so almost all MPI routines return an error value — C routines give it to you as the return result of the function, and Fortran routines stick it in the last argument. classic.

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/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.

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

• MPI_ERRORS_ARE_FATAL — Causes the program to abort all connected MPI processes. very "everyone gets in the group chat and everyone leaves the group chat" energy 😭
• 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. polite, hands you the L directly 💌

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. fr fr, plan accordingly.

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_Type_get_extent — the new main character, use this one bestie 👑

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🌈 COPYRIGHT 🌈

2003-2026, The Open MPI Community

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and that's the tea ☕ tysm for reading, this page is from Open MPI, released Sep 11, 2026, filing under MPI_TYPE_EXTENT(3) — slay, bye! 💖✨🎀