MPI_TYPE_EXTENT(3)

🎀 MPI_TYPE_EXTENT — like, the whole entire vibe 🎀

okay so bestie, this page is from Open MPI and it's all about MPI_Type_extent — the routine that returns the extent of a data type. 💅

🚨 real talk though: this routine is deprecated in favor of MPI_Type_get_extent. not me showing you the old way, but like, you gotta know it, iykyk.

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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). that's the thing you're measuring, bestie ✨

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💜 OUTPUT PARAMETERS 💜

• extent — Datatype extent (integer). the answer, the moment, the slay 🌈
• ierror — Fortran only: Error status (integer). 🙈

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👑 DESCRIPTION 👑

so like. heads up. use of this routine is deprecated as of MPI-2. please please please use MPI_Type_get_extent instead, okay? 🫶

MPI_Type_extent returns the extent of a data type — which is literally just the difference between the upper and lower bounds of the data type. no cap.

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

and 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, like, obviously:

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

and 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). math ate, periodt. 💅✨

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💀 ERRORS 💀

almost all MPI routines return an error value, bestie — 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) 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. 😭 it's a whole thing.

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

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. 💀
• 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. bestie gets a receipt 🧾

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. so like, no promises, fr fr.

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. 📚

👀 See also:

• MPI_Type_get_extent — the glow-up, the main character, use this one instead ✨

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📜 Copyright 📜

2003-2026, The Open MPI Community 💖

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aaaand that's the whole entire page, bestie!! go forth and get those extents (with MPI_Type_get_extent, obviously 🙈). this was Open MPI, MPI_TYPE_EXTENT(3), dated Sep 10, 2026 — mwah, slay, bye!! 💅🎀🦋✨