MPI_TYPE_HINDEXED(3)

💅 MPI_TYPE_hindexed — like, the old hindexed, bestie

okay so real talk first: this is an Open MPI man page (manual name MPI_TYPE_HINDEXED(3), section 3), and the whole vibe is "creates an indexed datatype with offsets in bytes" — but 🚨 this routine is deprecated in favor of MPI_Type_create_hindexed. Yes, deprecated. We'll get to that. Sit down, grab a boba. 🧋

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✨ NAME ✨

MPI_Type_hindexed — creates an indexed datatype with offsets in bytes. Also known as: the deprecated one, the legacy one, the "why are you still using this" one. It's literally deprecated in favor of MPI_Type_create_hindexed. 🫶

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🌸 SYNTAX 🌸

🎀 C Syntax

#include <mpi.h>

int MPI_Type_hindexed(int count, int *array_of_blocklengths,
     MPI_Aint *array_of_displacements, MPI_Datatype oldtype,
     MPI_Datatype *newtype)

🦋 Fortran Syntax

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

MPI_TYPE_HINDEXED(COUNT, ARRAY_OF_BLOCKLENGTHS,
             ARRAY_OF_DISPLACEMENTS, OLDTYPE, NEWTYPE, IERROR)
     INTEGER COUNT, ARRAY_OF_BLOCKLENGTHS(*)
     INTEGER ARRAY_OF_DISPLACEMENTS(*), OLDTYPE, NEWTYPE
     INTEGER IERROR

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💖 INPUT PARAMETERS 💖

• count — number of blocks. It's also the number of entries in array_of_displacements and array_of_blocklengths, so like... one number, three jobs. (integer)
• array_of_blocklengths — how many elements are in each block (array of nonnegative integers, so no negatives, bestie, I'm serious 🙈).
• array_of_displacements — the byte displacement of each block (C: array of MPI_Aint, Fortran: array of integer).
• oldtype — the old datatype (handle).

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👑 OUTPUT PARAMETERS 👑

• newtype — the new datatype (handle). Your fresh little icon. ✨
• ierror — Fortran only: error status (integer).

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💀 DESCRIPTION 💀

⚠️ Heads up: use of this routine is deprecated as of MPI-2. Use MPI_Type_create_hindexed instead. That's it. That's the note. Go use the other one. 💅

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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. So yes, check it, ngl.

Before that error value comes back to you, the current MPI error handler associated with the communication object (e.g., communicator, window, 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 will call the associated MPI error handler. And 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. That initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or by the mpi_initial_errhandler CLI argument to mpiexec, or the 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 you can use:

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. yeah. everyone. 😭
• 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. situational! 💅
• 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. fr fr, don't count on it. 🫠

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_create_hindexed ← the one you actually want, bestie 👀
• MPI_Type_create_struct
• MPI_Type_indexed

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🍓 COPYRIGHT 🍓

2003-2026, The Open MPI Community

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and that's the whole page, periodt. 💜 cute sign-off time: this lil page is from Open MPI, dated Sep 11, 2026, and it's MPI_TYPE_HINDEXED(3) all the way down. mwah. 🎀✨