MPI_T_INIT_THREAD(3)

💖 MPI_T_INIT_THREAD(3) 💖

okay bestie, this is the Open MPI page for MPI_T_INIT_THREAD(3) and it's literally the little sparkle that turns the MPI Tool information interface ON. no cap. 🦋

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✨ NAME ✨

MPI_T_init_thread — Initializes the MPI Tool information interface

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🌸 SYNTAX 🌸

C Syntax

#include <mpi.h>

int MPI_T_init_thread(int required, int *provided)

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🎀 INPUT PARAMETERS 🎀

• required — Desired level of thread support (integer). it's giving "here's what I want, no promises tho" 💅

🫶 OUTPUT PARAMETERS 🫶

• provided — Available level of thread support (integer). this is the reality check, the actual vibe you got 🌈

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💜 DESCRIPTION 💜

MPI_T_init_thread() initializes the MPI tool information interface. periodt.

so here's the tea: you can call MPI tool functions at any point in execution — including before MPI_Init() and after MPI_Finalize() — as long as MPI_T_init_thread() has been called at least once and the number of calls to MPI_T_init_thread() is greater than the number of calls to MPI_T_finalize(). it's a little counter situation, iykyk 🧮✨

and if at any point in execution the number of calls to MPI_T_finalize() equals the number of calls to MPI_T_init_thread(), then the MPI tool interface will no longer be available until another call to MPI_T_init_thread(). so like... balanced counters = interface gone, unbalance them again and it's back. iconic behavior. 💀

MPI_T_init_thread(), like MPI_Init_thread(), has a provision to request a certain level of thread support in required:

• MPI_THREAD_SINGLE — Only one thread will execute.
• MPI_THREAD_FUNNELED — If the process is multithreaded, only the thread that called MPI_Init_thread will make MPI calls.
• MPI_THREAD_SERIALIZED — If the process is multithreaded, only one thread will make MPI library calls at one time.
• MPI_THREAD_MULTIPLE — If the process is multithreaded, multiple threads may call MPI at once with no restrictions.

The level of thread support available to the program is set in provided. In Open MPI, the value is dependent on how the library was configured and built. Note that there is no guarantee that provided will be greater than or equal to required. 🔥 so like, you asked, but the build said "we'll see" 😭

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🌟 NOTES 🌟

It is the caller's responsibility to check the value of provided, as it may be less than what was requested in required.

fr fr, do NOT skip this check. provided could lowkey be less than required and that's on you to notice, bestie. 👑

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😭 ERRORS 😭

MPI_T_init_thread will fail if:

• MPI_T_ERR_MEMORY — Out of memory
• MPI_T_ERR_CANNOT_INIT — Interface not in the state to be initialized

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👑 SEE ALSO 👑

• MPI_T
• MPI_Init
• MPI_Init_thread

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that's the whole page, you ate it 💅

Copyright — 2003-2026, The Open MPI Community

this lil masterpiece dropped Sep 10, 2026, from the Open MPI team, and yes it's page MPI_T_INIT_THREAD(3) in section 3 of the manual. slay, go thread safely 🎀✨🦋