MPIX_Async_spawn(3)

💅 MPIX_Async_spawn — the manual page bestie edition 🦋

okay so you opened MPIX_Async_spawn(3), the MPI one, section 3, and honestly? slay. this is the girlies' guide to spawning async things. let's get into it ✨

🌸 NAME 🌸

MPIX_Async_spawn — [short description]

like, the name is literally right there and the description is genuinely just the placeholder [short description]. ngl that's giving "we'll fill this in later" but we move 💀

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✨ SYNOPSIS ✨

int MPIX_Async_spawn(MPIX_Async_thing async_thing,
MPIX_Async_poll_function *poll_fn, void *extra_state,
MPIX_Stream stream)

that's the whole vibe. four args, one int coming back at you 💖

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🎀 INPUT PARAMETERS 🎀

• async_thing — an opaque pointer for the async thing. default: None. it's giving mystery box, we don't peek inside 🔮
• poll_fn — your very own user defined poll function for progressing async things. it's a function, so that's the type of it, and yes you have to bring it yourself 🫶
• extra_state — extra state for the callback function. default: None. carry whatever little treasures you need, bestie 🍓
• stream — a stream object. that's a handle, periodt 💅

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🧚 THREAD AND INTERRUPT SAFETY 🧚

bestie listen: this routine is thread-safe. that means multiple threads can use it safely and you do NOT need to bring your own user-provided thread locks. no cap. 👑

but — and I need you to hear me — it is not interrupt safe. not even a little. this is typically because it uses memory allocation routines like malloc, or other non-MPICH runtime routines that are themselves not interrupt-safe. so don't come for it at interrupt time 😭

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🌈 NOTES FOR FORTRAN 🌈

every MPI routine in Fortran (except for MPI_WTIME and MPI_WTICK) has one extra argument, ierr, tacked onto the end of the argument list. ierr is an integer and it means exactly the same thing as the return value does in C. iykyk 💜

and in Fortran, MPI routines are subroutines, so you invoke them with the call statement. iconic behavior.

also!! all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. yes, even the ones that feel like they shouldn't be. that's just the rules 🌟

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💀 ERRORS 💀

okay so every MPI routine (except MPI_Wtime and MPI_Wtick) returns an error value — C routines as the value of the function, and Fortran routines in the last argument. before that value comes back to you, the current MPI error handler gets called. and by default, this error handler aborts the MPI job. not dramatic, extremely dramatic. 🚨

the error handler can be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). the MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated — so like, technically allowed, spiritually over 🙈

the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible. so it'll try, bless it 💖

here's the receipts:

• MPI_SUCCESS — no error; MPI routine completed successfully. the dream. the goal. the slay ✨
• MPI_ERR_ARG — invalid argument. some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK). something is wrong and it's not telling you which thing. rude, honestly 😭
• MPI_ERR_OTHER — other error; use MPI_Error_string to get more information about this error code. the catch-all. go read the string, bestie 📖

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👑 SEE ALSO 👑

there's genuinely nothing listed here, so the see-also section is me telling you to go re-read the top of this page. self-care 🫶

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that's the whole page, fr fr 💜 this version of MPIX_Async_spawn(3) (MPI man page, the MPIX_Async_spawn(3) one) is dated 4/10/2026 — go forth and spawn your async things responsibly, mwah 💅✨🌸