MPIX_Info_set_hex(3)

💖 MPIX_Info_set_hex — bestie edition 💖

okay so we're deep in the MPI manual pages rn and this one is genuinely a lil niche gem. it's MPIX_Info_set_hex(3), the MPI manpage girlies know ✨

✨ NAME ✨

MPIX_Info_set_hex — [short description]

(yes bestie the actual name is MPIX_Info_set_hex, and the manual section it lives in is 3, as in section three. we love a numbered era 💅)

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🌸 SYNOPSIS 🌸

int MPIX_Info_set_hex(MPI_Info info, const char *key, const void *value,
int value_size)

that's the whole vibe. one function, four args, no notes 🫶

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🎀 INPUT PARAMETERS 🎀

• info — an info object, and it's a handle btw (so treat it with the respect a handle deserves 👑)
• key — the key, and it's a string
• value — the value, and it's a choice
• value_size — the size of value, and it's an integer, periodt

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🧚 THREAD AND INTERRUPT SAFETY 🧚

good news first: this routine is thread-safe. translation? multiple threads can call it at the same time and you do NOT need to bring your own thread locks, no cap 💯

but the plot twist: it is not interrupt safe. and why, you ask? typically it's because of memory allocation routines — think malloc and other non-MPICH runtime routines — which are themselves not interrupt-safe. so like, the interrupt safety vibe check is failed, but not by this routine's fault fr fr 😭

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🌈 NOTES FOR FORTRAN 🌈

okay Fortran besties, this part is for you:

• every single MPI routine in Fortran (except MPI_WTIME and MPI_WTICK) gets an extra argument called ierr tacked onto the end of the argument list. ierr is an integer and it means exactly the same thing as the return value of the routine in C. iconic parallelism ✨
• in Fortran, MPI routines are subroutines, and you invoke them with the call statement
• and all MPI objects — like MPI_Datatype, MPI_Comm — are of type INTEGER in Fortran

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💜 ERRORS 💜

so listen. all MPI routines (except MPI_Wtime and MPI_Wtick) return an error value: C routines as the value of the function itself, and Fortran routines in that last argument. and before that value ever gets handed back to you, the current MPI error handler gets called. and by default? that error handler aborts the MPI job. like, full send, game over 💀

you can change the error handler tho:

• MPI_Comm_set_errhandler — for communicators
• MPI_File_set_errhandler — for files
• MPI_Win_set_errhandler — for RMA windows

also the MPI-1 routine MPI_Errhandler_set may be used, but heads up bestie, its use is deprecated 🙈

and if you'd rather get error values back instead of getting nuked, the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned 👑

⚠️ big caveat, pay attention: MPI does not guarantee that an MPI program can continue past an error. that said, MPI implementations will attempt to continue whenever possible. so like… hopeful, but not promised 🥲

here's the error code lineup:

• MPI_SUCCESS — no error, the MPI routine completed successfully. we ate and left no crumbs ✨
• MPI_ERR_ARG — invalid argument. some argument is invalid and it's not identified by a specific error class (for example MPI_ERR_RANK). kinda vague of it ngl
• MPI_ERR_INFO — invalid Info
• MPI_ERR_OTHER — other error; use MPI_Error_string to get more information about this error code

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k that's the whole page babes, go forth and set those hex values 💅🦋

sending u off with the receipts: this page is dated 4/10/2026, and it's the MPIX_Info_set_hex(3) page — section 3, MPI manuals, that's the source and version energy. love u, go compile something gorgeous 💖✨