MPIX_Session_create_errhandler_x(3)

💖 MPIX_Session_create_errhandler_x(3) 💖

okay bestie, welcome to the MPI manual page for MPIX_Session_create_errhandler_x — yes, that's a mouthful, but it's giving ✨main character✨ energy and we're gonna get through it together. grab a snack. 🍓

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🌸 NAME 🌸

MPIX_Session_create_errhandler_x — she creates an MPI-style session errorhandler with an extra_state. no cap, that's the whole job. 💅

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✨ SYNOPSIS ✨

lowkey the vibe is right here, copy it verbatim bestie:

int MPIX_Session_create_errhandler_x(MPIX_Session_errhandler_function_x *comm_errhandler_fn_x,
MPIX_Destructor_function *destructor_fn,
void *extra_state,
MPI_Errhandler *errhandler)

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🎀 INPUT PARAMETERS 🎀

• comm_errhandler_fn_x — your own user defined error handling procedure, except it also carries extra_state along for the ride (function). it's the glow-up version of the regular one, iykyk.
• destructor_fn — the callback that gets hit when the op is freed (function). it's giving "clean up after yourself" energy.
• extra_state — extra state (None). that's it, that's the state. 🫶

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🦋 OUTPUT PARAMETERS 🦋

• errhandler — the MPI error handler (handle). this is what you're walking away with. obsessed. 💖

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🔥 THREAD AND INTERRUPT SAFETY 🔥

good news first: this routine is thread-safe. that means multiple threads can use it at the same time and you do not need to bring your own thread locks. slay.

but — and listen — the routine is not interrupt safe, periodt. typically that's because it uses memory allocation routines like malloc, or other non-MPICH runtime routines that are themselves not interrupt-safe. so don't be out here interrupting her mid-malloc, okay? 💀

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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 on at the end of the argument list. ierr is an integer and means the same thing as the return value of the routine in C. in Fortran, MPI routines are subroutines and you invoke them with the call statement. that's just how Fortran does. 🎀

also: all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. write that down bestie. 📝

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⭐ ERRORS ⭐

so every MPI routine (except MPI_Wtime and MPI_Wtick) returns an error value — C routines as the value of the function, Fortran routines in that last argument. and before the value comes back to you, the current MPI error handler gets called. by default? that error handler aborts the MPI job. 😭 dramatic but true.

you can switch the error handler around with these:

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

there's the MPI-1 routine MPI_Errhandler_set too, but heads up: its use is deprecated. lowkey don't.

if you'd rather have error values handed back to you instead of the whole job dipping, use the predefined error handler MPI_ERRORS_RETURN. that's the move. 💅

⚠️ careful bestie: 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… fingers crossed, but no promises. 🙈

and here are the actual error codes:

• MPI_SUCCESS — No error; MPI routine completed successfully. ate, no crumbs. 👑
• MPI_ERR_ARG — Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).
• MPI_ERR_OTHER — Other error; use MPI_Error_string to get more information about this error code.

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and that's the whole page babes 🧚 you understood the assignment. this was MPIX_Session_create_errhandler_x(3) from the MPI manual, dated 4/10/2026. go forth and handle your errors with grace. mwah. 💜✨