MPI_Session_finalize(3)

💖 MPI_Session_finalize(3) 💖

okay bestie, so this is a page from the MPI manual — like, the whole MPI family — and today we're talking about MPI_Session_finalize. put your phone down for two seconds, this one's actually easy, i promise 🫶

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✨ NAME ✨

MPI_Session_finalize — Finalize an MPI Session

like, you're done with your session, you're closing it out, you're logging off, you're saying bye 👋

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✨ SYNOPSIS ✨

int MPI_Session_finalize(MPI_Session *session)

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✨ INPUT/OUTPUT PARAMETERS ✨

• session — the session to be finalized (handle). bestie this one is in and out, so it gets to be both an input and an output. iconic behaviour honestly 💅

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✨ NOTES FOR FORTRAN ✨

okay so for all you Fortran girlies 🌸 — every single MPI routine in Fortran (except for MPI_WTIME and MPI_WTICK, those two are the special little exceptions, no cap) gets an 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 of the routine does in C. literally the same concept, just vibing in a different language.

and in Fortran, MPI routines are subroutines, and you invoke them with the call statement. that's just how it is, periodt.

also, all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. no fancy types, just INTEGER. slay.

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✨ ERRORS ✨

so here's the vibe check on errors — every MPI routine (except MPI_Wtime and MPI_Wtick) returns an error value. C routines give it back as the function's value, and Fortran routines put it in that last argument. and before the value comes back to you? the current MPI error handler gets called. like, it shows up first, uninvited.

by default that error handler aborts the MPI job 💀 — so, like, if you weren't ready for that, know that's the default, okay?

you can swap the error handler out with:

• MPI_Comm_set_errhandler (for communicators)
• MPI_File_set_errhandler (for files)
• MPI_Win_set_errhandler (for RMA windows)

the MPI-1 routine MPI_Errhandler_set may be used, but its use is deprecated — girl, don't, it's giving old 🙈

and the predefined error handler MPI_ERRORS_RETURN can be used if you want error values to just be returned instead.

⚠️ heads up bestie: 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 like... don't count on it, but they'll try. 🧚

now the actual error codes, here we go:

• MPI_SUCCESS — No error; MPI routine completed successfully. ate and left no crumbs ✨
• MPI_ERR_SESSION — Invalid session handle. the handle was not giving what it needed to give 😭
• MPI_ERR_OTHER — Other error; use MPI_Error_string to get more information about this error code. when it's a mystery error, MPI_Error_string is your bestie, ask her 🔥

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and that's the whole page! 🎀 this was MPI_Session_finalize(3) from the MPI manual, dated 4/10/2026 — stamp it, frame it, it's canon. go finalize those sessions, queen 👑💜