MPI_File_fromint(3)

✨ MPI_File_fromint(3) ✨

okay bestie, this one's from the MPI fam, and it's literally the glow-up machine that turns a plain lil integer into a whole MPI_File. no cap. 💅

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🎀 NAME 🎀

MPI_File_fromint — converts an integer handle to MPI_File

like. that's it. that's the whole job. she's a converter, she's a translator, she's the bridge between "just a number" and "actual MPI file object." obsessed. 🦋

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🌸 SYNOPSIS 🌸

MPI_File MPI_File_fromint(int file)

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💖 INPUT PARAMETERS 💖

• file — file (integer). yes it's just an int, that's the whole point, that's her origin story ✨

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🔥 THREAD AND INTERRUPT SAFETY 🔥

okay so the tea here is two different things, don't mix them up:

This routine is thread-safe. that means you can hit it from multiple threads at the same time and you do NOT need to bring your own user-provided thread locks. she's self-sufficient, she's independent, she doesn't need you hovering. 🫶

BUT. she is not interrupt safe. and why? typically because of memory allocation routines like malloc — or other non-MPICH runtime routines — and those lil guys are themselves not interrupt-safe. so yeah. it's giving "managed by somebody else's vibes." 😭

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🌈 NOTES FOR FORTRAN 🌈

Fortran besties, this section is for you 💖

• All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. so there's always one extra lil guy trailing along at the back. 🍓
• ierr is an integer and has the same meaning as the return value of the routine in C. same energy, different outfit.
• In Fortran, MPI routines are subroutines, and they get invoked with the call statement. periodt.
• All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. yes, even the fancy ones. integer. iconic.

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💀 ERRORS 💀

okay so here's how error handling works in the MPI cinematic universe. every MPI routine (except MPI_Wtime and MPI_Wtick) returns an error value — in C routines it's the value of the function itself, and in Fortran routines it comes back in that last argument we just talked about.

Before the value is returned, the current MPI error handler gets called. and by default? that error handler aborts the whole MPI job. like, full dramatic exit. 😳

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)

there's also MPI_Errhandler_set, the MPI-1 routine, but its use is deprecated. lowkey don't.

If you'd rather have error values handed back to you instead of everything exploding, use the predefined error handler MPI_ERRORS_RETURN.

⚠️ important caveat bestie: MPI does not guarantee that an MPI program can continue past an error. however, MPI implementations will attempt to continue whenever possible. so like… fingers crossed? 🤞

Now, the actual error codes:

• MPI_SUCCESS — No error; MPI routine completed successfully. she ate and left no crumbs. 👑
• MPI_ERR_OTHER — Other error; use MPI_Error_string to get more information about this error code. when in doubt, ask the string. she'll tell you. 💜

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🌟 SEE ALSO 🌟

MPI_Error_string — because that's literally where you're headed if you get MPI_ERR_OTHER. iykyk. 🧚

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and that's the whole page babes — this was the MPI manual, page MPI_File_fromint(3), dated 4/10/2026. go forth and convert those integers. slay. 💅✨🎀