MPI_Buffer_flush(3)

🫶 MPI_Buffer_flush — the manual page

ok bestie, sit down, hydrate, because this one is short but it's doing IMPORTANT work. this is the manual page for MPI_Buffer_flush from the MPI manual collection, and by the end you're gonna understand it better than your group chat understands your situationship. let's go ✨

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✨ NAME ✨

MPI_Buffer_flush — block until all messages currently in the globally shared buffer of the calling process have been transmitted

that's it. that's the whole vibe. it waits. patiently. like a best friend holding your bag while you take pics. 💖

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🌸 SYNOPSIS 🌸

int MPI_Buffer_flush(void)

no arguments, no drama, no notes. just vibes and a return value. 👑

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💅 THREAD AND INTERRUPT SAFETY 💅

okay so the important tea:

this routine is thread-safe. that means it can be safely used by multiple threads at the same time, and you do NOT need to bring your own user-provided thread locks. she handles herself. main character energy, truly. 🎀

However — and this is the part where we all gasp — the routine is not interrupt safe. 😭

ngl the reason is usually kinda mundane: it's typically due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. so like, it's not her fault, it's the company she keeps. 💀

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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.
• ierr is an integer and it has the same meaning as the return value of the routine in C.
• in Fortran, MPI routines are subroutines, and they are invoked with the call statement.
• all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.

like yes, everything is INTEGER. that's just the Fortran house style, no cap. 🌈

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🔥 ERRORS 🔥

okay so this is the part where we talk consequences.

all MPI routines (except MPI_Wtime and MPI_Wtick) return an error value. C routines return it as the value of the function, and Fortran routines put it in the last argument. before that value is returned, the current MPI error handler is called. and by default? yeah, this error handler aborts the MPI job. 😭 so like, not a gentle lil tap on the wrist. full shutdown.

you CAN change that error handler:

• 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. 🚩 so like, don't. just don't.

there's also the predefined error handler MPI_ERRORS_RETURN, which may be used to cause error values to be returned instead. convenient, right?

⚠️ but real talk: MPI does not guarantee that an MPI program can continue past an error. however, MPI implementations will attempt to continue whenever possible. so it's giving "we'll try our best" not "we promise". 💀

now the error codes themselves:

• MPI_SUCCESS — No error; MPI routine completed successfully. 🎉 the only one we're manifesting.
• MPI_ERR_OTHER — Other error; use MPI_Error_string to get more information about this error code. like, go read the notes, bestie, the details are in there. 🙈

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🌟 SEE ALSO 🌟

go peek at these icons when you're done here:

• MPI_Comm_flush_buffer
• MPI_Session_flush_buffer

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and that's the whole page, bestie!! you ate that. go flush your buffers responsibly. 💖

this has been the MPI_Buffer_flush(3) page — dated 4/10/2026, footer source MPI_Buffer_flush(3), periodt. 🎀✨