MPI_Session_flush_buffer(3)

✨ MPI_Session_flush_buffer(3) ✨

okay bestie, welcome to the MPI manual page for MPI_Session_flush_buffer, and no cap this one is actually kind of a vibe 💅

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🌸 NAME 🌸

MPI_Session_flush_buffer — block until all the messages that are currently chilling in the session-specific buffer</> of the calling process have been transmitted 🦋

like. it waits. patiently. main character energy.

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✨ SYNOPSIS ✨

int MPI_Session_flush_buffer(MPI_Session session)

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🎀 INPUT PARAMETERS 🎀

• session — session (handle). that's it, that's the whole input. one handle, slay.

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🧵 THREAD AND INTERRUPT SAFETY 🧵

good news first: this routine is thread-safe. fr fr. that means multiple threads can use it at the same time with zero user-provided thread locks needed. no mutexes, no drama, no you-writing-lock-code-at-2am 😌

but — and this is the part where we read the fine print — it is not interrupt safe. typically that's because it uses memory allocation routines like malloc or other non-MPICH runtime routines, and those lil guys are themselves not interrupt-safe. so like, it's giving "great with friends, do not startle it" 💀

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🔮 NOTES FOR FORTRAN 🔮

every MPI routine in Fortran (except for MPI_WTIME and MPI_WTICK) has an extra argument ierr tacked onto the end of the argument list. ierr is an integer and it means the exact 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. periodt.

also, all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. iconic, honestly.

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💀 ERRORS 💀

all MPI routines (except MPI_Wtime and MPI_Wtick) return an error value; C routines as the value of the function, and Fortran routines in the last argument. before that value comes back to you, the current MPI error handler gets called. by default, this error handler aborts the MPI job — yeah, like, the whole thing. 🙈

the error handler can be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). the MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead.

heads up 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, don't count on it, but sometimes she survives 🫶

here's the error code lineup:

• MPI_SUCCESS — no error; MPI routine completed successfully. the dream. ⭐
• MPI_ERR_SESSION — invalid session handle.
• MPI_ERR_OTHER — other error; use MPI_Error_string to get more information about this error code.

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🌈 SEE ALSO 🌈

• MPI_Buffer_flush
• MPI_Comm_flush_buffer

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if you made it this far you're literally a Unix icon 👑 stay curious, stay caffeinated, and remember: blocking isn't a personality flaw, it's a feature. 💖

this page is from MPI, dated 4/10/2026, and it's the MPI_Session_flush_buffer(3) page — ty for coming to my ted talk, ily, bye 🎀✨