MPI_Comm_iflush_buffer(3)

💖 MPI_Comm_iflush_buffer(3) 💖

okay bestie, welcome to the MPI manual, this one's MPI_Comm_iflush_buffer and it's lowkey iconic 🦋

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✨ NAME ✨

MPI_Comm_iflush_buffer — starts a nonblocking flush in the communicator-specific buffer. that's it, that's the whole vibe 🌸

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✨ SYNOPSIS ✨

int MPI_Comm_iflush_buffer(MPI_Comm comm, MPI_Request *request)

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✨ INPUT PARAMETERS ✨

• comm — the communicator, aka a handle. it's giving "which friend group are we doing this in" 🫶

✨ OUTPUT PARAMETERS ✨

• request — the communication request, as a handle. you get one of these back so you can, yk, keep track of your nonblocking moment 💅

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✨ THREAD AND INTERRUPT SAFETY ✨

This routine is thread-safe, no cap. meaning: multiple threads can use it at the same time and none of them need you to hand them a user-provided thread lock. she's independent, she's self-sufficient, main character energy 👑

But — and this is the important part — the routine is not interrupt safe. 😭 typically this happens because memory allocation routines like malloc, or other non-MPICH runtime routines, get used in there, and those routines are themselves not interrupt-safe. so like, don't be sending signals mid-flush, bestie, that's a 💀 move.

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🌈 NOTES FOR FORTRAN 🌈

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr tacked on at the end of the argument list. ierr is an integer, and it means the exact same thing as the return value of the routine does in C. periodt.

Also, in Fortran, MPI routines are subroutines, and you invoke them with the call statement. yep, call. 🎀

And one more thing: all MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. so if you're out here declaring them as anything else, girl, no. 🙈

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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 itself, and Fortran routines in that last argument. before the value comes back to you, the current MPI error handler gets called. by default, this error handler aborts the MPI job, so yeah, it's giving dramatic 💀

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 — so like, don't, it's not the moment. 🙅

The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. Note that MPI does not guarantee that an MPI program can continue past an error — however, MPI implementations will attempt to continue whenever possible. fingers crossed fr fr 🤞

• MPI_SUCCESS — no error, the routine completed successfully. we slayed. ✅
• MPI_ERR_ARG — invalid argument. some argument is invalid and it's not identified by a specific error class (e.g., MPI_ERR_RANK). mystery behavior, honestly 💀
• MPI_ERR_COMM — invalid communicator. a common error is to use a null communicator in a call (which is not even allowed in MPI_Comm_rank). bestie. why.
• MPI_ERR_OTHER — other error; use MPI_Error_string to get more information about this error code. go read the details, she left a note 🍓

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🌸 SEE ALSO 🌸

• MPI_Comm_flush_buffer

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and that's the whole page, gorge 🧚✨ tysm for reading all the way through, you ate that. this was the MPI_Comm_iflush_buffer(3) man page, dated 4/10/2026, from the MPI manual set. mwah, go flush something nonblocking 💜👑🌷