MPI_WIN_FLUSH_LOCAL(3)

💅 MPI_WIN_FLUSH_LOCAL(3) — the Open MPI one 🫶

okay so bestie, you found it: the MPI_WIN_FLUSH_LOCAL page from the Open MPI manual. sit down, grab a strawberry 🍓, and let's get into it because this one is actually lowkey iconic for your RMA code.

✨ NAME ✨

MPI_Win_flush_local, MPI_Win_flush_local_all — Complete all outstanding RMA operations at both the origin

🌸 SYNTAX 🌸

C Syntax

#include <mpi.h>

int MPI_Win_flush_local (int rank, MPI_Win win)

int MPI_Win_flush_local_all (MPI_Win win)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_WIN_FLUSH_LOCAL(RANK, WIN, IERROR)
     INTEGER RANK, WIN, IERROR

MPI_WIN_FLUSH_LOCAL_ALL(WIN, IERROR)
     INTEGER WIN, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Win_flush_local(rank, win, ierror)
     INTEGER, INTENT(IN) :: rank
     TYPE(MPI_Win), INTENT(IN) :: win
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

MPI_Win_flush_local_all(win, ierror)
     TYPE(MPI_Win), INTENT(IN) :: win
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🎀 INPUT PARAMETERS 🎀

• rank — Rank of window (nonnegative integer). yeah, the target rank, and no, negative numbers are not the vibe 💀
• win — Window object (handle). the whole window situation, hand it over

🦋 OUTPUT PARAMETER 🦋

• ierror — Fortran only: Error status (integer). C girlies, you get your error back as the return value instead, iykyk

💖 DESCRIPTION 💖

okay so here's the tea ☕ — MPI_Win_flush_local locally completes, at the origin, all outstanding RMA operations that the calling process initiated toward the target process specified by rank, on the specified window. literally all of them, for that one target. and once this routine completes, you may reuse any buffers you handed to put, get, or accumulate operations. your buffers are free, bestie, go touch grass 🌱

and then MPI_Win_flush_local_all does the same local-completion thing at the origin but for all outstanding RMA operations to all targets. every single one. no cap. 👑

lowkey important: these can only be called from within a passive target epoch. that's the rule, periodt 💅

😭 ERRORS 😭

Almost all MPI routines return an error value — C routines as the return result of the function, and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions.

Open MPI includes three predefined error handlers that can be used:

• MPI_ERRORS_ARE_FATAL — Causes the program to abort all connected MPI processes. dramatic? yes. effective? also yes 💀
• MPI_ERRORS_ABORT — An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.
• MPI_ERRORS_RETURN — Returns an error code to the application. the chill one, she just hands you the code and lets you deal 🫶

MPI applications can also implement their own error handlers by calling:

• MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
• MPI_File_create_errhandler then MPI_File_set_errhandler
• MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
• MPI_Win_create_errhandler then MPI_Win_set_errhandler

ngl this one matters: note that MPI does not guarantee that an MPI program can continue past an error. so like... don't count on it, bestie 🙈

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.

🌈 SEE ALSO 🌈

• MPI_Win_flush
• MPI_Win_lock
• MPI_Win_lock_all

the whole friend group, honestly ✨

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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and that's the page, bestie — written by the Open MPI girlies, dated Sep 11, 2026, filed under MPI_WIN_FLUSH_LOCAL(3). now go flush those buffers locally and slay 💅💖