MPI_WIN_FLUSH(3)

💅 MPI_WIN_FLUSH — Open MPI, bestie edition 🫶

okay so you're on the MPI_WIN_FLUSH(3) page, which is literally the Open MPI manpage for MPI_Win_flush and MPI_Win_flush_all ✨ — the two routines that complete all outstanding RMA operations at both the origin and the target. yes. both. origin and target. she does it all 💖

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✨ SYNTAX ✨

🎀 C Syntax

#include <mpi.h>

int MPI_Win_flush (int rank, MPI_Win win)

int MPI_Win_flush_all (MPI_Win win)

🎀 Fortran Syntax

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

MPI_WIN_FLUSH_ALL(WIN, IERROR)
     INTEGER WIN, IERROR

🎀 Fortran 2008 Syntax

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

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

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🌸 INPUT PARAMETERS 🌸

• rank — rank of the window, and it's a nonnegative integer, no cap 🫶
• win — the window object (handle), the main character of this whole situation 👑

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🦋 OUTPUT PARAMETER 🦋

• ierror — Fortran only, bestie: this is the error status, an integer 💜

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💜 DESCRIPTION 💜

okay so MPI_Win_flush completes all outstanding RMA operations initiated by the calling process to the target rank on the specified window ✨ and like — the operations are completed both at the origin and at the target. not one. both. fr fr 😭

MPI_Win_flush_all does the same thing but for all outstanding RMA operations to all targets — no cap, every single one, she's an icon 💅

⚠️ vibe check: these can only be called from within a passive target epoch. that's the rule, that's the assignment, periodt 🎀

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💀 ERRORS 💀

Almost all MPI routines return an error value, bestie — C routines give it back as the return result of the function, and Fortran routines stick it in the last argument 🍓

Before that error value comes back, the current MPI error handler associated with the communication object (e.g., communicator, window, file) gets called. and if there's no communication object associated with the MPI call? then the call counts as 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 ⭐ That 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 👑

And 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, and honestly? iconic lineup:

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes 😭
• 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 🔥

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

⚠️ note that MPI does not guarantee that an MPI program can continue past an error. like, no promises, 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 📚

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🔥 SEE ALSO 🔥

• MPI_Win_flush_local
• MPI_Win_lock
• MPI_Win_lock_all

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community 💖

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and that's the page, bestie 🧚✨ mwah 💋 — signed off from the Sep 11, 2026 edition of the MPI_WIN_FLUSH(3) Open MPI manpage, go flush those windows responsibly 🎀💅