MPI_WIN_FLUSH_ALL(3)

okay so bestie, welcome to the MPI_WIN_FLUSH_ALL(3) page from Open MPI — yes, the manual name is long, but it’s literally the home of MPI_Win_flush and MPI_Win_flush_all, and we’re gonna make it make sense 💖

🌸 NAME 🌸

MPI_Win_flush, MPI_Win_flush_all — complete all outstanding RMA operations at both the origin and the target.

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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 window, and it’s a nonnegative integer. periodt.
• win — window object (handle). the whole vibe lives here.

🫶 OUTPUT PARAMETER 🫶

• ierror — Fortran only: error status (integer). iykyk.

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🌈 DESCRIPTION 🌈

MPI_Win_flush completes all outstanding RMA operations initiated by the calling process to the target rank on the specified window. The operations are completed both at the origin and at the target. like, both sides get the memo, no cap.

MPI_Win_flush_all completes all outstanding RMA operations to all targets. all of them. the whole group chat.

⚠️ caveat bestie: this can only be called from within a passive target epoch. that’s not a suggestion, it’s the rule 💅

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💀 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. so yes, check it.

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, but accurate.
• 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 “hand it back” option.

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. so don’t just yolo past 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.

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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

mwah 💋 this page is from Open MPI, dated Sep 11, 2026 — go off and flush those RMA ops, bestie 🫶