MPI_WIN_WAIT(3)

💫 MPI_Win_wait — the Open MPI glow-up (manual page MPI_WIN_WAIT(3))

okay bestie, sit down, hydrate, and let me tell you about MPI_Win_wait — she's an Open MPI girlie and she *completes an RMA exposure epoch started by a call to MPI_Win_post on *win** ✨

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🎀 SYNTAX 🎀

C Syntax

#include <mpi.h>

int MPI_Win_wait(MPI_Win win)

Fortran Syntax

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

Fortran 2008 Syntax

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

like, three whole syntaxes? she contains multitudes 💅

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🌸 INPUT PARAMETERS 🌸

• win — the Window object (a handle). that's the whole vibe check right there 🪟✨

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🦋 OUTPUT PARAMETERS 🦋

• ierror — Fortran only, bestie: error status (integer). the C girlies get their error as the return value instead, iykyk 💜

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🔥 DESCRIPTION 🔥

okay so MPI_Win_wait is a one-sided MPI communication synchronization call, and what she does is complete an RMA exposure epoch that got started by a call to MPI_Win_post on win. no cap.

she matches up with the calls to MPI_Win_complete(win) that each of the processes granted access to the window during this epoch went and issued. the way she works is: the call to MPI_Win_wait blocks until all the matching calls to MPI_Win_complete have happened. blocking era. main character energy. she is not moving until everybody shows up 🫶

and that's literally the point, because it guarantees that all these origin processes have finished their RMA accesses to the local window. when the call returns, all those RMA accesses will have completed at the target window. done. slayed. periodt 💅✨

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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. that's just how she rolls.

before that error value gets returned, 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 is considered attached to MPI_COMM_SELF and it'll call the associated MPI error handler. if 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 one can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when you're using the World model, or via the mpi_initial_errhandler CLI argument to mpiexec, or the 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 you can use, and yes they're iconic:

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. she's dramatic but she's clear 💀
• 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, it 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, it aborts only the local process. range, honestly 🔥
• MPI_ERRORS_RETURN — returns an error code to the application. lowkey the chill one 🍓

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

build your own, bestie, it's giving DIY 👑

⚠️ note that MPI does not guarantee that an MPI program can continue past an error. so like… don't count on it, fr fr.

see the MPI man page for a full list of MPI error codes. and see the Error Handling section of the MPI-3.1 standard for more information. 📚

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🌈 SEE ALSO 🌈

• MPI_Win_post — her other half, the one who starts the epoch 💖

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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and that's the whole page, bestie — this little gem dropped on Sep 11, 2026 with the Open MPI source/version energy all over it. go forth and MPI_Win_wait responsibly 🧚‍♀️💜✨