MPI_WIN_TEST(3)

💖 MPI_Win_test 💖

ok so real talk, bestie — this page lives in the Open MPI manual, section 3, and it's MPI_WIN_TEST(3) if you're the kind of person who cites things properly (you are, I see you 👑).

MPI_Win_test — Attempts to complete an RMA exposure epoch; a nonblocking version of MPI_Win_wait

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✨ SYNTAX ✨

🍓 C Syntax

#include <mpi.h>

int MPI_Win_test(MPI_Win win, int *flag)

🎀 Fortran Syntax

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

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Win_test(win, flag, ierror)
     TYPE(MPI_Win), INTENT(IN) :: win
     LOGICAL, INTENT(OUT) :: flag
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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📥 INPUT PARAMETERS

• win — Window object (handle). your lil window bb 🪟

📤 OUTPUT PARAMETERS

• ierror — Fortran only: Error status (integer).
• flag — The returning state of the test for epoch closure.

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🌈 DESCRIPTION 🌈

MPI_Win_test is a one-sided MPI communication synchronization call, and it's the nonblocking version of MPI_Win_wait. Here's the vibe check: it returns flag = true if MPI_Win_wait would return, and flag = false otherwise. 💅

And like, when MPI_Win_test comes back with flag = true, that effect is exactly the same as the effect of a return of MPI_Win_wait. iconic. But if flag = false comes back? then the call has no visible effect. nothing. it's giving ghosting 🙈

ok important bestie: Invoke MPI_Win_test only where MPI_Win_wait can be invoked. And once the call has returned flag = true, it must not be invoked anew, until the window is posted anew. don't be messy about it, i'm begging 😭

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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.

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. 💀 like, everyone. gone.
• 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 polite 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

⚠️ Note that MPI does not guarantee that an MPI program can continue past an error. no cap.

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_post
• MPI_Win_wait

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🎀 Copyright

2003-2026, The Open MPI Community

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and that's the whole page bestie, you ate it up, go post that window 👑🌸💜 — this was the Open MPI MPI_WIN_TEST(3) page, dated Sep 10, 2026. mwah, periodt. 💅✨