MPI_WIN_CREATE(3)

📦

version 5.0.10 · 7 versions

💖 MPI_Win_create — bestie, let's build a window 💖

okay so this is the Open MPI man page for MPI_Win_create, and I am obsessed with it, fr fr. It's a one-sided MPI call that hands you back a window object for RMA operations. main character energy tbh. 🪟✨

🌸 SYNTAX 🌸

C Syntax

#include <mpi.h>

MPI_Win_create(void *base, MPI_Aint size, int disp_unit,
     MPI_Info info, MPI_Comm comm, MPI_Win *win)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_WIN_CREATE(BASE, SIZE, DISP_UNIT, INFO, COMM, WIN, IERROR)
     <type> BASE(*)
     INTEGER(KIND=MPI_ADDRESS_KIND) SIZE
     INTEGER DISP_UNIT, INFO, COMM, WIN, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Win_create(base, size, disp_unit, info, comm, win, ierror)
     TYPE(*), DIMENSION(..), ASYNCHRONOUS :: base
     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: size
     INTEGER, INTENT(IN) :: disp_unit
     TYPE(MPI_Info), INTENT(IN) :: info
     TYPE(MPI_Comm), INTENT(IN) :: comm
     TYPE(MPI_Win), INTENT(OUT) :: win
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🎀 INPUT PARAMETERS 🎀

base — Initial address of window (choice). (yes bestie, you pick it 💅)
size — Size of window in bytes (nonnegative integer). nonnegative, periodt.
disp_unit — Local unit size for displacements, in bytes (positive integer). positive only, no negativity allowed 💚
info — Info argument (handle).
comm — Communicator (handle).

🦋 OUTPUT PARAMETERS 🦋

win — Window object returned by the call (handle). the moment we've all been waiting for 😭
ierror — Fortran only: Error status (integer).

✨ DESCRIPTION ✨

So MPI_Win_create is a one-sided MPI communication collective call — meaning every process in the group of comm has to run it. No skipping, bestie, it's giving mandatory group project but like, the good kind. 🫶

It returns a window object that all these processes can use to do RMA operations. Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm. That window? It consists of size bytes, starting at address base. And if a process is feeling antisocial, it may elect to expose no memory at all by specifying size = 0. iconically introverted. 🙈

If the base value used by MPI_Win_create was allocated by MPI_Alloc_mem, the size of the window can be no larger than the value set by the MPI_Alloc_mem function. don't try to be bigger than your alloc, it's not the vibe 😭

The disp_unit argument is there to make address arithmetic in RMA operations easier: the target displacement argument of an RMA operation gets scaled by the factor disp_unit specified by the target process, at window creation time. math but make it cute 🧮✨

The following info keys are supported:

`no_locks`

If set to true, then the implementation may assume that the local window is never locked (by a call to MPI_Win_lock or MPI_Win_lock_all). Setting this value if only active synchronization may allow the implementation to enable certain optimizations. faster vibes, as long as you're honest about it 👑

`accumulate_ordering`

By default, accumulate operations from one initiator to one target on the same window memory location are strictly ordered. If the info key accumulate_ordering is set to none, no ordering of accumulate operations guaranteed. The key can also be a comma-separated list of required orderings consisting of rar, war, raw, and waw for read-after-read, write-after-read, read-after-write, and write-after-write, respectively. Looser ordering constraints are likely to result in improved performance. 🔥

`accumulate_ops`

If set to same_op, the implementation will assume that all concurrent accumulate calls to the same target address will use the same operation. If set to same_op_no_op, then the implementation will assume that all concurrent accumulate calls to the same target address will use the same operation or MPI_NO_OP. The default is same_op_no_op. default noted, bestie, don't forget it 💜

`same_size`

If set to true, then the implementation may assume that the argument size is identical on all processes, and that all processes have provided this info key with the same value.

`same_disp_unit`

If set to true, then the implementation may assume that the argument disp_unit is identical on all processes, and that all processes have provided this info key with the same value.

🌈 NOTES 🌈

Common choices for disp_unit are 1 (no scaling), and (in C syntax) sizeof(type), for a window that consists of an array of elements of type type. The latter choice will let you use array indices in RMA calls and have those scaled correctly to byte displacements, even in a heterogeneous environment. slay, portable math 💚

Use memory allocated by MPI_Alloc_mem to guarantee properly aligned window boundaries (such as word, double-word, cache line, page frame, and so on). alignment is self care, no cap ✨

💀 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. everyone goes down together, yikes 💀
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. fr fr, an error can be the final boss 😭

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.

👑 Copyright 👑

2003-2026, The Open MPI Community

and that's the whole thing bestie, go expose some memory responsibly 🫶💖✨

this page came from the Open MPI 3.1-flavoured man page set, dated Sep 10, 2026 — MPI_WIN_CREATE(3), periodt 💅

📦 where this page comes from

ubuntu stonking: openmpi-doc 5.0.10-6 · other
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-03: a language model's rewrite of the original, under its terms