MPI_WIN_ATTACH(3)				     Open MPI					 MPI_WIN_ATTACH(3)

MPI_Win_attach,	 MPI_Win_detach <#mpi-win-detach> - One-sided MPI call that attaches / detaches a memory region to
/ from a window object for RMA operations.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  MPI_Win_attach(MPI_Win win, void *base, MPI_Aint size)

	  MPI_Win_detach(MPI_Win win, void *base)

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

	  MPI_WIN_DETACH(WIN, BASE, IERROR)
	       <type> BASE(*)
	       INTEGER WIN, IERROR

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Win_attach(win, base, size, ierror)
	       TYPE(MPI_Win), INTENT(IN) :: win
	       TYPE(*), DIMENSION(..), INTENT(IN) :: base
	       INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: size
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

	  MPI_Win_detach(win, base, ierror)
	       TYPE(MPI_Win), INTENT(IN) :: win
	       TYPE(*), DIMENSION(..), INTENT(IN) :: base
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • win: A window that was created with MPI_Win_create_dynamic

       • base: Initial address of window (choice).

       • size: Size of window in bytes (nonnegative integer).

OUTPUT PARAMETERS
       • win: Window object returned by the call (handle).

       • ierror: Fortran only: Error status (integer).

DESCRIPTION
       MPI_Win_attach is a one-sided MPI communication call used to attach a memory region of size bytes  starting
       at   address   base   to	  a  window  for  RMA  access.	The  window  win  must	have  been  created  using
       MPI_Win_create_dynamic <#mpi-win-create-dynamic>. Multiple non-overlapping memory regions may  be  attached
       to the same dynamic window. Attaching overlapping memory regions to the same dynamic window is erroneous.

       If  the	base value used by MPI_Win_attach was allocated by MPI_Alloc_mem <#mpi-alloc-mem>, the size of the
       window can be no larger than the value set by the MPI_Alloc_mem <#mpi-alloc-mem> function.

       MPI_Win_detach <#mpi-win-detach> can be used to detach a previously attached memory region  from	 win.  The
       memory address base and win must match arguments passed to a previous call to MPI_Win_attach.

NOTES
       Use  memory  allocated  by  MPI_Alloc_mem  <#mpi-alloc-mem> to guarantee properly aligned window boundaries
       (such as word, double-word, cache line, page frame, and so on).

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>/MPI_Init_thread  <#mpi-init-thread>,
       after  MPI_Finalize  <#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	<#
       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>/MPI_Comm_spawn_multiple	<#
       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.

       • 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 <#mpi-abort> was called on that communicator. If called
	 on a window or file, acts as if MPI_Abort <#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	 <#mpi-comm-create-errhandler>	   then	    MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	<#mpi-file-create-errhandler>	  then	   MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					 MPI_WIN_ATTACH(3)
