MPI_WIN_CREATE_KEYVAL(3)			     Open MPI				  MPI_WIN_CREATE_KEYVAL(3)

MPI_Win_create_keyval — Creates a keyval for a window.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Win_create_keyval(MPI_Win_copy_attr_function *win_copy_attr_fn,
	       MPI_Win_delete_attr_function *win_delete_attr_fn,
	       int *win_keyval, void *extra_state)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_WIN_CREATE_KEYVAL(WIN_COPY_ATTR_FN, WIN_DELETE_ATTR_FN,
	       WIN_KEYVAL, EXTRA_STATE, IERROR)
	       EXTERNAL WIN_COPY_ATTR_FN, WIN_DELETE_ATTR_FN
	       INTEGER WIN_KEYVAL, IERROR
	       INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Win_create_keyval(win_copy_attr_fn, win_delete_attr_fn, win_keyval,
		       extra_state, ierror)
	       PROCEDURE(MPI_Win_copy_attr_function) :: win_copy_attr_fn
	       PROCEDURE(MPI_Win_delete_attr_function) :: win_delete_attr_fn
	       INTEGER, INTENT(OUT) :: win_keyval
	       INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: extra_state
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • win_copy_attr_fn: Copy callback function for win_keyval (function).

       • win_delete_attr_fn: Delete callback function for win_keyval (function).

       • extra_state: Extra state for callback functions.

OUTPUT PARAMETERS
       • win_keyval: Key value for future access (integer).

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

DESCRIPTION
       The  argument  win_copy_attr_fn may be specified as MPI_WIN_NULL_COPY_FN or MPI_WIN_DUP_FN from either C or
       Fortran. MPI_WIN_NULL_COPY_FN is a  function  that  serves  only	 to  return  flag  =  0	 and  MPI_SUCCESS.
       MPI_WIN_DUP_FN  is  a simple-minded copy function that sets flag = 1, returns the value of attribute_val_in
       in attribute_val_out, and returns MPI_SUCCESS.

       The argument win_delete_attr_fn may be specified	 as  MPI_WIN_NULL_DELETE_FN  from  either  C  or  Fortran.
       MPI_WIN_NULL_DELETE_FN is a function that serves only to return MPI_SUCCESS.

       The C callback functions are:

	  typedef int MPI_Win_copy_attr_function(MPI_Win oldwin, int win_keyval,
		       void *extra_state, void *attribute_val_in,
		       void *attribute_val_out, int *flag);

	  typedef int MPI_Win_delete_attr_function(MPI_Win win, int win_keyval,
		       void *attribute_val, void *extra_state);

       The Fortran callback functions are:

	  SUBROUTINE WIN_COPY_ATTR_FN(OLDWIN, WIN_KEYVAL, EXTRA_STATE,
	       ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, FLAG, IERROR)
	       INTEGER OLDWIN, WIN_KEYVAL, IERROR
	       INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE, ATTRIBUTE_VAL_IN,
		       ATTRIBUTE_VAL_OUT
	       LOGICAL FLAG

	  SUBROUTINE WIN_DELETE_ATTR_FN(WIN, WIN_KEYVAL, ATTRIBUTE_VAL,
	       EXTRA_STATE, IERROR)
	       INTEGER WIN, WIN_KEYVAL, IERROR
	       INTEGER(KIND=MPI_ADDRESS_KIND) ATTRIBUTE_VAL, EXTRA_STATE

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_CREATE_KEYVAL(3)
