MPI_WIN_SHARED_QUERY(3)				     Open MPI				   MPI_WIN_SHARED_QUERY(3)

MPI_Win_shared_query — Query a shared memory window

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Win_shared_query (MPI_Win win, int rank, MPI_Aint *size,
				    int *disp_unit, void *baseptr)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_WIN_SHARED_QUERY(WIN, RANK, SIZE, DISP_UNIT, BASEPTR, IERROR)
		  INTEGER WIN, RANK, DISP_UNIT, IERROR
		  INTEGER(KIND=MPI_ADDRESS_KIND) SIZE, BASEPTR

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Win_shared_query(win, rank, size, disp_unit, baseptr, ierror)
	       USE, INTRINSIC :: ISO_C_BINDING, ONLY : C_PTR
	       TYPE(MPI_Win), INTENT(IN) :: win
	       INTEGER, INTENT(IN) :: rank
	       INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) :: size
	       INTEGER, INTENT(OUT) :: disp_unit
	       TYPE(C_PTR), INTENT(OUT) :: baseptr
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • win: Shared memory window object (handle).

       • rank: Rank in the group of window win (non-negative integer) or MPI_PROC_NULL.

OUTPUT PARAMETERS
       • size: Size of the window segment (non-negative integer).

       • disp_unit: Local unit size for displacements, in bytes (positive integer).

       • baseptr: Address for load/store access to window segment (choice).

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

DESCRIPTION
       MPI_Win_shared_query   queries	the   process-local  address  for  remote  memory  segments  created  with
       MPI_Win_allocate_shared	<#mpi-win-allocate-shared>.  This  function  can  return  different  process-local
       addresses  for  the  same  physical  memory  on	different  processes.  The returned memory can be used for
       load/store accesses subject to the constraints defined in MPI-3.1 section 11.7. This function can  only	be
       called	with   windows	 of   flavor  MPI_WIN_FLAVOR_SHARED.  If  the  passed  window  is  not	of  flavor
       MPI_WIN_FLAVOR_SHARED, the error MPI_ERR_RMA_FLAVOR is raised. When rank	 is  MPI_PROC_NULL,  the  pointer,
       disp_unit,  and	size  returned	are  the  pointer, disp_unit, and size of the memory segment belonging the
       lowest rank that specified size > 0. If all processes in the group attached to the window specified size	 =
       0, then the call returns size = 0 and a baseptr as if MPI_Alloc_mem <#mpi-alloc-mem> was called with size =
       0.

C NOTES
       The  parameter  baseptr	is  of	type  void  *  to allow passing any pointer object for this parameter. The
       provided argument should be a pointer to a pointer of arbitrary type (e.g. void **).

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.

       See also:

	  • MPI_Alloc_mem <#mpi-alloc-mem>

	  • MPI_Win_allocate_shared <#mpi-win-allocate-shared>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				   MPI_WIN_SHARED_QUERY(3)
