[mpiwg-rma] Single RMA synchronization for several window handles

[Rolf Rabenseifner]

Dynamic windows do not provide the easy-to-use window base mechanism,
i.e., the origin must know the absolute address on the target process.
Same for target_disp_unit.
Dynamic Windows also require that all have the same communicator
(because same win handle).

My proposal would allow full service for all RMA operations
(and not only MPI_BOTTOM Quality),
full service for Win_create or Win_allocate or Win_allocate_shared
and together with combined synchronization.

Is this worth to consider?

Rolf

----- Original Message -----
> From: "William Gropp" <wgropp at illinois.edu>
> To: "MPI WG Remote Memory Access working group" <mpiwg-rma at lists.mpi-forum.org>
> Sent: Friday, August 8, 2014 5:06:14 PM
> Subject: Re: [mpiwg-rma] Single RMA synchronization for several window	handles
> 
> Why not simply use MPI_Win_create_dynamic, attach the separate memory
> regions, and use that MPI_Win?  Adding an option for a collective
> memory allocator would make this almost equivalent, and wouldn’t add
> additional overhead beyond what is already requried.
>  
> Bill
> 
> William Gropp
> Director, Parallel Computing Institute Thomas M. Siebel Chair in
> Computer Science
> University of Illinois Urbana-Champaign
>  
> On Aug 8, 2014, at 9:18 AM, Rolf Rabenseifner < rabenseifner at hlrs.de
> > wrote:
> 
> 
> Jim,
> 
> your topic "Reducing Synchronization Overhead Through Bundled
> Communication" may get also help if we would be able to
> combine several window handles to one superset window handle.
> 
> If you have several windows for different buffers, but
> only one synchronization pattern, e.g. MPI_Win_fince
> then currently you must call MPI_Win_fence seperately
> for each window handle.
> 
> I would propose:
> 
> MPI_Win_combine (/*IN*/  int count,
>                 /*IN*/  MPI_Win *win,
>                 /*IN*/  MPI_Comm comm,
>                 /*OUT*/ MPI_Win *win_combined)
> 
> The process group of comm must contain the process groups of all win.
> The resulting window handle win_combined can be used only
> in RMA synchronization calls and other helper routines,
> but not for dynamic window allocation nor for any
> RMA communication routine.
> Collective synchronization routines must be called by all processes
> of comm.
> The semantics of an RMA synchronization call using win_combined
> is defined as if the calls were seperately issued for
> each window handle of the array win. If group handles
> are part of the argument list of the synchronization call
> then the appropriate subset is used for each window handle in win.
> 
> What do you think about this idea for MPI-4.0?
> 
> Best regards
> Rolf
> 
> ----- Original Message -----
> 
> 
> From: "Jim Dinan" < james.dinan at gmail.com >
> To: "MPI WG Remote Memory Access working group" <
> mpiwg-rma at lists.mpi-forum.org >
> Sent: Thursday, August 7, 2014 4:08:32 PM
> Subject: [mpiwg-rma] RMA Notification
> 
> 
> 
> Hi All,
> 
> 
> I have added a new proposal for an RMA notification extension: 
> https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/439
> 
> 
> I would like to bring this forward for the RMA WG to consider as an
> MPI-4 extension.
> 
> 
> Cheers,
>  ~Jim.
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> 
> --
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
> Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)
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> 
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-- 
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)