On Fri, Aug 8, 2014 at 7:18 AM, Rolf Rabenseifner <[email protected]> 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)

Let's consider whether the following makes sense: MPI_Comm_combine(/*IN*/ int count, /*IN*/ MPI_Comm comm[], /*OUT*/ MPI_Comm *comm_combined); This function would allow me to have an object to Barrier across multiple communicators at once. Make sense? I didn't think so... I would much rather think about MPI_Win_flush(_all)(_local)v that take a vector of windows. I don't see the need for MPI_Win_fencev. If the implementation can sync all the Windows on the first call, the subsequent calls should be cheap. ... MPI_Put(win1) MPI_Put(win2) MPI_Put(win3) MPI_Win_fence(win1) <<< all three MPI_Put operations are completed here MPI_Win_fence(win2) <<< essentially a no-op MPI_Win_fence(win3) <<< essentially a no-op ... Maybe I am forgetting that MPI_Win_fence requires a Barrier... Jeff

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" <[email protected]> To: "MPI WG Remote Memory Access working group" <[email protected]> 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. _______________________________________________ mpiwg-rma mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-rma

-- Dr. Rolf Rabenseifner . . . . . . . . . .. email [email protected] 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) _______________________________________________ mpiwg-rma mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-rma

-- Jeff Hammond [email protected] http://jeffhammond.github.io/