[Mpi3-rma] RMA working group mtg dialing info

[Jeff Hammond]

So I didn't catch everything that went on because clearly Keith was
referring to things projected from his laptop but not enumerated out
loud.  That, and 7-9 PM is usually beer-time not RMA-time in my house.

On the issue of "should MPI-3 support X (with performance)?" where
X={ARMCI,GASNet,etc.}, I think it is quite clear than MPI-3 RMA should
meet the criteria of implementing ARMCI RMA, either as ARMCI on top of
MPI-3 of GA on top of MPI-3 (replacing ARMCI altogether).  The
distinction between the latter two choices is mostly irrelevant; ARMCI
over MPI-3 can be pretty close to an #define implementation rather
than an abstraction layer which affects performance.  I suspect that
on some platforms, ARMCI may still be required to achieve optimal
performance for strided accumulate etc., but for leadership-class
machines with RDMA or otherwise powerful NICs, ARMCI will be nothing
more than syntactic sugar to make GA portable.  This fact has been
clearly demonstrated by the DCMF port of ARMCI, which completely
bypasses the ARMCI data server but compensates with low-level
communication-helper-thread support.

Although I don't doubt that user-defined accumulate provides a
mechanism for active-messaging (AM) capability, I do not fully
subscribe to the notion - sorry Pavan - that MPI-3 accumulate is
sufficient to implement GASNet if performance is a consideration.  I
sincerely hope that the Forum follows through on the AM working group
and produces a real AM interface that competes on all levels with
GASNet.  Keith is right that GASNet's direct targeting of low-level AM
functionality will preclude MPI-3 from ever being a
performance-oriented compromise.  However, it is useful to have MPI-3
as a portable fall-back for implementing AM via user-defined
accumulate.

Best,

Jeff

On Tue, Mar 9, 2010 at 6:32 PM, Jeff Hammond <jeff.science at gmail.com> wrote:
>> Tuesday: 4.15-7.00pm Pacific
>> Tel: (866) 432-9903  OR  (408) 525-6800
>> Meeting Number: 200 438 253
>
> Is this happening?  I called in but no one else is on.
>
> Thanks,
>
> Jeff
>
>
> --
> Jeff Hammond
> Argonne Leadership Computing Facility
> jhammond at mcs.anl.gov / (630) 252-5381
> http://www.linkedin.com/in/jeffhammond
>



-- 
Jeff Hammond
Argonne Leadership Computing Facility
jhammond at mcs.anl.gov / (630) 252-5381
http://www.linkedin.com/in/jeffhammond