[Mpi-forum] MPI One-Sided Communication

[Vinod Tipparaju]

Greg,
The scaling in the chart discussed below is immaterial because the comparision point is flawed. I tried to convey this to some of the developers on the phone  a couple of years ago but invain. The fact this claim of performance went no where beyond the white paper should convey something. Did you know dft (siosi6) doesn't scale (for various reasons) beyond 1k?
--
typing from phone..small keyboard big thumbs.

________________________

On 2009-04-24 13:33:56 -0400 Greg Lindahl <lindahl at pbm.com> wrote:

> 
> On Fri, Apr 24, 2009 at 07:38:39AM -0500, Jeff Hammond wrote:
> 
>> You're comparing ("scaled better than") apples ("an implementation on
>> top of 2-sided MPI-1 send/recv") and oranges ("real one-sided
>> hardware").  Please post the whitepaper (I cannot find it online) and
>> clarify what you mean here.
> 
> QLogic seems to have hidden it here:
> 
> http://www.qlogic.com/SiteCollectionDocuments/Education_and_Resource/whitepapers/whitepaper1/RealApplications-paper.pdf
> 
> I used the Siosi6 benchmark, since I needed something that had public
> benchmark numbers available.
> 
> Our implementation used 1/4 of the cores as "memory servers" which
> held the global memory and served as the counterparty to one-sided
> operations. Despite wasting 25% of the cores, it scaled great.
> 
> Now this result won't apply to all one-sided programs; GA's model and
> usage is somewhat different from most other one-sided models.
> 
>