[Mpi-forum] MPI One-Sided Communication

[Greg Lindahl]

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.

-- greg