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Dmitry Zaletnev dzaletnev at yandex.ru
Tue Oct 13 09:22:31 EDT 2009


Hi,
may be somebody will find interesting this CFD perfomance tests for different desktop i7/memory configs:

http://techreport.com/articles.x/15967/4

Sincerely,
Dmitry

> > On Behalf Of Dmitry Zaletnev
> > 
> > I just thinking about a 2-nodes Beowulf for a CFD application that
> > reads/writes small amounts of data in random areas of RAM (non-cached
> > translation). What would be the difference in overall performance (I
> > suppose, due to the memory access time) between Q9650/ 8 GB DDR2-800
> > and i7 920/ 6 GB DDR3-1866. 
> you probably mean "DDR3-1066".
> Concerning overall CFD performance, I would go for the i7 920.
> For CFD performance data, one good resource are the FLUENT benchmark pages:
> http://www.fluent.com/software/fluent/fl6bench/fl6bench_6.4.x/index.htm
> click on one of the 6 test datasets there and get tables of benchmark performance. For example the Aricraft_2m model (with at:
> http://www.fluent.com/software/fluent/fl6bench/fl6bench_6.4.x/problems/aircraft_2m.htm
> The Nehalem (same architecture as i7 920) generation:
> INTEL WHITEBOX (INTEL_X5570_NHM4,2930,RHEL5)*
> FLUENT rating at 8 cores: = 784.9
> The Harpertown generation (same architecture as Q9650, I think)
> INTEL WHITEBOX (INTEL_X5482_HTN4,3200,RHEL5)
> FLUENT rating at 8 cores: = 307.6
> * To help decode these brief descriptions of processors, systems & interconnects, you can often find more details at this page: http://www.fluent.com/software/fluent/fl6bench/new.htm
> THe FLUENT rating is a "bigger is better" metric relating to the number of jobs you can run in 24 hours, IIRC.
> So with the newer generation, on these FLUENT benchmarks anyway, you get approximately 2x the performance.
> > By the way, are local variables of
> > methods/functions stored in L2 cache? 
> There are 3 levels of cache in the i7, 2 levels in the Q9650.
> All your problems are likely to use all levels of cache. You are right that data you tend to reuse frequently will tend to live in the lower cache levels longer, but there are no hard and fast rules.
> Bets of luck,
> Tom
> > The code will use all the system
> > memory for data storage, excluding used by OS, no swapping supposed.
> > I'm going to buy motherboards next month.
> > 
> > Thank you in advance for any advice,
> > --
> > Dmitry Zaletnev
> > _______________________________________________
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