[Beowulf] Disappointing floating point performance for X5560 versus SPECmarks?
tom.elken at qlogic.com
Mon Oct 12 17:53:08 EDT 2009
> Gerasimatos, Dimitrios V (343K) wrote:
> > According to SPECfp2006, the X5560 should blow the doors off of the
> > The X5560 scores 36 while the E5430 scores about 18.
> > However, our own benchmarking using nbench, unixbench, and a home-
> > utility (twobod) all show that any differences are attributed to
> clock speed.
> I wouldn't use specfp**** ratios as a realistic guide for performance
> comparison. As always, use your own code.
What Joe says has a lot of merit.
But that said, if your applications have advanced along with the capabilities of modern CPUs, SPECfp2006 is a lot better metric than SPECfp2000, which is a better metric than SPECfp95. Each succeeding generation of SPEC CPU benchmark grows substantially in memory footprint and in the memory bandwidth performance required of a CPU/memory system.
I note that nbench and unixbench were last developed around 1996-1997 putting them in the same era of benchmarks as SPECfp95.
I see that the application components of SPECfp2006 for which X5560 blows the doors off E5430 (by 2x or more) are: 410.bwaves (CFD), 433.milc (QCD), 450.soplex (Linear Programming), 459.GemsFDTD (Computational Electromagnetics), 470.lbm (CFD). These are CFP2006 applications which I remember as having the most memory bandwidth demand from my days on the CPU committee.
Since the Nehalem X5560 can do McaCalpin's STREAM (memory bandwidth, OpenMP 8-thread version) benchmark at about 3x the rate of Harpertown E5430, that explains a lot of the difference.
If you applications have a small memory footprint, or have great cache re-use, you probably don't need the newer generation of CPU.
> If your code shows 2x,
> great. If not, then attribute the specfp**** to what they are
> (marketing numbers, with some grounding in reality, but not a firm
> comparison metric for dissimilar apps).
> Joseph Landman, Ph.D
> Founder and CEO
> Scalable Informatics Inc.
> email: landman at scalableinformatics.com
> web : http://scalableinformatics.com
> phone: +1 734 786 8423 x121
> fax : +1 866 888 3112
> cell : +1 734 612 4615
> Beowulf mailing list, Beowulf at beowulf.org sponsored by Penguin
> To change your subscription (digest mode or unsubscribe) visit
Beowulf mailing list, Beowulf at beowulf.org sponsored by Penguin Computing
To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
More information about the Beowulf