[Beowulf] Intel Quad-Core or AMD Opteron

[Greg Lindahl]

On Thu, Aug 23, 2007 at 06:09:09PM +0100, Miguel Dias Costa wrote:

> but we've run some benchmarks on both and the thing
> that at the time surprised me the most was that if your application
> makes much use of the functions provided by Intel Math Kernel Library,
> a single Xeon core (e.g Clovertown) can be up to twice as fast as a
> single Opteron core.

First off, I'm not sure why this is surprising; the Core 2 core has
twice as many FP units. Occasionally that results in a huge win.

Second off, you're still making the mistake of comparing 1 core to 1
core.  You should only compare whole nodes, if you intend on running
on all the cores all the time. The dialog then bcomes something like,
"hey, my app does really well with the extra FP units, what a shame
that the scalability was so bad on those cpus."

One app that gets a huge win on Intel in the end is Fluent. Most apps
don't see a huge win, especially if they're memory intensive. And us
commercial website guys, well, we're all integer.

-- greg

p.s. Please don't top-post on this mailing list.