[Beowulf] Win64 Clusters!!!!!!!!!!!!

Jon Forrest jlforrest at berkeley.edu
Sun Apr 8 17:41:28 PDT 2007

Toon Moene wrote:

> I wouldn't be to sure of that.  Recently I became interested in the 
> divisors of a given natural number.

I suspect small programs can be written to show almost any
kind of interesting behavior.

[program snipped]

> The execution time difference was about 2 orders of magnitude.

My guess is that this is a perfect x86-64 program. Everything fits
in the cache, and there are enough registers so that all the variables
fit in registers.

The experiment I tried was to build several fairly large programs
on Fedora Core 6 32 bit and then 64 bit using exactly the same
hardware. This is clearly not the same kind of test as your
example but it's more relevant as a systems-level comparison.
If I remember, I built mysql and apache. This took about the same
amount of time in both modes.

I suspect that the Beowulf crowd would have lots of experience
with 32-bits vs 64-bits question, so I'd welcome additional
comments, especially dealing with situations where programs
*don't* need the additional address space of the 64-bit model.

Jon Forrest
Unix Computing Support
College of Chemistry
173 Tan Hall
University of California Berkeley
Berkeley, CA
jlforrest at berkeley.edu

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