[R] Dismal R performance of Athlon moble CPU?

[Liaw, Andy]

Overall performance depends on a few other things besides CPU clock speed
(e.g., RAM speed and size, cache size, disk speed, etc.)  Unless your code
is spending great majority of the time in the CPU, you should not expect
speed-up to be equal to ratio of clock speeds.  (Also, as Prof. Ripley
pointed out, a P4 does less than a PIII at the same clock speed, and the
number AMD attach to Athlon is not clock speed.)

We do have a dual P4 Xeon 2.4 GHz with 8GB RAM, and jobs run more than twice
as fast as my PIII 933MHz laptop.

Andy

> -----Original Message-----
> From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk] 
> Sent: Wednesday, July 23, 2003 4:55 PM
> To: Jason Liao
> Cc: r-help at stat.math.ethz.ch
> Subject: Re: [R] Dismal R performance of Athlon moble CPU?
> 
> 
> On Wed, 23 Jul 2003, Jason Liao wrote:
> 
> > I have been using a laptop computer of Pentium III 1.13 
> Ghz. I heard 
> > that AMD's Athlon has excellent floating point capacity. So 
> I bought a 
> > Athlon 2200+ laptop yesterday. I expected that new Athlon 
> 2200+ will 
> > be twice as fast as the P III 1.13 GB. I ran a R simulation program 
> > and the new computer is only 30% faster, in fact slightly 
> slower than 
> > a Celeron 1.50 GB laptop. I am very disappointed by this. 
> What is your 
> > experience with Athlon? Should I stick to Intel in the 
> future? Thanks.
> 
> So I expect you think a P4M 1.4GHz (on which I am writing 
> this) should be a lot faster than a PIII 1GHz?  It is often 
> slower.  Don't compare laptop chips with desktop ones, nor 
> different chip families (an Athlon 2200 is not 2.2GHz, BTW).  
> PIIIs seem the fastest per GHz, but they don't do many GHz.
> 
> I am rather pleased with my dual Athlon 2600, but then P4's 
> don't allow 
> multiprocessors and the machine with dual Athlons was cheaper than a 
> comparable one with a single 2.4GHz P4.
> 
> You have tuned an ATLAS implementation to your CPU, I take 
> it?  If not, 
> that's the first step to optimal R performance.
> 
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
> 
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> 

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