Re: Performance on an alpha 21164 using egcs 1.0.3 ???

[Toon Moene <toon at moene dot indiv dot nluug dot nl>]

Peter Biechele wrote:

> I have written a small program which consist of just two nested loops and a
> square root calculation. I compiled this program under:
> 
> DEC Alpha 21164 600 / Linux / egcs 1.0.3:    35 seconds
> Intel PII 450 / Linux (Debian) / egcs 1.0.3:  6 seconds
> Intel PII 450 / Linux (Debian) /  gcc 2.7.2 : 12 seconds
> 
> How is this possible !!???????????
> 
> The DEC Alpha should be at least the same performance !!!

[ ... Snipped example code ... ]
> Our Question:

> How can we improve the performance of the egcs compiler under Linux Alpha !!!!

We can't.  This code spends most of its time computing SQRTs - that's
something the compiler can't help.

One way of improving the performance on this code is to use a faster
math lib implementation - see
http://people.frankfurt.netsurf.de/Joachim.Wesner/

That way you might gain a factor of three or so - even then you probably
won't beat the P II.  If all you ever want to do with a computer is to
compute square roots, there's no point in buying an Alpha ...

HTH,

-- 
Toon Moene (toon@moene.indiv.nluug.nl)
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
Phone: +31 346 214290; Fax: +31 346 214286
g77 Support: fortran@gnu.org; egcs: egcs-bugs@cygnus.com