Subject: Re: CCL:Linux on Alpha, math library

From: "Marc N." <[email-masked]>
Date: Mon, 31 Aug 1998 14:37:22 -0400 (EDT)

On Sat, 29 Aug 1998, Victoria Buch wrote:

> >>>>>>>>>>>>
> >>>>>>>>>
> > Igor J. Barani writes:
> >  > Dear CCL Readers,
> >  > 
> >  > I have just recently installed Linux on a DEC Alpha and when I compile
> >  > several programs in fortran on it, they seem to compile to twice the
> >  > size and require 9 times as long to run than on DEC UNIX.  Do you have
> >  > any idea why this may be so and how I may be able to speed up the
> >  > processes?  Any suggestions would be greatly appreciated.  Thank you.
> >>>>>>>>>>>>>>
> 
> We have just been there. You have the latest Red Hat Linux, dont you?
> So: the latest math library libm version 2.0.7 from gnu is messed up.
> Our system menager installed old version 2.0.1 - works faster by a factor 2. 
> More generally our sexperience suggests that
> Alpha / Linux for FP operations is good only
> for simple operations + - * / . My simulation
> programs are still 40% below
> the performance of Alpha-DEC, and only 10% faster than Petium II (400MHz)
> which is more than 2 times cheaper. Disappointing.

Well, this seems to be somewhat of an oversimplification.  Indeed, the
libraries are very important, and so one can probably say that the
standard libraries that come with [Red Hat] Linux/Alpha are good only for
"simple operations + - * /".

However, with the right, i.e., optimized libraries, we've found, e.g., 
Gaussian 94 on a 500MHz Alpha/Linux box to be 2.5 times as fast as on a
400MHz Pentium II Linux system.

Marc

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