> I am encountering some very strange performance numbers with sqrt in
> the glibc math library on the alpha.
> Executive summary: sqrt from the glibc-2.0.6-9.alpha.rpm appears to be
> over 10 times faster than sqrt in glibc-2.0.7-19.alpha.rpm.
> [...]
> So the question is:
> Why is the 2.0.7 sqrt so much slower than the 2.0.6??
> [...]
Have a look at PR libc/423 (via
http://www-gnats.gnu.org:8080/cgi-bin/wwwgnats.pl) and check exactly
why the following fix has been made (ignore the timestamp, the fix is
not in 2.0.6):
1997-09-04 13:19 Richard Henderson <rth@cygnus.com>
* sysdeps/alpha/w_sqrt.S: Removed.
* sysdeps/alpha/fpu/e_sqrt.c: New. Obey -mieee and -mieee-with-inexact
and build a version that is as fast as possible given the constraint.
[PR libc/423].
In a nutshell: The code is slower - but it gives better (exacter)
results.
Andreas
-- Andreas Jaeger aj@arthur.rhein-neckar.de jaeger@informatik.uni-kl.de for pgp-key finger ajaeger@aixd1.rhrk.uni-kl.de