Re: [patch] pow.3: Add note on performance characteristics of pow

[Siddhesh Poyarekar <siddhesh at redhat dot com>]

On Fri, Oct 17, 2014 at 07:24:38AM +0200, Michael Kerrisk (man-pages) wrote:
> > diff --git a/man3/pow.3 b/man3/pow.3
> > index d0a2ea8..3d2151a 100644
> > --- a/man3/pow.3
> > +++ b/man3/pow.3
> > @@ -320,6 +320,17 @@ The variant returning
> >  also conforms to
> >  SVr4, 4.3BSD, C89.
> >  .SH BUGS
> > +On 64-bits,
> > +.\"
> > +.\" https://sourceware.org/bugzilla/show_bug.cgi?id=13932
> > +.BR pow ()
> > +may be more than 10,000 times slower for some inputs than for other nearby
> 
> I plan to change "some" to "some (rare)". Sound okay? The point is not to
> worry people that this is a problem that is commonly encountered. (Or is it?)

Rare is OK, these points don't occur very frequently.

> > +inputs. The inputs that produce such behavior are different for
> > +.BR powf (),
> > +.BR pow ()
> > +and
> > +.BR powl ().
> > +

The slow fallback is only taken for pow, not powf or powl.

Siddhesh

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