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

On 17 October 2014 09:58, Siddhesh Poyarekar <siddhesh@redhat.com> wrote:
>> > +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.

Updated patch inline:

diff --git a/man3/pow.3 b/man3/pow.3
index d0a2ea8..1b05292 100644
--- a/man3/pow.3
+++ b/man3/pow.3
@@ -320,6 +320,18 @@ 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 (rare) inputs than for
other nearby
+inputs.  This only affects
+.BR pow (),
+and not
+.BR powf ()
+nor
+.BR powl ().
+
 In glibc 2.9 and earlier,
 .\"
 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6776

and attached in case gmail messes it up.

Cheers,

Manuel.

Attachment: pow.diff
Description: Text document

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