From 09ba59d40c98fde0949966410ddb49aedca34428 Mon Sep 17 00:00:00 2001 From: Michael Kerrisk Date: Mon, 25 May 2020 15:15:14 +0200 Subject: [PATCH] pow.3: Minor tweak to BUGS MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Remove the text ("rare)" after a note from Vincent Lefèvre: Subject: [Bug math/13932] dbl-64 pow unexpectedly slow for some inputs Date: Sat, 23 May 2020 21:31:52 +0000 From: vincent-srcware at vinc17 dot net To: mtk.manpages@gmail.com https://sourceware.org/bugzilla/show_bug.cgi?id=13932 --- Comment #26 from Vincent Lefèvre --- (In reply to Michael Kerrisk from comment #25) > Fix documented for man-pages-5.07. [...] > -On 64-bits, > +Before glibc 2.28, > .\" > .\" https://sourceware.org/bugzilla/show_bug.cgi?id=13932 > +on some architectures (e.g., x86-64) > .BR pow () > may be more than 10,000 times slower for some (rare) inputs > than for other nearby inputs. [...] The problematic values are uncommon, but not so rare, in the sense that they are close to simple values, i.e. are likely to occur in practice. An example given above: pow(0.999999999999999889, 1.5) 1 and 1.5 are very simple values, which are more likely to occur in practice than some fixed random value. Then it suffices to have a small rounding error on 1... For instance, this is very different from hard-to-round cases of exp, which are also very slow IMHO, but unless one writes a specific program for them, no-one should notice the slowness because such a case would typically occur only once among billions (I don't remember the accuracy before the slowest path in this library). Reported-by: Vincent Lefèvre Signed-off-by: Michael Kerrisk --- man3/pow.3 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/man3/pow.3 b/man3/pow.3 index d7f72b25bc..87b963dd0e 100644 --- a/man3/pow.3 +++ b/man3/pow.3 @@ -334,7 +334,7 @@ Before glibc 2.28, .\" https://sourceware.org/bugzilla/show_bug.cgi?id=13932 on some architectures (e.g., x86-64) .BR pow () -may be more than 10,000 times slower for some (rare) inputs +may be more than 10,000 times slower for some inputs than for other nearby inputs. This affects only .BR pow (), -- 2.39.2