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[Bug math/16531] New: cosine very occasionally takes an exceptionally long time
- From: "john.wilkinson at spirent dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Wed, 05 Feb 2014 15:56:59 +0000
- Subject: [Bug math/16531] New: cosine very occasionally takes an exceptionally long time
- Auto-submitted: auto-generated
https://sourceware.org/bugzilla/show_bug.cgi?id=16531
Bug ID: 16531
Summary: cosine very occasionally takes an exceptionally long
time
Product: glibc
Version: 2.18
Status: NEW
Severity: normal
Priority: P2
Component: math
Assignee: unassigned at sourceware dot org
Reporter: john.wilkinson at spirent dot com
Created attachment 7394
--> https://sourceware.org/bugzilla/attachment.cgi?id=7394&action=edit
demo code
The cosine function, cos, can be exceedingly slow for a few number of values.
>From my measurement on my PC using the attached C++ program I find that cos
almost always takes in the order of 2e-8 seconds, but occasionally it will take
around 1.5e-4 seconds, 0.15ms. It always takes around this time for particular
values, e.g. 1.27730245420149213 (radians). (This difference, 4 order of
magnitude, is quite a problem for us as we have to repeatedly perform a large
number of calculations within 1ms.)
GCC versions 4.6.3 and 4.7.2, GLIBC version 2.15, 2.18, i7 PCs, Ubuntu 12.04,
Yocto
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