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[Bug math/5769] New: Slow sine function for special values on AMD64
- From: "grugh at centrum dot cz" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 18 Feb 2008 23:07:53 -0000
- Subject: [Bug math/5769] New: Slow sine function for special values on AMD64
- Reply-to: sourceware-bugzilla at sourceware dot org
The math sin(double) function is in 64bit distribution (Kubuntu 7.10 AMD64 and
Fedora - unknown version) unreasonable slow (~400 microseconds on Atlon64 X2
4800+!!!) for some special values. In 32bit distribution is everything fine.
I captured some of those values:
0.93340582292648832662962377071381 0x3fedde75e36bb000
2.3328432680770916363144351635128 0x4002a9a9bb38add0
3.7439477503636453548097051680088 0x400df39ae0cdf500
3.9225160069792437411706487182528 0x400f615012801950
4.0711651639931289992091478779912 0x401048df854fdc20
4.7858438478542097982426639646292 0x401324b43fe92fc0
5.9840767662578002727968851104379 0x4017efb1d1df52a0
For example, this part of code takes a few seconds to complete:
volatile double value = 0.93340582292648832662962377071381;
for(int i=0; i < 10000; i++) {
volatile double out = sin(value);
}
--
Summary: Slow sine function for special values on AMD64
Product: glibc
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: aj at suse dot de
ReportedBy: grugh at centrum dot cz
CC: glibc-bugs at sources dot redhat dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=5769
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