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* [Bug math/15416] New: catan, catanh inaccuracy from atan2
@ 2013-04-29 16:25 jsm28 at gcc dot gnu.org
2013-04-30 11:30 ` [Bug math/15416] " jsm28 at gcc dot gnu.org
2014-06-13 18:10 ` fweimer at redhat dot com
0 siblings, 2 replies; 3+ messages in thread
From: jsm28 at gcc dot gnu.org @ 2013-04-29 16:25 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=15416
Bug #: 15416
Summary: catan, catanh inaccuracy from atan2
Product: glibc
Version: 2.17
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: unassigned@sourceware.org
ReportedBy: jsm28@gcc.gnu.org
Classification: Unclassified
When catan computes __real__ res = 0.5 * __ieee754_atan2 (2.0 * __real__ x,
den), the value of den may be inaccurate when close to 0, resulting in an
inaccurate real part of the result when __real__ x is also small. For example,
catan (0x1p-27 + 1.0i) gives a result with real part 0.785398163397448279 on
x86_64, which is only accurate to 8 decimal places, about half the precision
expected (the exact value is 0.785398165260093458846617868453411006955...).
The same applies to catanh.
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* [Bug math/15416] catan, catanh inaccuracy from atan2
2013-04-29 16:25 [Bug math/15416] New: catan, catanh inaccuracy from atan2 jsm28 at gcc dot gnu.org
@ 2013-04-30 11:30 ` jsm28 at gcc dot gnu.org
2014-06-13 18:10 ` fweimer at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: jsm28 at gcc dot gnu.org @ 2013-04-30 11:30 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=15416
Joseph Myers <jsm28 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
--- Comment #1 from Joseph Myers <jsm28 at gcc dot gnu.org> 2013-04-30 11:30:20 UTC ---
Fixed for 2.18 by:
commit caf84319c1614d8aa867d8db80219f4e9b1bf735
Author: Joseph Myers <joseph@codesourcery.com>
Date: Tue Apr 30 11:27:35 2013 +0000
Fix catan, catanh inaccuracy from atan2 denominators near 0 (bug 15416).
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* [Bug math/15416] catan, catanh inaccuracy from atan2
2013-04-29 16:25 [Bug math/15416] New: catan, catanh inaccuracy from atan2 jsm28 at gcc dot gnu.org
2013-04-30 11:30 ` [Bug math/15416] " jsm28 at gcc dot gnu.org
@ 2014-06-13 18:10 ` fweimer at redhat dot com
1 sibling, 0 replies; 3+ messages in thread
From: fweimer at redhat dot com @ 2014-06-13 18:10 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=15416
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Flags| |security-
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2013-04-29 16:25 [Bug math/15416] New: catan, catanh inaccuracy from atan2 jsm28 at gcc dot gnu.org
2013-04-30 11:30 ` [Bug math/15416] " jsm28 at gcc dot gnu.org
2014-06-13 18:10 ` fweimer at redhat dot com
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