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* [Bug math/10716] various problems in cacosh and cacos
[not found] <bug-10716-131@http.sourceware.org/bugzilla/>
@ 2011-11-23 8:45 ` kreckel at ginac dot de
2012-03-06 3:00 ` jsm28 at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 4+ messages in thread
From: kreckel at ginac dot de @ 2011-11-23 8:45 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=10716
Richard B. Kreckel <kreckel at ginac dot de> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |kreckel at ginac dot de
--- Comment #1 from Richard B. Kreckel <kreckel at ginac dot de> 2011-11-23 08:45:16 UTC ---
(In reply to comment #0)
> The classical branch cut for cacosh() is (-inf, 1). However, cacosh() is using
> a different branch cut.
Branch cuts being standardized in C99 this is now a matter of conformance!
> cacosh(-1 + -0 I) -> (0 + 3.14159265358979 I)
After applying the patch attached to BZ #13305 the correct result 0 -
3.14159265358979*I is returned.
> cacos(1 + 0 I) -> (0 + 0 I) [should be (0 - O I)]
This is how cacos is computed by glibc:
cacos(x)
-> Pi/2 - casin(x)
-> Pi/2 - casinh(x I)/I
So, cacos(1 + 0 I) eventually ends up computing casinh(-O + I) which, in turn,
is computed using log(x+sqrt(1+x^2)). But that formula stands no chance getting
the sign of zero in the real part right along the strip running from -I to +I.
To fix it, it would have to be rewritten using a formula that computes the real
and the imaginary part completely independently.
> Finally the documentation of cacosh says that the real part of the result is
> chosen non-negative, which is clearly wrong on this example:
>
> cacosh(-3.45677995681763 + -2.3456699848175 I) -> (-2.11780021549476 + 2.53187508681341 I)
This appears to have been fixed long ago with BZ #2153.
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^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug math/10716] various problems in cacosh and cacos
[not found] <bug-10716-131@http.sourceware.org/bugzilla/>
2011-11-23 8:45 ` [Bug math/10716] various problems in cacosh and cacos kreckel at ginac dot de
@ 2012-03-06 3:00 ` jsm28 at gcc dot gnu.org
2012-03-07 15:17 ` jsm28 at gcc dot gnu.org
2014-07-01 6:44 ` fweimer at redhat dot com
3 siblings, 0 replies; 4+ messages in thread
From: jsm28 at gcc dot gnu.org @ 2012-03-06 3:00 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=10716
Joseph Myers <jsm28 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
AssignedTo|aj at suse dot de |jsm28 at gcc dot gnu.org
--- Comment #2 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-03-06 02:58:52 UTC ---
Confirmed (as regards signs of 0) with current sources. Patch:
http://sourceware.org/ml/libc-alpha/2012-03/msg00112.html
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^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug math/10716] various problems in cacosh and cacos
[not found] <bug-10716-131@http.sourceware.org/bugzilla/>
2011-11-23 8:45 ` [Bug math/10716] various problems in cacosh and cacos kreckel at ginac dot de
2012-03-06 3:00 ` jsm28 at gcc dot gnu.org
@ 2012-03-07 15:17 ` jsm28 at gcc dot gnu.org
2014-07-01 6:44 ` fweimer at redhat dot com
3 siblings, 0 replies; 4+ messages in thread
From: jsm28 at gcc dot gnu.org @ 2012-03-07 15:17 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=10716
Joseph Myers <jsm28 at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
--- Comment #3 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-03-07 15:16:46 UTC ---
Fixed by:
commit d1d3431a3a9dd14501eedb701436bd5005b1db7d
Author: Joseph Myers <joseph@codesourcery.com>
Date: Wed Mar 7 15:15:19 2012 +0000
Fix signs of zeros from casinh, cacosh etc. (bug 10716).
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^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug math/10716] various problems in cacosh and cacos
[not found] <bug-10716-131@http.sourceware.org/bugzilla/>
` (2 preceding siblings ...)
2012-03-07 15:17 ` jsm28 at gcc dot gnu.org
@ 2014-07-01 6:44 ` fweimer at redhat dot com
3 siblings, 0 replies; 4+ messages in thread
From: fweimer at redhat dot com @ 2014-07-01 6:44 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10716
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Flags| |security-
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[not found] <bug-10716-131@http.sourceware.org/bugzilla/>
2011-11-23 8:45 ` [Bug math/10716] various problems in cacosh and cacos kreckel at ginac dot de
2012-03-06 3:00 ` jsm28 at gcc dot gnu.org
2012-03-07 15:17 ` jsm28 at gcc dot gnu.org
2014-07-01 6:44 ` fweimer at redhat dot com
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