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From: "jsm28 at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sources.redhat.com
Subject: [Bug math/13304] fma, fmaf, fmal produce wrong results
Date: Thu, 22 Nov 2012 17:39:00 -0000	[thread overview]
Message-ID: <bug-13304-131-ZIZfnVYn0G@http.sourceware.org/bugzilla/> (raw)
In-Reply-To: <bug-13304-131@http.sourceware.org/bugzilla/>

http://sourceware.org/bugzilla/show_bug.cgi?id=13304

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|x86_64-suse-linux-gnu       |
               Host|x86_64-suse-linux-gnu       |
              Build|x86_64-suse-linux-gnu       |

--- Comment #38 from Joseph Myers <jsm28 at gcc dot gnu.org> 2012-11-22 17:39:07 UTC ---
FWIW, the ldbl-128ibm version of fmal, which I think would better be replaced
by a generic version such as that discussed here (which would also be useful
for platforms without FE_INEXACT / FE_TOWARDZERO), not only is incorrect in
that it doesn't provide a fused operation, but also appears to produce results
that are actually invalid long double values, when in directed rounding modes,
e.g.:

Failure: Test: fma_towardzero (max_value, max_value, min_value) == max_value
Result:
 is:          1.79769313486231590772e+308   0x1.ffffffffffffffffffffp+1023
 should be:   1.79769313486231580793e+308   0x1.fffffffffffff7ffffffp+1023
 difference:  1.79769313486231550856e+308   0x1.ffffffffffffe0000000p+1023
 ulp       :  81129638414606663681390495662080.0000
 max.ulp   :  0.0000

(Such edges cases for ldbl-128ibm might end up as separate issues, but it
probably doesn't make sense to file such separate issues for them until fmal
for ldbl-128ibm is basically right, most likely through use of a generic
implementation.)

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  parent reply	other threads:[~2012-11-22 17:39 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-10-17  2:02 [Bug math/13304] New: " bruno at clisp dot org
2011-10-17  2:03 ` [Bug math/13304] " bruno at clisp dot org
2011-10-17  2:05 ` bruno at clisp dot org
2011-10-17  2:05 ` bruno at clisp dot org
2011-10-17  2:05 ` bruno at clisp dot org
2011-10-17  2:06 ` bruno at clisp dot org
2011-10-17  2:06 ` bruno at clisp dot org
2011-10-17  2:07 ` bruno at clisp dot org
2011-10-17  2:08 ` bruno at clisp dot org
2011-10-17  2:08 ` bruno at clisp dot org
2011-10-17  2:08 ` bruno at clisp dot org
2011-10-17  2:09 ` bruno at clisp dot org
2011-10-17  2:10 ` bruno at clisp dot org
2011-10-17  2:10 ` bruno at clisp dot org
2011-10-17  2:11 ` bruno at clisp dot org
2011-10-17  2:11 ` bruno at clisp dot org
2011-10-17  2:11 ` bruno at clisp dot org
2011-10-17  2:11 ` bruno at clisp dot org
2011-10-17  5:54 ` jakub at redhat dot com
2011-10-17  7:19 ` aj at suse dot de
2011-10-17  7:32 ` jakub at redhat dot com
2011-10-17  8:24 ` aj at suse dot de
2011-10-17  9:14 ` bruno at clisp dot org
2011-10-17  9:28 ` jakub at redhat dot com
2011-10-17  9:50 ` bruno at clisp dot org
2011-10-17  9:51 ` bruno at clisp dot org
2011-10-17 12:20 ` jakub at redhat dot com
2011-10-17 14:07 ` joseph at codesourcery dot com
2011-10-17 20:10 ` bruno at clisp dot org
2011-10-17 20:23 ` zimmerma+gcc at loria dot fr
2011-10-17 22:36 ` vincent-srcware at vinc17 dot net
2011-10-17 22:40 ` bruno at clisp dot org
2011-10-17 22:42 ` bruno at clisp dot org
2011-10-17 22:47 ` bruno at clisp dot org
2011-10-17 23:34 ` bruno at clisp dot org
2011-10-18  7:24 ` aj at suse dot de
2011-10-18 16:40 ` bruno at clisp dot org
2012-02-26 17:46 ` jsm28 at gcc dot gnu.org
2012-02-26 17:49 ` jsm28 at gcc dot gnu.org
2012-09-27 20:08 ` law at redhat dot com
2012-09-27 20:26 ` joseph at codesourcery dot com
2012-11-22 17:39 ` jsm28 at gcc dot gnu.org [this message]
2013-12-17 14:23 ` jsm28 at gcc dot gnu.org
2014-06-27 11:51 ` fweimer at redhat dot com
2015-09-25 17:30 ` cvs-commit at gcc dot gnu.org
2015-09-25 17:32 ` cvs-commit at gcc dot gnu.org
2015-09-25 17:35 ` jsm28 at gcc dot gnu.org

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