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From: "joseph at codesourcery dot com" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug math/14473] Inaccurate CPOWF function on x86_32 and x86_64 Date: Wed, 15 Aug 2012 15:23:00 -0000 [thread overview] Message-ID: <bug-14473-131-ghuqyZ0x1B@http.sourceware.org/bugzilla/> (raw) In-Reply-To: <bug-14473-131@http.sourceware.org/bugzilla/> http://sourceware.org/bugzilla/show_bug.cgi?id=14473 --- Comment #1 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2012-08-15 15:22:55 UTC --- Again, please give testcases that use hex floats rather than using type punning, so that the test inputs can more readily be extracted for use elsewhere. cpowf, cpow, cpowl are generically inaccurate for all architectures and floating-point formats - there's nothing x86-specific. They are also by far the hardest complex functions to make accurate; the errors in this example are tiny compared to those you can get with properly chosen examples. In general for long double you need to compute log and atan2 results to over 16000 places to get good results for cpowl. Consider cpowl (LDBL_MAX, I * LDBL_MAX) for example - you need to compute LDBL_MAX * log (LDBL_MAX), reduced mod 2pi. Many cases will overflow or underflow but you still need to determine the signs of zero or infinity in those cases. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.
next prev parent reply other threads:[~2012-08-15 15:23 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-08-15 15:10 [Bug math/14473] New: " liubov.dmitrieva at gmail dot com 2012-08-15 15:23 ` joseph at codesourcery dot com [this message] 2012-08-16 7:52 ` [Bug math/14473] " liubov.dmitrieva at gmail dot com 2013-01-25 16:49 ` glisse at gcc dot gnu.org 2013-04-04 16:12 ` [Bug math/14473] Inaccurate CPOW* function on all machines carlos at redhat dot com 2013-04-04 16:13 ` carlos at redhat dot com 2013-08-05 19:27 ` licquia at linuxfoundation dot org 2013-12-06 14:07 ` mwelinder at gmail dot com 2013-12-06 14:17 ` mwelinder at gmail dot com 2014-06-17 18:38 ` fweimer at redhat dot com
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