From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 976 invoked by alias); 24 May 2012 17:46:46 -0000 Received: (qmail 967 invoked by uid 22791); 24 May 2012 17:46:43 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO sourceware.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 24 May 2012 17:46:29 +0000 From: "martin.brain at cs dot ox.ac.uk" To: glibc-bugs@sources.redhat.com Subject: [Bug libc/14163] New: Software implementation of cosf is not decreasing on range [0,pi/2] Date: Thu, 24 May 2012 17:46:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: glibc X-Bugzilla-Component: libc X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: martin.brain at cs dot ox.ac.uk X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact glibc-bugs-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: glibc-bugs-owner@sourceware.org X-SW-Source: 2012-05/txt/msg00316.txt.bz2 http://sourceware.org/bugzilla/show_bug.cgi?id=14163 Bug #: 14163 Summary: Software implementation of cosf is not decreasing on range [0,pi/2] Product: glibc Version: 2.15 Status: NEW Severity: normal Priority: P2 Component: libc AssignedTo: unassigned@sourceware.org ReportedBy: martin.brain@cs.ox.ac.uk CC: drepper.fsp@gmail.com Classification: Unclassified Created attachment 6421 --> http://sourceware.org/bugzilla/attachment.cgi?id=6421 An example of one of the glitches While verifying parts of the software trigonometric functions using CBMC I found that __kernel_cosf ( glibc-2.15/sysdeps/ieee754/flt-32/k_cosf.c ) has 5530 points in the range [0.1,pi/2] where inaccuracies in the last bit mean that the function is not descreasing. I.E. x < y but cos(x) < cos(y). The attached code demonstrates this effect on x86_64 (x86 uses the x87 sin and cos hardware and so is not effected). Interestingly the corresponding code for sin does not have this issue. -- 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.