From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 4734 invoked by alias); 3 Mar 2012 21:28:02 -0000 Received: (qmail 4726 invoked by uid 22791); 3 Mar 2012 21:28:01 -0000 X-SWARE-Spam-Status: No, hits=-2.8 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,TW_JS X-Spam-Check-By: sourceware.org Received: from localhost (HELO sourceware.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Sat, 03 Mar 2012 21:27:51 +0000 From: "jsm28 at gcc dot gnu.org" To: glibc-bugs@sources.redhat.com Subject: [Bug math/13629] clog() returns wrong values around z=1 Date: Sat, 03 Mar 2012 21:28:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: glibc X-Bugzilla-Component: math X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: jsm28 at gcc dot gnu.org 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: AssignedTo Message-ID: In-Reply-To: References: 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: 2012-03/txt/msg00047.txt.bz2 http://sourceware.org/bugzilla/show_bug.cgi?id=13629 Joseph Myers changed: What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|aj at suse dot de |unassigned at sourceware | |dot org --- Comment #4 from Joseph Myers 2012-03-03 21:26:56 UTC --- Confirmed in current source code by inspection. The implementation approach of log(hypot) for finding the real part of clog will cause undue overflows for large input, inaccurate results from undue underflow for subnormal input, and inaccurate results for z close to |z|=1 (not just close to 1 itself). The general case of z close to that circle will be more complicated to fix than the overflow and underflow cases. clog10 (a GNU extension, name reserved in ISO C) has the same issues. -- 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.