From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 14093 invoked by alias); 30 Apr 2013 05:41:33 -0000 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 Received: (qmail 14036 invoked by uid 48); 30 Apr 2013 05:41:30 -0000 From: "siddhesh at redhat dot com" To: glibc-bugs@sourceware.org Subject: [Bug math/14412] Removal of sysdeps/x86_64/fpu/s_sincos.S causes regressions Date: Tue, 30 Apr 2013 05:41:00 -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: enhancement X-Bugzilla-Who: siddhesh at redhat dot com X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: 2.18 X-Bugzilla-Changed-Fields: 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 X-SW-Source: 2013-04/txt/msg00250.txt.bz2 http://sourceware.org/bugzilla/show_bug.cgi?id=14412 --- Comment #45 from Siddhesh Poyarekar 2013-04-30 05:41:27 UTC --- (In reply to comment #32) > I suspect this is just a boundary issue (the [] should be () in the range) > since slightly smaller values give more reasonable, but still badly wrong, > results. For example if x is 0x1p62, Yes, it is () and not [], according to the manual. > > -0.702922443619209 -0.707132927452779 > > which is wrong in the third decimal place. > This is not restricted to numbers on the boundary. A quick google search on accuracy of fsincos will show that there are numbers even close to pi/2 that are way off in terms of accuracy. > Siddhesh, could you explain the motivation for "overloading" the meaning of > "_finite" with "fast but wrong"? I'm guessing the idea is that you're thinking > finite math implies not just lack of infinities but also "unreasonably large" > inputs? This is definitely the glibc team's call, since there's no reasonable > basis for assuming you'll get correct results from non-default > performance-oriented math settings, but I think some justification would be > nice. That was a mistake - I somehow muddled it up with -ffast-math in my head. I'm going to first try to see if the default sincos can be made faster. Jakub pointed out offline that the argument reduction code is duplicated in the calls to __sin and __cos and consolidating that in sincos should definitely be a good first step. -- 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.