From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <glibc-bugs-return-18517-listarch-glibc-bugs=sources.redhat.com@sourceware.org>
Received: (qmail 5656 invoked by alias); 29 Apr 2013 14:04:41 -0000
Mailing-List: contact glibc-bugs-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <glibc-bugs.sourceware.org>
List-Subscribe: <mailto:glibc-bugs-subscribe@sourceware.org>
List-Post: <mailto:glibc-bugs@sourceware.org>
List-Help: <mailto:glibc-bugs-help@sourceware.org>, <http://sourceware.org/lists.html#faqs>
Sender: glibc-bugs-owner@sourceware.org
Received: (qmail 5573 invoked by uid 55); 29 Apr 2013 14:04:38 -0000
From: "neleai at seznam dot cz" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug math/14412] Removal of sysdeps/x86_64/fpu/s_sincos.S causes regressions
Date: Mon, 29 Apr 2013 14:04:00 -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: neleai at seznam dot cz
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: <bug-14412-131-NVR9pyPyOv@http.sourceware.org/bugzilla/>
In-Reply-To: <bug-14412-131@http.sourceware.org/bugzilla/>
References: <bug-14412-131@http.sourceware.org/bugzilla/>
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/msg00224.txt.bz2

http://sourceware.org/bugzilla/show_bug.cgi?id=14412

--- Comment #38 from Ondrej Bilka <neleai at seznam dot cz> 2013-04-29 14:04:37 UTC ---
On Mon, Apr 29, 2013 at 01:28:10PM +0000, bugdal at aerifal dot cx wrote:
> http://sourceware.org/bugzilla/show_bug.cgi?id=14412
> 
> --- Comment #33 from Rich Felker <bugdal at aerifal dot cx> 2013-04-29 13:28:10 UTC ---
> Ondrej, the results are not pure garbage. There are only two correct results
> sin(0x1p1000) can give, either of the nearest representable neighbors (less
> than 1ulp error) of the number 2**1000. Your fallacy is writing PI in your
> example. There is no such floating point number as PI, and this is part of why
> implementing correct trig functions is nontrivial; implementing ones that work
> in degree units, or a base-2 division of the unit circle, would be much easier.
>
Ok, assume you wrote function cos_deg that takes input degree in
degrees. You still have
cosdeg(360*(2**60)) == cosdeg(360*(2**60)+180)
In short when you have inputs with zero significant digits you can
expect only garbage as output.

-- 
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.