From owner-freebsd-numerics@FreeBSD.ORG  Sun Jan  4 05:27:25 2015
Return-Path: <owner-freebsd-numerics@FreeBSD.ORG>
Delivered-To: freebsd-numerics@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id 3657A1D2
 for <freebsd-numerics@FreeBSD.org>; Sun,  4 Jan 2015 05:27:25 +0000 (UTC)
Received: from mail.apache.org (hermes.apache.org [140.211.11.3])
 by mx1.freebsd.org (Postfix) with SMTP id D69BA645E9
 for <freebsd-numerics@FreeBSD.org>; Sun,  4 Jan 2015 05:27:24 +0000 (UTC)
Received: (qmail 79212 invoked by uid 99); 4 Jan 2015 05:27:23 -0000
Received: from mail-relay.apache.org (HELO mail-relay.apache.org)
 (140.211.11.15)
 by apache.org (qpsmtpd/0.29) with ESMTP; Sun, 04 Jan 2015 05:27:23 +0000
Received: from [192.168.0.103] (unknown [190.157.136.22])
 by mail-relay.apache.org (ASF Mail Server at mail-relay.apache.org) with
 ESMTPSA id 8C8221A0155; Sun,  4 Jan 2015 05:27:17 +0000 (UTC)
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 8.1 \(1993\))
Subject: Re: glibc math improvements
From: Pedro Giffuni <pfg@freebsd.org>
In-Reply-To: <20150104043745.GA79370@troutmask.apl.washington.edu>
Date: Sun, 4 Jan 2015 00:27:03 -0500
Content-Transfer-Encoding: quoted-printable
Message-Id: <CE6A1215-FD5E-4535-9CF7-081649C06898@freebsd.org>
References: <884D1A4A-76B7-4E7B-939A-6FD7D6D6D18D@freebsd.org>
 <20150104043745.GA79370@troutmask.apl.washington.edu>
To: Steve Kargl <sgk@troutmask.apl.washington.edu>
X-Mailer: Apple Mail (2.1993)
Cc: freebsd-numerics@FreeBSD.org
X-BeenThere: freebsd-numerics@freebsd.org
X-Mailman-Version: 2.1.18-1
Precedence: list
List-Id: "Discussions of high quality implementation of libm functions."
 <freebsd-numerics.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-numerics>, 
 <mailto:freebsd-numerics-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-numerics/>
List-Post: <mailto:freebsd-numerics@freebsd.org>
List-Help: <mailto:freebsd-numerics-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-numerics>, 
 <mailto:freebsd-numerics-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 04 Jan 2015 05:27:25 -0000


> Il giorno 03/gen/2015, alle ore 23:37, Steve Kargl =
<sgk@troutmask.apl.washington.edu> ha scritto:
>=20
> On Sat, Jan 03, 2015 at 10:00:58PM -0500, Pedro Giffuni wrote:
>>=20
>> This blog post was covered by Phoronix:
>> =
http://developerblog.redhat.com/2015/01/02/improving-math-performance-in-g=
libc/ =
<http://developerblog.redhat.com/2015/01/02/improving-math-performance-in-=
glibc/>
>>=20
>> Not sure any of that stuff is applicable to our implementation but it =
looks like an interesting link to share nevertheless.
>>=20
>=20
> AFAICT, it is not applicable.   The improvements are in
> a 768-bit multi-precision computation of pow() to get an
> accurate answer.  The article mentions that the technique
> may be applied to exp() and log(), but the table-driven
> methods that Bruce, David, and I used for logl, expl, and
> exp2l are quite accurate (somewhere around ulp < 0.55 or so).
>=20

OK, I see, apparently the improvements only apply for worst-case
scenarios but we never hit them.

A test suite would have been interesting but there is no trace of
them in the blog.

thanks,

Pedro.=20