From owner-freebsd-numerics@FreeBSD.ORG Sun Aug 12 23:09:23 2012 Return-Path: Delivered-To: freebsd-numerics@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id BCCCD106564A for ; Sun, 12 Aug 2012 23:09:23 +0000 (UTC) (envelope-from peter@rulingia.com) Received: from vps.rulingia.com (host-122-100-2-194.octopus.com.au [122.100.2.194]) by mx1.freebsd.org (Postfix) with ESMTP id 3FAF98FC12 for ; Sun, 12 Aug 2012 23:09:22 +0000 (UTC) Received: from server.rulingia.com (c220-239-249-137.belrs5.nsw.optusnet.com.au [220.239.249.137]) by vps.rulingia.com (8.14.5/8.14.5) with ESMTP id q7CN9Muu075780 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 13 Aug 2012 09:09:22 +1000 (EST) (envelope-from peter@rulingia.com) X-Bogosity: Ham, spamicity=0.000000 Received: from server.rulingia.com (localhost.rulingia.com [127.0.0.1]) by server.rulingia.com (8.14.5/8.14.5) with ESMTP id q7CN9GIX021525 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 13 Aug 2012 09:09:16 +1000 (EST) (envelope-from peter@server.rulingia.com) Received: (from peter@localhost) by server.rulingia.com (8.14.5/8.14.5/Submit) id q7CN9GDc021524 for freebsd-numerics@freebsd.org; Mon, 13 Aug 2012 09:09:16 +1000 (EST) (envelope-from peter) Resent-From: Peter Jeremy Resent-Date: Mon, 13 Aug 2012 09:09:16 +1000 Resent-Message-ID: <20120812230916.GM20453@server.rulingia.com> Resent-To: freebsd-numerics@freebsd.org Received: from vps.rulingia.com (host-122-100-2-194.octopus.com.au [122.100.2.194]) by server.rulingia.com (8.14.5/8.14.5) with ESMTP id q6JHQGMs016057 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 20 Jul 2012 03:26:17 +1000 (EST) (envelope-from stephen@missouri.edu) Received: from wilberforce.math.missouri.edu (wilberforce.math.missouri.edu [128.206.184.213]) by vps.rulingia.com (8.14.5/8.14.5) with ESMTP id q6JHQEZB081701 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Fri, 20 Jul 2012 03:26:16 +1000 (EST) (envelope-from stephen@missouri.edu) Received: from [127.0.0.1] (wilberforce.math.missouri.edu [128.206.184.213]) by wilberforce.math.missouri.edu (8.14.5/8.14.5) with ESMTP id q6JHPsME048856; Thu, 19 Jul 2012 12:25:54 -0500 (CDT) (envelope-from stephen@missouri.edu) Message-ID: <50084322.7020401@missouri.edu> From: Stephen Montgomery-Smith Mail-Followup-To: freebsd-numerics@freebsd.org User-Agent: Mozilla/5.0 (X11; Linux i686; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: Bruce Evans References: <20120714120432.GA70706@server.rulingia.com> <20120717084457.U3890@besplex.bde.org> <5004A5C7.1040405@missouri.edu> <5004DEA9.1050001@missouri.edu> <20120717200931.U6624@besplex.bde.org> <5006D13D.2080702@missouri.edu> <20120718205625.GA409@troutmask.apl.washington.edu> <500725F2.7060603@missouri.edu> <20120719025345.GA1376@troutmask.apl.washington.edu> <50077987.1080307@missouri.edu> <20120719032706.GA1558@troutmask.apl.washington.edu> <5007826D.7060806@missouri.edu> <5007AD41.9070000@missouri.edu> <20120719205347.T2601@besplex.bde.org> In-Reply-To: <20120719205347.T2601@besplex.bde.org> Content-Type: multipart/mixed; boundary="------------020105090904080608070404" X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Diane Bruce , John Baldwin , David Chisnall , Bruce Evans , Steve Kargl , David Schultz , Peter Jeremy , Warner Losh Subject: Re: Use of C99 extra long double math functions after r236148 X-BeenThere: freebsd-numerics@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Discussions of high quality implementation of libm functions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Date: Sun, 12 Aug 2012 23:09:23 -0000 X-Original-Date: Thu, 19 Jul 2012 12:25:54 -0500 X-List-Received-Date: Sun, 12 Aug 2012 23:09:23 -0000 This is a multi-part message in MIME format. --------------020105090904080608070404 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 07/19/2012 06:16 AM, Bruce Evans wrote: > On Thu, 19 Jul 2012, Stephen Montgomery-Smith wrote: > >> I did a ULP test on clog. The test code is attached. (Not the >> cleanest code, I know, but it does the job.) It needs the mpfr and >> unuran ports installed. >> >> To my shock, I found that under certain circumstances, the ULP in the >> real part was huge. The problem is when hypot(x,y) is close to 1, >> because then the real part of clog is close to zero. I was seeing >> ULPs in the thousands. > > Better than GULPs in the thousands :-). > > This is not the problem that I first thought it might be. > >> I struggled to find a solution, and now I think I have the ULP down to >> about 2. I am going to work on it more tomorrow to see if I can get >> ULP down even further. I have the ULP down to about 1.2 now. I don't see how I can do better, because I have to invoke log functions twice, and probably each one has a ULP of about 0.6. Also I decided to use 1/2 log(x*x+y*y) when x and y are not too large. I am really rather proud of how I got around the large ULP when hypot(x,y) is close to 1. I would be glad if any of you could look at the code when you get a chance. Also, now that I see how hard clog was, I have more appreciation of Steve's objections. --------------020105090904080608070404--