From owner-freebsd-numerics@FreeBSD.ORG Sun Aug 12 23:08:24 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 47C6B106564A for ; Sun, 12 Aug 2012 23:08:24 +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 D176F8FC12 for ; Sun, 12 Aug 2012 23:08:23 +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 q7CN8N1K075737 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 13 Aug 2012 09:08:23 +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 q7CN8HGO021431 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 13 Aug 2012 09:08:17 +1000 (EST) (envelope-from peter@server.rulingia.com) Received: (from peter@localhost) by server.rulingia.com (8.14.5/8.14.5/Submit) id q7CN8H5D021430 for freebsd-numerics@freebsd.org; Mon, 13 Aug 2012 09:08:17 +1000 (EST) (envelope-from peter) Resent-From: Peter Jeremy Resent-Date: Mon, 13 Aug 2012 09:08:17 +1000 Resent-Message-ID: <20120812230817.GD20453@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 q6IN1hRg006417 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 19 Jul 2012 09:01:44 +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 q6IN1frE078418 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Thu, 19 Jul 2012 09:01:43 +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 q6IN1Jlr061471; Wed, 18 Jul 2012 18:01:20 -0500 (CDT) (envelope-from stephen@missouri.edu) Message-ID: <5007403F.8000909@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: Peter Jeremy References: <20120713155805.GC81965@zim.MIT.EDU> <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> <20120718224222.GA6022@server.rulingia.com> In-Reply-To: <20120718224222.GA6022@server.rulingia.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Diane Bruce , Steve Kargl , John Baldwin , David Chisnall , Bruce Evans , Bruce Evans , David Schultz , 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 23:08:24 -0000 X-Original-Date: Wed, 18 Jul 2012 18:01:19 -0500 X-List-Received-Date: Sun, 12 Aug 2012 23:08:24 -0000 On 07/18/2012 05:42 PM, Peter Jeremy wrote: > On 2012-Jul-18 10:07:41 -0500, Stephen Montgomery-Smith wrote: >> I went on a long road trip yesterday, so I didn't get any code written, >> but I did have a lot of thoughts about clog and casinh. > > Can I suggest you have a read through "Implementing the Complex > Arcsine and Arccosine Functions Using Exception Handling" by > T. E. Hull Thomas F. Fairgrieve and Ping Tak Peter Tang, ACM > Transactions on Mathematical Software, Vol. 23, No. 3, September 1997. > Based on a quick skim, it includes fairly detailed pseudocode, > together with an error analysis. OK, I will do that. My pseudo code is different in that I use clog, and they do not. I'll probably go with my approach, but use lots of ideas from this paper as seems appropriate. I might even try both approaches and see which seems to be the winner, > > On 2012-Jul-18 16:09:06 -0500, Stephen Montgomery-Smith wrote: >> Am I to understand that the inexact flag should be set anytime a >> floating point operation produces an answer that is not guaranteed >> exact? > > My understanding is, yes. For the transcendental functions, that > means the inexact flag should almost always be raised and the problem > becomes when not to raise it. Eg sin(0) == 0 and presumably doesn't > set the inexact flag. > >> For example, should 1.0/3.0 and sqrt(2.0) raise the inexact flag? > > Yes and yes. I notice our sqrtl() actually tests the inexact flag of > an intermediate calculation to determine the correct rounding for the > result. Thank you for the clarification. I will definitely set the inexact flag under the circumstances pointed out by Steve. Otherwise, I will rely on clog and csqrt to set the inexact flag. (And clog will depend upon log, hypot and atan2 to set the inexact flag.)