From owner-freebsd-numerics@FreeBSD.ORG Sun Aug 12 23:08:55 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 1BB42106566B for ; Sun, 12 Aug 2012 23:08:55 +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 AADEC8FC19 for ; Sun, 12 Aug 2012 23:08:54 +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 q7CN8ssH075762 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 13 Aug 2012 09:08:54 +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 q7CN8mKD021482 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 13 Aug 2012 09:08:48 +1000 (EST) (envelope-from peter@server.rulingia.com) Received: (from peter@localhost) by server.rulingia.com (8.14.5/8.14.5/Submit) id q7CN8mmp021481 for freebsd-numerics@freebsd.org; Mon, 13 Aug 2012 09:08:48 +1000 (EST) (envelope-from peter) Resent-From: Peter Jeremy Resent-Date: Mon, 13 Aug 2012 09:08:48 +1000 Resent-Message-ID: <20120812230848.GI20453@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 q6J3RBXO009208 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 19 Jul 2012 13:27:11 +1000 (EST) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (troutmask.apl.washington.edu [128.95.76.21]) by vps.rulingia.com (8.14.5/8.14.5) with ESMTP id q6J3R8YB079135 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Thu, 19 Jul 2012 13:27:10 +1000 (EST) (envelope-from sgk@troutmask.apl.washington.edu) Received: from troutmask.apl.washington.edu (localhost.apl.washington.edu [127.0.0.1]) by troutmask.apl.washington.edu (8.14.5/8.14.5) with ESMTP id q6J3R605001598; Wed, 18 Jul 2012 20:27:06 -0700 (PDT) (envelope-from sgk@troutmask.apl.washington.edu) Received: (from sgk@localhost) by troutmask.apl.washington.edu (8.14.5/8.14.5/Submit) id q6J3R6ta001597; Wed, 18 Jul 2012 20:27:06 -0700 (PDT) (envelope-from sgk) From: Steve Kargl Mail-Followup-To: freebsd-numerics@freebsd.org To: Stephen Montgomery-Smith Message-ID: <20120719032706.GA1558@troutmask.apl.washington.edu> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50077987.1080307@missouri.edu> User-Agent: Mutt/1.4.2.3i Cc: Diane Bruce , John Baldwin , David Chisnall , Bruce Evans , Bruce Evans , 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 23:08:55 -0000 X-Original-Date: Wed, 18 Jul 2012 20:27:06 -0700 X-List-Received-Date: Sun, 12 Aug 2012 23:08:55 -0000 On Wed, Jul 18, 2012 at 10:05:43PM -0500, Stephen Montgomery-Smith wrote: > On 07/18/2012 09:53 PM, Steve Kargl wrote: > > > >The inexact flag will get raised by the fpu, but you need to > >cause the condition. For your 'sqrt(y*y-1) = y' example, > >you would do something like 'sqrt(y*y-1) = abs(y) - tiny' where > >tiny is much less than abs(y). Search msun/src for inexact > >(ie., grep -i inexact msun/src/*.c) > > > > Couldn't you do this instead? > > #include > > feraiseexcept(FE_INEXACT) > I haven't checked, but I suspect you're looking at a speed issue. It's faster to let the hardware raise the flag. It seems that libm only uses the above in the fuse-multiple-add code: laptop:kargl[206] grep feraise src/*c src/s_fma.c: feraiseexcept(FE_INEXACT); src/s_fma.c: feraiseexcept(FE_UNDERFLOW); src/s_fmal.c: feraiseexcept(FE_INEXACT); src/s_fmal.c: feraiseexcept(FE_UNDERFLOW); src/s_lround.c: feraiseexcept(FE_INVALID); -- Steve