Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!think.com!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!mcsun!hp4nl!cwi.nl!dik From: dik@cwi.nl (Dik T. Winter) Newsgroups: comp.arch Subject: Re: IEEE arithmetic Message-ID: <3709@charon.cwi.nl> Date: 17 Jun 91 00:16:21 GMT References: <9106150258.AA16308@ucbvax.Berkeley.EDU> <3707@charon.cwi.nl> Sender: news@cwi.nl Organization: CWI, Amsterdam Lines: 36 In article mccalpin@perelandra.cms.udel.edu (John D. McCalpin) writes: > >>>>> On 15 Jun 91 22:23:08 GMT, dik@cwi.nl (Dik T. Winter) said: > > Dik> In article <9106150258.AA16308@ucbvax.Berkeley.EDU> > Dik> jbs@WATSON.IBM.COM writes: > > JBS> [....] 3. Do you know of any machine where the above code will > JBS> average 3x (or less) the time of a single multiply? > > Dik> So this is irrelevant. > > Winter is claiming that Shearer is trying to obfuscate the issues > about the performance of interval arithmetic (in terms of timing, not > the usefulness of the results. > > I see Shearer asking a very simple question: Please provide *specific* > information on machines where Winter's algorithms for interval add and > interval multiply perform less than 3 times slower than the equivalent > simple operation with a single rounding mode. > > Then I suppose that the next step is to compare the performance of > interval arithmetic with 128-bit arithmetic on a machine like the > RS/6000. To do this, we will first need to find someone who knows how > expensive the rounding mode change is in the RS/6000 FPU pipe, and > then someone who knows the timings of quad-precision arithmetic on the > RS/6000. (I will be able to learn the latter as soon as I get xlf > version 2 installed on my machine). > -- > John D. McCalpin mccalpin@perelandra.cms.udel.edu > Assistant Professor mccalpin@brahms.udel.edu > College of Marine Studies, U. Del. J.MCCALPIN/OMNET -- dik t. winter, cwi, amsterdam, nederland dik@cwi.nl