Path: utzoo!attcan!uunet!husc6!endor!reiter From: reiter@endor.harvard.edu (Ehud Reiter) Newsgroups: comp.lang.fortran Subject: Re: Sun 3 vs uVAXII floating point speed.... Message-ID: <4973@husc6.harvard.edu> Date: 17 Jul 88 18:53:52 GMT References: <25065@ucbvax.BERKELEY.EDU> <4953@husc6.harvard.edu> <1284@csuna.UUCP> Sender: news@husc6.harvard.edu Reply-To: reiter@harvard.UUCP (Ehud Reiter) Distribution: na Organization: Aiken Computation Lab Harvard, Cambridge, MA Lines: 22 In article <1284@csuna.UUCP> bcphssrw@csunb.csun.edu (Stephen R. Walton) writes: >The deleted lines from Ehud's posting show a Sun 3/160 to be about >half the speed of the VAX 11/780. This is true but incomplete. On the >Savage benchmark, the Sun comes up 5 times FASTER than Vax. What's >happening? Well, the Linpack benchmark does matrix manipulation and >therefore its real work is all * and /. The Savage benchmark consists >entirely of transcendental functions, which are microcoded on the >68881 chip on the Sun but done in software on the Vax. Let me emphasize the point, which I should have made in my earlier posting of LINPACK benchmark figures, that no benchmark can predict the performance of real application programs with any accuracy (because application programs differ so widely - as Steve points out, whether a Sun or a VAX is faster depends on what kind of computation you're doing). Anyone who wants to buy a computer and is seriously interested in performance should test-run his own software on the computers in question, and not rely on benchmarks. Benchmarks are fun to argue about, but please don't take them too seriously when you're spending real money buying real machines. Ehud Reiter reiter@harvard (ARPA,BITNET,UUCP) reiter@harvard.harvard.EDU (new ARPA)