Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!stat!stat.fsu.edu!mccalpin From: mccalpin@masig3.masig3.ocean.fsu.edu (John D. McCalpin) Newsgroups: comp.arch Subject: Re: linpack Message-ID: Date: 19 Oct 89 13:06:41 GMT References: <35825@lll-winken.LLNL.GOV> <127@csinc.UUCP> <9079@batcomputer.tn.cornell.edu> <2203@brazos.Rice.edu> <9089@batcomputer.tn.cornell.edu> Sender: news@stat.fsu.edu Organization: Supercomputer Computations Research Institute Lines: 37 In-reply-to: kahn@batcomputer.tn.cornell.edu's message of 19 Oct 89 05:13:31 GMT In article <9079@batcomputer.tn.cornell.edu> kahn@tcgould.tn.cornell.edu writes: >Throw away ALL your copies of the LINPACK 100x100 benchmark if you >are interested in supercomputers. The 300x300 is barely big enough In article <2203@brazos.Rice.edu> preston@titan.rice.edu (Preston Briggs) writes: >Danny Sorenson mentioned recently that linpack is sort of intended >to show how *bad* a computer can be. The sizes are kept >deliberately small so that the vector machines barely have a chance >to get rolling. In article <9089@batcomputer.tn.cornell.edu> kahn@batcomputer.tn.cornell.edu (Shahin Kahn) writes: >It certainly is biased towards micros with limited memory and is >absolutely irrelevant as a *supercomputer* application. Yes, it >can show how bad a supercomputer can be. Well, I'll through in my $0.02 of disagreement with this thread. It has been my experience that the poor performance of the LINPACK 100x100 test on supercomputers is *entirely typical* of what users actually run on the things. There a plenty of applications burning up Cray, Cyber 205, and ETA-10 cycles which have average vector lengths *shorter* than the average of 66 elements for the LINPACK test, and which are furthermore loaded down with scalar code. The 100x100 test case is not representative of *everyone's* jobs, but it is not an unreasonable "average" case, either. I think it is much more representative of what most users will see than the 1000x1000 case, for example. The 1000x1000 case is a very good indicator of what the *best* performance will be with *careful optimization* on codes that are essentially 100% vectorizable. Most of the supercomputer workload does not fall into that category.... -- John D. McCalpin - mccalpin@masig1.ocean.fsu.edu mccalpin@scri1.scri.fsu.edu mccalpin@delocn.udel.edu