From chemistry-request@www.ccl.net Thu Feb 25 09:53:37 1999 Received: from foreman.ac.rwth-aachen.de (foreman.ac.RWTH-Aachen.DE [134.130.100.31]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id JAA03207 Thu, 25 Feb 1999 09:53:26 -0500 (EST) Received: (from landrum@localhost) by foreman.ac.rwth-aachen.de (AIX4.2/UCB 8.7/8.7) id PAA27910; Thu, 25 Feb 1999 15:53:03 +0100 (NFT) Date: Thu, 25 Feb 1999 15:53:03 +0100 (NFT) From: "Gregory A. Landrum" To: chemistry@www.ccl.net Subject: Re: CCL:Summary: AMD-K6/linux for G98 In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Normally I stay silent on these things, but this comment was just a bit too indicative of general "benchmark abuse". > For pinene using DFT/B3LYP with large basis sets, for >example, the machine i bought for $11,000 was faster than a Cray T3E-600 >with 4 processors and only 15% slower than a Cray T3E-1200 with 4 >processors, both running parallel Gaussian 94. (The G94 calculations were >done by Sosa and Frisch, so were probably pretty well optimized for the >machine, see last July 15 number of J. Comput. Chem. Sosa et al. Vol 19, >p. 1053). I haven't priced those machines but they must be >$100k. If you >want to benchmark against one of your own machines, Pulay would be happy >to do some calculations for you. The comparison here is *completely* invalid. If you want to compare the speed of machines, you must be running the same program. In this case, a highly-optimized DFT implementation (the one from Pulay) is being compared to an implementation which can charitably be called "not so great", this does not say a single thing about the relative speeds of the computers running those programs. Having Pulay do a benchmark for you would be altering two variables at the same time: (a) the hardware (b) the software it is impossible to decouple the effects of the two changes. One more time, for good measure: If you want reliable benchmarks of *hardware* performance, you must compare the same programs on the different hardware. -greg -- --------------------- Dr. Greg Landrum (landrum@foreman.ac.rwth-aachen.de) Institute of Inorganic Chemistry Aachen University of Technology Prof.-Pirlet-Str. 1, D-52074 Aachen, Germany Phone: 049-241-80-7004 Fax: 049-241-8888-288