Re: PowerPCs

*To*: mathgroup at yoda.physics.unc.edu*Subject*: Re: PowerPCs*From*: Richard Mercer <richard at rmercer.wright.edu>*Date*: Fri, 01 Jul 1994 14:25:48 -0700

To: Dave Withoff Thanks for your knowledgable and informative review of timing methods. I was primarily concerned with two things: (1) People unintentionally comparing "Timing" results with "front end" results because they were unaware of what the other person was doing. (2) I know that the front end timing on a certain NeXT workstation is systematically off by about 20%. I don't know that this problem does not arise on other platforms. That's why I asked people to CHECK timings with a stopwatch, NOT RELY on stopwatch timings. An example of what I am trying to avoid is on p.5 of the 5.30.94 MacWeek, where a "Timing" result of ListPlot is given as 4.48 seconds on a PowerMac, which does not include the considerable time for rendering the Postscript graphic. This is claimed to take 27.3 seconds on a Quadra 700, a result which almost certainly is total elapsed time. In fact this same calculation on the aforementioned NeXT, which uses the same processor as the Quadra 700 (25mhz 68040), takes 28 seconds elapsed time but gives a Timing result of 8.4 seconds. (The front end shows 34 seconds!) The result is that WRI, in a national publication, seems to be claiming (I assume unintentionally) that Mathematica on the PowerMac is 6 times as fast as on a Quadra 700; the truth seems to be that it is roughly twice as fast on this particular calculation. While the comparison shown may serve the short-term interests of Apple Computer and/or WRI, in the long run we'll all be better off with the more more realistic comparison. (Incidentally, I have recently bought a PowerMac 7100, am very pleased with it, and think the combination of this machine with the Macintosh front end is the best or close to the best Mathematica platform currently available. If I didn't think Mathematica was a great program, I wouldn't be on this list!) Personally, I think "Timing" results are much less useful for users than for systems engineers. Users likely want to know how long something actually takes, and are less interested in why. ********************************************************************* Richard Mercer 513-873-2191 office Department of Mathematics and Statistics 513-873-2785 message Wright State University 513-429-2179 fax Dayton, OH 45435 NeXTmail welcome! richard at rmercer.wright.edu or rmercer at desire.wright.edu *********************************************************************