Re: Help! Mathematica on my 500MHz outperforms my GHz machine!
- To: mathgroup at smc.vnet.net
- Subject: [mg23120] Re: Help! Mathematica on my 500MHz outperforms my GHz machine!
- From: "Martin Richter" <martin.richter at worldnet.att.net>
- Date: Wed, 19 Apr 2000 02:30:50 -0400 (EDT)
- Organization: AT&T Worldnet
- References: <8d3s48$omg@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Just curios, that memory type did you use at your Pentium, also 100MHz bus or 133MHz. Normally you get a boost upgrading the speed even on the purely cpu-runtime test, so could it be Matematica way to handle the memory ? Have you tried to running simulation test in a C/C++ environment ? Martin <terryis at my-deja.com> wrote in message news:8d3s48$omg at smc.vnet.net... > Fellow Mathematica Users, > > After spending some time investigating the lackluster > performance of my gigahertz Athlon machine I have finally > discovered why it only performs at about the same level > as my 500MHz Pentium III. In short my Athlon is bottle- > necking on the relatively slow 100MHz bus between cache > and main memory (as some of you had suspected). > > To start with I ran the various benchmarks suggested > to me. From http://fampm201.tu-graz.ac.at/karl/mma.html I > ran the MMA-Test.nb (for Mathematica 3.0) and got the > following results: > > Version = Microsoft Windows 3.0 (April 25, 1997) > Times = > {0.531,0.591,0.18,0.371,1.91,0.661,0.181,0.28,0.551,0.641,0.47,0.862,0.5 > 81,0.49,0.461} > Total Kernel Time = 8.763, Total Time = 9. > Benchmark = 11.2 > > The benchmarks at www.scientificweb.com/sciencee/mathstef2.html could > not be found and the ones at > www.geocities.com/SiliconValley/Lab/2255/bytemark.html worked on one of > my computers but gave a 'numeric sort' error condition on the gigahertz > machine. > > The link 205.181.113.18/zdbop/zdbop2.html could not be contacted despite > multiple attempts on different occasions. > > > Next I split up my simulation and timed each piece individually > on each machine. For each piece my Athlon kicked ass even though > it performed poorly on the whole simulation. Finally I > was able to localize the difference in performance to a > single piece of code that saved intermediate results to > memory. With the code to save intermediate results in, > my Athlon took on average 27 minutes to run 25000 > iterations of my simulation compared to 24 minutes on the > Pentium. Without the code to save intermediate results the > Athlon was averaging 1 minute compared to 3 minutes on my > Pentium! My conclusion was that without saving intermediate > results, the sum total of all the parts of my simulation > was able to fit completely in cache and so could run at the > full 200MHz bus speed between cache and CPU. Interestingly > enough the performance of the Pentium also improved > dramatically (from 24 minutes down to an average of 3 > minutes!) which to me indicated that the cache hit ratio on > the Pentium was not that high either. > > As it turns out, my simulations can be re-written to take > full advantage of this machine. Even if I have to go back > and re-run segments of my simulation to re-capture those > intermediate results that are worth capturing, it's still > worth it for me. > > Bottom line: if you are certain that what you are doing > can fit into cache then this could very well be one of > the faster machines for you to run Mathematica on. > Otherwise I'd stick with a Pentium based machine. > > Finally check out > www.zdnet.com/pcmag/stories/firstlooks/0,6763,2426421,00.html > for a good article that sums up this machines deficiencies. > > > Sent via Deja.com http://www.deja.com/ > Before you buy. >