Author: Vincent Diepeveen
Date: 07:06:42 05/28/02
Go up one level in this thread
On May 28, 2002 at 09:06:36, K. Burcham wrote: for computerchess that is way too optimistic Kim. programs like Cray Blitz or DIEP might do pretty well at 8 processors, but crafty, fritz, sos, shredder, patzer, junior and these programs scale pretty bad at 8 processors. bandwidth is not the issue here. speedup is the issue here. If you split at random like most of these programs do, then you have simply major speedup problems soon. In case of patzer a big issue is that it is tactical extending a lot, so the search space is not identical (i don't even know whether it runs at 8 processors). So where crafty gets 1.7 speedup at 2 processors and like 2.5 speedup at 4 processors at crucial moments (when score drops a little) in the game, there the speedup at 8 processors for these random splitting programs is very horrible at 8 processors; in some positions you get 10 times speedup, in other positions a 2 times speedup. When you need the speedup you don't get it. Anyway this is all theoretic discussion. I am pretty sure chessbase doesn't want to buy a 8 way Xeon system, even though they can afford the $100k easily. With regard to memory i need to mention that memory is faster on these systems than at our slow dual systems (with respect to memory), memory goes in parallel at the big machines, it doesn't at dual machines. Best regards, Vincent >In absolute terms, the 8-way Pentium 3 Xeon systems are only 44% faster than the >4-way ones, which means that with the 4 extra CPUs, the system only gets 1.76 >CPUs worth of extra performance, which is poor value for money. This level of >scalability is not that surprising since each group of 4 CPUs share 0.8GByte/s >of memory bandwidth. As a side note, it seems likely though that 252.eon fits >almost perfectly into the 2MByte cache the Pentium 3 Xeons have as it gets >nearly linear scalability - the higher the cache hit rate, the less main memory >is needed, which leaves more for the other CPUs. > >Even worse, in some tests, the 8-way system actually does worse than the 4-way >system, and this could possibly be due to differences in the chipsets or because >the extra contention itself on the shared Pentium system bus causes efficiency >to drop. It's unlikely that the compilers/OS would have made much difference as >for each CPU type the tests were done at similar times with the same compilers. > > >http://www.aceshardware.com/read.jsp?id=45000338 > >kburcham
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.