Author: Yen Art Tham
Date: 14:12:53 01/29/03
Go up one level in this thread
On January 29, 2003 at 12:06:50, Robert Hyatt wrote: >On January 29, 2003 at 11:38:37, Vincent Diepeveen wrote: > >>On January 28, 2003 at 10:33:15, Robert Hyatt wrote: >> >>>On January 28, 2003 at 09:07:35, Vincent Diepeveen wrote: >>> >>>>On January 28, 2003 at 03:33:44, Mig Greengard wrote: >>>> >>>>>According to the tech I talked with, Amir and Shay were testing both machines >>>>>before the match to see which one they would use. To my knowledge it wasn't >>>>>decided until a day or two before the match. Obviously there isn't a big >>>>>difference in performance. >>>>> >>>>>Saludos, Mig >>>>>http://www.chessninja.com >>>> >>>>thanks. >>>> >>>>DIEP onto the 8 processor 1.6 would be running 16 processes and speed would >>>>be about expressed in K7: >>>> 8 x 1.6 Ghz / 1.4 = 9 Ghz >>> >>> >>>No it wouldn't. You haven't tried an 8-way intel box yet. It doesn't scale >>>nearly as well as the 2-way and 4-way intel boxes do. The chipset for >>>supporting 8 cpus is simply not very good... >> >>DIEP isn't demanding much bandwidth Bob in case you missed it, it works >>great on a cc-NUMA machine too. > >It demands _enough_ bandwidth. My comment wasn't only about "crafty" It was >about the 8-way boxes in general. I ran on a dell 8450, with 8 700mhz xeon >processors, and it was about 1.5X faster than my box. And again, _not_ with >Crafty. I ran 8 copies of the same thing on the 8450, 4 copies on the quad, >and compared the total run times. The 8450 was only about 50% faster when it >should be 100% based on clock... > > > >> >>>The 8-way box using the same clock speed for the processors will only be about >>>1.5X faster than the 4-way box, and that doesn't count parallel search overhead >>>at all. >> >>That's not true. It's 8 times faster for good software. Of course there is >>algorithmic loss but there is no sequential loss unless the software sucks, >>to say it rude. > >Have you ever run on one? Of course not. I have. So your "that's not true" >is simply nonsense... There are _plenty_ of good benchmarks that can be used >to draw conclusions about the 8-way memory bottleneck problem. > >It _might_ be 8x faster if you can fit in the L2 cache (this machine had >2mb of L2 per processor compared to my 1mb on my quad 700). But if you have >any memory bandwidth at all, it has a problem. And a 8-probe hash table is >more than enough to highlight the problem. I have a dumb question: you said "fit in the L2 cache", what fits in the L2 cache? engine? hash? > > > > >> >>Doesn't say that it is easy to make software that can handle the latencies. >> >>It sure isn't easy to make a chessprogram that is having a good speedup >>(without a too big sequential loss first like Zugzwang which was slowed down >>first like 100 times or so in order to then have a decent speedup at like >>256 processors; 50% speedup even incredible much i would be *very* happy with >>around 15% already). >> >>But it is possible to make. >> >>DIEP is such a program that shows it can. DIEP runs like the sun on 8 cpu's >>(2 nodes quad SGI), even at the slowest partitions (slowest latency speeds >>are of course at the biggest partitions: 512 cpu partition). >> >>A 8 processor Xeon is hell for pc software like Fritz, Junior, Crafty, but it >>is very good for DIEP. >> >>Best regards, >>Vincent
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