Author: Matthew Hull
Date: 20:31:19 01/29/03
Go up one level in this thread
On January 29, 2003 at 23:20:11, Vincent Diepeveen wrote: >On January 29, 2003 at 12:06:50, Robert Hyatt wrote: > >Bob let me explain to you. DIEP is written for machines which have a bit slower >latency for global memory accesses. whereas the world champs 2002 version wasn't >like that and would probably act like crafty on that 8 processor, the end of >august 2002 versions and further are using a new type of parallellism which >doesn't need much locking. Each processor takes care of itself without hurting >bandwidth while searching too much. > >There is no dead slow global locks which is killing the 8 processor thing of >course. > >therefore it works great for example at cc-NUMA machines and all types of Xeon >machines. Wow dude. Impressive. Could you supply some time-to-ply benchmarks for Diep on 8-way Xeon vis-a-vis 4-way Xeon. That would refute the proffessor like nothing else. Sincerely, Matt > >Now you have some examples of software written for fast latency shared memory >machines and then claim the thing is slower because the software isn't written >for such types of machines? > >That already should give you the answer. Writing parallel programs is 1 thing. >Writing something that works well without inventing numbers yourself is another >thing. > > >>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. >> >> >> >> >>> >>>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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