Author: Robert Hyatt
Date: 09:10:15 08/09/00
Go up one level in this thread
On August 09, 2000 at 05:31:52, Andrew Williams wrote: >On August 08, 2000 at 16:00:32, Christophe Theron wrote: > >>On August 07, 2000 at 05:58:44, Andrew Williams wrote: >> >>>On August 06, 2000 at 20:10:49, Vincent Diepeveen wrote: >>> >>>>On August 06, 2000 at 19:17:18, Tom Kerrigan wrote: >>>> >>>>>On August 06, 2000 at 16:37:24, Vincent Diepeveen wrote: >>>>> >>>>>>On August 06, 2000 at 12:45:11, Dan Andersson wrote: >>>>>> >>>>>>>Vincent has had this idea of MTD and never managed/bothered to defend it. I >>>>>>>believe it to be an unsupported opinion. >>>>>> >>>>>>No commercial program uses MTD. End of proof man. >>>>> >>>>>I thought the MP version of Fritz does. >>>>> >>>>>-Tom >>>> >>>>I never saw any MP version of Fritz in the shops so far, >>>>perhaps someone is gonna state soon that DB used MTD too. >>> >>>Oddly enough, this seems to be what Hsu says in his IEEE Micro article. >>>Unfortunately, he doesn't say quite enough to be clear: >>> >>> "The search control does not really implement the regular >>> alpha-beta search algorithm [Ref: Knuth & Moore 1975]. Rather, >>> it implements a minimum-window alpha-beta search algorithm >>> [Ref: Pearl 1984]" >> >> >> >>The reference "Pearl 1984" clearly indicates that they are using PVS/Negascout. >> >> Christophe >> > >I'm not certain that this is true. This is a reference to: "Heuristics : >intelligent search strategies for computer problem solving". Addison-Wesley, >1984. I'm pretty sure that this book is where he first talked about the use >of MT (Memory Test) as a way investigating the performance characteristics of >alpha-beta searches. > >Andrew > I am certain they don't use mtd(f). For many reasons, but most notably the fact that the hardware chess processors don't have hash tables. Hsu designed hashing into the last DB chip (DB2) but did not have time to design and fab a memory system to put on the DB2 boards. Also since the SP2 is a message passing machine, and since mtd(f) heavily depends on hashing to save time, even half of the software search would have trouble since it is distributed over the message-passing frame of the SP2. mtd(f) with no hashing really does suck. >> >>>This is a bit ambiguous, because of course PVS could be called a "minimum >>>window algorithm". But the rest of the paragraph (which is too long to type >>>here) does seem to suggest that DB was using something more like MTD than >>>PVS. I don't know if Bob knows for sure (maybe it's in Hsu's book?). Either >>>way, I'd recommend looking at the article, "IBM's Deep Blue Chess Grandmaster >>>Chips", Feng-hsiung Hsu, IEEE Micro March-April 1999. The relevant section >>>is "Search Control" on page 80. >>> >>>Having said all that, I think your argument about commercial programs and MTD >>>is flawed (whether DB used MTD or not). The problem is that MTD is a relatively >>>new technique, like bitboards. AFAIK, no commercial program uses bitboards >>>either. I know you don't like that technique, Vincent, but no sane person >>>would say that the fact that they're not widely used in commercial programs >>>"proves" that they're no good as an approach to creating chess programs. >>> >>>Andrew
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