Author: Robert Hyatt
Date: 07:01:56 08/02/01
Go up one level in this thread
On August 02, 2001 at 09:03:41, Vincent Diepeveen wrote: >On August 02, 2001 at 08:45:06, Robert Hyatt wrote: > >>On August 02, 2001 at 07:32:41, Vincent Diepeveen wrote: >> >>>On August 02, 2001 at 03:44:01, Janosch Zwerensky wrote: >>> >>>>Hi all, >>>> >>>>I read some time ago that Deep Blue wasn't using heuristic game tree pruning >>>>methods (like, for example, the null-move technique). >>>>Since null-move was known when DB was around, can anyone here tell why the DB >>>>team decided not to use it (or wasn't able to do so)? >>> >>>There are a number of reasons >>> a) IBM focussed upon nodes a second, search depth was not important, >>> the only PR argument was their machine was FASTER than anyone elses. >>> b) they searched 12 ply which was deeper as anyone else anyway >>> c) nullmove back then was considered dubious, scientists didn't know >>> much from it >> >>What are you talking about in (c)? in 1996/1997 null-move was as well- >>understood as it is today... >> >> >> >>> d) look at the historic picture. The deep blue designers were busy >>> improving their machine. Well they could search deeper as the previous >>> machine could, so why look to for sure tough to figure out things >>> like nullmove? >>> e) in hardware using nullmove is nowadays easier as it was back then. >>> Back then timing issues were of major importance. >> >>Eh? That doesn't compute at all. Hardware design today is just as it was >>10 years ago. Only the circuits are smaller and the clock frequencies are >>faster, which has made things more complicated, not easier... > >Can only take your word for that :) > >> >> >>> f) Important to realize is that the processors didn't even USE >>> hashtables. >> >>Important to remember that they _could_. DB2 had the hash probe stuff in >>it, but Hsu had no time to design/build the multi-ported memory to provide >>a hash table for the chess processors. But they _did_ use it in software, >>which was the first 10-12 plies plus extensions... that isn't horrible. > >I don't doubt it was used the first 6 ply in software. It was used the first 10-12 plies in software. Nothing has changed. As Hsu and Campbell reported in the past, the first 5-6 plies of search were done on one processor, the next 5-6 plies were spread over 32 SP nodes (which did have hash tables). The last 5-6 plies were done in the chess processors which did not have the ability to do hashing as already mentioned. > >> >>> >>>Bob has given a very plausible explanation. Hsu was busy getting >>>hashtables to work, but did run out of time to get them to work on >>>chip. >> >> >>No... he got them to work on the chess processor. But he didn't have >>time to build the memory units for each DB2 circuit board. He barely >>got DB2 itself running for the second match. > >>> >>>I can completely imagine Hsu here. >>> >>>IMHO hashtables are more important than nullmove is, >>>nullmove only gets important when all the things are well done. >>> >>>Why get nullmove to work when hashtables aren't working yet? >>> >>>We all do as if Deep Blue was a well tested and well playing machine. >>>It was not! >>> >>>It was not even finished! >>> >>>What played kasparov were a few bare chips without hashtables even! >>> >>>No one, including me, could imagine that Kasparov would play a few games >>>in his life that bad! >>> >>>Of course, Kasparov is just human, IBM had said all kind of things like >>>that this would be the last match they would play, "BECAUSE DEEP BLUE >>>ALWAYS LOST". >> >>IBM never said that. I don't think they were convinced they would win this >>match either, and you could bet there would be another. Otherwise they would >>have stopped after match 1. > >In fact they even had said they would attach it to the >internet after the match. They did this. A web-based version, which was requested by the marketing guys. A single-chip version doing a very short search, with no ability to handle repetitions or whatever because it was based on a stateless web-based GUI. They just never thought that people would try to play against it with another chess program and then claim "I beat Deep Blue."
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