Author: Bruce Moreland
Date: 20:48:43 06/28/98
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On June 28, 1998 at 20:32:58, jonathan Baxter wrote: >So all this recent discussion about DB says it doesn't null move, and I saw >another post which said in some positions it was getting no more than 11-ply. >Since PC based programs now reach that easily (without heavy forward pruning >apart from Null move), but PC programs are not close to challenging Kasparov, >can't we only conclude one of two things: > >1) DB has a much better evaluation function than the PC programs. > >and/or > >2) Null moving makes *lots* of mistakes. There's a lot more than this. Their search isn't just a normal full-width search without null moves. In the past they have relied upon the singular extension heuristic to produce trees that are extended at points they consider crucial. So, the tree they search isn't just the normal full-width tree with the null-move pruned branches filled in. Next, the strength of DB hasn't been accurately evaluated. What do we know about the strength of something like Rebel or Hiarcs, who have played hundreds or even thousands of games that we can examine? How do you really evaluate these programs? If there is any question about how strong they are, then how could there not be many more questions about how strong DB is, when we only have six games from its newest incarnation? Also, even if it is very strong, the project was a hardware project, so it is hard to compare it with software projects. The issue is computer power and its effect upon rating against various opponents at various time controls, and while this has been studied and conjectured about, I don't think that there has been any conclusive result, instead all we have is an incomplete set of lemmas that are repeated by a lot of people but aren't really proven true. So even if we had a better idea what they were doing, it would be hard to evaluate the effectiveness of their algorithms. It is difficult to know how their project would compare to a similar hardware project conducted by someone who came from microcomputers, and chose to use techniques that are prevalent on microcomputers. I prefer to look at the DT/DB projects as sources of ideas, rather than as a set of blueprints. There are interesting ideas scattered throughout the project, I think. But I don't think that the DB project proved anything at all about search or evaluation techniques. I don't think that you can look at the project from our point of view as outsiders, and say that any technique is shown to be good or bad because of what they did. Anyone who tries to say the project proved anything ends up making arguments based upon painfully little real evidence, most of the evidence is anecdotal *at best*. bruce
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