Author: Robert Hyatt
Date: 15:54:35 07/29/98
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On July 29, 1998 at 13:21:05, Danniel Corbit wrote: >On July 29, 1998 at 10:48:44, Tom Kerrigan wrote: > >>On July 29, 1998 at 10:06:43, Danniel Corbit wrote: >> >>>Let's say, for the sake of jihad, that we define sensible moves in the following >>>manner: >>>From a given FEN position, look at what every GM who has ever visited that >>>position has done. >>>From the same FEN position, let every top commercial and amateur program examine >>>that position for 24 hours. >>>At this point, we would have, I suspect, a small list of possible very good >>>moves, a mid sized list of so-so moves, and a large list of bad moves. >> >>Perhaps. >>I don't know what this would accomplish, and it seems like similar things have >>been done by people who do opening book stuff. >>Basically, what you're writing isn't really related to the topic at hand. >I disagree. It is related, because I believe that an exhaustive search has very >little value, and a careful analysis of the "ahem" good moves has a very high >value. > >Here is an experiment that will demonstrate my point [I think]. Run any chess >engine you like against a set of 100 arbitrarily chosen FEN positions achieved >by at least 3 different GM's at least 6 moves into the game. Analyze the >position for 7 plys, exhaustive. Analyze the position for 8 ply's exhaustive. >See how often a move that was not considered one of the top three from previous >exhaustive searches gets introduced as the new choice. I suspect it will be >less than one in a thousand. > >If that is the case, then exhaustive searching has very, very little value. > >We will certainly not be able to search 12 plys exhaustive for a long time, >anyway. Exhaustive search will therefore never be competitive with Alpha-Beta >or any other real searching technique. So what is it's value? Only to find the >rare gem that conventional searching techniques might miss. 99.99999% of the >bogus games generated by the exhaustive search will be utter crap that even a 9 >year old novice would not play. Here I have some data. In the "Crafty goes Deep" experiment last year, we ran such a test with Crafty, searching 347 different positions to depth=15. We were interested in how often does one more ply produce a different move. The result? Somewhere in the 20% range which was surprising. In fact, within close limits, adding one ply changed the PV about 20% of the time no matter whether it was going from ply 6 to ply 7, or ply 14 to 15. The JICCA has the exact results, while the raw search output is on my ftp machine... Bob
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