Author: Robert Hyatt
Date: 07:39:33 02/02/98
Go up one level in this thread
On February 02, 1998 at 02:10:30, Jouni Uski wrote: >>only if tablebases are on a CD. for the 3-4 piece files, the slowdown >>is no more than 50% worst case, and the perfect knowledge gained is far >>more valuable, because way out in the tree, after every trade that ends >>in 4 pieces, you know *exactly* whether you win lose or draw. If you >>try to read from the CD, that is going to slow it *way* down. And might >>not be worthwhile in the search... > >Even from hard disk dynamical makes no sense with Mchess 7 - I am quite >sure! >About TB benefit: I wonder if the probability to meet position where we >1) >find win/draw from TBs , BUT 2) can't win without them is quite small, >may >be about 1/1000 game. it's at least 10x higher than that. But 1 of every 100 games is not a big advantage, although it is measurable. But *if* you toss in 5-piece tablebases, this goes up to about 1 in every 10 games. That is, in the games I have watched, computer vs computer where Crafty is using all the tablebases for KRP vs KR, and the opponent is not excessively weak or using a bad machine, so that the games are pretty even) then Crafty will win games that it would otherwise draw or it will draw games that it would probably lose. Against very strong computer opposition I have seen as many is 4 games in a row ending up in KRP vs KR. That can make a big difference. You (or someone) might grab a sample of the SSDF games that they post and determine how many games end up in a KRP vs KR (or potential KRP vs KR, don't forget the case where it might be KRNPPP vs KRBPP or some such ending that the search can transpose right into the KRP ending quite easily.) And pick games between top programs, not games where one is so much better that the game is decided before the endgame. The data would be interesting. Other useful ending databases are KRB vs KR and KRN vs KR, because the winning side can wait to convert until it is a winnable position, while the losing side can be a piece down and still draw easily. For 4 piece endings, KQ vs KR, KR vs KB and KR vs KN are important because those are fairly common 4 piece endings. The latter two being more common where one side is an exchange up, but lets the other side trade the last few pawns into what looks like +2 for the program not using tablebases, but which is 0.00 for the program with them...
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