Author: Gian-Carlo Pascutto
Date: 22:48:21 04/17/02
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On April 17, 2002 at 18:56:19, Dann Corbit wrote: >On April 17, 2002 at 17:45:03, Peter McKenzie wrote: > >>On April 17, 2002 at 16:53:30, Gian-Carlo Pascutto wrote: >> >>>On April 17, 2002 at 16:40:01, Dann Corbit wrote: >>> >>>>I don't see how it can completely remove the tactic from ever being seen unless >>>>the implementation of null move is broken. >>> >>>If it has a zugzwang, you will _never_ see it if you don't check for it >>>(verification search, double nullmove), or use another trick like force >>>nullmoves away from the root (that is what Crafty does). >>> >>>You can always play the 'nullmove' no matter what depth, so you'll >>>never realize the nullmove is no good. >>> >>>i.e. you make an illegal move that is not possible in the real game, and >>>increasing search depth won't change this. >> >>Yes, you are correct. Some programs can never solve the following: >> >>[D]8/8/2p5/pkp3R1/7B/P7/2p3K1/8 w - - >> >>http://homepages.caverock.net.nz/~peter/eg_test/pet013.htm > >How do we know that they can never solve it? Maybe they just take a >stupendously long time. Here is a crafty session, where I let it reuse the hash >table on subsequent searches: As I wrote above, Crafty pushes nullmoves away from the root in the endgame, so it _will_ find the solution after a long while. But this is not the pure nullmove algorithm. -- GCP
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