Author: Robert Hyatt
Date: 08:40:40 09/08/00
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On September 08, 2000 at 07:41:57, Jan Pernicka wrote: > Hi, >summer is almost over and I return from holidays to Internet :) > >I have just implemented (= and debugged) hashing in my chess program and >have to face (at least) 2 problems: > > 1) How to update Best Variation when using hash? > My solution: Do everything as normal and when transposition is detected, > trace (with help from best move saved in hash table) > partial best line through chain of positions in hash > table. > That works. You can occasionally get a bogus move, particularly when you consider that for every move on the PV that had a fail high, the next move could be a fail-low node and the hash has no (or a wrong) "best move" > 2) (more "dangerous"): When detecting 3-fold repetition (in fact 2-fold) > in the tree in position A - I return score=DRAW_SCORE and e.g. in the > position (B) immediately above position A I store in hash table score > which is influenced by score of position A, but this score (of A) is > relative to the root(it is repetition): in position B - when it will > occur somewhere else in the tree - it could cause errors. > My solution: I simply ignore this fact. I do the same thing. Hashing fails when you deal with three-fold repetition and the 50-move rule. The fix is ugly and hurts more than it helps. > > Thanks for your answers and have a nice day. > > Jan
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