Author: Robert Hyatt
Date: 19:44:02 06/03/99
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On June 03, 1999 at 14:48:05, Charles L. Williams wrote: >On June 03, 1999 at 14:43:31, Robert Hyatt wrote: > >>On June 03, 1999 at 12:59:02, William Bryant wrote: >> >>>Every time I try to improve my program, I seem to break it in innumerable ways. >>> >>>The killer move heuristic should be rather easy to implement. >>> >>>At every ply, any move that generates a cutoff (I interpret as a beta cutoff, a >>>fail high), this move is added to the current killer table. >>> >>>Is it an alpha cutoff (score > alpha) more appropriate? >>> >> >>score > alpha isn't a cutoff, unless it is also >= beta. There are two >>reasons for killer updates. (1) current move fails high (>= beta); (2) >>current move gets backed up as a best move (ie score > alpha, < beta, so it >>is a potential PV move). >> >> >>>Also, does this move automatically displace previous killer moves, or do you use >>>some qualifier such as the search score, keeping the moves with the greates >>>score? >>> >> >>I store 2 killers. when one of the two causes a cutoff, it is moved to the >>front to try the next time. New moves always replace the second killer. >> >> >> >> >>>Finally, in using the killer moves for move ordering the ranking I am using is: >>>1. Hash Table Move >>>2. PV Move (in not the same as #1) >>>3. Captures with a net positive score (captured piece > capturing piece) >>> Promotions >>>4. Killer moves and Captures with an equal score (exchange) >>>5. Loosing Captures >>>6. All other moves--sorted by the history heuristic. >> >> >>get rid of 5. Let those drop into 6... >> >> > > >Should a hash table move precede the PV? > > > I don't have a "PV" option. After each iteration, the first thing I do is 'stuff' the PV moves into the hash table... which means that following the hash table move will suck me right down the PV as I want... all without having to have _any_ special code in the move ordering stuff... The other answer is 'yes' pv should come first... but if done right, the PV should be in the hash table, so there should never be a 'choice' anyway... >>> >>>Any help will be appreciated, I am missing something simple because this is >>>slowing down, not speeding up my search. >>> >>> >>>William >>>wbryant@ix.netcom.com
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