Author: Charles L. Williams
Date: 11:48:05 06/03/99
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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? >> >>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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