Author: Will Singleton
Date: 11:18:52 06/03/99
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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? > >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? > >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. > >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 All this stuff takes a lot of tweaking, so stick with it. Some of my suggestions might make things worse, but are worth trying nonetheless: 1. PV before hash, unless you stuff the HT with the PV anyway. 2. Defer exchanges until after killers, perhaps put them with the general history moves at the end. 3. Do losing captures last 4. Don't store captures in the killer move list, and you might try also not storing escapes from check. 5. I have a max of 4 killers, which is more than most other folks, I think. 6. If a killer is already in the list, detect that (don't store same one, so you end up with a list of identical moves). So if it's in the list, and it occurs again, swap it to the top, else put a new one at the top. I don't use a score or any other qualifier. 7. I just use beta cutoffs. Lastly, lose is spelled with one O. I know it doesn't make sense, it should have two O's, but it doesn't. Lots of folks make that mistake. Will
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