Author: Harald Lüßen
Date: 16:54:53 04/08/04
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On April 08, 2004 at 12:22:15, Ed Schröder wrote: >On April 08, 2004 at 09:04:15, Harald Lüßen wrote: > >>On April 08, 2004 at 07:10:29, Daniel Shawul wrote: >> >>>Hi >>>Here are some questions >>> >>>2.In Ed's paper there are some tricks done at horizon. >>> trick one if(score - (margin + largest hanging piece) > beta) >>> don't do quiescence >>> trick two if(score - 900 > beta) >>> don't do quiescence >>> My question is every body does >>> score=eval() >>> if(score > beta) >>> don't do quiescence; >>> So i don't see how the tricks work? > > >>His alpha is our beta and vice versa. > >Really? Sometimes. I explained this sentence with two models of search algorithms, mine and another one that would produce this confusing alta bepha. :-) My assumption that you use a search algorithm like the second example was wrong but the effects are similar. Thank you and others for making this clear. At least my explanation has helped the original poster. >If true I need to re-read some papers :) No, no. You should _write_ more papers. >To clarify, suppose an aspiration search with a 0.50 window and a best move with >a 0.20 score then going to the next iteration I get a window of: > >ALPHA = -0.30 >BETA = 0.70 I know that our general understanding of the meaning of alpha and beta is the same. I get the same window (at root level). >Your comment suggests: > >ALPHA = 0.70 >BETA = -0.30 No, what I meant and could not explain clear enough is: One ply deeper in a recursive negamax-like-search we get alpha = -0.70 and beta = 0.30. Many chess programmers are used to this kind of strange (anti-)symmetry. Are you aware of this different use of vocabulary? I like the idea that you should include an explanation of your search and use of alpha beta and the difference to negamax/PVS in your very interesting writing. Harald
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