Author: S J J
Date: 06:09:25 01/19/05
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On January 18, 2005 at 10:33:57, Andrew Platt wrote: >On January 18, 2005 at 09:44:29, S J J wrote: > >> >> I have a very novice program working without an alpha beta search. On the >>surface, it looks like an alpha-beta search can miss a good sacrifice move. >> >> It does may sense that an alpha-beta search will help speed the evaluation >>of a tree of, say, 6 ply. >> >> However, if there is a sacrifice on the sixth ply that does not gain >>the material back until, for example, the 8th ply, won't the node be trimmed >>when the sixth ply is evaluated and never have additional moves from that >>node generated? > >I understand your apprehension - I had the same thoughts the first time I was >implementing alpha-beta. I had to run many tests with mini-max and alpha-beta to >prove (to myself) I was getting the same results. As I really understood >alpha-beta I realized that what I was mixing up was the algorithm and the >limitations of search-based chess programs. In your example the problem isn't >with alpha-beta, it's a fundamental problem that if you search to depth 6 you >might find what looks like an excellent move only to find on depth 8 that it >loses. That is not a problem with alpha-beta, it's a limitation with search. > >Read up on quiescent search, SEE, search extensions to see how chess programs >try to extend the search down critical lines. > >Andy. Thank you, Andy. So then the alpha-beta is used to help select (and reduce) the nodes for a follow up seach and extension will SEE, quiescent search, etc. being the methods used to search those nodes? Steve
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