Author: Sune Fischer
Date: 13:13:03 04/19/04
Go up one level in this thread
On April 19, 2004 at 15:50:41, Robert Hyatt wrote: >On April 19, 2004 at 13:11:59, Andrew Wagner wrote: > >>Some have suggested this could possibly be a problem with how I store and >>retrieve the bounds in my hash table, so let me explain what I do and see if the >>logic is right. Much of it comes from Bruce Moreland's web site. >> >>My Search function calls a function called ProbeHash(). Probehash looks in the >>Transposition table to see if the position has an entry stored there already. If >>so, and the leaf distance of the hash entry is >= the current leaf distance, it >>looks at the score and at what type of entry it is. If it's a beta entry (stored >>when the move fails high), and the score is >=beta, Probehash returns beta. if >>it's an alpha entry (stored after a fail high), You mean fail-low here I assume. >and the score is <=alpha, alpha >>is returned. If it's an exact score (the first time it was searched, the score >>was between alpha and beta), the score itself is returned. If none of this is >>true, it passes back a best move as a parameter. Once we arrive back at >>Search(), if any of the above three cases with scores (alpha, beta, or the hash >>entry score) were returned, Search immediately returns that score. Otherwise, it >>continues on. >> >>I hope this makes sense. Does this sound correct to the rest of you? Dan, is >>this similar to the logic of how you do it? Thanks! Andrew > > >It doesn't sound right. > >First, terminology: I don't think it helps much to go into this academic terminology, by "beta entry" he clearly means lower bound and by "alpha entry" upper bound. >It sounded to me like you were comparing the wrong bounds... I think he is doing it right. >IE what you want to prove is that the search windows do not overlap. If the >lower bound (from table) is > current beta value, you stop searching and "fail >high here". If the upper bound (from table) is < current alpha value, you stop >searching and fail low. Andrew suggests you improve on that by using >= current beta and <= current alpha. :) -S.
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