Author: Robert Hyatt
Date: 07:28:10 12/31/00
Go up one level in this thread
On December 31, 2000 at 02:40:25, Steve Maughan wrote: >José, > > >>> Beta := CurrentHash.Value; >> >>And this is wrong. You can't modify beta here, cause you inherit beta from >>down level alpha, and it means a value high enough that the opponent wouldn't >>chose this branch. You're not allowed to modify beta inside the tree. Only >>alpha. This statement can't possibly be right, because when you modify alpha at any node in the tree, you modify beta for any part of the tree below that point in the tree, and since you can back up this new alpha if everything here fails low, it can propagate backward to the previous level as well. Lowering beta does _not_ mean that the score is above alpha. It only means that your current alpha/beta window is too wide. You can change beta without any thought of where the score must lie, except for the fact that you know it will be <= the new beta, which is a lower bound than <= old beta. But note that it says the score is <= some new lower beta value, not that it is also >= the old alpha value... > >Yes this sounds right although Bob says he does alter Beta. > >Regards, > >Steve
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