Author: Robert Hyatt
Date: 07:41:39 01/21/02
Go up one level in this thread
On January 21, 2002 at 06:52:57, David Rasmussen wrote: >What are the best techniques for dealing with the search instabilities of PVS, >null move pruning, hashing and repetitions? > >Specifically, is there a way to limit the number of false fail highs at the >root? > >/David You have to do two things: 1. If you get a fail high at the root on a zero-width window (any move after the first move should be searched with a zero-width window) you can't trust it unless you re-search it with a bigger beta bound and make _sure_ that it doesn't then fail low. Such fail-high (zero window) fail-low (non-zero window) is an artifact of null-move and if you play such a fail high move even if it fails low on the re-search, you will die... 2. If you get a fail high at the root on the zero-width window, and when you re-search you get another fail high on the original aspiration window, or you get a true score, then you can trust it. Case 1 is the killer although it doesn't happen every move, once in a game is more than enough.
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