Author: José Carlos
Date: 13:11:59 01/21/02
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On January 21, 2002 at 10:55:50, Daniel Clausen wrote: >Hi > >On January 21, 2002 at 10:41:39, Robert Hyatt wrote: >[snip] >>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... > >Anyone has a trivial example at hand which demonstrates this behaviour? > >Why is it that a fail-high with a zero window can't be trusted but a fail-high >with a non-zero window can? Is "non-zero window" enough to be trusted? Or does >it have to be a certain minimum window? I'm sure that as soon as someone posts a >mini-example which shows this behaviour, even I will understand it. :) > >Sargon There's no easy example since it depends on the engine (eval, extensions, hashing). It also happens sometimes with open windows, but the wider the window is, the more difficult tu happen. Note that null move, hashing and some extensions give different cutoffs for different bounds, and this is the key to understand this behaviour. José C.
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