Author: Robert Hyatt
Date: 07:41:50 01/22/02
Go up one level in this thread
On January 22, 2002 at 01:53:53, Uri Blass wrote: >On January 22, 2002 at 00:44:53, Robert Hyatt wrote: > >>On January 21, 2002 at 14:27:34, David Rasmussen wrote: >> >>>On January 21, 2002 at 10:41:39, Robert Hyatt wrote: >>> >>>> >>>>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... >>>> >>> >>>If you mean, do I count value >= alpha+1 from zero-window search as a fail high, >>>then no. In that case, I research with the original alpha;beta window. Isn't >>>that ok? >>> >> >> >>What if you run out of time? You failed high on the null-window search. >>You started a new search with a wider window and time expired. Do you play >>the fail-high move or stick with the previous best move? I stick with the >>last verified move. >> >>Unless I fail high a second time which means the original aspiration window >>was too small and I am now going to +infinity. I trust the second fail high >>but not the first. > >Does it mean that even if the evaluation before the fail high was mate against >youself you are not going to play the fail high move if you have not time to >verify it? Maybe. I _always_ invest the necessary time to complete the _second_ re-search so that this doesn't happen. Of course, it is _possible_ that I don't have enough time to do this, but it has not happened (or even come close to happening yet). > >In this case it is a mistake. >It seems better to have a rule based on the previous evaluation when to play the >fail high move that you cannot trust and when not to play it and not to play it >only when the evaluation is bigger than some number. > >I have no idea about the exact number and looking at positions when Crafty did >not play a move that fail high may help to get a better idea. > >Uri I have a program that goes thru my old logs looking for this (among other things). That is how I originally found that I was failing high on the null- window search, playing that move, and getting ripped for doing so...
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