Author: Robert Hyatt
Date: 16:07:15 12/24/98
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On December 24, 1998 at 14:14:19, KarinsDad wrote: >On December 24, 1998 at 13:34:04, Roberto Waldteufel wrote: > >Roberto, > >You mention that if the null move search hits a zugzwang, the search is broken. >But you do not mention how to fix it. I assume that if you could detect zugzwang >(possibly by finding that all Ply x+2 moves have a lower score than their parent >Ply x+1 move as indicated in my previous message), you could back out and >re-search the Ply x+1 moves without the null move search. > >Would this method of detection and re-search work? no... because when the null fails high, we return immediately. That is where the savings comes from. Searching other stuff after the null-move fails high simply nullifies the gain from doing the null in the first place... > >And I am totally confused on how one would go about using multiple null move >searches within a single path (do you alternate between sides or what, and what >does this buy you?). > >Thanks, > >KarinsDad > >> >>Hi KD, >> >>Basically you are taking a gamble that the position is *not* zugzwang whenever >>you use null move. The speed-up is substantial, but if you do hit a zugzwang >>then your search is broken completely (unless you are lucky and he PV is not >>affected). This gamble is fairly safe in the opening and middlegame, but very >>dangerous in the endgame when zugzwang is common, so normally we disallow null >>moves when the material falls below some critical threshold. >> >>Hope this makes it clearer. >>Merry Christmas >>Roberto
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