Author: Omid David Tabibi
Date: 14:09:00 10/13/03
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On October 13, 2003 at 16:45:20, Robert Hyatt wrote: >On October 13, 2003 at 14:39:15, Gerd Isenberg wrote: > >>On October 12, 2003 at 06:32:25, Omid David Tabibi wrote: >> >>>Recently I conducted some extensive experiments with two versions of Falcon, one >>>with checks in quiescence and one without. Falcon already has lots of >>>extensions, but adding checks in quiescence resulted in a significant boost for >>>tactical strength. >>> >>>I tested the following options: >>> >>>a) checks everywhere in quiescence >>>b) checks only in the first ply of quiescence >>>c) no checks in quiescence >>> >> >>Some triggers in the current path (checks and other foreced moves), some >>heuristics and you may decide whether using a,b or c at runtime. >> >>Gerd > >That's the way to control tree size. > >IE I don't have the specifics in front of me, but for Cray Blitz, I didn't do >any q-search checks/check-evasions unless there were at least N checks in the >basic part of the search. N varied based on the number of plies in the basic >part of the search including all extensions. IE there's not a lot of point >in fooling with checks in the q-search if there were no checks/tactical-moves >in the base search. You are most likely just exploding the tree. But if >there are a lot of checks in the base search, then looking at multiple >(always consecutive of course) checks in the q-search to follow-through on >the tactical theme makes pretty good sense. Actually I have found checks in the first ply of quiescence to be quite helpful when used with null-move pruning. Assume that you are at depth = 3 and use R = 2, the null-move search will be conducted by depth 0, i.e., direct call to quiescence. Also assume that no matter what you do, you are mate in 1. If you have checks in quiescence the opponent will checkmate you immediately, returning a mate score which in turn will trigger a mate trheat extension in the main search. But if you don't do checks in quiescence you will miss the checkmate and have a good chance of failing high on the null-move search resulting in a cutoff. I.e., you think that the position is good enough to justify a cutoff when in fact you are mate in 1! I think mainly for this reason adding checks in the first ply of quiescence results in such an improved performance in solving test suites. But it doesn't seem to be as helpful in actual games. > > >> >><snip>
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