Author: Robert Hyatt
Date: 10:13:50 06/04/03
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On June 04, 2003 at 07:19:20, Fermin Serrano wrote: >I have hadache in how to avoid so many nodes spended in quiescent search. > >I have a new idea that came to my mind “on the fly”, and before test something I >want to know other opinions and if this could be saccessful. I have not a clear >concept yet, but I want to experiment samething. In qsearch, SEE is expensive, >but save time in search. I was thinking that when you use other method like >MVA/LVD is faster but lot of nodes are evaluated. What about if when you enter a >position in qsearch with this method and in ply x+3 where x>3 of quiescent >before contining, test if last 3 captures were in the same square, and if not, >then you could safe return a negative score (maybe -INFINITE) because there is a >big probability that move secuence would finished in a waste of time. >Maybe playing with this number (3, 4 or 5 plays after enter qsearch) could bring >good results. >What I have in mind is playing with last square where capture was, because most >time captures are solved there, of course not always, but maybe the time wasted >in go around all other moves is better used in depth+1. > >What are you opinions? There are several ways you can shrink the q-search. 1. If the current alpha (lower bound) value is (say) 0, and the current material score is -5 (you are a rook down in the current path) then you can cull captures where you only capture a pawn, since that will still leave you down -4. I do this kind of thing in Crafty with a little more refinement. I have a good idea of how big the positional score can get, so if the current material + the captured piece + the largest positional score is < alpha, I don't bother searching since the score can't get above alpha anyway. 2. If you are looking at a move like pxq there is no need to use SEE. pxq wins material no matter _what_ happens, so for obvious captures like that you can avoid any SEE computation since the captured-capturing score is still way positive. There are other tricks as well, of course. And as you go deeper into the q-search, you can afford to be more aggressive since there is already _plenty_ of error in the q-search anyway.
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