Author: Antonio Dieguez
Date: 09:34:41 12/31/03
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On December 31, 2003 at 10:32:33, José Carlos wrote: [] > Yes, but only in my latest versions. I couldn't quantify it because I've been >changing many things in Averno lately, but it reduces the tree a little. Nothing >impressive, however. > As I see it, futility pruning creates kind of a bridge between regular search >and qsearch, like a selective part, but really too thin to make a difference. > I don't like the idea of extended futility as described by Heinz because it >doesn't make sense to me. Let's think of it: > We are at depth 2 (to me, depth 0 calls qsearch directly, depth 1 tries all >move with futility pruning) and we are about to make a move. Our material score >is below alpha and this move won't raise the score above alpha-margin, being >margin a constant which, for now, is not important. We know we will move and >then force the opponent to make a move and well drop into qsearch. Then, it's me >who will have the option to stand pat or try a capture, so being at depth 2, and >assuming any move by the opponent won't worsen his position (this assumption we >always make in null move), the only thing we have better than in depth 1 is that >we'll be given the chance to stand pat. > Since we assume the opponent won't >worsen his position, we'll be given the option to stand pat in a bad position, >so no advantage. I suposse the chance to eat makes the difference, no? at depth 2 you could make the preparation for the kill and in depth 0 the kill. That is the advantadge, like pinning or attacking with other piece and may be also more subtle stuff. There is something similar with prunning when >beta at depth 2 and 3, thinking in "quiet" moves whe could think at depth 3 it is even safer, but tactically one never knows what can happen! the always very usefull antonio d. > Under this point of view, I would try futility with the same margin at depths >1 and 2, and then a bigger margin at 3 and 4, and so on. > But I haven't had time to test all of this. For now, I stay on the safe side >and use a bigger margin at depth 2 and, so far, both futilities seem to save >some nodes to me. > > José C.
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