Author: Colin Frayn
Date: 09:13:49 04/07/00
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>>No, razoring is when you do futility pruning at the last ply of your full-width >>search. I think most people don't like it. I tried it and all my test suite >>scores went way down, even when the futility threshold was pretty conservative. >>It just causes to the search to miss too much... > >I thought that was called "extended futility pruning" and razoring was >simply reducing the depth of the search by 1 ply if nothing interesting >was going on near the leaf and the move made does not bring the score >near alpha. You are correct. "Extended futility pruning" is what Tom described, i.e. if the following condition is met at pre-frontier nodes (depth 2) then prune; mat_balance(node) + mat_gain(node)+ extd_futil_margin(node) <= alpha (from Heinz, 1998) In general, the efm() is about a rook to a rook+pawn. Razoring similar to what you described, but an enormous material unbalance is generally required, i.e. a queen's value or more. The search depth is reduced by one ply. This is normally applied at pre-pre-frontier nodes, i.e. depth 3. I do agree with Tom, though, that in my experience, both these methods, and also normal futility pruning, vastly reduce tactical accuracy. I know that Ernst will disagree, but that's just my experience. Cheers, Col
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