Author: Rick Bischoff
Date: 20:56:39 09/25/04
Go up one level in this thread
Hi, But this is what Bob Hyatt does in crafty-- quote verbatim from search.c: if (depth - null_depth >= INCPLY) value = -Search(tree, -beta, 1 - beta, Flip(wtm), depth - null_depth, ply + 1, NO_NULL, 0); else value = -Quiesce(tree, -beta, 1 - beta, Flip(wtm), ply + 1); ... snip ... if (value >= beta) { HashStore(tree, ply, depth, wtm, LOWER, value, mate_threat); return (value); } if (value == -MATE + ply + 2) mate_threat = 1; } > >if (x >= beta) return beta > >means that you don't return the actual scores, just the cutoff. This is fine >until you try to detect threats. Then you need to return the actual scores >because only those will have the mate in them. > >In WAC 141 you should hit a bunch of mate threat extensions on the way to the >lowest ply because each time your Rooks take a pawn, and then the bishop, you >should trigger one. In my search it still isn't enough to counteract the drop >into qsearch where I don't consider checks. I've given up on generating the mate >score in a short time right now (I have plenty of other problems!). It's enough >that the first few plies in the PV are correct so if it actually hit it, it >would find it. Of course that only works here because it turns out that the >Queen sacrifice is good more material as well as mate! > >Andy.
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