Author: Russell Reagan
Date: 13:12:40 01/04/04
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On January 04, 2004 at 14:03:08, Tord Romstad wrote: Hi Tord, >Another >idea I have experimented with is to include passed pawn pushes in the qsearch in >pawn endgames. I think this is a good idea. I don't think of qsearch as "capture and check search." I think of it as "forcing move search." Pushing a passed pawn in the endgame is certainly a forcing move. The goal of qsearch is to hand off quiet positions to the evaluation function. If there is a passed pawn that can promote in a few plies, that isn't a quiet position at all! Your evaluation may be off by a whole queen or more in that situation. I think it is better here to take the time to resolve things correctly. Otherwise you can say, "my evaluation may be off by a queen here, but look at that full-width depth!" Search depth and nodes per second are only a means to an end. Maybe you will search one full-width ply less, but if you detect the passed pawn several plies earlier, is that not an improvement overall? Looking at it from the other side, is it possible that you will now miss something because of the slighly shallower full-width depth? >Endgame evaluation is also tricky, because the evaluation should be very >different >depending on the type of endgame. I am tempted to write several different >evaluation >functions (one for pawn endgames, one for rook endgames, one for bishop vs >knight >endgames, one for endgames with unequal coloured bishops, and so on), but I am >afraid this would cause too big jumps when exchanges occur, make my static >exchange >evaluator too unreliable, and perhaps have other unfortunate side effects. Is >the idea >still worth a try? I don't understand why this would make it unreliable. Wouldn't it make it more reliable? Your program might switch to another "plan" all of the sudden, but as long as you implemented your specific endgame evaluation correctly, it should be a better plan, right? This seems like a similar situation to using endgame tablebases. Your program is searching along, evaluating the position at +2, and all of the sudden it sees mate in 46 :)
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