Author: Tord Romstad
Date: 11:57:52 01/05/04
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On January 04, 2004 at 16:12:40, Russell Reagan wrote: >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. I agree that it looks like a good idea, but it didn't work very well when I tried it. However, I still think it should be possible to make the idea more effective with some refinements. Perhaps it is better to only search the most dangerous-looking passed pawn pushes. In most cases, it is probably a waste of time to search the move e4-e5 if black's king is on e7. >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? Hopefully. I also don't understand this very well, but Bob and others have warned against big evaluation discontinuities in the past. I'll probably give it a try and see if I notice any side effects. Tord
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