Author: Scott Gasch
Date: 13:33:10 06/28/02
I've been experimenting with checks in the qsearch. While implementing this I ran across a couple of old posts from Bob who said, in essence: If side to move is in check in the qsearch but has had a chance to stand pat at a previous ply in the qsearch then the check is not forced and generating all replies to check is wasted nodes. I am struggling with this idea. If you are in check and have no good way out your opponent will fail high and you will just stand pat where you could at a previous ply. I get that. So is the idea to only generate responses to check that have a chance at not failing low? Maybe only capturing responses and blocking or king flees? Imagine you are in check and have no capture responses so you conclude there is no good way out of check -- is it sound to return -MATE to force your side to stand pat where it could have at a previous ply? I suppose the assumption here is that if you are in check and way below alpha running away or blocking the check is not going to do the trick and you will end up standing pat at a previous ply anyway. Another idea that I read from was that generating non-capturing checks in the qsearch against a side that has had a chance to stand pat already is a waste. I really don't understand this idea and disagree with it. Imagine black has had an oppertunity to stand pat but instead plays RxN (N appears hung). Well this looks really good unless white then generates Qd4+ forking blacks R and K and winning the R. If you neglect to generate checks on a side who has already had the chance to stand pat you let him get away with RxN and like it. If the only reason to add checks to the qsearch is to find mates then I agree -- checking after a side could stand pat is wasted. But if the goal is to improve tactical play then I think this idea is not sound. Scott
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