Author: Sune Fischer
Date: 04:45:16 04/20/04
Go up one level in this thread
>>>>2. Don't make a null move if the static eval is far below beta. >>> >>>Actually, you can drop 2 as well :) >>> >>>Move ordering is much better if you just nullmove everywhere. That way, you can >>>also throw out IID. > >That's not my experience. Nullmoving everywhere doesn't noticably improve >my move ordering, and it increases the size of the game tree (by around >15-20%, if I recall correctly). Throwing out IID doesn't help. > >Perhaps this depends on how your move ordering works. Number 2 doesn't seem to work for me either, I think the explanation is rather simple. A nullmove is relative cheap, if I detect correctly 75% of the time that a nullmove is futile, then that still means I detect it wrong 25% of the time. As it turns out these 3 savings of a nullmove doesn't outweigh the 1 full search which could have produced a fast cutoff. The end result is a bigger tree for me. In principle it can work, but you must be very accurate in guessing when not to nullmove because a full search is very expensive. >>In addition, throw out the 2nd half of 1 as well. If my opponent is going to >>checkmate me, I want to know so I can extend. > >I don't understand what you say here. In the 2nd half of 1, I suggested to >avoid null move search if you already know (without search) that mate in >1 is threatened. What extra information do you expect to get from a null >move search? I think there are some practical problems in detecting when you are mate in 1. I requires a lot of coding and a big eval with attack scanning around the king etc. A faster implementation of the same thing is simply to nullmove and fail-low. Btw, extending on threats completely blows up the tree for me, it seems there are certain position in the tree where you just have to live with a constant mate threat. Practicly all nodes gets extended here and a blowup is unavoidable. I think it would be better to extend on a newly detected mate threat, ie. the ply before we wasn't being mated. -S. >Tord
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