Author: Don Dailey
Date: 13:10:03 07/21/99
Go up one level in this thread
> My point is this. Your checks are good for some tactical shots. They are > awful for common positions. Because you are running down stuff in the q-search > that is totally wasted. And if you waste time here, you lose time elsewhere. > > For every position you find where a check in the q-search helps, There are > hundreds of positions where it hurts just as much or more. If my game results > were bad, I'd be looking at why. But I do just fine at present. I have older > versions of Crafty that _did_ do checks in the q-search (trivial to implement) > but they don't play better because of it, IMHO. > > If you want to solve tactical problems, it is probably a good idea to do them. > If you want to win _games_ I am not so sure. IE when you use my quad p6/200, > you are about 1/2 as fast as my quad xeon, yet when we play I don't see any > tactical oversights by my program, generally... And the extra depth on the > positional moves I get helps significantly when there are no king-chasing > tactics... Very well said Bob. You have to look at the whole picture. I have discovered a whole class of tactical algorithms and tricks that can greatly improve a programs tactical ability and yet, when push comes to shove makes the program weaker. Have you ever noticed just how often you find the right move just in the nick of time? No matter how fast my program gets, which hardware and which time control, I easily and often see cases where it is about to play a losing move, and switches over just in time. There is no doubt in my mind this is happening all the time in little positional ways that I would never notice. It happened at the world championship and I see it happening to Occam on the chess server. THAT is the reason that even with modern hardware and awesome speeds every little bit of speed is guaranteed to help. It's the same with knowledge, if it slows down the program and is highly specific to a position, it might be great knowledge to have, but it might make your program weaker. The question is how often does the missing knowledge make you lose half a point or more, versus the 1/2 percent slowdown it might create in your program? Even 1/2 percent slowdown will CAUSE you to lose games once in a while. So the extra knowledge better make you win at least as much. Now if you add an algorithm to pick up tactics, such as checks in quies, you are guaranteed to drop your speed just below this threshold and suddenly you miss a whole class of positional nuances and even tactics (that don't happen to involve needing to see a check in quies.) All the positions that you just barely saw in time, you now miss. To compensate, there is a (much smaller) class of positions that you definitely improve at, namely any tactic (or even positional nuance) that involves needing to see a critical check in the quies search. I think what happens in peoples minds is that these little things go completely unnoticed and the little slowdowns are too easily forgiven when compared to the sensation tactics that make it appear that your program must be stronger now when in fact it's just flashier. But still, I am not so quick to dismiss checks in quies. They introduce a real value and benefit to null move selectivity, which is quite weak in picking up mate threats. But I suspect that once you give them up, it may enable you to do a host of other optimizations that may in the long run be a win. It's all about tradeoffs isn't it? Also, who knows what works and doesn't in any particular program. My programs usually covers some classes of mate threats with a static analysis that improves the quality of the selectivity, I have no idea what others may do. I don't think using or not using a particular algorithm can be easily criticized since each programmer must measure the tradeoff for his own program. The proof is in the pudding. Does a program play awesome chess? Then the programmer has probably made a lot of good tradeoffs. - Don
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