Author: Robert Hyatt
Date: 14:00:18 02/19/02
Go up one level in this thread
On February 19, 2002 at 15:40:33, Gian-Carlo Pascutto wrote: >On February 19, 2002 at 14:13:36, Robert Hyatt wrote: > >>I claim that such is _impossible_. You might get the error down to .0001% if >>you are very lucky. But that is not zero, and it will fail. > >Just a quick question. I didn't manage to read the whole thread >so I don't know the whole context, but is there any reason why >the pruning rules aren't allowed to fail, ever? The discussion was about creating "perfect pruning rules" that do not fail. I maintain there is no such thing, for obvious reasons... and even if they only fail in .01 % of the cases, that is a killer if you have 1000 pruning rules where each has that probability of going astray.... > >>>The pruning rules should detect illogical moves and reduce the size of the chess >>>tree. >>> >>>They should not resuce it to 0. >>> >>>If you prune in every move only 40% of the possible moves you are goinbg to >>>reduce the size of the chess tree significantly but you are not going to solve >>>chess. >> >>Correct. The error rate will be so huge that it won't prove anything at all >>about the game. > >Wow, wow, hold on a little here. Sure, it won't prove anything. Still, >I'm pruning >80% of my moves, and my program still plays damned fine >chess. Sure, I'm not proving anything, but it's still winning games >nicely. And you know what? You are, too.\ wrong kind of pruning. You are talking about _backward_ pruning using alpha/beta. I am talking about forward-pruning as in selective search. There is a huge difference. Backward pruning is provably correct and doesn't cause errors. Forward pruning is a different story. > >>>I do not think that you need billions of lines and I believe that some millions >>>may be enough because one rule can be good for many position. >> >>Pick an iron-clad position where you can eliminate a move for a specific >>reason. And let's see if we can break it. Then you fix it. Then we >>break it. And this goes on almost forever... > >Sure, sure, if you can't possibly accept that it'll never fail. But >I'll be happy as soon as it's correct more than it fails, i.e. when >it starts getting productive. In that case, play me (me being a human) using your program. Set it to generate a random number between 1 and 100. If N is <= 51, then you play the move alpha/beta says is best. If N > 51, then you play a random move in the current position. I'll bet you whatever you want on the result of such games. :) Just because something works more often than it fails is not a terriffic endorsement of the idea. :) One bad move can lose a game, even if you played the correct move every other chance you had. That is the bad thing about chess... > >>No it isn't. Any good software engineering book will explain the problems and >>why software is in the shape it is in today. The concept of a "bug-free >>program" is and always will be an oxymoron, when "program" means something with >>thousands of lines. > >Insert obligatory Knuth quote here ;) > >>>>Note that Junior5 pruned under promotions in it search and in I think that in >>>more than 99% of the games it caused no problems. >> >>but in 1% it caused it to blunder. The more you prune, the more those >>probabilities add up... > >The more the gains add up, too ... Yes, but if you play the best move 50% of the time, you aren't guaranteed to win. If you play a bad move once, you most likely will lose... > >>And 1000 rules isn't going to be even _close_ to what you need. > >You did some kind of experiment to support this hypothesis, >or is it just an unfounded unsubstantiated claim to support >whatever point you're trying to make? > >-- >GCP I once had a selective search program. The selective part of the program went _way_ beyond 50,000 lines of code. And the special cases were still being found on a daily basis. It became obvious that such was not the way to write a chess program. In 1978 I switched to full-width again and dropped the thousands of special cases into the trashcan. COKO is another 1970's era program that ended up near 100K lines of code. Most for special cases in forward pruning...
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