Author: Bella Freud
Date: 16:44:10 11/17/99
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On November 17, 1999 at 19:01:57, Christophe Theron wrote: >On November 17, 1999 at 18:00:33, Bella Freud wrote: > >>On November 17, 1999 at 15:53:40, odell hall wrote: >> >>>Hi >>> >>> >>> Does anyone know any details about Chess Tiger? >> >>I have heard that it goes deeper. Deeper wins on the whole as you know. >> >>It is a fast program, so I would imagine the programmer has found a way to focus >>the search better with relation to the others. > > >It is not a fast program. It's more than twice as slow as Fritz. > That is still fast. You do work evaluation work and maybe more move sorting work, but it is still fast. > > > >>They are fighting for a narrow, specific part of the tree. Null move pruning by >>mostly material factors makes that. > > >No Chris, you don't get it. Two points. You don't get it if you make incorrect naming assertions. And I do get it. You don't more like it. If you prune too much on material criterias you >completely destroy the positional skills of the program. But this is what you don't get. Null move prunes, you know that. A blind piece square table program will play terrible. You know that. But imagine the blind program's tree. Narrow, with null move prune decisions made entirely on material evaluations at effectively low search depth. One type of tree. It will win if this is the 'important' or main tree. Now make a program with some postional sense. This will amke another tree, partially overlapping with the main material tree, and probably a little smaller. So now winning depends on who makes the 'truer' tree at that depth, more often, and for most moves. Most chess programs are in the second category. Yours too, I suspect. Just what positional sense and how long it takes to evaluate will determine the tree structure, degree of overlap etc. So I have to see programs on SSDF and tuning with autoplayers as forcing all programs into this battle. Very hard to make wild parameters. Whenever you make that passed pawn on the sixth rank worth 3 pawns, you'll win a spectacular game where the 6th rank pawn was vital, but lose 5 games where you blow a knight to get it. So all tuned parameters tend to the normal, to a very boring normal. Because that is what wins percentage points. In chess. In computer chess. Also very likely on ICC, where just brute depth and counting on errors is what guides 'progress'. Positional parameters tuned to the norm. Material counting. So null move gets evaluations to tell it to prune anything a bit wild. Hence narrow material tree via null move pruning. And you said you null move prune. QED. > >If I wanted to go deeper tactically, I could do it easily. I think I could go 2 >plies deeper. But in this case my program would be completely crushed because of >incredible positional holes. > >Before the game goes on a tactical field, my program would have a totally lost >position. > >Each time I have tried to sacrifice the positional understanding to get deeper, >it was a disaster. I have found that it works in the opposite direction: with >better positional understanding the program goes deeper. Because it sees the >right moves earlier, and spends less time analyzing sonense moves. > Agreed. But my real question is how far can you take this? How far can you use your chess knowledge to override what results and SSDF and win/loss driven insane users are telling you? > >You make it sound as if I had found a very specific way to shoot on a very >specific weakness of a very specific subset of chess programs. > >You make it sound as if I was not programming chess. > Computer chess. Different. > >You completely overlook the fact that several testers including our friend >Thorsten have noticed that Chess Tiger has a large amplitude in its evaluation >function. It's usual to see Tiger at +1.90 when the opponent is still close to >0.00. > Good. You're being courageous. I think any competent chess player can program in a good deal of positional knowledge which dares to take risks with evaluations. This would be sufficient to deal with the Craftys and Fritzs and other fast ones. And it expands the tree area over which this type of program will roam. But I think these are still not chess trees. In the sense that they still don't naturally expand over the checking attack regions of the tree. Null move stops that. > > >>Getting an edge on this particular tree makes for good percentage increases in >>winning chances against other programs. > > >Maybe, and I would like to know how to do it. But as I don't tune my program >against other programs I unfortunately don't know how to do it. > >Can you please explain how to do it? I would like to get a better rating on the >SSDF. If you know anti-computer tricks, please share them with me. > I think the best anto-computer trick is to try to get and stay in the tree regions that programs do not understand. Bella > > Christophe
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