Author: Sune Fischer
Date: 11:53:09 10/04/02
Go up one level in this thread
On October 04, 2002 at 14:31:16, Vincent Diepeveen wrote: >On October 04, 2002 at 12:28:54, Sune Fischer wrote: > >>On October 04, 2002 at 12:14:18, Omid David wrote: >>>>>Wrong. I've conducted hundreds of tests, and in no single case has my heuristic >>>>>returned an inaccurate result. There exist blockades that it fails to detect, >>>>>but it never declares a false draw. >>>> >>>>Perhaps this is too restrictive too. >>>>You could have some confidence variable, if you draw detector cannot say with >>>>100% certainty that it's draw, then interpolate the evaluated score with the >>>>confidence level: score=eval()*(100-confidence)/100. >>>> >>>>It might help the engine to steer clear of those drawish positions? >>> >>>But as Vincent pointed out, such heuristics have an overriding nature. Even the >>>slightest inaccuracies can result in a total disaster. >> >>Yes I know, you have to be careful, right now I don't even score KRKR as draw, >>because what if the one to move can give a check and take the other rook hiding >>behind the king... >> >>If there is a high probability of a draw, eg. a risk of perpetual check because >>your king is exposed and his queen is near by, then be less optimistic in your >>score even if you are way ahead in material. It is probably easier to win >>without the queens on the board if you have an extra knight, for instance. At >>least you have eliminated the risk of perpetual check. > >One of the things we are talking about here is that black is a pawn >down. Not about KR KR or something. Yes, I know that, it was just an example of why it is dangerous to score accurate, as you said yourself. >KR KR is not a 'blocked position'. He talks about recognizing something >as blocked and therefore giving a pawn up. In that 'easy' to recognize >draw from kramnik you put the black king on a7 and dang it's a zero. > >see my position example elsewhere. So your engine exchanges to a position >with pawn down to reach somewhere in far horizon a draw score from eval. I saw your position, and you are assuming his detector ignores the position of the kings. Had the king been within the square it would have been draw, right? >then when you get near that position it is simply a pawn down as it sees >that position is tactical lost completely. This happens to be a lot of times >the case in blocked positions. What I was suggesting was to use a confidence score, in your position it would evaluate (staticly) white as +1 up, then it would say "but there is a 30% chance of a draw for black because of a lot of blocked pawns", the score would then be +1*(1-0.3)=+0.7 and not 1.0. So black wouldn't sac a pawn here because +0.7 is still worse for black than 0.0, which might have been the material score had it not sacrificed a pawn. I don't see anything wrong with this, as long as your draw detector is reasonably accurate of course. The idea is the program might choose a different more secure way to the win, rather than entering a type of position where the opponent has a lot of drawing chances. I would like to get this "there is a danger of draws here, so pick a different variation if possible" knowledge into my program. >GMs are world champion winning blocked positions, let me tell you that... >...blocked positions that Omar scores of course each time as a draw :) Yes, which is why it is all the more important to remove this human advantage :) -S.
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