Author: Sune Fischer
Date: 01:30:14 04/22/03
Go up one level in this thread
On April 22, 2003 at 04:14:44, Uri Blass wrote: >On April 22, 2003 at 03:13:41, Sune Fischer wrote: > >>On April 21, 2003 at 18:24:45, Drexel,Michael wrote: >> >>>On April 21, 2003 at 18:09:03, Uri Blass wrote: >>> >>>>On April 21, 2003 at 17:18:46, Robin Smith wrote: >>>> >>>>>On April 20, 2003 at 17:20:11, Uri Blass wrote: >>>>> >>>>>>It may be possible to use it in a productive way to avoid problems >>>>>>that I mentioned(the program prefers loss by KR vs KPPP and not drawn KR vs KPP) >>>>>>by having rules to trust tablebases scores only in part of the cases but I do >>>>>>not like it. >>>>> >>>>>Uri, >>>>> >>>>>I know such things are possible in theory. Can you give an example of it >>>>>actually happening? >>>>> >>>>>Robin >>>> >>>>No >>>>If I remember correctly I saw a case when it happened but >>>>I did not care to save the position and I do not plan >>>>to look for it now. >>>> >>>>Uri >>> >>>[D] 8/8/8/7P/4K1P1/r6P/k7/8 b - - 0 1 >>> >>> >>>Anaconda 1.0 lost this position with tablebases. >>>It would take the pawn without. >> >>It's a fluke. >> >>I think what happens here is that table bases tell the engine it has a draw if >>it wants it, however the engine is "stupid" and believes it is better and will >>not be satisfied with a draw. >> >>So it's a simple horizon problem as far as I can tell, the TBs provide >>"infinite" depth but the engine does not like the truth it sees and prefers to >>kid itself. Without TBs it doesn't know it choosing a drawing line, so it >>happily eats the pawn. >> >>If the engine was a little better it would know the draw was the best option >>anyway. I don't know about Anaconda, but Ruffian and Frenzee both get a draw >>score showing pretty fast with TBs, so maybe this is related to a bug in >>Anaconda? > >I think that it is related to the knowledge that frenzee and Ruffian has and >ankadota and movei have not. >Movei does not use tablebases so it plays the right move but >Movei has a negative score for white after Ra4+ even after a long time and I >hope that it will be changed after adding score of pawns relative to kings. Frenzee doesn't have any knowledge of this, but it also chooses the wrong move Ra4+, and so does Yace btw. It's a little strange that they both show a draw score for a non-drawing move, apparently they are content with a draw, so I'm not sure why they don't chose Rxh4 immediatly. Ruffian must have special knowledge so it is a bad example, it shows a draw score from ply 1 :) >The point is that movei likes it's king in the centre in the middle game so it >is not very happy with king supporting the passed pawns and 3 passed pawns are >evaluated as clearly less than a rook and I cannot say that this knowledge is >generally wrong because black can win the game if I change the place of the >kings. > >I guess that frenzee see positive score for white after Ra4+ thanks to >positional knowledge(king relative to the pawns) or thanks to overevaluating >passed pawns(in case that it has not that knowledge) and not because of seeing >the queen in the board. I have no idea why it's showing a draw score for Ra4+, but Yace does the same and takes several minutes and 17 plies to fail low. Apparently it's tough to find the right move for the right reason, it is easier to find it for the wrong reasons. I'd still call it a fluke though. Yace has now switched to Ka2b2 with a draw score, Ruffian agrees that that is also a drawing move. -S. >Uri
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