Author: Mark Young
Date: 14:02:27 08/29/99
Go up one level in this thread
On August 29, 1999 at 16:18:10, Ricardo Gibert wrote: >On August 29, 1999 at 14:20:16, Mark Young wrote: > >>On August 29, 1999 at 13:30:20, Robert Hyatt wrote: >> >>>On August 29, 1999 at 12:36:18, Ralf Elvsén wrote: >>> >>>>This is a position from a game Hiarcs 7.32 - Crafty 16.6 >>>>Time 25 min/game, ChessBase interface etc, but that is not >>>>important. >>>> >>>>6k1/1p4p1/p7/2Ppp3/1P6/P4KP1/5P1P/8 b - - 0 49 >>>> >>>>What is interesting is that Crafty (black) >>>>thinks the position is about even, with a score fluctuating >>>>around equality, while Hiarcs for several plies >>>>has realized that it has a won position and >>>>has a score about +2 (an exchange of rooks has just >>>>taken place some plies ago). >>>> >>>>I checked 16.6 as a winboard engine, also 16.16: >>>>same result. >>>> >>>>This is a serious mis-evaluation of >>>>the pawn structure since white easily can produce >>>>passed pawns on both sides of the board, while >>>>blacks connected free pawns can do nothing. >>>> >>>>Bob, maybe you want to look into this... >>>> >>>> >>>>Regards, Ralf >>> >>> >>>This is a bit speculative by hiarcs... ie I have seen it do this same sort >>>of evaluation and be dead wrong as well... >>> >>>the only thing I don't evaluate at present is pawn majorities which turn into >>>distant passed pawns. It is on my todo list, and I have some code written that >>>does pretty well but is not ready for testing on the servers yet... >>> >>>My version of crafty (16.17 as released) thinks black is worse here, by about >>>1/3 of a pawn... and as it advances pawns to make passed pawns, this gets >>>worse. But there is always danger in these positions... and I only hope that >>>I get more right than wrong... however, +2 here? Seems hard to fathom... >> >>I don't know if this is a case of specuation by Hiarcs or something else. I did >>test some other programs on this position and they tend to agree with Hiarcs >>7.32. >> >>5 min search. >> >>Crafty 16.13 Fritz 5 Junior 5 Hiarcs 6 Hiarcs 7.32 >> >> +/= .43 +- 1.56 +- 2.07 +- 2.16 +- 2.23 > >Hard to fathom? This position is a good example of a type of position that >strong players find easy while computers suck at in comparison. In a matter of >seconds, a strong player would use schematic thinking to solve it by dividing >the position into 3 sections: > >Section 1 are the a, b & c files, where the 3 vs 2 pawn majority will prevail >unless the black K assists. > >Section 2 are the d, e & f files where the white K & f pawn will hold off the >black pawns even with the assistance of the black K. > >Section 3 are the g & h files where the 2 vs 1 pawn majority will prevail unless >the black K assists. > >Unfortunately, The black K can only assist in a single section so white Queens. >The 2.23 pawn advantage given by H7.32 is ludicrously low! > >For example, even if we alter the position drastically in blacks favor, he still >loses uneventfully. We can move the white K back to d1 and put the black K on d3 >and white still wins easily. I agree the eval 2.23 is low, but for a program in this type of endgame this is a shout that black is dead. Hiarcs and Junior found this position very easy to understand. They both showed a +2 score from the start of the search. Fritz used its search to see that white and a big advantage. I am not sure why Craftys search could not see the big advantage even without some endgame code to help it understand this position better.
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