Author: Robert Hyatt
Date: 20:47:04 08/29/99
Go up one level in this thread
On August 29, 1999 at 21:55:56, Mark Young wrote: >On August 29, 1999 at 21:23:15, Robert Hyatt wrote: > >>On August 29, 1999 at 17:02:27, Mark Young wrote: >> >>>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. >> >> >>I find it interesting that Fritz (a piece/square program) evaluates this so >>high, but now that I now this, I'm going to exploit it. :) >> >>But in any case, it is obviously a position where crafty (at present) doesn't >>evaluate it properly. Once the majority code is solid, it will make quite a >>difference, although I don't think it will ever be +2 here as I am _very_ >>suspicious that such an eval is dangerous since material is even and both sides >>end up with passed pawns. Tough to evaluate that statically... and get the >>right score in the majority of cases.. > >Material is not even in the position I am looking at. I have 6 white pawns to >blacks 5 pawns. Black does have a free d pawn, and I guess this is why Crafty >slips in this position. It does not understand whites king can blockade its two >center pawns, and then let whites pawn majority on both sides of the board win >the game as black king is helpless is such a position. ah yes... my cut and paste failed... I was looking at a position with material even. That explains the score a bit better...
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.