Author: Robert Hyatt
Date: 07:32:10 08/31/99
Go up one level in this thread
On August 31, 1999 at 06:16:22, Ralf Elvsén wrote: >On August 31, 1999 at 04:51:18, Ricardo Gibert wrote: > >>On August 31, 1999 at 00:30:24, Howard Exner wrote: >> >>>On August 30, 1999 at 19:41:54, Ralf Elvsén wrote: >>> >>>>Some while ago I posted a position where I was >>>>impressed by Hiarcs accurate evaluation in a pawn ending: >>>> >>>>6k1/1p4p1/p7/2Ppp3/1P6/P4KP1/5P1P/8 b - - 0 49 >>>> >>>>The fact that white can create passed pawns on >>>>both sides of the board makes the victory clear, >>>>and Hiarcs gave an evaluation of about +2. Note however >>>>that white is a pawn up. >>>> >>>>Not being entirely convinced about the >>>>impeccabilty of its evaluation, I decided to test >>>>some similar "clean" positions. >>>> >>>>First position: >>>> >>>>4k3/p6p/8/4p3/3p4/3K4/PP4PP/8 b - - 0 1 >>>> >>>>This is (from a human point of view) an "identical" position but >>>>with material equality. A win for white. Here Hiarcs thinks black >>>>is slightly better! >>>> >>>>Second position: >>>> >>>>4k3/p6p/8/3p4/2p5/2K5/P4PPP/8 b - - 0 1 >>>> >>>>Here one pawn is moved from one side of the board to the other >>>>(compared to the previous position) and that makes it a clear draw, >>>>but Hiarcs thinks white has an advantage, although not decisive. >>>>So Hiarcs thinks position 2 is better for white than position 1, >>>>when in fact it is worse. >>>> >>>>I am now inclined to believe (or rather convinced...) >>>>that Hiarcs correct score in the position from my >>>>original post was due to the fact that white was a pawn up in a pawn ending, >>>>(which is heavily weighted, understandably) and not from some accurate >>>>evaluation of the pawn structure... >>>> >>>>Don't investigate the chess "knowledge" of your favourite chess software, >>>>your illusions can be shattered :) >>>> >>>>Ralf >>>> >>>>PS: I always screw things up when I post positions and other stuff. >>>>Hope I got it right this time... >>> >>>6k1/1p4p1/p7/2Ppp3/1P6/P4KP1/7P/8 b >>> >>>Here is your original position minus the white pawn on f2, >>>so now material is equal. Like Hiarcs' eval of the original >>>Rebel 10 also gives a big plus for white. But now in this equal material >>>position which remains a very simple win for white, Rebel 10 thinks black is >>>much better. It seems that only deep calculation will aid computers here >>>while humans see this at a glance. >> >>Yes. Computers cannot calculate far enough to "understand" these positions. >>Their evals are not much better than "random noise". They can do tactics & in >>many respects positional play, but stategy (i.e. planning) is neglected, which >>is what is needed here. To do stategy, they need to be able to generalize and >>they don't do that. > >I don't know if strategy is needed. As a naive non-programmer >I imagine that you could add something like this in the evaluation: > >local pawn majority (plus check for non-block e.g. >white pawns g2, h4, black pawn h5) -> future passed pawn > >if (the above) on both sides of the board -> big plus in score > >Of course it depends on the position of the kings etc. >Might get messy... I think Bob indicated a scheme similar to this >in a previous post (or maybe I misunderstood him). > >Note that in the last positions I posted, if you let >black have pawns on e.g. e4 and d4 and alter the location >of the kings slightly, then black can win in some situations... > >Ralf Note also that there is a special case crafty already handles. IE white has pawns at g4/h5 and black has a pawn at h6. White has a 'hidden' passed pawn because if he plays g5, he gets a passer immediately that out-runs the opponent's passer...
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