Author: Robert Hyatt
Date: 19:16:16 08/06/04
Go up one level in this thread
On August 06, 2004 at 19:07:24, GeoffW wrote: >On August 06, 2004 at 18:33:26, Robert Hyatt wrote: > >>On August 06, 2004 at 18:21:51, GeoffW wrote: >> >>>Hi >>> >>>My program has been playing some test games against Dorky and getting soundly >>>beaten, it got me thinking about my eval function which is pretty dumb and badly >>>in need of some chess knowledge ! >>> >>>What I noticed in some of the games was that Dorky was seeing threats sometimes >>>10 or 15 plies earlier than my program, as we were searching to similar depths >>>it could only be that Dorky has much better eval function. >>> >>>Here is one of the positions that showed this effect, material is even, but >>>black looks to me to be in a horrible position >>> >>>[D]1b3rk1/4qb1p/2r1pRpP/2ppP1P1/P3pQB1/1PB1P3/8/5RK1 b - - 9 44 >>> >>>My program (Black)reckoned that it was only 0.25 of a pawn down, where as Dorky >>>reckoned white was winnning by 2.2. >>> >>>I tried this position with a few programs, only Dorky and Crafty scored white >>>ahead by > 1.5 pawns. >>> >>>Any suggestions as to what the important factors are to evaluate this position >>>as strongly good for white ? >>>My program hasnt really got any mobility scoring, no king tropism and rather >>>basic pawn structure eval. Wondering which area I ought to try first ? >>> >>> Regards Geoff >> >> >>Crafty's static eval here is +1.5 as you mentioned... >> >>The primary points are (a) the f-file is open and occupied by white's three >>major pieces. The pawn at h6 makes g7 another weakness, not to mention being a >>potential passer if the h7 pawn goes away. >> >>Main problem here is king safety, with the white majors pointed right at the >>black king. > >Hello Bob > >Thanks for the quick reply, I was checking the score with Crafty as you posted > >note: scores are for the white side >material evaluation................. 0.00 >development......................... 0.00 >pawn evaluation..................... -0.13 >passed pawn evaluation.............. 0.00 >passed pawn race evaluation......... 0.00 >king safety evaluation.............. -0.46 >interactive piece evaluation........ 1.88 >total evaluation.................... 1.29 >Black(1): > >king safety as listed here is actually good for black, the important factor >though is the large interactive piece evaluation of 1.88 That is "first order king safety". Second-order king safety includes piece locations and coordination. It is more important. The first-order term is purely pawn structure around the king... > >Is this term simply adding up the combined attacks against the enemy king , or >does it look for more subtle factors as well? >I assume Crafty must look at the squares adjacent to the enemy king and also >ignore the defending rook and bishop ? It is a combination of things. But the main problem is the f-file. White owns it and has multiple threats because of this.. Black should never have allowed the white heavies to triple-up uncontested... > >I guess the position above would have scored highly for this term as I think >Crafty may have a non linear scaling for this type of multi piece attack ? Correct. It is an exponential-type function where each additional piece ramps up the score exponentially. IE 4 pieces are not twice as good as 2. They may be 8x better... > >Incidently, even a strong engine like Gothmog after analysing this position for >30 seconds, still only reckons white is ahead 0.4. Some types of attacks are very deep. But with black paralyzed because of the f-file, it appears to be only a matter of time... > > Geoff
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