Author: Tony Werten
Date: 09:22:58 05/20/04
Go up one level in this thread
On May 20, 2004 at 09:52:56, Tom Likens wrote: >On May 20, 2004 at 05:48:25, Tony Werten wrote: > >>On May 19, 2004 at 15:40:35, Tom Likens wrote: >> >>> >>>Afternoon all, >>> >>>I've been reworking some of the evaluation elements of my engine >>>and one of the items I wanted to modify is the scoring of pinned >>>pieces. So with that in mind I thought I'd share some my thoughts >>>on the subject (and maybe obtain a few new ideas in the process). >>> >>>Currently, I'm including this items my pinned pieces evaluator. >>> >>>1. If one side is pinning a piece *and* has the right to move, then use >>> the SEE function to determine if the piece can be profitably captured. >>> >>>2. If a piece is "absolutely" pinned (a Nimzowitsch term) penalize it. >>> An absolute pinned piece can't move at all (e.g. a knight pinned to >>> the king by an enemy bishop would be an absolute pin, whereas >>> a bishop pinned to the king by a queen would not be since the bishop >>> could move along the diagonal of the pin). >>> >>>3. If the piece is absolutely pinned and the attacking piece's value is >>> less than the value of the pinned piece (regardless of who has the >>> move) penalize the defender a percentage of the difference between >>> the attacking piece and the pinned piece. >>> >>>4. If the attacker has a queen/rook, queen/bishop or rook/rook battery >>> attacking the pinned piece then increase the penalty. >>> >>>5. If multiple pieces are pinned increase the penalties. Also if multiple >>> pieces are pinned then accessed the pinned side some percentage >>> of the *largest* pinned piece from either 1 or 3 above. >> >>I don't think 1 and 3 should be evaluated as pinned pieces but just as hung >>pieces. >> >>Furthermore 3 should be adjusted. If the "pinned piece" is higher than the >>"pinning piece", you should evaluate the square of the "pinned on piece". (So >>just assume the hanging piece will move) > >Hello Tony, > >I agree to a large extent with most of your comments, but I'm not sure >I understand this point clearly. I believe what you're saying is that that if... > >a) the pinned piece is more valuable than the attacking piece it will need > to move and so... >b) when it moves evaluate the attack on the piece it was pinned against > >This is correct in general, except when a piece is absolutely pinned >against the king (as in case 3). Also, if the piece being pinned is more >valuable than the piece it is pinned against then this wouldn't apply >either (impossible of course, in the case of the king but not in the more >general case). Yes, sorry, it was incomplete. You should score the lowest one, wich automaticly takes care of an absolute pin, since that would score +inf for the "pinned on piece", wich means you always take the see value of the pinned piece. > >>4 is needed to evaluate the pins correctly, and 5 won't be hit very often. > >I use 5 as one of the measures for determing the "turbulence" of a >position, which is then further used to determine how safe it is to >prune various positions etc. That would be the best ( and only ?) use for it. Tony > >--tom > >>Tony >> >>> >>>As I mentioned earlier, I'd be interested in how others handle pinned >>>pieces. I'd also be interested in just hearing thoughts on the above and >>>if I've missed anything obvious. >>> >>>cheers, >>>--tom
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