Author: Tom Likens
Date: 06:52:56 05/20/04
Go up one level in this thread
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).
>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.
--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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