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Subject: Re: detecting and evaluating pins

Author: Gerd Isenberg

Date: 06:06:31 02/23/04

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On February 23, 2004 at 07:02:59, martin fierz wrote:

>aloha,
>
>i have a question about pins. pins are a rather important feature in chess; some
>of them are not so bad, some are deadly. i just happened to chat briefly with
>anthony cozzie on ICC, and he said he didn't do any pin detection. i detect
>pins, but i don't evaluate whether a pin is not so bad or deadly. my questions
>are:
>-> are you detecting pins in your program?
>-> if yes, do you try to distinguish between different pins?
>
>cheers
>  martin

Hi Martin,

yes i detect pins, (not only) because i do legal move generation.
With disjoint direction attacks (from sliders as well from the king as
metasliders) it is rather cheap to get them without branches.

In Eval i consider (from memory):

1.) what kind of piece/pawn is pinned.
2.) whether the pinner (?) is en prise or attacked by equal valued pieces.
3.) The distance from pinned piece to the king (>2) and whether the pinned piece
is member of the "own" side of the board...
4.) whether the pinned piece is defended or defendable (in one move) by pawns.
5.) whether the piece is attackable by opposite pawns.
6.) a kind of SEE value considering all other attackers/defendes.

In Eval i even consider other "tactical" stuff, like forks, overloading pieces
and pins to other valueable or hanging pieces.

Cheers,
Gerd





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