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Subject: Re: passed pawn evaluation.

Author: Tord Romstad

Date: 02:52:07 01/12/04

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On January 11, 2004 at 21:18:30, macaroni wrote:

>I have recently been fiddling arround with some passed pawn code, however I just
>can't seem to get it working very well. Can you give me an idea of what sort of
>values you give different types (in different stages) of passed pawns?

Here is a rough description of what I do:

Start by giving the passed pawn a bonus depending on which rank it occupies.
You then adjust this bonus depending on the placement of the other pieces
on the board.  Some examples:

Protected passed pawns and passed pawn duos are especially dangerous.
Adjust the bonus up if there is a friendly pawn beside or diagonally
behind the passed pawn.

Adjust the bonus up if there is a friendly rook behind the pawn, and down if
there is an enemy rook behind it.

A passed pawn is usually more dangerous if it is supported by a king.
Increase the bonus if the friendly king is close, especially if it is
somewhere in front of the pawn.  Likewise, you should increase the bonus
if the enemy king is far away.  In rook endgames, it is probably a good
idea to further increase the bonus if the enemy king is cut off by
a rook (I don't do this yet, but I plan to add it in the near future).

Passed pawns are most dangerous if they are able to advance safely.
If the passed pawn is blocked by an enemy piece, adjust the bonus down.
If it is unblocked, increase the bonus if your static exchange evaluator
decides that it is safe to push the pawn, and reduce the bonus if it is
not safe to push it.


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