Author: Robert Hyatt
Date: 07:23:08 02/27/01
Go up one level in this thread
On February 26, 2001 at 16:21:15, Severi Salminen wrote: >>Note that in crafty I don't do the attack_to/attack_from stuff, I dynamically >>compute it as needed with the rotated bitmap table lookups... that might make >>a difference. > >What is this attack_to/attack_from you are talking about? I do this in >gen_captures(bishop, for example): I take one white bishop from Board.Bishops. >Then I extract the necessary diagonal states which I use to get a bitboard which >has all bits on where a bishop might capture to. Then I AND this with black >pieces and scan through those. In make_move() I just move the pieces around and >update all bitboards. My board structure has only the necessary bitboards which >are needed to store the board and 3 rotated bitboards. So what are these >attack_to and _from bitboards and where are they used? > >Severi The original Slate/Atkin paper described their incremental move generator. They maintained (for each piece) a bitmap that defined the squares that piece could move to. Whenever the board was updated, the affected bitmaps were also updated. This means that at any instant in time, you _always_ have a bitmap showing which piece attacks which squares. They also incrementally updated the inverse bitmaps as well, those bitmaps that indicate which squares hold a piece that attacks one specific square. I did this in early versions of crafty, but the rotated bitmap approach soon made that approach obsolete...
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.