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Subject: Re: bitboard vs 0x88 again?

Author: Tord Romstad

Date: 05:17:17 10/08/03

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On October 08, 2003 at 06:33:00, Sune Fischer wrote:

>What are the many advantages of 0x88-like systems?

I suppose what I use can be described as a "0x88-like system", although I use
the &0x88 trick just a few times during program startup to initialise some
tables.

My board is an array with 256 entries, visualised as a 16x16 board where
the real chess board occupies the left half of the middle eight ranks.  I
use the "mailbox" technique for edge detection; all squares outside the
real board contain the value OUTSIDE.  Originally I used a 10x12 board
like in most other mailbox programs, but I switched to 16x16 in order
to be able to detect the geometrical relationship between two squares
with a simple minus operation (like in 0x88 programs).  As Russell once
pointed out in an e-mail, I could just as well have used a 16x13 board
with three ranks below the board and two ranks above it, but I'm to
lazy to change it.

I don't know much about the "many advantages".  My main reason for this
board representation is that it is extremely simple to use, and that
the code is clear and easy to understand.  I also find the above-mentioned
ability to easily determine geometrical relationships to be very
convenient.  It is possible that other board representations could
enable me to do certain operations a bit faster, but at the moment what
I have is fast enough (my program is slow as a tortoise, but not because
of the board representation).

Tord




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