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Subject: Re: Most compact way to store chess positions with all the data EPD contains

Author: Peter Klausler

Date: 06:28:10 08/10/98

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On August 09, 1998 at 00:24:27, Danniel Corbit wrote:

>What is the most compact known method for storing a chess position with all the
>relevant information like castling status, en-passant squares, etc.? [Also best
>move from here .. don't really care about what the test set is though...]
>I want to store a large database of chess positions, and compaction would really
>help.  When I am finished, I will share the final specifications and the data
>also, if anyone is interested.

The smallest representation that I know for a FEN position, which sounds
like what you want here, is 173 bits, but it is extremely hard to
encode and decode.  CDB uses a 192-bit (24 byte) representation
for some positions that require a context-free representation,
and the details are elaborated in the CDB internal documentation
(http://reality.sgi.com/pmk_craypark).  In a database, however,
one seldom needs to use a context-free representation, and great
space savings are possible.  Most positions in a CDB database
are represented with a 12-byte record.

If you really want a scheme for storing "all the data EPD contains",
you'll need something much larger and more general than just the
basic chess position.



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