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Subject: Re: Dabbaba needs an openingbook

Author: Steven J. Edwards

Date: 21:14:30 05/27/98

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On May 27, 1998 at 16:45:38, Jens Baek Nielsen wrote:

>My chessprogram Dabbaba needs an openingbook.

The OCD project includes an opening book constructor and probe system.
It uses a regular PGN fiel as input (the more games the better).  The
final output isa file of fixed length records, each containing three
components: the main hash code (eight bytes), the move (full flags and
values, 4 bytes), and the count of occurances of that move in that
position for the winning side.  The output file is sorted by hash code
and the probe is a simple binary search with vaious fseek() calls.
Probes are very fast.  Maybe two or three of the hash code bytes could
be dropped withotu too much threat of false matches.  Lkewise, the move
could be compressed and the usage count could be limited to a smaller
range.

The book probe selects a move from alternatives (if any) a generates a
uniformly distributed integer with an upper bound of the total frequecy
count for all moves for that position.

-- Steven (sje@mv.mv.com)



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