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Subject: Re: Looking for papers about generating and compressing egtb

Author: martin fierz

Date: 12:22:21 08/20/03

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On August 19, 2003 at 13:39:34, Igor V. Korshunov wrote:

>Hello!
>
>Is someone know links to papers about generating and compressing endgame
>tablebases?
>
>I am going to implement tablebases for game "Russian checkers".
>I do not want to reinvent well known things. This is very time consuming.
>
>The most important question for me is compressing and later fast access to
>compressed tablebases.
>I have not any ideas about it at the moment.
>
>Thanks for help,
>Igor

hi igor,

definitely the right place for you to look is the chinook webpage at
http://www.cs.ualberta.ca/~chinook/publications/ ; in particular the paper
called "Solving Large Retrograde Analysis Problems Using a Network of
Workstations". just forget about all the stuff they write about using a network
and parallelization, and it's perfect. i reinvented the wheel in march 2002 and
also computed the english checkers 8pc endgame database, because at that time,
the chinook database was not yet available to the public (and had not been since
they computed it around 1995, so i assumed it would "never" be). i relied
heavily on this paper - and found it a very good and complete guide to endgame
database computation.

when you compress your database, don't use the chinook scheme of 5 win/loss/draw
values per "uncompressed" byte (3*3*3*3*3 = 243 numbers) and 256-243=13 skip
values; instead, use only 4 win/loss/draw values (=81 numbers) and use the much
larger skip value range that you get this way. this improves the compression by
around 20%.

cheers
  martin



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