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Subject: Re: detecting result by evaluation in Kp vs K positions

Author: Dieter Buerssner

Date: 16:15:13 02/07/04

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On February 07, 2004 at 18:26:00, Uri Blass wrote:

>I started to work on having some evaluation about endgame and
>I wrote something to detect draws in KP vs K.

If you have access to a good library, have a look at: Beal, D. F. and Clarke, M.
R. B.; the construction of economical and correct algorithms for King and Pawn
against King. Advances in Computer Chess 2, M. R. B. Clarke (ed.), pp. 1-30,
Edinburgh University Press, 1980, ISBN 0-852-24377-4.

>It does not detect every possible draw but at least hopefully when it detect
>draw it is correct if I have no bugs.

For testing such code, having access to Nalimov TBs can be very useful. Just
write a small routine, that creates all possible KPK positions and compare the
eval or your routine with the result of TB probing. I have done this for several
routines in Yace. Especially, when you are going to use it for pruning, the
knowledge should be perfect.

>I read that yace is using bitbases even for 4 piece endgames when the bitbases
>give only win draw loss information and I guess that the bitbases were
>calculated from nalimov tablebases.

Correct. However, the usage of bitbases is optional in general. For KPK I have a
builtin bitbase. It needs (without many tricks) 24 kbyte (64*64*24*2/8). It is
much easier to write a little program that puts out the table, than to write
good kpk code "by knowledge".

Regards,
Dieter



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