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Subject: Re: here it is: a mate in 8

Author: leonid

Date: 04:54:21 01/19/01

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On January 19, 2001 at 06:34:32, Heiner Marxen wrote:

>>Only one thing I see as practical why saving the moves that lead
>>to given position, is the taken of pawn "en passant". There you need "previous"
>>move to know if it pawn should be taken.
>
>Ah, I see.
>But I would not store a cemplete last move, but rather, if and into which
>column an e.p. may happen just now. That takes 4 bit (9 cases).
>I have also 4 bits for the castling rights, and one bit for the side to move.
>Total: 64*4 bit square contents, 4+4+1 Bit extra info.

Interesting to see that you do this some other possible way. Actually rocks with
all the details about this (where rock already happened, what king or rook ever
changed its initial place and some other data) is kept in one variable. 2 bytes.
Previous move program keep in 4 bytes long variable as every move. This I do
probably because I could not see other way but mainly for simplicity. Even
description of the board I keep in exact 64 bytes chain. It could be reduced to
much less volume but then the simplicity will vanish.

Leonid.


>> But probably the best way is just to
>>recognize position that can end with this kind of taken and never save it on the
>>first place.
>
>That is sometimes the best strategy: avoid the problem altogether  ;-)
>
>Heiner



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