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Subject: Re: Practical Tablebases (much smaller) ?

Author: Uri Blass

Date: 06:16:09 11/13/01

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On November 13, 2001 at 08:31:09, William Penn wrote:

>I suspect this has been discussed before but I didn't pay attention, so please
>pardon my redundancy. If you could just point me in the right direction, much
>appreciated...
>
>Can't we make some assumptions without compromising very much practical playing
>strength and significantly reduce the size of the endgame tablebases? For
>example it seems a waste to generate separate positions for "white to move" and
>"black to move".

It is also a waste of space to remember the exact number of moves to mate and
knowing the number of moves divided by 2 is enough and if you know it you can
calculate the exact number of moves to mate.


 Surely there is a reasonable simplification in that regard
>based on symmetry.

Symmetry is used in building the tablebases


 Promotion of a pawn to less than a Queen is rare and could be
>disregarded.

This is going to save time in generating the tablebases with pawns but it is not
going to chnage much the space that is needed for the 3-4-5 piece tablebases.

 Perhaps castling can be disregarded because it seldom happens in
>the endgame.

It is already disregarded.

 I suppose we must keep en passant(?). I'm guessing that the size
>could be reduced to perhaps only 1GB for all of the 3-4-5 piece positions vs the
>current 7GB.

Part of the 7GB is for generating unimportant tablebases of a king and three
pieces against a king when there is no position with king and 3 pieces against
king when programs cannot win.

Uri



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