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Subject: Endgame database symmetry levels

Author: Ian Kennedy

Date: 12:37:02 08/08/01


Is it always possible to predict what level of symmetry exists in a given eg db
given only knowledge of how the pieces move?

I initially thought yes but after mucking around with generating KBNK I'm now
less sure. I thought it reasonable that this was 4-way symmetric* until it
failed to get the 'right' results (as measured against other dbs, books) and
more importantly I reread Reuben Fine where he says that the king must first be
driven to a corner with opposite color to the bishop before mating in a
same-coloured corner. Even then, how do you know that some solutions do not
cross midway into a third quadrant, or whether 2-way symmetry will now suffice?

Or is there some simple ruleset that always applies eg any pawn eg will always
have horizontal symmetry only, any with Rook, Queen, Knight will have horizontal
and vertical, and with Bishop(s) ...?

* eg if a dark squared bishop is mating the bk on a1 then that will mirror to h8
and a *light squared* bishop mate will mirror at a8 and h1

Ian Kennedy



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