Tuesday, November 1, 2011

The KBBKB ruleset is done

So as announced in the previous post I was working on a rule set to recognize a draw in a king and 2 bishops vs bishop endgame. I verified the rule set against the Gaviota table base for that endgame and it is now correct. It was unfortunately much more complicated as I first thought.
For simplicity I always assume White is the side with the 2 bishops, so I have to check all cases where the white king is on one of the 10 core squares in a pawnless endgame (A1, B1, C1, D1, B2, C2, D2, C3, D3, D4). Due to symmetry reasons this is enough. For those 10 squares I now recognize

Incorrect Draws :           0
Spotted   Draws : 146.068.302
Missed    Draws :  44.341.638
Spotted   Wins  :  16.484.560

which is pretty good as in the missed draws also a lot of positions are contained where the attacker bishops travel on the same color, which I did not bother to recognize.

So another little piece of endgame knowledge added. If iCE 0.2 would have already possessed it, it would have won at least 1 more game :-)

Still a lot is missing, like King Rook and Minor vs King Rook which also did cost half a point already.