Saturday, March 30, 2013

Positional evaluation in chess

Chess engine are very good a tactics because it fits their way of approaching a position. To play moves that improve the position without gaining an immediate material advantage or even sacrifice material for a better position is much harder to program. It requires a careful coding of positional chess concepts and a fair amount of chess knowledge in its programmer.

My automated tuner seems to help here a bit. The tuned version is much more willing to give up some material to improve its position then the old "materialistic" version was.

In Jeremy Silman's "The Amateurs Mind" he discussed the following position

1r4k1/5p1p/1p3np1/pR6/P1Pr3P/2R2B2/1P4P1/7K w - -


Fischer - Taimanov, Palma de Mallorca 1970, White to Play
White has the queen side pawn majority and an active bishop targeting the queen side. The black knight wants to relocate to c5. Also Black threatens to take the white pawn at h4 with check.

I gave this position to my original version and it wasn't really understanding the position. At lower depths it tried to save the pawn with g3 and at higher depths it suggested 1. h5 Ne4 2. Bxe4 Rxe4 giving up its strong bishop and its advantage.

The tuned version very quickly found a better move. 1. c5! (1. .. Rxh4+ 2. Kg1 Rb4 3. Rb3 Rxb3 4. Rxb3 Nd7 5. c6). The pawn then queens after a rook sacrifice (Rxb6) which was a tactics my engine still missed so deep down the tree.

But it seems to make a little progress in the area of positional understanding.