Author: Steffen Jakob
Date: 23:09:30 09/19/99
Hi all! I still try to improve the playing skill of Hossa in pawn endgames (which is not very difficult because he plays them very badly). About underpromotions: I know that Amir Ban doesn't generate underpromotions in the search tree. I don't like that very much. What I am doing now is to reduce the search depth for underpromotions (one ply). It helps a lot in some positions, e.g. in the pawn endgame position where crafty saw that mate in 4 although it is a mate in 6. As you can see below I need 158616 nodes to see the mate without pruning and 135713 with underpromotion pruning. I think about reducing the depth by two plies for bishop underpromotions (can someone please give me some positions where the winner move is to promote the pawn to a bishop?). What are you thinking about this? Are there other ways to prune underpromotions? E.g. if you are sure that queen promotions are searched before underpromotions and alpha > xxx then it might be useless to try those moves (at least rook and bishop promotions). analysis without forward pruning: --------------------------------- +---+---+---+---+---+---+---+---+ 8 | | | | | | | | | +---+---+---+---+---+---+---+---+ Black: Hossa v1.63 (C) (0) 7 ||P|| | | | | | | | +---+---+---+---+---+---+---+---+ Black material: 4 6 | P | | | | | ||P|| | +---+---+---+---+---+---+---+---+ 5 | | | | | | | ||P|| +---+---+---+---+---+---+---+---+ White to move 4 | | | | | | | | P | +---+---+---+---+---+---+---+---+ 8/p7/P5p1/7p/7P/4kpK1/8/8 w 3 | | | | ||K|||P|| K | | +---+---+---+---+---+---+---+---+ White material: 2 2 | | | | | | | | | +---+---+---+---+---+---+---+---+ White: opponent (0) 1 | | | | | | | | | +---+---+---+---+---+---+---+---+ a b c d e f g h depth value time nodes pv 1 -5.23 0.00 2 1.g3h3 <1> -5.23 0.00 3 1.g3h3 2 -5.35 0.00 38 1.g3h3 f2 2.h3g2 <2> -5.35 0.00 48 1.g3h3 f2 2.h3g2 3 -5.37 0.00 84 1.g3h3 f2 2.h3g2 e3e2 <3> -5.37 0.00 90 1.g3h3 f2 2.h3g2 e3e2 ? 4 -510.92 0.01 194 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q ? <4> -510.92 0.01 207 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 5 -510.92 0.01 322 1.g3h3 f2 2.h3g2 <5> -510.92 0.01 335 1.g3h3 f2 2.h3g2 6 -510.92 0.01 531 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q <6> -510.92 0.01 552 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 7 -510.92 0.02 1182 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q 4.h2g3 <7> -510.92 0.02 1203 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q 4.h2g3 8 -510.98 0.05 2817 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 4.h2h3 f2f1Q 5.h3h2 <8> -510.98 0.05 2867 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 4.h2h3 f2f1Q 5.h3h2 9 -510.97 0.09 5587 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 f1f2 5.h2h3 e2f3 <9> -510.97 0.09 5644 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 f1f2 5.h2h3 e2f3 ? 10 -512.01 0.24 14405 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 ? <10> -512.01 0.24 14556 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 11 -512.03 0.64 41493 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 <11> -512.03 0.65 41840 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 ? 12 #-6 2.11 158616 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 ? <12> #-6 2.12 159367 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 analysis with forward pruning: ------------------------------ depth value time nodes pv 1 -5.23 0.00 2 1.g3h3 <1> -5.23 0.00 3 1.g3h3 2 -5.35 0.00 38 1.g3h3 f2 2.h3g2 <2> -5.35 0.00 48 1.g3h3 f2 2.h3g2 3 -5.37 0.00 84 1.g3h3 f2 2.h3g2 e3e2 <3> -5.37 0.00 90 1.g3h3 f2 2.h3g2 e3e2 ? 4 -510.92 0.01 194 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q ? <4> -510.92 0.01 207 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 5 -510.92 0.02 322 1.g3h3 f2 2.h3g2 <5> -510.92 0.02 335 1.g3h3 f2 2.h3g2 6 -510.92 0.03 531 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q <6> -510.92 0.03 552 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 7 -510.92 0.03 1182 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q 4.h2g3 <7> -510.92 0.03 1203 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 f2f1Q 4.h2g3 8 -510.98 0.04 2726 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 4.h2h3 f2f1Q 5.h3h2 <8> -510.98 0.04 2776 1.g3h3 f2 2.h3g2 e3e2 3.g2h2 e2f3 4.h2h3 f2f1Q 5.h3h2 9 -510.97 0.08 5403 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 f1f2 5.h2h3 e2f3 <9> -510.97 0.08 5460 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 f1f2 5.h2h3 e2f3 ? 10 -512.01 0.16 12077 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 ? <10> -512.01 0.16 12228 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 11 -512.03 0.46 33004 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 <11> -512.03 0.46 33351 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 e2e3 5.h2g3 f1xa6 6.g3g2 ? 12 #-6 1.71 135713 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 ? <12> #-6 1.72 136462 1.g3h3 f2 2.h3g2 e3e2 3.g2g3 f2f1Q 4.g3h2 g5 5.h4xg5 e2f3 6.g6 f1g2 Best wishes, Steffen.
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