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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