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Subject: Revisiting WCSAC #398

Author: Steven Edwards

Date: 07:54:17 08/22/03


The following position is #398 from _Winning Chess Sacrifices and Combinations_:

[D]2qrr1n1/3b1kp1/2pBpn1p/1p2PP2/p2P4/1BP5/P3Q1PP/4RRK1 w - - 0 1

It has been referenced in a number of CC papers over the past three decades
including the description of the NWU program Chess 4.x by Slate and Atkin.  It
was also a test position for the MacLisp Paradise program by David Wilkins at
SRI.

The position is a mate in ten.  My old program Spector, moribund for seven
years, picks the key move 1. Qh5+ at iteration eight as "obviously winning" and
sees the full mate PV on iteration nine.

PV: Qh5+ Nxh5 fxe6+ Kg6 Bc2+ Kg5 Rf5+ Kg6 Rf6+ Kg5 Rg6+ Kh4 Re4+ Nf4 Rxf4+ Kh5
Rg3 Re7 Bg6#

Spector requires over fifty million nodes for the complete search and I'll guess
that the numbers aren't all that much different for most programs using common
search techniques.

BUT, the above mentioned Paradise chess program pulls out the mate PV with a
search tree containing only 109 nodes.  It solves many other tactical puzzles
with similarly small search trees.

Are there any programs out there today that emphasize knowledge per node rather
than nodes per second?



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