Author: Tord Romstad
Date: 08:56:42 08/22/03
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On August 22, 2003 at 10:54:17, Steven Edwards wrote: >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. 50 million nodes is a lot. I think most modern programs (even weak ones) should solve this a lot faster, and I'm sure Spector would too if you had continued developing it. I use MTD(f), but otherwise my search is very common. I extend at checks (a full ply), single-reply-to-check (1/2 ply), and mate threats (1/2 ply). Recursive nullmove pruning (R=3) throughout the tree, static pruning in the last 3 plies. My program finds Qh5+ at ply 7 after 403799 nodes, and needs 578145 nodes (still at ply 7) to find the mate. >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. Where can I find more information about the "Paradise" program? I am a Lisp programmer myself, and I would be very interested in reading about it. Tord
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