Author: Uri Blass
Date: 09:12:42 08/22/03
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On August 22, 2003 at 11:56:42, Tord Romstad wrote: >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 think that you overestimate other programs. I believe that a lot of programs need more than 50M nodes I checks some good programs and my movei is also relatively good in problems with a lot of checks so they did better but shredder cannot solve it even after more than 300 miliion nodes. New game 2qrr1n1/3b1kp1/2pBpn1p/1p2PP2/p2P4/1BP5/P3Q1PP/4RRK1 w - - 0 1 Analysis by Shredder 7.04: 1.exf6 Nxf6 2.fxe6+ Bxe6 3.Rxf6+ Kxf6 4.Qe5+ Kf7 5.Rf1+ Kg8 6.Rf8+ Rxf8 7.Bxe6+ Rf7 8.Bxc8 Rxc8 9.Qe6 Ra8 10.Bc5 +- (6.02) Depth: 15/46 00:28:29 335678kN (Blass, Tel-Aviv 22.08.2003) > >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. Shredder cannot at depth 14. Maybe you do not use enough pruning so you can solve it fast. I believe that solving it too fast is a mistake because it means that in a lot of cases you extend bad lines. The fact that a program can solve it is not enough and we need other positions to know if it is better in tactics. It is easy to be able to solve some positions that you planned to solve but to fail in positions that you did not plan to solve them. Uri
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