Author: Tony Werten
Date: 07:10:21 04/10/02
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On April 10, 2002 at 08:20:24, Steve Maughan wrote: >I came across this position. > >[d]6k1/6np/5ppq/pp1p4/3Pp1K1/4P3/P6Q/8 w - - No problem for XiniX ply:12/17 score:-4.737 time:5s 68Kn/s 1.Qxh6 Nh5 2.Kh3 b4 3.Kg2 a4 4.Kf2 a3 5.Ke2 b3 6.Qxh5 gxh5 ply:12/24 score:-4.637 Qb8 fail high ply:12/24 score:-4.058 time:17s 68Kn/s 1.Qb8 Ne8 2.Qxe8+ Qf8 3.Qd7 h5+ 4.Kh3 Qa8 5.Kh4 b4 6.Qe6+ Kg7 7.Qe7+ Kh6 8.Qxf6 Qg8 9.Qe5 Tony > >I first encountered this position back in ~1987 in Eric Hallsworths excellent >newsletter - it was with regard to improvements in Richard Lang's engine. I >thought I'd see how todays programs compare. > >The whole point of the position is that after the obvious Qxh6 black can play >Nh5, trapping queen and allowing the Queenside pawns to promote. So the >position is a good test of how an engine handles trapped pieces and pawn >promotion. > >I tested the engines on my 1.5 GHz P4 with 96 Mb of Hash. I recorded the time >for the programs to show that Qh6 is negative and the time to suggest an >alternative (usually Qb8+). These are the results: > >Program Negative Alternative (Qb8) >Fritz 7 56 sec > 10 min >Crafty 18.14 2 sec 15 sec >Tiger 23 secs > 10 min >LGoliath 1.5 7 sec 24 sec >Junior 7 2 min 27 sec > 10 min >Monarch 5 secs 23 secs >Nimzo 7.32 3 secs > 10 min >Shredder 6.02 6 sec 1 min 55 sec >Yace 2 secs 11 secs > >As you can see many top programs struggle to suggest a better move. The normal >scenario is that they see the problem associated with Qh6 but then 'freeze' >while searching Qb8. Monarch has no specific knowledge in this position so I >was surprised that it did so well - null move will be disabled for most of the >search so maybe this is the problem with the other programs. I also wonder if >the others are doing Internal Iterative Deepening which *may* help (Monarch >does). My other thought is that maybe this position would be solved quicker if >the fail soft move was recorded along with upper bounds (alpha) since this would >give the search and may prevent the 'freeze'. > >Regards, > >Steve Maughan
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