Author: Dana Turnmire
Date: 21:41:10 07/10/02
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- BP WK -- -- -- BP -- -- -- -- -- -- -- -- -- -- -- -- -- WN -- -- -- WP -- -- -- -- BP BQ -- -- -- -- -- WR BB BK In this position Chessmaster 8000 (running on an AMD Athalon 1800+ system) set on default with a selective search of 6 takes 3'7" to find Rb1 with a score of 3.45. Chessmaster set on 0 selective search only takes 2'41" for the same problem. Chessmaster set on 12 selective search cannot find the Rb1 move even after a half hour. This is what Graham Burgess says about the position in his book "The Mammouth Book of Chess," page 394. "Unfortunately, the standard algorithms to prune the variation tree are very likely to prune out the winning line, as the moves only make sense when you have seen to the end of the line. After more than 7 hours, Junior 6 (using tablebases, which one would expect to help speed up the assessments in some of the sidelines) considered 1 Rb1 to be winning, but it also thought 1 Rd1 to be equally good! Crafty 17, after several hours, opted for 1 Re1 or Ra1, and considered the position in either case (correctly) to be drawn, but did not see the winning line. Fritz 6, also using tablebases and with its Selectivity option set to zero, found the solution, including 1 Rb1 and 4 Ka8 in less than three minutes. In fact, it takes the same time without tablebases, so this isn't a significant factor here. The same engine, with a normal selectivity setting, is far less successful. 1 Rb1! c4 (1...h4 2 Kc6 h3 3 Kb7 c4 comes to the ssame thing.) 2 Kc6! h4 3 Kb7! h3 Even at this point, when the calculation is not so deep, some of the engines still take a while to find White's next move (Junior 6 and Hiarcs 7.32 are quickest - about 10-15 seconds to find the win; others, including Fritz 6 and Crafty 17, take longer, though Fritz 6 with Selectivity set to zero finds it in a split second). 4 Ka8! Only when this position is reached do most of the engines' assesments jump dramatically in White's favour." I would be interested in how Chessmaster 9000 handles this problem.
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