Author: Howard Exner
Date: 04:17:44 09/01/98
Here are some positions taken from CCL games that proved difficult for the computers to solve. They are 40/2 standard time control games played on seperate P200's. How do other programs navigate these positions? 1. Hiarcs6 played f7f5? which is a blunder because Qd5+ would easily win. It seems that some positions that are easy for humans to solve can still pose problems for computers.Why would programs find this position hard to solve? 8/5pk1/4p3/7Q/8/3q4/KP6/8 b - - id "Genius 5.0 - Hiarcs 6.0"; bm Qd5; 2. Nimzo played the losing move, Kxb3 when Kxa4! would have been a routine draw. 8/8/8/5P2/Pk5K/1N6/6b1/8 b - - id "Genius 5.0 - Nimzo 98"; am Kxb3; 3. This position illustrates the trapped piece theme. Rxa2, played by Genius 5.0, should be avoided because of the game continuation ... 1. ... Rxa2 2. Rxa2 Bc4 3.Qd2 Bxa2 4. b3 and the bishop on a2 was eventually lost. 1q3rk1/p3b1pp/1n2p3/r2bPp2/1p6/4BN2/PPB1QPPP/R2R2K1 b - - id "Hiarcs 6.0 - Genius 5.0"; am Rxa2; 4. Hiarcs played Ke2 but Kxe7 is white's only practical chance of winning. Pawns on both wings generally favour the Bishop over the Knight. Allowing opposite bishops to remain (even with knights on the board) is an error in judgement in this position. 8/4bkp1/2N2n2/8/8/2pB3P/5PP1/5K2 w - - id "Hiarcs 6.0 - Nimzo 98; bm Nxe7; 5. Rebel missed a chance to immediately transpose to a won ending with the moves 1. Qxe6+ Qxe6 2. Rxe6 Kxe6. Black's passed d pawn can be easily stopped while white's pawns are unstoppable. Instead Rebel played the liguidating sequence 1. Qb7+ Kd4 2. Qb6+ Kd3 3. Qxe3+ Rxe3 4. Rxe3 Kxe3. Note the better location now of black's king. Black should be able to draw this now by advancing his d pawn. 4R3/5Q2/3pr3/p2k1p2/5P2/1P2q1PP/P6K/8 w - - id "Rebel 9.0 - Hiarcs 6.0"; am Qb7+; 6. This position is a continuation of the previous discussion of Rebel9 vs Hiarcs6. The only chance of a draw is for Hiarcs6 to play d6-d5 and rely on a perpetual check in the Q vs Q ending. Instead Hiarcs follows the mistaken path of 1. ... Kxf4? 2. gxf5 Kxg5 when white's outside passer on the h file can only be stopped at the expense of white queening on the other wing. 8/8/3p4/p4p2/5PP1/1P2k2P/P6K/8 b - - id "Rebel 9.0 - Hiarcs 6.0"; am Kxf4; 7. Avoid the move 1.Rh5 because 1. ... Rh6! 2. Bxf5 Rxh5 3.Bxh3 and black is winning because of the passed h pawn combined with the advance of the king. Nimzo did play Rh6 and lost. A better try is the simple 1. Bxf5 Bxf5 2. Rxh4. 7R/5k2/1r6/1pN2n2/1Pp4p/2P4b/1K6/1B6 w - - id "Nimzo 98 - Shredder 2.0"; am Rh5; 8. Shredder2 should play Qb8. Instead Shredder played 1. ... Ng4? 2. f4 Nxe3 3. Qxb2 Nxf1 4. fxe5 and now the Knight on f1 is trapped. 3r2k1/2qp1ppp/2p1pn2/4b3/4P3/2PBB3/Pr3PPP/R1Q2R1K b - - id "Nimzo 98 - Shredder 2.0"; am Ng4;
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