Author: Mike Hood
Date: 03:01:49 02/19/04
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On February 19, 2004 at 01:13:46, William Penn wrote: <--- snip ---> >I verified your result with my Shredder 8 (CB GUI) installation, also that this >bug does not occur in other engines which I have available such as Shredder >7.04. So it is unique to Shredder 8. I also verified that it only happens if the >tablebases are active, so it is definitely a problem with tablebase >utilitization by Shredder 8. > >I then played around a little... If you replace the Queen with a Rook, the same >thing happens. If you replace it with a knight or bishop, nothing happens - >Shredder 8 refuses to calculate anything whatsoever! I received a fatal system >exception when making these tests, closing the GUI automatically. I then >replaced the Queen with a Pawn, and discovered that it refuses to capture the >pawn. It doesn't even see that capturing move, so the problem may be more >serious than I originally thought. Again, these problems only happen with >tablebases active. >WP Right, William. I discovered the pawn bug as well. In this position Shredder's move generator thinks there are only two legal moves. [D] 4k3/8/8/8/8/8/3p4/4K3 w - - 0 1 Analysis by Shredder 8: 1. = (0.00): 1.Kd1 Kd8 2.Kxd2 2. = (0.00): 1.Ke2 d1Q+ 2.Kxd1 But thanks for the tip about tablebases. I hadn't thought of that. I removed all the tablebases, restarted Shredder, and..... Analysis by Shredder 8: 1. = (0.00): 3.Kxd2 2. = (0.00): 3.Kd1 Kd8 4.Kxd2 3. = (0.00): 3.Ke2 d1Q+ 4.Kxd1 4. -+ (-12.90): 3.Kf2 d1Q 4.Ke3 Kd7 5.Kf4 5. -+ (-12.91): 3.Kf1 d1Q+ 4.Kf2 Kd7 5.Ke3 Much better already, even though Shredder's endgame skills aren't strong enough to recognize the mate after Kf2 or Kf1. Concerning your tests with a bishop or knight in the pawn's place. My GUI didn't crash, but the Shredder engine did freeze. It stopped calculating before outputting a move. Arguably, these are illegal positions, because it is already insufficient material before playing White's move. But the positions with pawn, rook or queen could all occur in normal games.
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