Author: Bruce Moreland
Date: 00:50:59 02/01/99
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On February 01, 1999 at 00:51:40, Don Dailey wrote: >We had an assertion failure during one tournament I am embarassed to admit. >I am embarassed for two reasons, the debugging should have been turned >off, and the program should not have failed. It was one of those >castling bug things. The assertion picked up the error fortunately, >it would have been tough finding this one without the assertion. >It was a very beautiful bug though. Every assumption and test about >castling failed due to a rare set of circumstances that had to happen all >together in order to produce the bug. It was beautiful like a composed >chess problem. The program was restarted and fortunately the bug did >not occur again and I fixed it after the game was over. But if the >bug had continued to occur, we would have lost the game unless the >tournament director had allowed a recompile and I doubt he would have. I once asked a group of chess programmers how many of them would mess up in the following situation, and I got one or two sheepish "me" responses. White has rooks on h1, a1, king on e1, can castle either way, black has bishop on h8, king on e8, black to move. Black plays Bxa1, and while black fiddles with his king, white plays Rh2, Ra2, Rxa1 and O-O-O. The reason this might cause problems is that the a1 rook never moved. bruce
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