Author: Heiner Marxen
Date: 18:06:49 12/31/01
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On December 31, 2001 at 17:07:31, Uri Blass wrote: >My program had problems with WAC 250 so I decided to ask it to calculate the >perft function and found that it cannot calculate perft 4 correctly > >The bug is that my program believed that double check from 2 rook directions is >impossible > >Here is the position of WAC 250 >[D]1b5k/7P/p1p2np1/2P2p2/PP3P2/4RQ1R/q2r3P/6K1 w - - 0 1 > >When I asked my program to calculate perft it failed in perft 4. > >My program did not count correctly the number of moves after >1.a5 Ng8 hxg8Q+ > >it turns out that my program simply did not see that the rook does a check so it >believed that Qxg8 is a legal move. Hehe! >My program also believes that double check from 2 diagnols is impossible and I >hope that at least it is not wrong with it. I think, this time you are right. At least, I cannot construct it. But other funny things are possible with e.p., like a double discovery check: [D]8/8/3k4/2pP3K/8/B7/8/3R4 w - c6 ... which can be pinned through two pawns, like in: [D]8/8/3k4/r1pP3K/8/B7/8/3R4 w - c6 The e.p. is not legal, here. Still, no triple check is possible :-) Heiner
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