Author: Robert Hyatt
Date: 20:17:40 12/18/01
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On December 18, 2001 at 20:15:09, Mike S. wrote: >On December 18, 2001 at 18:54:09, Kurt Utzinger wrote: > >>In the position shown below Fritz 7a sees that 1...Rxb2 is a fault, but after >>making this move, the program is unable to win a piece with 2.0-0-0 and so we >>must assume that there is a castling bug in Fritz7: > >I notice the same on my system. OTOH, Fritz 7a can see long castlings at the >root: > >[D]8/8/8/8/2p5/2pkp1N1/8/R3K3 w Q - 0 1 > >Analysis by Fritz 7: > >1.0-0-0# > +- (#1) Tiefe: 2/2 00:00:00 > +- (#1) Tiefe: 2/2 00:00:00 > >The case must be more complicated... > >Are there games where Fritz 7a did castle to the queenside (except book moves)? > >Regards, >M.Scheidl The bug is probably this: For castling, the king can't pass over a square that is attacked. On the kingside, Rxg2 would render castling impossible since the king ends up on g1 and is in check there. On Rxb2, it is very likely that the programmer simply tested one _extra_ square for being under attack (it is tempting to test all squares between the king and rook, which is right for kingside, wrong for queenside castling). I'd bet that is what he did. This bug has appeared in several programs. It was actually in a _very_ early version of Crafty as well...
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