Author: Ralf Elvsén
Date: 23:50:32 12/18/01
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On December 18, 2001 at 23:17:40, Robert Hyatt wrote: >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... I read that once Korchnoi asked the referee in a tournament whether the rook was allowed to pass an attacked square when castling. He actually didn't know :) Ralf
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