Author: Robin Smith
Date: 16:59:56 06/27/00
Go up one level in this thread
On June 27, 2000 at 18:23:52, Mike S. wrote: >On June 27, 2000 at 14:44:10, Robin Smith wrote: > >>On June 27, 2000 at 08:43:49, Enrique Irazoqui wrote: >> >>>Thorsten posted an interesting position in >>>http://www.oxford-softworks.com/cgi-bin/forums/mschess/558.html: >>> >>>[D]2R5/4k1pp/p3p3/4P1p1/p3N3/q1P4P/2P1P1P1/1K6 w - -; bm e4d6; >>> >>>(...) >> >>Very interesting position!! The pieces on both sides are in zugswang, so the >>pawns decide everything. After 1.Nd6 g6 2.e3 h6 3.e4 I think 3. ... h5 instead >>of 3. ... g4? is a better defensive try, but afterwards 4.g3! g4 5.h4! (5.hg? hg >>=) g5 6.hg h4 7.g6 hg 8.g7 g2 9.g8=N+! and mate in two. So programs that can't >>see underpromotions (Junior5) won't ever solve this one. And the underpromotion >>occuring on ply 17 in a position where black threatens mate in one doesn't make >>it easy for ANY program. Congratulations to CSTal! > >I don't think CSTal has to calculate for the mate to decide playing 1.Nd6: As >explained in the posting (see link above), it does it mostly by giving a penalty >to black for the bad queen mobility. > >But white doesn't need to move the knight immediatly, because black's queen >cannot move anyway at the moment. Therefore, if a program would play 1.e3 for >example, it still can play Nd6 at the next move and has possibly (? I haven't >tested) seen that. No! It must be 1.Nd6 right away. If you play 1.e3 Black's King can escape with Kf7. After 1.Nd6 the only legal king move is Kd7 which fails to 2.Nc4 (attacking the queen) Qe7 (only escape square for the queen) 3.Nb6 mate. This is a truely interesting and beautiful problem because it is not at first obvious that black IS in zugzwang and then once that is seen, it is not clear that whites TWO k-side pawns will be able to defeat blacks THREE pawns on that same side. >It's good if a program plays Nd6, but it is not an optimal >test position when the order of the moves to play isn't forced - there may be >several 1st moves which allow white to win by 2.Nd6 for example. Only 1.Nd6 wins, keeping black from playing Kf7. >It seems to me >that white's rook is free to make tempo moves in the c file if necessary. >Somebody please tell me if I'm wrong. Tempo moves by the rook on the c-file let blacks king escape and thus no zugzwang. You will be able to keep the queen traped, but blacks king will march over to the kingside. Seeing 1.Nd6 with a large fail high should be a good and hard test position for computers. >Regards, >M.Scheidl Robin Smith
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