Author: blass uri
Date: 15:08:03 01/27/99
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On January 27, 1999 at 17:45:16, Robin Smith wrote: >I have been playing over some chess positions with my computer (Pentium 166) and >have found some very strange behavior in the program Junior 5 in some endgames. > >strange position #1 >white Kd5, Pb5, Pc6 >black Ka2, Rb1 > >White to move wins easily with Kc5; but Junior wants to play c7??, thinking that >this also wins (evaluation ~=+2.5 pawns). Only after a think of several minutes >does it switch to Kc5, but not because it sees that c7? Rxb5+ draws, it is >because it decides Kc5 is even better than +2.5 pawns. All of this wouldn't be >all that odd since the draw involves a perpetual check, except that once Junior >5 plays c7 it INSTANTLY (less than 1 second) correctly sees the position is >drawn! > >even stranger position #2 >white Kd3 Ra2 >black Kd1 Pe2 > >Black to move, Junior wants to play Ke1, thinking that white will be mated in 7 >after Rxe2+; but e1=N+ draws! No mater how long Junior thinks it doesn't see >the underpromotion. It is a known fact that Junior5 does not consider underpromotions. I think that this was done to save time by not considering underpromotions. I understood that it is not simple to change the code of Junior5 to give Junior5 the possibility of considering underpromotions. > >strangest position #3 >white Kf6, Be5 >black Kh8, Bg8, Pg6 > >White to move can mate on the move with Kxg6 mate, but Junior 5 shuns both the >mate and the win of the pawn, preferring to draw the game with some silly bishop >move. This occurs no matter how long you let Junior 5 think! This bug must >have to do with Junior thinking that it "knows" B vs. B is "insufficient >material" and thus it shuns taking the pawn in the hopes that it might find a >win by keeping the pawn on the board. Incredible! Junior5 can find the win if you change the engine parameters of insufficient material. Uri
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