Author: Robin Smith
Date: 16:21:09 01/27/99
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On January 27, 1999 at 18:08:03, blass uri wrote: > >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 Thanks for the info. I will try your suggestion on position #3. It still seems to me to be odd behavior for a program to miss mate in one using it's default settings. But no doubt the insufficiaent material knowlege improves Juniors play more often than it hurts it. Robin
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