Author: John Stanback
Date: 13:11:47 06/22/98
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This is a nice position for testing/debugging transposition tables and draw by 50 move rule. I modified Zarkov to allow it to search beyond 100 plies, but it didn't find the draw. Then I added 1 line of code to store positions which were scored by the 50 move rule or draw by repetition in the transposition table before returning from search(). Now it gets a score of 0 after a 101 ply search, which takes about 6.7 seconds. John On June 22, 1998 at 13:07:30, Bruce Moreland wrote: > >On June 22, 1998 at 12:15:25, Amir Ban wrote: > >>On June 22, 1998 at 10:02:42, blass uri wrote: >> >>>The position 3k4/2p1p1p1/p1P1P1Pp/P6P/4K3/8/8/8 >>>white to move. >>> >>>every human can understand it is a draw but my programs cannot evaluate >>>the position as 0.00 >>>Is there a program that understand it is a draw? >>>( it is enough to use an hash table of 36*9*2=648 positions) >>> >>>Uri >> >>This is a good example to see what your hash table can't do for you. >> >>The problem is that all the positions here evaluate the same. None of them are >>obviously drawn or obviously won, so the only way the search can find a draw >>score is to find a repetition or 50 moves in the PV. White cannot be forced to >>make a repetition, so the only hope is to search this to 100 ply, but this takes >>too much time. > >Mine completes a 101 ply search here in 1.9 seconds, returning a draw by the >50-move rule. > >It actually made it through 161 plies in 3.0 seconds, but then something broke. > >I had to relax my normal 40-ply maximum for this, so perhaps I need to increase >another compile-time constant. > >Here is the PV at ply 101. > >PV 00:00:01.875 101 0 [] Kd5 Ke8 Ke5 Kd8 Kd4 Ke8 Kd5 Kd8 Ke5 Ke8 Kd4 Kd8 >Kd3 Kc8 Kc2 Kd8 Kc3 Ke8 Kb2 Kd8 Kc2 Ke8 Kc3 Kd8 Kc4 Kc8 Kb3 Kd8 Kb2 Ke8 Ka3 Kf8 >Kb4 Ke8 Kc4 Kd8 Kb3 Ke8 Ka2 Kd8 Kb1 Ke8 Kc1 Kd8 Kd2 Ke8 Ke3 Kd8 Kf3 Ke8 Kf4 Kd8 >Ke3 Kc8 Kf2 Kd8 Kg2 Ke8 Kg3 Kd8 Kf2 Ke8 Kg2 Kd8 Kh2 Ke8 Kg1 Kd8 Kf1 Ke8 Ke1 Kd8 >Kd1 Ke8 Kd2 Kd8 Kc1 Ke8 Kd1 Kd8 Ke2 Ke8 Kd3 Kd8 Ke4 Ke8 Kf3 Kd8 Kg3 Ke8 Kh2 Kd8 >Kg1 Ke8 Kf1 Kd8 Ke1 Ke8 Ke2 Kd8 > >bruce
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