Author: J. Wesley Cleveland
Date: 12:59:43 02/10/99
Go up one level in this thread
On February 09, 1999 at 23:22:20, Robert Hyatt wrote: >On February 09, 1999 at 04:17:18, blass uri wrote: > >> >>On February 08, 1999 at 16:25:33, Robert Hyatt wrote: >> >>>On February 08, 1999 at 11:18:50, José de Jesús García Ruvalcaba wrote: >>> >>>>On February 07, 1999 at 18:30:17, Robert Hyatt wrote: >>>> >> >>>> I see that crafty would never give up the h-pawn to reach a drawn QP vs Q >>>>ending. So I assume that the position after 96. Qxh5+ is won for black. >>>> I do not understand why, in a tablebase position, crafty allowed the same >>>>position to appear twice (however, I understand why it allowed the third >>>>repetition now). If crafty is in a won tablebase position, the distance to mate >>>>should decrease every move. >>>> >>> >>>that was the 'bug' I reported. in my search, I tried all moves at ply=1, >>>but at ply=2 did the tablebase probe _before_ trying any opponent moves. And >>>since I did this, I made a move that led to the shortest possible mate, but >>>also led to a position where when the opponent moved, it repeated the position >>>for the third time. >> >>I did not understand it. >>If you are in a won position then it is enough to look only at all moves at >>ply=1 and to choose the best move(shortest distance to mate). >> >>If the distance to mate is decreased every move then repetition is impossible >>because repetition of distance to mate is impossible. >> >>Uri > > >this is wrong.. the problem is that a DTM database says 'n moves to mate from >this position' without knowing what has happened already in the game. So it is >quite easy to follow a path to the shortest mate and stumble over a position >that leads to a draw. the 50-move rule is the classic, because there are _lots_ >of mates in > 50 with no pawn moves or captures before the mate is delivered. > >In my case, it was just a problem of probing the table _before_ checking for >a repetition... But why did crafty allow the first repetition a few moves earlier ?
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