Author: Uri Blass
Date: 00:00:00 07/26/03
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On July 25, 2003 at 19:44:43, Sune Fischer wrote: >On July 25, 2003 at 19:24:21, Eran wrote: > >>On July 25, 2003 at 17:50:21, Ernst Walet wrote: >> >>>This afternoon my account on the chessbase server played a game against Rebel >>>12. To my astonishment Rebel missed a mate in one, and got mated right away. >>>Any thoughts on this, Ed? >>> >>[D]8/8/6p1/6k1/3p2P1/4b2Q/4Bq2/7K w - - 0 151 >> >>If Fritz 8 or Crafty 19.03 plays the same game instead of Rebel 12, Fritz or >>Crafty will play the same problem as Rebel 12. Please see below. >> >>So, do Fritz and Crafty have a bug for a long time? > >I suspect most engines has that bug, including mine. >I've known about it for over a year, but have decided not to fix it because I >can't find a way to do it. > >The reason is the engine makes the 50th move, checks the 100 ply counter and >returns the draw score. > >To fix it, the engine needs to check for check mate _before_ it checks the >counter, but most engines can't do that staticly, they have to search another >ply to see the mate. No There is a more simple solution. If counter=100 the engine check for checkmate before it decides that it is a draw. If counter<100 you do not need to do it. I do not do it in that way and I check for checkmate at every node first. Thanks to my legal move generator I do not need to search another ply but only to generate a move if I want to verify no checkmate. Uri
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