Author: Eric Oldre
Date: 09:18:40 04/17/04
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I experienced a similar situation in a test game last week. My engine had 2 queens a rook and a few pawns to the opponent's king and bishop, but it refused to mate. I had logic to not use null move in the endgame but due to the amount of material one side had it did not register that is was the end game. My solution was to change the function which detected when it was the end game. Instead of using all the material on the board, it would base the decision on the amount of material the side with less material had. so if either side is down to it's last few pieces, it would stop doing null move. It seemed to do the trick for the particular board position I had the problem with, but i'm not sure what if any additional problems it may cause... Have other people used this approach with any luck? (i'm sure someone has at least tried it) Eric Oldre On April 17, 2004 at 08:16:21, Joachim Rang wrote: >This position is an easy mate in 4: > >[D]6Q1/8/8/7k/8/8/3p1pp1/3Kbrrb w - - 0 1 > >Certain engines however have problems to see the mate and return instead a draw >score. So ie Crafty. > >I think it is related to nullmove, since the solution involves a zugzwang for >the black side and since it's so many material on board most engines will use >nullmove in this position. However I thought Nullmove will produce a reduction >rathern than a complete cutt-off and hence the solution should be found a few >plies later. Or did I understand the mechanism of Nullmove wrong? > >I know that this position is not of any interest if it comes to playing >strength, but it is rather funny to watch certain engines reach depth 20 quickly >while being unable to spot the mate. > >regards Joachim
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