Author: Stan Arts
Date: 09:44:00 04/17/04
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On April 17, 2004 at 12:18:40, Eric Oldre wrote: >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 > Hi Eric When you are looking at material to deside if it's safe to do a nullmove, you only need to look at the material of the side that's going to do the pass/ nullmove, the amount of material of the other side isn't all that important, at that point. For instance : If one side has a king, queen, a bishop and a bunch of pawns, and the other side a lonely king, then it's sort of safe to do nullmoves for the side with all the material, but not for the lonely king. Where the king might be forced into a near mating position by having to move, but would be safe one or several moves if not. That would be the danger of a nullmove then for instance. However the side with all the material will probably be worse when it doesn't move, and then nullmove is beneficial, and not dangerous. My program Neurosis P3-550 48 MB hash , on the position Joachim gave. It uses a different form of nullmove, and is not affected by the zugzwangs in this position. Legal moves: 22 Static score: -1092 Ply Score Time Nodes Best move and expected line ------------------------------------------------------------ 2 -1092 6 6281 Qe8+ Kh4 Qg6 3 -1092 6 7672 Qe8+ Kh4 Qg6 4 -1092 44 40423 Qe8+ Kh4 Qg6 Kh3 Qf5+ Kg3 Qg6+ Kh2 Qd3 Qg6 Qd3 Qg6 5 -1092 127 116639 Qe8+ Kh4 Qg6 Kh3 Qf5+ Kg3 Qg6+ Kh2 Qd3 Qg6 Qd3 Qg6 6 -1092 517 481303 Qe8+ Kh6 Qf7 Kg5 Qg8+ Kh5 Qe8+ Kh6 Qf7 Kg5 Qg8+ Kh5 6 9993 605 559337 Qg7 < + > Kh4 Qg6 Kh3 Qg5 Kh2 6 9993 610 566481 Qg7 <M4> Kh4 Qg6 Kh3 Qg5 Kh2 Qh4+ 7 9993 852 784274 Qg7 <M4> Kh4 Qg6 Kh3 Qg5 Kh2 Qh4+ Total nodes:1416603 n/sec:90100 (Q-nodes:10% max depth:12) Goodluck and greetings Stan
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