Author: Daniel Jackson
Date: 12:23:43 09/22/04
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On September 22, 2004 at 07:53:37, Andrew Platt wrote: >Actually, more accurately a problem with null move and a position that appeared >in this week's Washington Post Chess column: > >[D] 3K4/8/2ppp3/2pkp3/2ppp3/8/4P3/3Q4 w - - 0 1 > >The main thing to do is to wait for black to commit suicide, something that null >moves are very bad at doing! The solution is to make an active waiting move that >will position the Queen directly later: > >1. Qa1 d3 2. Qc3 e3 3. exd3 cxd3 4.Qxd3# > >However, Schola does not want to get this mate. I can run it as long as I like >and it still goes for the longer mate: > >1. Kd7 d3 2. e3 c3 3. Qb3+ c4 4. Qb4 c2 5. Qxd6# > >If I disable null move it finds this very quickly. I suspect that there's a bug >in the search somewhere though I can't find it and the traces look sane. The >main problem is that the null move for Qa1 always cuts off so it retains Kd7 >which is the first move it considers. > >Has anyone else had problems with positions like these and null moves? BTW, I >have verified null move implemented but that doesn't help either. That does make >a small difference if I jump the position to 1. Qa1: It then finds the fastest >mate which the regular null move still doesn't do. I've also disabled some other >things like the hash table which sometimes get in the way for me but that didn't >change anything. > >Andy. Andy, could you provide me the details of this puzzle, the year and composer? Thank You. Daniel
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