Author: Robert Hyatt
Date: 07:48:01 09/22/04
Go up one level in this thread
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.
Crafty on my PIII/750mhz laptop:
6-> 0.23 4.37 1. Qa1 d3 2. Qc3 e3 3. exd3 e4 4. dxc4#
7 0.23 +1 1. Qa1!!
7 0.24 +3 1. Qa1!!
7 0.24 +M 1. Qa1!!
7 0.32 Mat04 1. Qa1 c3 2. Qa2+ c4 3. Qa5+ c5 4.
Qa8#
7-> 0.54 Mat04 1. Qa1 c3 2. Qa2+ c4 3. Qa5+ c5 4.
Qa8#
time=0.55 cpu=74% mat=2 n=200591 fh=99% nps=364K
ext-> chk=17795 cap=856 pp=4066 1rep=1417 mate=0
predicted=0 nodes=200591 evals=39305 50move=0
endgame tablebase-> probes=0 hits=0
mate in 4 moves.
I'm not so sure why this one would be hard...
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