Author: Omid David Tabibi
Date: 05:36:48 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
Falcon 2.5.2.11 on AMD Athlon(tm) 64 Processor 3200+, 1999MHz, 1024MB:
depth time nodes nps score variation
7/19 0.02 8k 531k 3.63 1.d8e7 d4d3 2.e2e3 c4c3 3.d1g4 c5c4
4.g4e6 d5c5 5.e6d6 c5b6 6.d6e5
8/19 0.03 10k 337k 3.93 1.d8e7++
8/19 0.03 11k 346k 4.53 1.d8e7++
8/21 0.03 13k 421k 5.37 1.d8e7 c4c3 2.d1b3 c5c4 3.b3b8 d5c5
4.b8d6 c5b5 5.d6e5 c6c5 6.e7e6
9/18 0.03 14k 465k 5.67 1.d8e7++
9/21 0.03 18k 591k 6.27 1.d8e7++
9/21 0.05 19k 408k 8.07 1.d8e7++
9/22 0.05 21k 449k 9.62 1.d8e7 c4c3 2.d1b3 c5c4 3.b3a3 e4e3
4.a3d6 d5e4 5.e7e6 e4f4 6.d6e5 f4g4
7.e5d4 g4h5 8.d4e3
9/22 0.05 23k 492k #4 1.d1a1++
9/22 0.05 24k 513k #4 1.d1a1 c4c3 2.a1a2 c5c4 3.a2a5 c6c5
4.a5a8
>
>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.
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