Author: Miguel A. Ballicora
Date: 18:33:47 04/17/02
Go up one level in this thread
On April 17, 2002 at 18:56:19, Dann Corbit wrote:
>On April 17, 2002 at 17:45:03, Peter McKenzie wrote:
>
>>On April 17, 2002 at 16:53:30, Gian-Carlo Pascutto wrote:
>>
>>>On April 17, 2002 at 16:40:01, Dann Corbit wrote:
>>>
>>>>I don't see how it can completely remove the tactic from ever being seen unless
>>>>the implementation of null move is broken.
>>>
>>>If it has a zugzwang, you will _never_ see it if you don't check for it
>>>(verification search, double nullmove), or use another trick like force
>>>nullmoves away from the root (that is what Crafty does).
>>>
>>>You can always play the 'nullmove' no matter what depth, so you'll
>>>never realize the nullmove is no good.
>>>
>>>i.e. you make an illegal move that is not possible in the real game, and
>>>increasing search depth won't change this.
>>
>>Yes, you are correct. Some programs can never solve the following:
>>
>>[D]8/8/2p5/pkp3R1/7B/P7/2p3K1/8 w - -
>>
>>http://homepages.caverock.net.nz/~peter/eg_test/pet013.htm
>
Gaviota 0.32 sees the draw in AMD-K2 400 mhz in 148 secs.
There are two components in this problem
1) realizing that after Rxc5 and Bg5 the game is won by black, otherwise,
white will not care about finding a line that draws.
2) seeing the zugswang.
When gaviota finds 1, immediately detects 2. Gaviota does well in this
particular problem because it does not prune after nullmove, it reduces the
depth accordingly. It could be bad in the rest of the search? then so be it.
Kf3-e4
216068 9 4.0 +0.46 Rg5xc5 Kb5xc5 Bh4-g5 Kc5-c4
Kg2-f3 Kc4-b3 Bg5-c1 c6-c5
Kf3-e4 c5-c4
362312 9: 6.6 +0.46 Rg5xc5 Kb5xc5 Bh4-g5 Kc5-c4
Kg2-f3 Kc4-b3 Bg5-c1 c6-c5
Kf3-e4 c5-c4
554096 10 9.5 +0.34 Rg5xc5 Kb5xc5 Bh4-g5 Kc5-c4
Kg2-f3 Kc4-b3 Bg5-c1 Kb3-a2
Kf3-e3 Ka2-b1 Ke3-d2
955468 10: 16.8 +0.34 Rg5xc5 Kb5xc5 Bh4-g5 Kc5-c4
Kg2-f3 Kc4-b3 Bg5-c1 Kb3-a2
Kf3-e3 Ka2-b1 Ke3-d2
1462125 11 24.9 +0.26 Rg5xc5 Kb5xc5 Bh4-g5 Kc5-c4
Kg2-f3 Kc4-b3 Bg5-c1 Kb3-a2
Kf3-e3 Ka2-b1 Ke3-d2 c6-c5
2600239 11: 45.2 +0.26 Rg5xc5 Kb5xc5 Bh4-g5 Kc5-c4
Kg2-f3 Kc4-b3 Bg5-c1 Kb3-a2
Kf3-e3 Ka2-b1 Ke3-d2 c6-c5
3422811 12 57.0 :-( Rg5xc5
8526149 12 148.3 +0.00 a3-a4 Kb5-b6 Bh4-f2 c2-c1=Q
Rg5xc5 Qc1xc5 Kg2-h1 Qc5xf2
9846012 12: 171.9 +0.00 a3-a4 Kb5-b6 Bh4-f2 c2-c1=Q
Rg5xc5 Qc1xc5 Kg2-h1 Qc5xf2
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