Author: Vincent Lejeune
Date: 16:04:52 07/21/99
Go up one level in this thread
On July 21, 1999 at 17:52:40, Christophe Theron wrote:
>On July 21, 1999 at 01:33:46, Paulo Soares wrote:
>
>>On July 21, 1999 at 00:56:56, Christophe Theron wrote:
>>
>>(snip)
>>>
>>>Some programs don't see the mate in 2 (with both pawns on the 7th rank) because
>>>after 1. Ra6! black is in zugzwang.
>>>
>>>Looks like nobody has read my previous post and I'm just losing my time trying
>>>to explain it...
>>>
>>>Both Hiarcs and Fritz would fail on some zugzwang positions. Not on this one,
>>>which is solved by Hiarcs, but there are positions where Hiarcs fails completely
>>>because of its null move algorithm.
>>>
>>>...OK, just losing my time... :)
>>>
>>>
>>> Christophe
>>
>>Christophe, this question was made by Eric Guttemberg, and was without
>>reply. Could you answer, I have the same doubts of Eric.
>>
>>"With regard to the zugzwang problem, I am a little confused. I know that
>>many basic endgames techniques rely repeatedly on the zugzwang theme. In
>>many of them the weaker side would never lose if he could waive his move
>>when it suited him(mating with K and R vs K is a whole different ballgame
>>if the weaker side can not be forced to move)
>>Yet Fritz does not seem to have any trouble with any of the basic endgame
>>positions. What kinds of zugzwang positions does Fritz and other null-movers
>>have trouble with?"
>>
>>Paulo Soares, from Brazil
>
>I don't know exactly which kind of positions Fritz will have trouble with. But
>every programmer that uses null move knows about the "overlooking zugzwang"
>disaster.
>
>So they try to avoid it by disabling the null move algorithm in positions where
>a zugzwang is likely. Obviously, in endgame positions.
>
>They set some kind of material thresold, and if the current material on the
>board is under this thresold, the null move selectivity is simply disabled.
>
>This can even be smarter. For example, it is unlikely that a side will be in
>zugzwang if he has a queen. It is also unlikely that it will happen if a side
>has more than 2 pieces (excluding pawns and king), though it is more risky to
>assume this. Needless to say, you can find positions where one side, even with a
>queen and another piece, is in zugzwang. But it is very very rare.
>
>Such a position has been posted recently, and guess what... Hiarcs fails to
>solve it for example (I'm almost sure Fritz would fail too).
[cut]
I've found the original post
I've verified the position but Fritz find the right move (h4 !) without problem,
so I doubt that's a nullmover killer position, or Fritz have special algorithm
for this kind of position ...
original post:
On July 12, 1999 at 12:48:08, Vincent Lejeune wrote:
>When I watched a game a reach this position
>
>2k1q3/2p3n1/p1Np4/3P3p/P2P1p2/1Q5P/1KP5/8 w - -
>
>and I notice that Hiarcs 7.32
>don't find h4 after 4 min, depth (10/30). (the best it find is Qc4 +1.00)
>but after h4 is played on the board, it instantly see an high score (+2.20)
>
>
>(time on celeron 464 Mhz)
Thanks Vincent!
This is a nice zugzwang position. I think that after 1.h4 black is in zugzwang!
It is very interesting since each side has still one queen and one knight, and
the position comes from a real game.
Try with Fritz and you should see that he has the same problem.
Now we know that Hiarcs uses null move!!!
Christophe
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