Author: Andrew Williams
Date: 15:19:22 06/26/02
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On June 26, 2002 at 14:09:03, Uri Blass wrote: >On June 26, 2002 at 13:53:11, Andrew Williams wrote: > >>Aha! >> >>This is a null-move problem, caused by a stupid bug in PM. My null-move >>verification search was not working in this position. Now that I've fixed it, >>this particular error doesn't occur. I'm still interested in what others see >>here. >> >>Regards >> >>Andrew > >In that case how could PM find it? >Movei is a null mover without null move verification and it had no problem to >solve it. > >The main line is Kg3 h4+ Kh3 Rc2 > >I do not see no threat. >The opposite. >I see threats of Bg1 and Rxh2# so there is no zunzwang. > >Null move can cause a program to be slower but it cannot prevent a program to >see it. > I'm not sure I understand your question. PM finds Kh3, but it takes too long. >The target of null move verification is to prevent the problem of zunzwang so I >do not see how it can help here. > I'm not sure either. Somewhere in PM's search a null move is generating a beta cutoff which the null move verification search doesn't agree with. If this cutoff (wherever it is) is accepted by the search, PM needs 13 seconds to see that Kg3 loses. If this cutoff is rejected, PM needs zero seconds to switch to Kh3. However, the test I've been running this evening has been unsuccessful (to say the least). This certainly requires more investigation. >Maybe you mean to say that your had a bug in the mate threat detector. > >Uri Thanks to you and Dieter for your responses. Andrew
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