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Subject: Re: Crafty-IsiChess,CCT4,r11 ==> A move to avoid?

Author: Andrew Williams

Date: 05:08:18 01/30/02

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On January 29, 2002 at 16:54:20, Dann Corbit wrote:

>On January 29, 2002 at 16:43:28, Roy Eassa wrote:
>
>>On January 29, 2002 at 16:36:23, Thomas Mayer wrote:
>>
>>>Hi Roy,
>>>
>>>>>Wow, Fritz 7b is blind to this one.  It does not see in advance that 37...Nxe5
>>>>>is good for Black (it thinks Black is down more than 3 pawns).  Must be
>>>>>null-move / zugzwang, right?
>>>>
>>>>
>>>>To be more specific, in the following position Black can play ...Re6 and be in
>>>>very good shape (certainly not behind).  However, Fritz 7b evaluates this
>>>>position as being better for White by about 5 pawns:
>>>>
>>>>[d] 8/8/1p1r1k2/p1pRN1p1/P3K1P1/1P6/8/8 b - - 0 2
>>>
>>>strange... Quark fully disagrees and thinks that black is little bit better...
>>
>>
>>Quark is right.  Fritz is wrong.
>>
>>I guess this is a very good example of a blindness caused by using null move.
>>
>>My question is, do all zugzwang positions confound null move, or only some?
>
>Since Thomas uses NULL MOVE in Quark, it makes you wonder what could be causing
>the blind spot for Fritz?  Using it past the time when it is appropriate
>perhaps?

Are we sure that this blind spot is caused by null move? I tried switching
off null move completely and it makes very little difference to what my program
does in this position. My score still starts out at -1.something for black then
goes to +1.something, then goes back to -1.something before drifting back up to
around +0.9, all in the first 5 minutes of search (up to depth 20). Does anyone
else find that null move doesn't make much difference here? Obviously using null
move helps with the number of nodes, but it doesn't change the scores very much
at all.

Andrew




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