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Subject: Re: Problem: knowing nothing about a position = score 0??

Author: Jeremiah Penery

Date: 21:12:47 10/27/02

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On October 28, 2002 at 00:10:00, Robert Hyatt wrote:

>On October 27, 2002 at 21:03:59, Robin Smith wrote:
>
>>On October 27, 2002 at 20:56:58, Robert Hyatt wrote:
>>
>>>On October 27, 2002 at 17:14:22, Ingo Lindam wrote:
>>>
>>>>Hello...
>>>>
>>>>I just thought about some questions from Bob that lead me to a problem.
>>>>I know the engines should have as much knowledge as the programmer can give to
>>>>it. But ofcourse in may searchtree may appear some positions I can't apply a lot
>>>>(or in worst case any) of that knowledge: material is equal and all the other
>>>>knowledge doesn't fit to current position (in the tree). Will my score 0 (or
>>>>atleast very near to 0)?
>>>>
>>>>If yes...I just ask me whether this could lead the computer to optimize the best
>>>>move sequence into complete knowing nothing about the position the sequence of
>>>>moves end in... as more as I evaluate the positions for my opponent the same
>>>>way?
>>>>
>>>>Shouldn't I better substract something from my score and add something on the
>>>>opponents score in case I know nothing about the position?
>>>
>>>
>>>Any such idea is very dangerous.  It is amazing how a full-width search to
>>>reasonable depth will mangle your evaluation if you have a big hole in it.
>>
>>Bob,
>>
>>But isn't this exactly what you do in Crafty for locked pawn positions ....
>>penailze Crafty for being in such a position?
>>
>>Robin
>
>
>Yes.. But the point is that Crafty has specific code to recognize that kind
>of position, and a specific (and appropriate) score for such.
>
>That is quite a bit different than saying "I don't know how to evaluate this
>so I will just call it zero.  Or something less than zero."

I think they were saying not to call it zero, but to take the normal score you
would give for that position and lower it some degree corresponding with your
non-understanding of the position.  So if the evaluation is already -9.00, it
would become -10.00 (or worse) if there are parts of the evaluation you don't
understand.  This way, the search will try to AVOID those parts of the tree more
than normal.



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