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Subject: Re: Arasan finds a new WAC bust

Author: Robert Hyatt

Date: 05:31:12 09/16/04

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On September 16, 2004 at 07:30:26, Ricardo Gibert wrote:

>On September 15, 2004 at 23:16:05, Jon Dart wrote:
>
>>> Qd1 is an inferior --
>>
>>> after Qd1+ Kg2 Qg1+ Kf3 -- you are back to the starting position  and Qf1+ is
>>> clearly best...looks like a bug in Arasan
>>
>>There is no penalty here for repeating the position once. If a mate score was
>>found things are different, since the score encodes the distance to mate. But
>>without that, Arasan doesn't know that a farther away gain of material is any
>>worse than a nearer gain.
>>
>>--Jon
>
>A "horizon effect" possibility would indicate this to be a bug unless you have
>some other way of dealing with them. Wouldn't such repetitions have the effect
>of diluting the strength of the engine by inflating the depth analyzed by 4 ply
>or more in many of the lines arasan analyzed? I would think such a thing would
>be worth avoiding.


4 plies into the tree 2-fold repetition should be scored the same as a 3-fold
repetition to avoid this.  This also points out that the program would have a
problem with repetition detection if it can only see a 2-fold repetition but not
the 3rd, letting it overlook a forced draw it might want to avoid or accept
depending on game circumstances...




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