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Subject: Re: Fruit 2.2's strength

Author: Lance Perkins

Date: 19:00:27 10/25/05

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On October 25, 2005 at 14:56:43, Will Singleton wrote:

>On October 25, 2005 at 12:56:43, Dann Corbit wrote:
>
>>On October 25, 2005 at 12:28:07, Lar Mader wrote:
>>
>>>I realize that this is a difficult question...
>>>
>>>I'm curious about what makes Fruit 2.2 so strong.  Also, it is impressive how
>>>quickly Fabien achieved this strength.  Fritz 9 and Shredder 9 seem to be close
>>>to Fruit 2.2 in strength, and yet they have been in development for a much
>>>longer time with a lot more resources.  Has anyone spent any time examining the
>>>2.1 source code, or have any other insights into what this program does that
>>>makes it so effective?
>>
>>Fabien does everything well.  He is a magnificent and careful programmer.  He
>>obviously puts a lot of effort into making things correct.  He has a lot of
>>insight to pick out what is important and concentrate on that.
>>
>>His search is excellent and innovative.  He does some things that nobody else
>>does.  I'm not really sure how he is able to not hash the PV and still have a
>>stupendously fast search, but that is pretty amazing.
>>
><snip>
>
>I haven't looked at Fruit's code, but I'm interested in your pv comment.  What
>is the difference between storing the pv to hash, and simply playing the pv out
>of an array?
>
>Will

Using pv arrays:
- requires computing cycle to maintain the pv array
- guarantees that the moves in the pv are always valid

Relying on hash alone:
- requires computing cycle to validate the pv moves (since hash collision can
overwrite a pv move)



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