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Subject: Re: Researching after a fail-low

Author: J. Wesley Cleveland

Date: 10:53:16 08/18/00

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On August 18, 2000 at 09:23:38, Robert Hyatt wrote:

>On August 17, 2000 at 18:05:41, Gian-Carlo Pascutto wrote:
>
>>On August 17, 2000 at 14:43:08, J. Wesley Cleveland wrote:
>>
>>>When you have a fail-low in a deep search where the value drops significantly,
>>>finding an alternate move can take a very long time. This is largely because >the
>>>values in the hash table are largely useless, so in effect we are researching
>>>the entire tree. It seems to me one should use iterative deepening, and start
>>>from ply 1 again.
>>
>>This technique has been described by Schaeffer a long time ago...
>>
>>(Obvious question: Why is nearly no-one doing it?)
>>
>>--
>>GCP
>
>
>I'm not sure what you mean by described a long time ago.  But there is a big
>problem.  If you start over at 1 ply, you don't get the fail low score.  You
>find (again) the _wrong_ move, until you get deep enough.  When there is a big
>score swing between two iterations, you take your lumps.  There is no way to
>cheat alpha/beta there.

You should get the fail low score, since it is in the hash table. They should
stay there as they are analyzed to a greater depth than you are likely to get
to.



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