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Subject: Re: History based pruning question

Author: Uri Blass

Date: 13:58:21 08/26/05

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On August 26, 2005 at 14:54:32, Robert Hyatt wrote:

>On August 26, 2005 at 14:21:34, Alvaro Jose Povoa Cardoso wrote:
>
>>Hi,
>>some of you compare the number of times a move failed high to the number o times
>>the same move failed low in order to decide if a move can be reduced one ply.
>>I've tested this and also tested using the actual values of the history table
>>(using of course another history table for fail lows).
>>I couldn't reach a conclusion though.
>>What is your experience on this?
>>
>>best regards,
>>Alvaro
>
>
>My first thought is that the number of "fail lows" is irrelevant.  What you
>really want to avoid is a reduction on a move that might fail high.  Any move
>will fail low in some situations, but you want to handle the "typical" case
>correctly and not reduce if there is a reasonable chance the reduction will hide
>something.

I think that it is relevant.

If a move was never tried and never had an option to fail low then you do not
want to reduce it.

If you know that a move failed low many times but did not fail high then it
seems more safe to reduce it.

Uri



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