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Subject: Re: Fail soft alpha-beta

Author: Russell Reagan

Date: 20:21:53 09/08/03

Go up one level in this thread


On September 08, 2003 at 20:30:33, Dieter Buerssner wrote:

>On September 08, 2003 at 06:51:55, scott farrell wrote:
>
>>It [fail soft alpha-beta] really only helps with the hashtable with regards to >transpositions.
>
>It can also help in the case of a fail high in zero window search, when the
>original window is not a zero window. With fail hard, you will always get back
>alpha+1, and you will need to research. With fail soft, you can get back a value
>>= (original - not zero window) beta, and in that case, you can save the
>research.
>
>It can also help aspiration search. In fail hard with a fail high, you will
>always get back beta. For an engine, that gradually adjustes beta (say oldbeta +
>1 pawn first), it may save one (or more) adjustment cycle(s). Fail soft might
>return beta+5 pawns, making the gradual adjustment to oldbeta+1 futile.


These all sound like good reasons to use fail soft. What are the drawbacks to
fail soft, and the reasons to use fail hard?



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