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Subject: Re: Alpha/Beta adjustments via the hashtable or why Fritz 7 has messy PV's

Author: Matthias Gemuh

Date: 02:49:27 12/03/01

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You say :

"Basically, if during the search you get a hashtable hit which
tells you that this position is 0.5 pawns 'or more' advantage, you
raise your alpha (alpha is the value that says: a move must be
_better_ than this to become the new mainvariation) to 0.5 and prune
away everything that is less.

This is, AFAIK, theoretically sound. The only problem is that if
the value of this branch was _exactly_ 0.5, you will also have pruned
away your mainvariation."


Why then adjust by 0.5? Why not 0.49? Does that still prune away the PV?



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