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Subject: Re: Changing alpha / beta based upon hash?

Author: Steve Maughan

Date: 14:51:03 12/31/00

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Heiner,

>>As an example, suppose that initially Alpha = 1.00, Beta = 5.00 .  From the
>>hash we find a deeper search with a lower bound of 3.00.  It is possible that
>>had we not changed alpha and after the node has been searched the score for
>>this node would be +2.00 and it could have formed part of the PV.

The key here is that the hash info pertains to a _deeper_ search.

>I don't follow here:  you just stated that the TT says "this node's value
>(for this depth)

No not for this depth but for a deeper search.

>is 3.00 or even higher".  And we are trusting the statements
>from the TT, right?

At a depth greater than the current search depth the value is indeed +3.00 or
higher but at the current depth it could be below this value (e.g. +2.00) and
this could still justify being part of the PV.

>So, we expect a search here to not return anything below 3.00, especially not
>2.00 as value.

At a 'shallow' depth it could be +2.00

Regards,

Steve



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