Computer Chess Club Archives


Search

Terms

Messages

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

Author: Robert Hyatt

Date: 20:16:28 12/31/00

Go up one level in this thread


On December 31, 2000 at 17:51:03, Steve Maughan wrote:

>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.

That is one of the reasons we can solve fine #70 so quickly... we graft
deeper searches onto shallower searches.  The deeper search is more
accurate, of course...



>
>>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



This page took 0 seconds to execute

Last modified: Thu, 15 Apr 21 08:11:13 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.