Computer Chess Club Archives




Subject: Question for Hyatt about Alpha/Beta

Author: Bob Durrett

Date: 09:22:44 02/05/04

Bob Hyatt:

I was going through the older CCC bulletins to make sure I didn't miss anything
important and noticed the thread begun by Russell,  After checking Russell's
reference, I saw something you wrote cited below.  This made me really curious
about how the alpha/beta algorithm might be impacted by improvements in the
position evaluation code.  It seems to me, intuitively, that accurate assessment
of positional [and other non-material] factors in a position, along with the
correct assessment of material factors, would give
values which would change the interpretations of failing alpha or beta tests.
It seems that this would significantly alter the way searching would proceed.

If this is unclear, I can try to be more detailed if you wish.  [I never claimed
to be a Pulitzer Prize winning author.]

Bob D.

Referenced by:

> An alpha cutoff is what happens when you search the second move,
>> and you prove that if you play that move, your opponent has a move
>> he can play that will produce a score less than your "lower bound"
>> you established for the first move.  There is no need to search
>> further.
>> For example, after that +1 on the first move, you try the second
>> move and after trying the first move the opponent has in reply to
>> that move, you discover you _lose_ a pawn.  The score is -1.0...
>> There is no need to search other opponent moves to produce a
>> score even lower than -1.00, because you already know this move
>> is at _least_ -1.00 and possibly worse, while the first move is
>> +1.00.  You stop searching this move and move on to your third
>> choice...

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