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Subject: Re: "ALL node" definition

Author: Robert Hyatt

Date: 18:46:44 02/23/03

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On February 23, 2003 at 10:30:26, Tony Werten wrote:

>On February 21, 2003 at 23:48:52, Robert Hyatt wrote:
>
>>On February 21, 2003 at 13:26:34, Alvaro Jose Povoa Cardoso wrote:
>>
>>>Could someone please define what "ALL node" is and axplain how do we process
>>>these type of nodes?
>>>
>>>Best regards,
>>>Alvaro Cardoso
>>
>>If you look at a perfectly ordered alpha/beta tree, after you search the first
>>branch at a node to establish alpha, you search the rest of the branches, and
>>at each successor you search only one node (the refutation move).  But at the
>>next ply below that you have to search _all_ moves.  This alternates down
>>through the tree.  At "all" nodes, move ordering is totally irrelevant.  At
>>successors to all nodes, you get "cut" nodes where you only need to search one
>>move, if you can search a good move first...
>
>If you're sure the other moves don't give a cutoff, why bother searching them at
>all ?
>
>Tony


I am not sure, as I said.  92% of the time the _first_ move causes a cutoff
if one occurs.  That only leaves 8% for the rest.  What is the probability
that the good captures, the hash move, the killer moves and a few history
moves won't cause a cutoff but a move left over will?  Very low.  But _not_
zero.

However, this is what forward pruning ideas are based on, and several programs
are using the idea to good effect, at the risk of overlooking something that
is obscure.  I just haven't elected to take that "jump" yet, but it is on my
list of things to play with.





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