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Subject: Re: "ALL node" definition

Author: Tony Werten

Date: 23:45:08 02/23/03

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On February 23, 2003 at 21:46:44, Robert Hyatt wrote:

>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.

You should I think. That 92% seems quite high. I'm happy with the
branchingfactor of my program, but I come nowhere near 92%. If I would I would
certainly try to "report fail low" after trying hashmove, captures, killers, 4
history, all checks and say 2 highest positional moves.

Or the opposite. Report fail low at a cut node if the previous ones didn't give
a cutoff. Might be safer because you'll end up researching the node (and if
beta-alfa!=1 you won't skip)

Tony




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