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Subject: Re: Root Move Ordering

Author: Miguel A. Ballicora

Date: 08:15:42 01/15/02

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On January 15, 2002 at 08:51:26, David Rasmussen wrote:

>On January 15, 2002 at 08:45:21, Severi Salminen wrote:
>
>>>Many people use node count (or time) to order root nodes, apart from always
>>>ordering the pv move of last ply first, of course. This seem to work ok. But as
>>>some people have suggested (Christophe, for one), this method isn't very much to
>>>the point and might have unwanted sideeffects.
>>
>>How is it "not to the point" and what side effects he means? For me it works.
>>
>>Severi
>
>It works for me too.
>
>The phrases "not to the point" and "side effects" are mine, not Christophe's.
>But he has expressed similar things.

It works for me and I do not care if it is indirect or whatever. Because
there is a real simple way to see it is working. Measure the tree size
and that's it. For me, it was significantly smaller than doing
the same ordering I do in the rest of the tree. It had another positive side
effect! Killers started to work! Killer did not work for me, it was a wash.
When I added the root ordering, Killers added a ~15% decrease in tree size (
as far as I remember).

Now the question is... is there a better way to do it? I am all ears :-)

>When I said "not to the point", I meant that 'nodes used' is not a very direct
>measure of the quality of a move, it's rather an indirect one. If I somehow
>could get the score of each root move after an iteration, I would certainly use
>that for ordering, but I can't since I use PVS.

I am not sure if I agree. I do not want ordering accoring to the score, what
I want is "what is the move that has more chances to beat the main move?"
Sometimes, it is not the second best move (according to the evaluation after
depth = X) but another move that is "promising" even though at depth X does not
have a high score but it has chances to have a high one at score X + 1. For
instance, attacking moves that fall just short.

Regards,
Miguel


>
>I can't name any tangible side effects, I said it "might" have side effects.
>
>/David



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