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Subject: Re: Root Position

Author: Severi Salminen

Date: 05:28:07 01/05/01

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>What is the best way to sort moves at the root after each iteration?

I sort root moves so that PV comes first then other moves sorted by number of
nodes that were visited searching that particular move.

>What is the best way adjust alpha and beta at the root after each iteration?

First I do a 1 ply search. Then I do search with 1 pawn wide window. If I fail
high or low I do a research: score-1, INF (fail high) or -INF,score+1 (fail
low). The score is the score returned from the search that failed low or high in
the first place. Notice those +1 and -1. Without those you'll get fail lows and
highs again. I use fail soft and this means that you have to be sure what to
return from search, qsearch and evaluate. A wrong value returned from (say)
futility pruned node means problems. The point is that if you fail high or low
in the first search you have to be sure that the score returned is the other
bound of the true score.

>I notice I sometimes when I get a fail low at the root, I do a research, and
>then get a fail high! The most likely explanation is that I am a moron and it >is bug.

Well, we are all morons, so that can't be an explanation. But yes, it must be a
bug.

>Are there other issues that are important in the root position, or any "tricks"
>that one should know?

Don't know.

>Spank you.

Oooh yeah!

Severi



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