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Subject: Re: Nullmove: when to avoid it? Why not when depth=1?

Author: Ernst A. Heinz

Date: 20:07:49 03/02/01

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>>>Why does it make sense? I have not yet tried it but I don't understand why
>>>should it be better? Do you have any opinions? I allways want to understand the
>>>features I put into my engine and I don't get this one...
>>
>>Easy -- the relative cost of a depth-reduced null-move search
>>at frontier nodes (with a remaining depth of 1 ply) is just
>>too high. Most normal searches from there also go straight into
>>quiescence mode and the gain of null-move cutoffs does not seem
>>to outweigh the added null-move search effort.
>>
>>=Ernst=
>
>I tried this for a quick test.  It is actually slower overall than doing
>null-move everywhere.  A couple of positions were faster.  But more were
>slower.  I ran all the kopec positions...

As usual, your mileage may vary and it does not work for
all programs. Do you apply futility pruning at frontier nodes?

If not, this may explain your negative results because you are
much less selective at frontier nodes then which increases the
chances of the null-move overhead to pay off.

=Ernst=




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