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

Author: Ernst A. Heinz

Date: 13:01:21 03/02/01

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Hi Severi,

>>>>I can save bunches of nodes by not nullmoving on the last ply before
>>>>qsearch. So if depthleft == 1 ply then not nullmoving reduces
>>>>for me the number of nodes considerably.
>>>Interesting idea, I'll give it a try in my engine.
>>Try it severi!
>>I have observed the same thing. I don't do nullmove
>>unless depth > 1. I think it makes sense.
>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.


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