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

Author: Severi Salminen

Date: 13:35:43 03/02/01

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>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.

Yes, this seems to be the case - has this been tested in even higher remaining
depths (2,3...)?. Maybe in some situations your could turn null moves off at
pre-frontier nodes also? After all, this would lead straight to qsearch? Maybe
limiting null moves to levels where remaining depth after the depth reduction is
at least 1 to allow any kind of move for opponent. I'll have to test this.

I tested the version that disables when d==1 and got 0-10% reduction in the node
count (only in a couple of positions...) so this seems to be a very good idea.

Severi




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