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Subject: Re: when to store nullmove failure in hashtable?

Author: Steve Maughan

Date: 10:59:58 09/28/04

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Bob,

>What I do is this:  When I get a hash hit, and the draft is not enough to let
>me stop the search at that point, I then test the table draft against the
>depth I would use for a null move search at this point. If the table draft is >= that depth, and the table entry says "No way I would fail high here" then
>there is no point in trying a null-move search, if a normal move search would
>not fail high...

Interesting - I know that you alluded to this in the past but this is the first
time the penny has dropped for me as to exactly what you're doing.

So to use example numbers:

Alpha = 100
Beta = 101
Depth to Go = 5 ply

Hash Score = 50
Hash Bound = UPPER
Hash Draft = 4 ply

In this case you'd skip the null move - seems sensible.

Do you know how much is it worth in speedup?

Thanks for the explanation,

Steve



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