Computer Chess Club Archives




Subject: Re: Null-Move: Difference between R = 2 and R = 3 in action

Author: Sune Fischer

Date: 00:16:40 07/21/02

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On July 20, 2002 at 22:22:22, Robert Hyatt wrote:

>On July 20, 2002 at 08:13:44, Gian-Carlo Pascutto wrote:
>>On July 20, 2002 at 08:04:01, Sune Fischer wrote:
>>>I think it matters "a factor of 2".
>>>1) it helps you to prune
>>>2) you get better evaluation in the upper plies when you can return a score
>>>based on a deeper search.
>>>number one will show itself directly because you iterate deeper, the second one
>>>you don't "see", but it does improve depth along some branches in the same way.
>>1) I get +- 10% hash hits (and less prunes) in typical middlegame. Not enough to
>>matter a factor of two (but I didnt check this so not 100% sure).
>>2) Uh?
>Run your program with a tiny hash and a deep search.  Then a big hash and
>a deep search.  In middlegame positions this will be at least a factor of
>2x.  Measure time to depth.  Small hash might take 4 minutes to get to depth
>12, then big hash will take around 2 minutes...

You shouldn't measure time to ply, that would not give you the full benefit of
the hash. You should use time to find the right move.

I have never seen the hash bring only a factor of 2, even in middlegame.
Last I tested I saw a mate in 5 being solved in 1/4 of the nodes with the hash.
Some things are also spotted a ply sooner because of the hash, so time to ply
wouldn't be the right way to estimate the value of the hash.


>I posted a bunch of this kind of analysis a few years ago when prompted by
>Komputer Korner (Alan Tomalty).

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