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Subject: Re: search changes: really a question about programing, not rybka

Author: Dann Corbit

Date: 17:10:00 01/17/06

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On January 17, 2006 at 19:34:27, Joseph Ciarrochi wrote:

>The CEGT list suggests that just maybe Rybka has made a big performance increase
>(but we really don't know yet of course).
>
>Still, i was wondering.
>
>In terms of practical results, is it possible for changes in a search algorithim
>to only be observable at longer time controls. Or should you observe differences
>in both blitz and long time controls. I guess what i'm asking is, "what sort of
>change in a search algorithim would only become apparent at longer time
>controls."

Sure.

Consider sorting as a model.  For small data sets, the O(n^2) sorts like
insertion sort or shell sort are fastest.  So, if I have 20 things to sort,
insertion sort will beat introspective sort.

But if I have millions of things, then introspective sort is going to clobber
insertion sort because it is O(n*log(n)) and shell sort is O(n^2)

In a similar vein, suppose that I invent a search technique that has a branching
factor of 1.5.  Now, the problem with my search technique is that it takes 20
minutes to gather data.  So, if we are playing 40/2hrs, you are going to kill me
with your 2.0 branching factor program.  But if we are playing correspondence
chess, I will outsearch you by 40 plies and you won't have a chance (depending
on whether I am looking at the right nodes and throwing out the bad ones, of
course).

>Also, is it possible that some search features will work better in 64 bit
>compared to 32 bit machines and engines?

Why wait until the future?  Rybka 64 bit outperforms Rybka 32 bit by a large
margin, and (I am fairly sure) that it is exactly the same code.

Any 64 bit operations are going to benefit from 64 bit CPUs.



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