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Subject: Re: Proving something is better

Author: Omid David Tabibi

Date: 08:15:01 12/18/02

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On December 18, 2002 at 02:28:29, Tony Werten wrote:

>On December 17, 2002 at 17:30:36, Bruce Moreland wrote:
>
>>Omid wrote an article that's in the ICGA that I received today, and there are
>>two tables:
>>
>>D        R=1               R=2            R=3           VR=3
>>9     1,652,668,804    603,549,661   267,208,422    449,744,588
>>10   11,040,766,367  1,892,829,685   862,153,828  1,449,589,289
>>
>>D        R=1               R=2            R=3           VR=3
>>9        64                62             53            60
>>10       71                66             65            71
>>
>>The first table is nodes taken to search to depth D with four techniques, which
>>are standard null-move with various R values, and a "verified" null move search
>>with R=3.
>>
>>The second table is the number of problem solutions in a test suite, given
>>particular depths of search and using these techniques.
>>
>>The conclusion is that VR=3 is better.
>>
>>Does anyone else see the two problems here?
>
>Yes, but 2 different ones then yours :)
>
>1)R2-3 is expected to search a number of nodes between r=2 and r=3, just as v3.
>Yet R2-3 is not in the table.
>
>2) Time to solution is missing (maybe the same as your point 2). I think that
>that table would be a good addition. Number of solutions at depth x would make
>the algoritm "extend every move at the root with 3 ply" look very good.
>
>I don't understand why time to solution is not used. The only argument I saw was
>"it's too hardware dependend". But I don't think that a good argument since a a
>percentile speedup ( ie 10% faster ) will still be the same no matter how much
>faster the hardware is.
>
>Furthermore, time to solution is the only thing I care about. My program has to
>produce a good move within a certain time, not within a certain amount of nodes
>or depth.
>

Of course. If you try to implement it on  XiniX, or GCP on Sjeng, or Uri on
Movei, then you certainly care about fixed time. But if I want to present the
data in a generic manner, I have to persent them in the most hardware/software
independant way I can.

I further don't understand why all the fire is directed at me; fixed depth
comparisons are the common accepted comparison methods, which are completely
hardware independant.

For the most recent examples take a look at Heinz and Plaat's numerous articles,
all of which were conducted in fixed depth.

Omid.


>Tony
>
>>
>>1) The amount of time taken to process a leaf node may very well be less than
>>the amount of time taken to process an interior node (not including its
>>children, of course).  So if the tree shape changes, it is possible that it
>>could take longer to search a smaller tree.  Unless that is ruled out, all that
>>has been proven is that VR=3 works in fewer nodes.  That is pretty interesting,
>>but I think it makes a stronger case if *time* is used as well, so we will know
>>that there is at least one real case where this technique makes the program
>>faster.
>>
>>2) The amount of nodes traversed to get through ply 10, with R=3, is about 60%
>>of the number taken to get through ply 10 with VR=3.  It can be assumed (perhaps
>>wrongly, due to my previous point) that this search takes 60% as long.  The
>>number of solutions found by R=3 is fewer than with VR=3, granted.  But what is
>>the R=3 version doing while the other version is trying to finish up ply 10?  It
>>is going on to ply 11.  How many solutions has it found in ply 11 before VR=3
>>has finished ply 10?  In this case, 65 is sufficiently less than 71 that the
>>answer is probably less then 71.  But maybe not!
>>
>>It seems likely that VR=3 is tactically faster than R=3, but I cannot know for
>>sure, since the results have not been reported!  We do not know if VR=3 is
>>tactically *faster* than R=3.  Isn't that an important point, since all of us
>>who read this article are wondering if we can stick this in our own programs and
>>obtain benefit?
>>
>>I have seen people report results like this forever.  I wish that they would use
>>a the more sensible method of reporting number of solutions found correct in a
>>certain amount of *time*, since that is the true measure of tactical speed.
>>
>>Nothing personal, Omid.
>>
>>I'm trying to verify your results by using ECM with Gerbil.  First I have to get
>>good numbers for R=2 and R=3.
>>
>>By the way, if anyone wants to take Gerbil and use it as a second example when
>>writing articles like this, I'm all for it.  It's simple so it should be pretty
>>easy to modify.
>>
>>bruce



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