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Subject: Re: Proving something is better

Author: Robert Hyatt

Date: 10:10:09 12/18/02

Go up one level in this thread


On December 17, 2002 at 18:11:20, Vincent Diepeveen wrote:

>On December 17, 2002 at 17:30:36, Bruce Moreland wrote:
>
>if you go back in time a bit you see that i had
>major problems with Omids article and posted it here.
>
>there is more than just the problems you see there.
>
>also look at his homepage and get the positions he tested
>and then look to his node counts. for a mate in 2 position
>where i need like a couple of hundreds of nodes to get to 10 ply
>he needs 10 million nodes. then R=3 reduces that more.
>
>also his implementation is buggy of course. it doesn't take into
>account problems with transpositions. a classical beginners problem.
>
>But most important is that verification search is not something new
>it is a buggy implementation of something already described years ago
>with only 'novelty' that omid turns off nullmove *completely*
>after he finds a nullmove failure.
>
>All with all a very sad article. The only good thing about it is
>the quantity of tests done.
>
>The test methods and the implementation and the conclusions are
>grammar school level.
>
>I do not know who proofread it, but it gotta be idiots or people who
>didn't care at all.
>
>Amazingly Bob defended Omid here and said nothing was wrong with
>the article.

No, Bob didn't say that.  Bob said that _both_ methods of measuring improvement
have merits and that both would have been better than just time to raw depth.
Time by itself is also misleading.

It would not be hard to search the PV quickly and then bog down on refuting
the rest of the moves, which would allow time-only to produce a false
impression.

>
>>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?
>>
>>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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