Computer Chess Club Archives




Subject: Proving something is better

Author: Bruce Moreland

Date: 14:30:36 12/17/02

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

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.


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