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Subject: Root move ordering - an experiment

Author: Stuart Cracraft

Date: 20:45:54 09/27/04


I experimented with reordering root ply at iterative depth iply >  1
where 1 is the root ply, with the results of iply-1 sorted by the
total nodes of quiescence and main search defined as the # of entries
for each of those subroutines.

I didn't sort at root node on the first sort by quiescence but instead
by my normal scheme though I tried quiescence and it was worse. I felt
this gave a better chance to the above method.

I sorted moves at the root ply for iply > 1 in the following way
for 7 different parts to the experiment.

   sort by normal method (history heuristic, mvv/lva, see, etc.
   sort exactly by subtree node count, nothing else
   sort by subtree node count added to normal score (hh, mvv/lva, see, etc.)
   same as previous but node count x 10 before addition
   same as previous but node count x 100 before addition
   same as previous but node count x 1000 before addition
   same as previous but node count x 10000 before addition

The results, measured by # right on Win-at-Chess varied from
250 for the first in the list above to 234 for the last.
Most bunched up between 244-247 except the first was 250,
my current best on WAC with handtuning everything.

For me, I'm convinced that this style of sorting root ply is
slightly less good for my short searches compared to what I am using:
a combination of history, heuristic, see(), and centrality with
various bonuses, about a half page of code sprinkled about.

The advantage  of sorting root node by subtree is the simplicity.
It eliminates about a half a page of code and introduces
about a quarter page of code for only slightly lesser results
(within 1-2% of my current result) so that is good.

Still I think I'll leave it #ifdefed out for now and use it as
a baseline that is only improvable upon with handtuning of my
current methods and others to be discovered.

Stuart



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