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Subject: Re: Root move ordering - an experiment

Author: Robert Hyatt

Date: 11:05:13 09/28/04

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On September 28, 2004 at 13:50:34, J. Wesley Cleveland wrote:

>On September 28, 2004 at 10:45:07, Robert Hyatt wrote:
>
>>On September 28, 2004 at 05:17:26, Peter Fendrich wrote:
>>
>>>On September 27, 2004 at 23:45:54, Stuart Cracraft wrote:
>>>
>>>>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
>>>
>>>I've noticed that you often refer to WAC and also do very quick searches.
>>>If you get 247 in one test and 250 in another that doesn't mean a thing
>>>if you don't examine the positions that changed. Very often you will find that
>>>the difference is due to random coincidents.
>>>I'm sure that you could get such differences just by making some innocent change
>>>somewhere in the code...
>>
>>Correct.  Change the move ordering.  Change the hash table order of storing
>>things.  Occasionally change the best move or score as a result.
>>
>>1 sec WAC runs is not the way to test for performance, particularly when 1 sec
>>really means 1 sec +/- N where N is a non-trivial amount of quantization error
>>in timing...
>>
>
>Wouldn't the right way to test this be to search to a fixed depth and compare
>node counts ? You would expect to get the same results except for equal evals or
>nullmove hash table, or extension wierdness.


Yes.   Too many variables otherwise, including the fact that the operating
system can vary your 1 second interval a bit itself due to quantization errors
in the system clock...



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