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Subject: Re: Move ordering at root

Author: Robert Hyatt

Date: 18:06:14 04/06/04

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On April 06, 2004 at 20:32:59, Dann Corbit wrote:

>On April 06, 2004 at 17:05:18, Gerd Isenberg wrote:
>
>>On April 06, 2004 at 14:56:39, Robert Hyatt wrote:
>>
>>>On April 05, 2004 at 16:29:00, Gerd Isenberg wrote:
>>>
>>>>On April 05, 2004 at 15:51:43, Robert Hyatt wrote:
>>>>
>>>>>On April 05, 2004 at 15:02:56, Gerd Isenberg wrote:
>>>>>
>>>>>>On April 05, 2004 at 14:11:34, Robert Hyatt wrote:
>>>>>>
>>>>>>>On April 05, 2004 at 12:27:50, rasjid chan wrote:
>>>>>>>
>>>>>>>>On April 05, 2004 at 11:05:30, Robert Hyatt wrote:
>>>>>>>>
>>>>>>>>Thanks, but I don't need to test yet as you have tested !
>>>>>>>>
>>>>>>>>I think using nodes searched should be good.
>>>>>>>>If a move fails low with very few nodes searched, it probably
>>>>>>>>mean being rejected easily, so sort low.
>>>>>>>>
>>>>>>>>Rasjid
>>>>>>>
>>>>>>>Correct most of the time.  Sometimes a move will have a high node count just
>>>>>>>because there are lots of checks and extensions.  But I've been sorting by node
>>>>>>>counts for 15+ years with good results, of course forcing the PV move to always
>>>>>>>be at the top regardless of its node count...
>>>>>>>
>>>>>>
>>>>>>I use node count per root move too.
>>>>>>What about following "enhancement":
>>>>>>If PV changes, to store (some) "previous" PV moves and to use them early after
>>>>>>current PV move, regardless of their node counts?
>>>>>
>>>>>
>>>>>It is worth testing.  It didn't work for me in crafty or Cray Blitz, but it
>>>>>might work for another program.  I always had the best luck overall by just
>>>>>using pure node counts...
>>>>>
>>>>>It helps the most when there is a "best" move that you won't find until deeper
>>>>>depths.  It will percolate up the list, iteration by iteration, so that it is
>>>>>near the top on the iteration where it becomes best.  I also use this
>>>>>information in my parallel split/dont-split at the root adaptive algorithm in
>>>>>Crafty...
>>>>
>>>>
>>>>Yes, exactly my experience. Anyway i occasionally noticed a former PV move had
>>>>low node count (e.g. a forced draw line) but a new PV move suddenly fails below
>>>>draw score. Im such cases trying the "safe" drawline earlier may help to waste
>>>>some time.
>>>
>>>Those are the cases that blow my adaptive "split/don't-split at the root" SMP
>>>code.  A repetition will produce a very small tree.  If this is best, then most
>>>of the remaining root moves might produce larger node counts, which makes it
>>>look like they are all potential new best moves.  I catch this, but not very
>>>well...
>>
>>Another point i had problems with was during games, less node count due to
>>(exact) hash hits from the previous search two plies before. Then finding
>>something better which fails low next iteration - and the best move was searched
>>at the end ;-(
>
>Why not store the last node count in the hash table then?

Wastes memory. :)



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