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Subject: Re: Move ordering at root

Author: Gerd Isenberg

Date: 14:05:18 04/06/04

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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.
>>>>>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
>>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

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 ;-(

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