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Subject: Re: NullMove efficiency

Author: Tord Romstad

Date: 00:44:15 12/06/03

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On December 05, 2003 at 18:49:37, Matthew McKnight wrote:

>On December 05, 2003 at 18:31:34, Matthias Gemuh wrote:
>
>>
>>
>>
>>The ratio nullmove_cutoffs / main_search_moves_searched is only 15%...20%
>>in my program. Is this extremely low ?

I am not quite sure I understand what you are measuring here.  Is
main_search_moves_searched
the total number of non-qsearch nodes, or something different?

>180 kN/s is not bad if you are doing a lot of work in eval, or other things that
>slow you down, as long as you are compensated.  With BigLion's performance, I'd
>say you are succeeding here.

Agreed on both counts.  180 kN/s is fine.  Gothmog is not much faster (at least
not in the
middle game, but it speeds up more in the endgame than your engines), and I
expect the
new engine I am writing to be even slower when it is finished.  The main
weakness of
BigLion and Taktix seems to be their search.  With your big and high-quality
eval, you
should be able to search about 2 plies deeper in the middle game by using the
eval to
do forward pruning and/or depth reductions.

One thing I have noticed is that your engines' behaviour in the first few
iterations is rather
unusual.  In almost all other engines, the first 4 or 5 plies flies by so
quickly that it is not
possible to follow the lines on the computer screen.  In BigLion and Taktix,
each of the first
5 plies take about a quarter of a second to complete.  This is strange in two
different ways:
It is strange that a 1-ply search should take as much as a quarter of a second,
and it is
strange that the amount of time needed is apparently almost linear (rather than
exponential)
as a function of the search depth.  For bigger search depths, things begin to
look more
normal.  What's happening in the first few iterations of your search?

Tord



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