Computer Chess Club Archives




Subject: Re: When to do a null move search - an experiment

Author: Uri Blass

Date: 05:02:57 04/30/04

Go up one level in this thread

On April 30, 2004 at 07:49:10, Vincent Diepeveen wrote:

>On April 29, 2004 at 09:28:53, Ed Schröder wrote:
>>On April 29, 2004 at 07:37:23, Vincent Diepeveen wrote:
>>[ snips ]
>>>>This is all very poor Vince, I assume you don't play much with nowadays top
>>>>programs. From 1982 to 2001 Rebel won its games by positional understanding and
>>>>not by search and Rebel lost its games because it was outsearched. Today Rebel
>>>>isn't outsearched at all, it now loses its games because the current top
>>>>programs have a better positional understanding than Rebel.
>>>>You should have a good look at the current tops, the positional progress has
>>>>been great the last years. To me it all seems to indicate (provided your search
>>>>is okay) the only way to make progress is to improve on chess knowledge. But
>>>>what's new, I already came to that conclusion in 1986 after some intensive talks
>>>>with Hans Berliner.
>>>What i mean is Ed, is that you would not have accomplished the great results
>>>with Rebel which you managed, had you just searched with a fullwidth search +
>>>bunch of checks in qsearch.
>>No of course not, brute force is silly, Rebel since day 1 has been a selective
>>program. But I am getting your point, in the days before the nullmove was
>>discovered Genius and Rebel had the best (static) selective search, a dominant
>>factor in their successes, is that what you meant to say? If so, it is true.
>That's what i mean, using a simple form of search in those days meant fullwidth.
>>If only Frans had kept his mouth shut to Chrilly (Chrilly leaking nullmove in
>>the ICCA journal) it is very likely Fritz would been the next Richard Lang still
>>dominating all the rating lists and WCC's for the last decade. But Frans didn't
>>and then all bets were off.
>Frans' world title in 1995 had a huge positive impact.
>>>I am under the impression that you just like diep try checks at several depths
>>>in the qsearch. In diep i can try at the entire 32 ply of the qsearch checks.
>>Checks in QS are relative cheap nevertheless I have limited them more and more
>>the last years. There is little sense doing long range QS checks if you already
>>hit 12-14 plies.
>I see that different, but i must add the note that Rebel is basically tactical
>selective in main search already and DIEP isn't. I do very little extensions in
>diep other than singular. Even check hardly gets extended, i'll extend it when
>it's singular.
>>>Doing things like attacks in eval and mobility and scans for all kind of things
>>>which are trivial for chessplayers and i do not even dare to write down the name
>>>for here, they slow down once engine.
>>>I would search 3 ply at 1991 hardware with it, simply because the code size is
>>>so huge, the nps at 1991 machine (i had a 10Mhz XT at the time) would be around
>>>a 100 nodes a second or so.
>>You are overreacting of course.
>Well of course when programming for a 10Mhz machine i would add huge selectivity
>too, but i'm just talking about a theoretical math here now.
>My code size doesn't even fit within the ROMs you had in 1991 :)
>>>My point is would you have become world champion in 1991 searching 3 ply?
>>8-10 plies was sufficient.
>8-10 plies at 10Mhz with for its time a great eval is really a grandmaster piece
>of work. I actually was not so long ago at a friend of mine (IM) having a
>chessmachine with inside an Ed Schroeder program. I really was amazed that you
>got such a depth out of such a tiny hardware!
>In fact it completely outsearches diep 1997 which got 8 ply at the world champs
>1997 at a PII300Mhz.
>>>I very deliberately ask it this way, because fritz3 (1995) searching at todays
>>>hardware handsdown would search 20 ply in any middlegame, when it would be
>>>converted. Apart from that it single cpu would search 3.5 million nodes a second
>>>hands down.
>>20 plies?
>>Come on.
>No kidding.
>Huber clearly has proven that with MTD and a simple eval (basically material)
>you can search depths of 30+ ply.
>The passive way in which fritz3 developed its pieces is very helpful. You get
>*everywhere* nullmove cutoffs.
>With an agressive tuned engine such a thing is of course a lot more difficult to
>do, if not nearly impossible at todays hardware.
>>>Todays fritz searched in 2003 world champs at a quad xeon 2.8Ghz about 13-15
>>>The 2003 fritz at a 386 , 10Mhz would have a problem getting beyond 4 ply.
>>I don't believe that.
>In 1999 fritz searched 17 ply everywhere at a quad xeon 500Mhz in middlegame.
>In 2003 fritz at a quad xeon 2.8Ghz searched 14 ply in middlegame.
>Those 14 ply from fritz2003 however completely destroy that 17 ply from
>I know why this happens. I see it at many engines including DIEP.

I can only say that number of plies is meaningless.
It even does not mean that it is better in tactics.

I can search more than 100 plies forward if I do enough reductions and every
move is reduced by at least 10 plies.

I do not understand why do people discuss about it.


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