Computer Chess Club Archives




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

Author: Ed Schröder

Date: 06:28:53 04/29/04

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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.

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.

>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.

>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.

>My point is would you have become world champion in 1991 searching 3 ply?

8-10 plies was sufficient.

>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.

>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.

>Would you beat it with Rebel-Madrid?

Fritz3 was a weak program, in tactics and positional play. Fritz5 was a
revelation, excellent search for those days (the nullmove era starts here) still
Fritz5 was positional weak. Rebel at that time was typically out-searched by 2-3
average, it had to win its games by positional play. Then from Fritz6,7 and 8
Fritz slowly became an excellent positional player.

And regarding Rebel at 1991, don't get too exited, you can't imagine the number
of holes in its selective search at that time.

My best,


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