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Subject: Re: muliti probcut

Author: Vincent Diepeveen

Date: 04:54:24 07/05/01

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On July 05, 2001 at 04:58:45, martin fierz wrote:

>On July 05, 2001 at 03:36:39, Tony Werten wrote:
>
>>On July 04, 2001 at 07:01:55, martin fierz wrote:
>>
>>>On July 04, 2001 at 05:41:22, Dan Andersson wrote:
>>>
>>>>ProbCut and MultiProbCut:
>>>>http://www.neci.nec.com/homepages/mic/publications.html
>>>>AFAIK this is the canonical source.
>>>
>>>thanks! i had missed the multiprobcut paper there.
>>>
>>>has anyone ever tried this in chess?
>>
>>My guess, based on some talking with Ed en Richard, is that Rebel and Genius are
>>using it. ( As a replacement for nullmove, or rather nullmove has replaced
>>probcut )
>>
>>cheers,
>>
>>Tony
>
>you mean nullmove is better than probcut for chess? or is it 'unclear'? in
>checkers, probcut works fine.

Checkers is a game where there are no professional human players.
draughts is a similar game where the level of human players is way
higher, also it gets played way more as checkers.

draughts is also a tougher game, because you can capture backwards and
the board is bigger: 10x10 versus 8x8 for checkers.

Some other differences there are in rules.

The problem of nullmove in both checkers, draughts and all those
checker-games is that in general doing nothing is the *best*
thing to do, whereas in chess is usually is the *worst* thing
to do nothing.

So in short nullmove, despite that i used it for 1 year in
draughts, i soon found out that it was dubious to use.

Searching fullwidth is very boring way of searching. Even though
you search deep, there is this feeling that 99.9999% of everything
you search is completely nonsense.

Fullwidth has the bad habit to *never* prune stupid lines. All lines
get search to depth n and in case of captures you even extend those
idiotic lines even deeper.

Of course you have beta pruning, but still you search subtrees
to a certain depth.

What you want is to somehow smartly reduce that depth.

ProbCut is a good try in trying to achieve that.

Regrettably its only usage was in a game where the one eyed program
with probcut was king in the land of the blinds, as we use to say
in dutch.

>cheers
>  martin

Best regards,
Vincent



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