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Subject: Re: muliti probcut

Author: Tony Werten

Date: 01:09:33 07/06/01

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On July 05, 2001 at 08:30:20, martin fierz wrote:

>On July 05, 2001 at 07:47:43, Vincent Diepeveen 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?
>>>
>>>cheers
>>>  martin
>>
>>Yes it didn't work here. Apart from that it gametree technical
>>seen is dubious to do, it's reduction factor is too big.
>>
>>Both for my draughts program as well for my chessprogram it didn't work.
>>
>>Fullwidth search is way better for draughts. I get 40 to 60 ply
>>fullwidth in endgame anyway (and still it cannot win won endgames).
>>
>>Best regards,
>>Vincent
>
>hi vincent,
>
>what do you mean by "it's reduction factor is too big"? you can make probcut
>more or less aggressive by changing the probe depth and by changing the cutoff
>value. obviously some settings will make the program play much worse, while
>sensible settings make it play better. at least for my checkers program that is
>true - and it's not just a small improvement... (works for othello too, which is
>a much more complex game than checkers).
>i assumed that the problem of probcut with chess is that there is a king, which
>makes the game hard to predict. for instance, you can sacrifice a large amount
>of material for a mating attack, and the pruning algorithm isn't allowed to
>prune there, else you don't see it.
>in checkers, things are very different, because there is no king. it is usually
>very stupid to sacrifice material. therefore forward pruning gets good results.
>i'm surprised (and i can hardly believe!) that it doesnt work in 10x10 draughts!
>do you really use no pruning at all? can kings in draughts move like queens in
>chess or like kings?

Like queens.

Tony

>
>cheers
>  martin



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