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Subject: Re: One stupid(?) null-move question

Author: Bernhard Bauer

Date: 20:19:21 08/12/98

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On August 12, 1998 at 05:52:50, Robert Hyatt wrote:

>On August 11, 1998 at 23:13:03, Bernhard Bauer wrote:
>
>>
>>I suppose you have used your latest version of crafty and it is really good
>>news. It sounds that you have overcome that nasty null move problem.
>>Congratulations!
>>
>
>no... my point was that any 15.x should repeat this.  The only changes in 15.18
>are evaluation changes.  The search is identical to the past few versions.  No
>changes for null-move, no changes in ordering or extensions, nothing.  The only
>pieces of code that are different are evaluation-related...

I disagree.
To my knowledge *no* version of crafty up til now was able to solve this
position. Definitely not v. 15.15 anv not 15.17 as I showed you. On the other
hand seting DO_NULL=0 and NO_NULL=1 solves this position in about 2 min.
So it is not completely unreasonable to think its a null move problem.

>If older versions couldn't find this, it is either (a) hashing (b) evaluation
>bugs or (c) something else...  null-move does effect the search in odd ways,
>but I don't see how it is a problem here as this isn't really about zug as much
>as it is about sufficient depth with extensions...
>
I have noticed that changing the hash size may change the results sometimes
in a random manner and it looks to me that there are still several bugs in
crafty. Of course you may be right that it is not a null move problem but I
think the position is a zug position.

>15.18 will be out soon, once I am sure the evaluation is back under control and
>it is playing reasonably again.  So far, so good, but I'm looking carefully...
>
Good luck and keep on the good work

Kind regards

Bernhard




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