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Subject: Re: a question to Tord about detecting threats in null move

Author: Uri Blass

Date: 09:57:22 10/03/03

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On October 03, 2003 at 12:47:23, Uri Blass wrote:

>On October 03, 2003 at 12:13:13, Anthony Cozzie wrote:
>
>>On October 03, 2003 at 12:03:49, Uri Blass wrote:
>>
>>>
>>>I can detect every big threat by adding a special search after making null move.
>>>
>>>For example if I like to detect threats of at least 2.2 pawns I can do
>>>val=-alphabeta(depth-4,-beta+219,-beta+220,...)
>>>
>>>if (val<=beta-220)
>>>threatmove[ply-1]=1;
>>>//ply-1 because I still did not undo the null move.
>>
>>small error here: beta should be replaced by eval, or you will have massive
>>instability problems.
>
>If I am a queen down in the search and I threat to win a bishop then I do not
>consider it as a threat  because a threat is a threat relative to beta.
>
>I believe that Tord does the same(he replied that your example of threating the
>queen twice by sacrificing material is solved by extending only big threats so
>if you sacrifice a rook and a bishop the threat on the queen is not a big
>threat).
>
>I think that the idea that an extension should not be dependent on beta is a bad
>idea.
>It is better to have stronger engine with stability problems and not
>weaker engine without them.
>
>I prefer even not to care about using hash tables for pruning because my
>experience told me that I cannot get significant gain there easily(I have a lot
>of stuff that means that pruning or extension is not defined only by the
>position).
>
>Uri

I can add that I believe that there is also a lot to improve in movei without
using hash tables for pruning(otherwise I could prefer to try to use it for
pruning inspite of the problems).

Uri



Uri



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