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Subject: mate threat extension/null move

Author: Rick Bischoff

Date: 07:30:52 09/25/04


Hi,

I am confused about the mate threat extension.  I have the following code:

search ( depth, alpha, beta )

->check extension
->else pawn extension

->if depth <= 0 do the queiscent

->if checkReps return draw
->if insufficnetMaterial return draw

->Probe the hash table and return if good

->if not in check and depth>3 and last move was not null and material is ok:
->-> do null move
->-> x = -search(depth - 3, -beta, -beta +1 )
->-> undo null move
->-> if ( x >= beta ) return beta
->-> if ( x < (-MATE+MAXPLY) ) cout << "found mate"

->normal alpha/beta stuff

end search

"found mate" never gets printed out in WAC141 unless I change the null move to a
full width search... Why?  Well, I shouldn't say never, but I let it run to ply
9.



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