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Subject: Re: mate threat extension/null move

Author: Michael Henderson

Date: 13:10:30 09/25/04

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On September 25, 2004 at 10:30:52, Rick Bischoff wrote:

>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.

some questions:
fail soft or fail hard alpha beta?
How do you detect mates in the search? -- king capturing or static IsMate()
function?

If your depth is >= 4 only then you do null move, that might be too high up in
the tree for mate threats--I think your mate threats are going to your main
alpha beta stuff.  Try doing null move regardless of depth and see what result
you get.

Michael



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