Computer Chess Club Archives




Subject: Re: mate threat extension/null move

Author: Michael Henderson

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

Go up one level in this thread

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

>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

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

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.


This page took 0.03 seconds to execute

Last modified: Thu, 07 Jul 11 08:48:38 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.