Author: José Carlos
Date: 04:10:41 03/31/02
Go up one level in this thread
On March 31, 2002 at 06:17:15, Klaus Friedel wrote:
>Has anybody ever tried something like that in his null move code :
>
>
> int nullDepth = depth - (NULL_REDUCE + 1)*DEPTH_BASE;
>
> if(tryNull){
> executeNullMove();
> beta -= NULL_BONUS;
> value = - search(nullDepth, -beta, -beta+1, ply + 1);
> undoNullMove();
> if(value >= beta){
> beta += NULL_BONUS;
> ttStore();
> return beta;
> }
> beta += NULL_BONUS;
> }
>
>
>Bigger values of NULL_BONUS increase the count of nodes prunded (but you migth
>oversee some tactics). Values of about 30cp made my engine ply slightly better
>than the default null-move (NULL_BONUS = 0).
>
>
>Klaus
A couple of thoughts:
- You can be a bit faster declaring nullDepth inside the "if" and doing "beta
+= NULL_BONUS;" just once, before "if(value >= beta){"
- Most of the time you'll try null move in null window searches (Alpha,
Alpha+1) so with your idea of decreasing beta you're actually moving the
threashold for null move below alpha, which seems dangerous. I've never tried
it, so I can't say for sure it is bad, but failing high with a null move value
below alpha seems too risky.
José C.
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