Author: Dieter Buerssner
Date: 04:24:36 09/20/00
Go up one level in this thread
On September 20, 2000 at 06:36:13, Mike Adams wrote:
> I'm having some trouble realizine the gain ive heard i should from nullmove
>in Pulsar on icc. So i wanted to show you the alorithm that i'm using. its not
>exactly the code my own code is unique to my program and might confuse but its
>essentially the code that i use.
>
>variables:
>endgames: is it endgame 1 or 0
>null: has there been a previous null call
I don't see that this is set or reset in the code snippet you posted.
Maybe this is your problem? Perhaps the easiest is to spend a new argument
to your search.
search(alpha, beta, depth, side, myenpassant, passhash, do_null)
When calling inside the null move snippet, call with 0 as the last argument,
otherwise with 1.
>side: side to move counts up from 1. odd for pulsar even for opponent
>depth: counts down always 0 on first call of qsearch
>beta: could be 10,000 or -10,000 if evaluate hasn't been called
>
>if(endgames==0 && null==1 && side>1 && beta!=10000 && beta!=-10000)
You certainly need to avoid the null move, when you're in check as well.
>{
> if(depth-2<=0)
> value=-qsearch(-beta, -alpha, 0, (side+1), myenpassant);
> else
>{ /* you can ignore the hash it just changes side to move and
> I only use hashing for move ordering anyway so shouldnt have big impact
>*/
> passhash=computecurrenthash(currenthash, 0, 0,0, 1);
> value=-search(-beta, -alpha, depth-2, (side+1), myenpassant, passhash);
You can savely use a search window of -beta, -beta+1 here, because you only
want to prove, that value >= beta. The depth-2 seems very calm. I think
most people use depth-3 or even greater reduction of depth.
Also, the myenpassant seems suspicious, but probably won't make a difference,
because the opponent certainly can not capture on that square.
>}
> if(value>=beta)
> return beta;
>
>}
One idea I use is, that (depending on depth) I search before the null_move
at even more reduced depth for the side to move. Only when this call fails
high, I try the null move. The cost of this is very little, but it will avoid
typical null move blunders (of course higher depth is needed to see the threat).
-- Dieter
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.