Author: Dieter Buerssner
Date: 04:24:36 09/20/00
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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
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