Author: Klaus Friedel
Date: 05:55:54 03/31/02
Go up one level in this thread
On March 31, 2002 at 06:29:43, Gian-Carlo Pascutto wrote:
>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).
>
>I tried this before, but no settings made my engine play stronger.
>
>The reason why this doesn't work very well is what I would call semi-zugzwangs.
>
>Say you have a program using piece-square tables, that does not consider
>attacked pieces in the evaluation.
>
>You have a knight on e5 that is attacked by a pawn. If you nullmove now,
>you are assuming that any move would be better than not moving. In reality,
>the best you can do is retreat the knight to f3 where it will get a smaller
>bonus from the piece-square tables. The NMO will fail, because not moving
>would have given you a higher score than moving.
I can't follow your example... If the knight doesn't move qsearch will get a
score far below the score you get by moving to f3. So not moving won't give a
higher score than moving.
Klaus
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