Author: Carlos del Cacho
Date: 12:51:05 11/26/00
Go up one level in this thread
On November 26, 2000 at 14:40:16, Dieter Buerssner wrote:
>On November 26, 2000 at 13:03:49, Bruce Moreland wrote:
>
>>The quiescent search included at the end of this does null-moves implicitly. If
>>the score returned after a null-move is better than the score returned after any
>>capture, it will return the null-move score.
>
>...
>
>>int qsearch(int alpha, int beta)
>>{
>> int cur;
>>
>> cur = eval();
>> if (cur >= beta)
>> return beta;
>> if (cur > alpha)
>> alpha = cur;
>> while (captures()) {
>> make_next_capture();
>> cur = -qsearch(-beta, -alpha);
>> unmake_move();
>> if (cur >= beta)
>> return beta;
>> if (cur > alpha)
>> alpha = cur;
>> }
>> return alpha;
>>}
>
>I cannot see any null move here. What am I missing? The usual definition of
>null move is, that you pass the right to move to the opponent. For qsearch, this
>would mean, instead of me, let the opponent capture. If I am still better than
>beta, this is a fail high node. Otherwise, I try my captures in the ususual way.
Actually, if the null-move failed high it would also do it with the stand-pat
score... I think.
Carlos
>While I have not tried this idea, I would think, that it won't save anything in
>qsearch, to the contrary, probably more nodes will be searched on average.
>
>The qsearch routine above looks to me like a "standard" qsearch, that returns
>the stand-pat when >= beta without generating any moves.
>
>Let me add one thing to the good advice you gave in you other post.
>Skipping moves, that obviously cannot bring the score to alpha can have a few
>traps. I.e. say alpha is -0.5 and the stand-pat is -4.5 in KNPK. Capturing
>the last opponent pawn would not bring back the stand-pat to alpha, even not
>with a considerably large safety margin. Nevertheless, the score is 0.0 which is
>> alpha.
>
>-- Dieter
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