Author: Bruce Moreland
Date: 21:06:03 02/03/99
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On February 03, 1999 at 22:54:36, James Robertson wrote:
>Help!!
>I am trying to implement null move into my program. Unfortunately, I have spent
>a ton of time and gotton nowhere. I thought I had it when my program won it's
>first ever game against EXchess, but realized it was a fluke when it hung first
>a bishop and then a queen against Faile. Then I found a huge bug, and after
>fixing, the null move doesn't seem to be speeding up the search at all. Anyway,
>here is my AB code: what am I doing wrong?
It looks good except for some details that might just be features of this
minimal code. Sorry I can't be more helpful, but you didn't mess up, it looks
like.
You might have to watch out for strange en-passant behavior, you may have to
reset the en-passant square. You just generally have to be careful not to screw
up because you don't really do a "make_move" before you call the null move
search.
>int AB (int wtm, int alpha, int beta, int depth, int ply, int do_null) {
>
> if (do_null && NotInCheck()) {
> if (depth > 3) score = -AB(wtm^1, -beta, -beta+1, depth-3, ply+1, false);
> else score = -Quiesce(wtm^1, -beta, -alpha, ply+1);
> if (score >= beta) return beta;
> }
This looks perfect except you can window Quiesce the same way you windowed AB.
You are doing R=2, which is the right thing to do, IMHO.
bruce
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