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Subject: Re: more info

Author: John Coffey

Date: 17:23:09 09/27/98

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On September 27, 1998 at 19:49:42, Serge Desmarais wrote:

So is it not the
>pruning of the lines that allow the program to reach a depth of 11 plies (if not
>even more)?
>
>Serge Desmarais


Based upon my limited understanding, Null move pruning is cheap way to get
a huge savings because if your opponent can't improve his position by
making two moves in a row, then you can eliminate the whole branch of the
tree.  This might lead to some inaccuracies, and Hyatt did say it is
potentially dangerous, but the benefits seems to outweigh the risk by far.

It is my understanding that a null move search allows the opponent to make
2 moves in a row, and is done to depth -1, so the search takes about 25
times less than what the search would have taken otherwise.  So if the
null move search fails, we have only added about 4% to our computation time.
But if on the other hand the null move search succeeds, then we save 96% of
the time on that particular branch of the tree.

I hope that I got the facts right.  If not, I hope somebody sets me straight.
:-)

John Coffey



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