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Subject: Re: NULL MOVE

Author: Don Dailey

Date: 12:37:58 02/24/99

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On February 24, 1999 at 01:16:56, Sylvain Lacombe wrote:

>I just finished implementing the null move. At first, i thought it wasn't saving
>much time. Then, i reallize that it does save alot, but only at deeper plys. On
>the first few plys, i think, it evens slow me down. Is that normal? Am i doing
>something wrong?
>I don't use the null move at the first ply, only at the second. It save about
>40% reaching deep 6. But it takes about 10% more for reaching deep 3 and 4.
>Hope, you can help.

This sounds to me as if you are doing something less than optimal
near end nodes.  The issue is what do you do when you only have
1 or 2 ply left to search anyway?  Do you go into quies or call
your main search again?  It's easy to get this wrong if you are
not careful.  "Wrong" doesn't mean a broken program, it means
something much less than optimal.

My program is a mixture of static rules and null move.  I do null
move when I have significant depth remaining, but when I am near
end nodes I do a simple static attack analysis.  This has proven
to be a significant improvement to my chess program.  It is faster
than null move and slightly riskier, but the net affect is
a stronger chess program (for me.)   Even though it's probably
riskier, it does pick up things null move will miss although the
converse is also true.

- Don

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