Author: Stan Arts
Date: 07:11:11 06/13/05
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On June 13, 2005 at 09:37:46, Claude Le Page wrote:
>Some years ago , many considered that evaluation of a move has not the same
>value if the depth is even than same eval at odd depth
>Is it always true , or only to small depth , and what is the reason of this
>difference?
Hi,
Those scoreswings of even/odd depths often come from the horizon of quiet
("positional") search mostly. If you search to 8 ply, there will be captures
and some special moves beyond that, but mostly not positional moves. So for
instance, in the opening searching developing pieces end there. At 8 ply, the
opponent got to move last, (so maybe eval returns a small advantage for him, he
developed an extra piece) If you search to 9 ply, you got the last move in the
tree, and you could now develop a piece. (so eval might be even again.)
But it's hard to say where an evaluationvalue comes from when a program has
things like Q-search, extentions, reductions, and so on.
When there are some tactics, scores often stay the same for several iterations,
(because Q-search or extentions picked something up, and regular search has to
catch up.)
I can see these even/odd scoreswings especially in the opening, where the
scoreswing is often the value of a piece being developed. But when the game is
well underway it's hard to notice anymore (because of tactics) , but it does
also seem to happen a lot in quiet/blocked positions, because of the same
reason as in the opening.
Greetings
Stan
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