Author: Robert Hyatt
Date: 17:18:24 05/30/00
Go up one level in this thread
On May 30, 2000 at 19:57:00, Tom Kerrigan wrote:
>Bob has suggested (in a thread below) that quiescence search nodes should
>account for 50% or less of the total nodes searched.
>
>Here's what my code looks like:
>
>int search(int alpha, int beta, int depth)
>{
> if (depth <= 0)
> return qsearch(...);
> ++nodes;
> ...
>}
>
>int qsearch(int alpha, int beta)
>{
> ++nodes;
> ...
>}
A couple of points need to be clearly defined, because this discussion always
gets way out of hand.
There are three kinds of nodes in the tree:
(1) interior nodes. These occur at any ply where depth is > 0. IE these are
standard interior nodes.
(2) quiescence-frontier nodes. These occur at any ply where depth == 0. IE
you _must search one of these for every node at the previous ply in the tree.
You have no choice aboug getting here, but you have a lot of choice in
(3) quiescence nodes. These are nodes produced by your making a decision to
search a capture after reaching (2) above. And these are the _only_ thing you
can control.
I don't count (2) above as a "quiescence node". There is no choice in searching
that node, any more than there is any choice in searching each interior tree
node.
What can you do to control (3)? Futility testing for one thing. If the current
score is so bad when compared to alpha, that the proposed capture doesn't have a
chance of lifting this score back over alpha, then this capture can be safely
ignored. Ditto if the current score is so far over beta, why try to improve
something that can not be improved?
If you count q-search nodes as above, (3) can be held to well below 50% of the
total nodes. Just don't factor in (2) since that can not be controlled at all.
>
>With this code, I find it hard to believe that anyone could get a percentage <
>50. Are people doing things differently than me? Is anyone getting more than
>50%?
>
>-Tom
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