Author: Ed Schröder
Date: 09:12:42 05/31/00
Go up one level in this thread
On May 30, 2000 at 20:18:24, Robert Hyatt wrote:
>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?
"score with alpha" is a safe thing to do. "score with beta" is tricky tricky.
Using "score with beta" you have to exclude cases like "king in check" and
"opponent promotion" + a window of 9.00 and even then I get move and score
differences which smell badly. Not many but still.... All in all I don't like
the "score with beta" idea.
Ed
>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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