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Subject: Re: Cutting down my qsearch

Author: Ulrich Tuerke

Date: 06:45:45 04/23/01

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On April 23, 2001 at 09:34:20, Robert Hyatt wrote:

>On April 23, 2001 at 05:52:00, JW de Kort wrote:
>
>>Dear friends,
>>
>>I have added a qsearch to my program and as a result the number of nodes in my
>>search has exploded. Sometimes the program searches ten times as much nodes in
>>the qsearch than in the regular search. Can anybody give me some advice on
>>methodes i can use to limit the number of nodes in the qsearch?
>>
>>Thanks in advance.
>>
>>Jan Willem
>
>
>A simple idea works well:
>
>When you enter a q-search node, if the current score is (say) a queen below
>alpha, then capturing a pawn or piece is not going to bring the score back up
>to alpha.  Those captures are useless to examine..

I think that this is just what I had suggested in my reply, but you have
explained far better why this should work.

You say "useless to examine" . After all, this algo involves some kind of
forward pruning and there is a certain risk in missing some tactics.

However, I admit that this trick appears to be reasonably safe. I guess,
everybody is doing it.

Nevertheless I had observed that in some rare cases, a test position will be
solved later (i.e. in a higher iteration) as a consequence of this trick.

Do you agree ?

Uli




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