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Subject: Re: Evaluation-based Reductions and/or Extensions

Author: Bob Durrett

Date: 17:54:36 12/28/03

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On December 28, 2003 at 13:32:05, Tom Likens wrote:

>Hello Everyone,
>
>I've been experimenting recently with using the evaluation function to shape
>the search tree.  Specifically, I've been using the static evaluation of
>the current position and the previous position to determine if a move should
>be extended or reduced.  I also have been making allowances for moves that
>increase or decrease the pressure against the king, attack hung pieces,
>save hung pieces etc.
>
>So far the results have been exciting, but also potentially frustrating.
>The main problem I've encountered is that any pruning or extensions based on
>the previous node's score cause hashing problems because this becomes path
>dependent. In a way, I suppose this isn't much different then making these
>type of decisions based on the value of alpha or beta as well, but these new
>effects have (at least for my program) seemed more detrimental.
>
>My (obvious) question, how do other programmers deal with this phenomenon?
>I suppose ignoring it is one option, but I'm hoping there is a better
>solution.
>
>regards,
>--tom

Your bulletin is exciting since it shows there is still room for innovation in
engine design.  As you and others here develop and implement this idea the
overall level of play of chess engines will go up simply because the
front-runners will be forced to adopt some of your new ideas.  I have often had
the suspicion that "current wisdom" regarding searching, pruning, and the like
is holding back the truly innovative people who might feel obligated to cling to
the old ideas.  I think the whole current theory about "extending and reducing"
needs to be re-thought, although I am definitely no authority on that subject.
The Earth is not flat after all!

Perhaps the next extension of your idea is to perform and utilize complete
dynamic position evaluations to refine the searching.

Congratulations to you and the others for corageously pursuing a new idea which
perhaps may go against "current wisdom."  It is only through original innovation
and invention that advances will be made.  Old ideas are not always the best
ideas.

Bob D.




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