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

Author: Uri Blass

Date: 14:34:27 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

I simply use hash tables only for order of moves.
I believe that the potential gain from using the evaluation function to shape
the search tree is simply too big to miss it.

I do not believe that I am close to using the evaluation in the optimal way to
shape the search tree and I do not use part of your ideas(I do not evaluate
today attacking hung pieces or saving hung pieces and I believe that it is one
of the things that should help me if I get the energy to write the relevant
code).

Uri



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