Computer Chess Club Archives




Subject: Evaluation-based Reductions and/or Extensions

Author: Tom Likens

Date: 10:32:05 12/28/03

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


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