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Subject: Alternatives to Using Position Eval FUNCTIONS?

Author: Bob Durrett

Date: 06:49:55 11/27/02



Disclaimer:  I do not know the specifics of how position evaluation is
accomplished in the top chess engines.


From what I have read here, position evaluation is typically accomplished with a
"function."  This function appears to be fairly simple.  Otherwise it would be
called a position evaluation "subprogram."  Since a large number of positions
are evaluated, the evaluation must be very quick and hence simple.

Less processor time is available for searching if the amount of processor time
used for position evaluation is increased.  In an extreme example, one might
devote 90% of the processor time to position evaluation.  I do not know what
this percentage is in practice. If a huge number of positions are evaluated,
then the total amount of processor time devoted to evaluation might be large.

It seems that there is a tradeoff between complexity of position evaluation and
the number of positions evaluated. My impression is that current engines devote
only a very small percentage of the processor time to evaluation of any given
position.

Devoting a large amount of processor time to position evaluation of each
individual position would make sense, or so it seems, only if the evaluation
were very very good.  Essentially, this would mean evaluating only a relatively
few positions but evaluating them extremely well, using a complex position
evaluation subprogram.

In theory, a perfect evaluation subprogram would have to evaluate only one
position for each move made.  Maybe someone would say that chess engines do just
that.  They "evaluate" the position after the move was made.  They just do it
using search algorithms.


So, this leads to the following question:

Has anybody yet explored the option of using complex evaluation subprograms
[which do not rely primarily on the use of search algorithms] for position
evaluation?

Bob D.



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