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Subject: Ply 1 scoring factors

Author: Will Singleton

Date: 15:30:08 12/07/98



I have an issue I've been thinking about for awhile, appreciate any
comment.

In order to play reasonable moves, I have special scoring functions that
apply only to the ply 1 move.  They include a queen-move when not
developed penalty, castling bonus, kside pawn move penalty,
development bonus, king move after castle penalty, and a couple more.
These scores are set at the time of the ply 1 move, and added to the
evaluation score for all ensuing ply.

Now I have a theory about this, which is that this is a bad thing.  I think it
can lead to inconsistencies in scoring, and also result in a bigger search
tree.  For example, the hash table will contain a certain score for a
position, which will differ from that same position reached thru
transposing the moves at ply 1 and 3.  While the stored hash move may
be good, the score is not good as a valid or as a limit score.

Another example: let's say I want to inhibit White from moving his
castled kside pawn at g2.  The ply 1 score penalty will handle this, but
ply 3 might like g4.  That will cause the ply1 move to be suspect,
because it relies on a bogus ply 3 move.

So I have convinced myself that this ply 1 scoring method is wrong, and
I want to replace it.  The possibilities are 1) use a piece-square table to
inhibit/promote moves, and 2) keep ply 1 out of the search.  Method 1
would seem to suffer from the familiar problem of getting the program to
understand that it must play a certain move (like castling) *now*, and
not put it off until ply 3.  Method 2 would involve scoring each ply 1
move, then doing the search starting from ply 2, and adding the ply 1
score to the score returned from the search.  That would seem to avoid
the hash-table problem, because the ply 1 scores would never be
stored.  But I don't know, seems like there are still problems with this.

Comments?

Will




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