Computer Chess Club Archives




Subject: The Limits of Positional Knowledge

Author: Michael Neish

Date: 00:37:10 11/11/99


I sent in a question to a while ago about how best to
improve a newly-written Chess program, either by sharpening up its search
routine or by programming a better positional sense.  In reply I was recommended
to study the available source code for ideas.

This has led me to another question.  Supposing you stubbornly insist on using
alpha-beta, and not add any of the sophisticated embellishments that everyone
talks about (killer move, null move, etc).  How far can you expect to go just on
programming positional sense alone?  I ask this because it seems to me (as
someone mentioned only last week on rgcc) that positional sense in a program is
to a large extent only window dressing, and that the strength in a program lies
mainly in its ability to search deep.  From my meagre experience as a Chess
programmer it seems to me that positional sense provides nothing more than
general pointers to the program to play sensibly.

To Dr. Hyatt, who was one of those who replied to me: have you ever tried
feeding nonsensical positional variables to Crafty to see how its play is
affected?  Okay, maybe nonsensical values will ruin the evaluation function
completely (like a value of 5,000 for putting the Queen on a1) but what about
different weighting values from the one you use in Crafty, but still sensible?
Won't the values that enable Crafty to search for the right move in one position
be useless (or detrimental) in other positions?  What difference can it make for
the Bishop to get a score of 32 instead of 30 for landing on e4?  Wouldn't
incurring a heavy penalty for moving, say, Pawn to h5 in a front of your castled
King prevent Crafty from playing h5 when it would be correct to do so?  You will
of course excuse me for not having studied every single line of Crafty's code.

Thanks for your time.


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