What tool did you use to perform this analysis?
From: owner-jess-users
Sent: 05/04/2004 01:53 PM
To: [EMAIL PROTECTED]
Subject: Re: JESS: Cryptarithmic exercise
I think Mitch Christensen wrote:
> Hey,
>
> I'm reading "Expert Systems Principles and Programming" by Giarratano and
I
> decided to try using Jess to solve the cryptarithmic problem at the
bottom
> of page 39. I've got a rule that produces no valid solutions :(. I've
> spent several hours looking over the code can't see my fault. I was
> wondering if someone else might be interested in having a look.
>
Well, first of all, note that Jess comes with a solution to this exact
problem, although that solution takes a different approach than the
one you've taken here. This isn't wrong, though, and I'd think it'd be
possible to make it work.
A (The?) "right" answer is
G = 1
E = 9
R = 7
A = 4
L = 8
D = 5
O = 2
N = 6
B = 3
T = 0
So what I did was load up your facts and your rule, and use the "view"
command to visualize the network, and then double-clicked on the green
join nodes to see what was happening in each one. If you look at the
ones near the bottom, you'll see that the left memories don't contain
any facts for B=3; they allow other values of B, but not 3. So
something's wrong with the rule. If you open up each node one at a
time, you can see that it's the tests for G that eliminate the correct
values of B. That makes sense, as if you look lower down, G is getting
assigned the value 3. So it looks as though one of your assumptions
about G is wrong.
Looking at the rule, we see in the "G" pattern that ?Rn being used
before it's bound to a value. Jess' static analyzer is fairly weak,
and this kind of error is generally reported at runtime; in this case
it looks like Jess may be trying to do the right thing anyway, but
failing. These tests have to be moved down to the "R" pattern; this
may or may not be the only problem, but it's one problem, anyway. I'll
have to look at why you weren't getting an error message.
---------------------------------------------------------
Ernest Friedman-Hill
Science and Engineering PSEs Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://herzberg.ca.sandia.gov
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