JESS: definstances & undefinstances -- Rete Exception

[Larner, Dan <[EMAIL PROTECTED]>]

I'm not sure whether I've hit a bug, misunderstand what I'm
doing (it's happened before!-), or misunderstand what's
legal to do in Jess 5.0a2. (I'm using MS Visual J++ 6).

Basically I'm trying to have a running rete (actually calling
(run 1) repeatedly from Java), and be able to add and remove
java objects (definstances) from it.

To experiment with this, I modified the pumps example, 
MainInJava.java file as shown at the end of this message.
[and to speed things up, I changed 
 line 72 in Tank.java to addWater(-20);  
 and 
 line 36 in pumps-fromjava.clp to  (set ?pump flow (+ ?flow-rate 1))
]

I run for a while with the main tank and pump.  Then, after 
a bit, I add another tank and pump using definstance.

Sometimes, but not always, after I do these additions, 
I'll get an exception (see below) while calling rete.executeCommand("(run
1)");

Rete Exception in routine NodeNot2::RunTestsVaryLeft while executing rule
LHS: 
[NodeNot2 ntests=1 [Test2:
test=EQ;tokenIdx=0;leftIdx=2;leftSubIdx=-1;rightIdx=2;rightSubIdx=1] 
;usecount = 1] while executing defrule raise-rate-if-low.
  Message: Corrupted Negcnt (< 0)  at line 0:  ( run 1 ) .
  
After a bit more, I remove the main tank and pump from rete using 
undefinstance [ It's interesting to note that the tank and pump 
removePropertyChangeListener don't get called during this -- shouldn't
these get called?]

After the undefinstance sometimes, but not always, I'll get (the same)
exception on 
the next call to rete.executeCommand("(run 1)"); 

Rete Exception in routine NodeNot2::RunTestsVaryLeft while executing rule
LHS: 
[NodeNot2 ntests=1 [Test2:
test=EQ;tokenIdx=0;leftIdx=2;leftSubIdx=-1;rightIdx=2;rightSubIdx=1] 
;usecount = 1] while executing defrule raise-rate-if-low.
  Message: Corrupted Negcnt (< 0)  at line 0:  ( run 1 ) .


Sometimes I'll actually run to completion.  Now I'm sure the 'sometimes'
parts are due
to thread timing.  I was thinking that my running the rete by 
repeated calls to (run 1) would be safe.  My best guess (without really
diving into the Jess code) is that this is possibly wrapped up in rule 
agendas/activations.  

Any thoughts?


-- Dan


public class MainInJava
{
        public static void main(String[] argv) throws ReteException
        { 
                Rete rete;
                Tank t, t2 = null;
                Pump p, p2 = null;
                Funcall f;
                int i_count = 0;
                Value pv;
                
                try {
                        rete = new Rete();
                        rete.addUserpackage(new MiscFunctions());
                        rete.addUserpackage(new
jess.reflect.ReflectFunctions());

                        // Read in the rules
                        rete.executeCommand("(batch
/larner/jesspumps/pumps-fromjava.clp)");
                        rete.executeCommand("(reset)");
                        // Create the Beans
                        t = new Tank("MAIN");
                        p = new Pump("MAIN", t);
                        
                        // Tell Jess about them
                        f = new Funcall("definstance", rete);               
                        f.add(new Value("pump", RU.ATOM));
                        f.add(new Value(p, RU.EXTERNAL_ADDRESS));
                        pv = f.simpleExecute(f, rete.getGlobalContext());
                        
                        f = new Funcall("definstance", rete);               
                        f.add(new Value("tank", RU.ATOM));
                        f.add(new Value(t, RU.EXTERNAL_ADDRESS));
                        f.simpleExecute(f, rete.getGlobalContext());
                        
                        while (true) {
                                rete.executeCommand("(run 1)");
                                i_count++;
                                if (i_count == 10) {
                                        t2 = new Tank("Secondary");
                                        p2 = new Pump("Secondary", t2);
                                        // Tell Jess about them
                                        f = new Funcall("definstance",
rete);               
                                        f.add(new Value("pump", RU.ATOM));
                                        f.add(new Value(p2,
RU.EXTERNAL_ADDRESS));
                                        f.simpleExecute(f,
rete.getGlobalContext());
                                        
                                        f = new Funcall("definstance",
rete);               
                                        f.add(new Value("tank", RU.ATOM));
                                        f.add(new Value(t2,
RU.EXTERNAL_ADDRESS));
                                        f.simpleExecute(f,
rete.getGlobalContext());
                                        System.out.println("--- Secondary
tank and pump added to rete ---");
                                        
                                }
                                if ((t != null) && (t.getLevel() < 200)) {
                                        // remove main tank and pump from
rete
                                        f = new Funcall("undefinstance",
rete);               
                                        f.add(new Value(p,
RU.EXTERNAL_ADDRESS));
                                        pv = f.simpleExecute(f,
rete.getGlobalContext());
                                        // return from simpleExecute is true
                                        
                                        f = new Funcall("undefinstance",
rete);               
                                        f.add(new Value(t,
RU.EXTERNAL_ADDRESS));
                                        f.simpleExecute(f,
rete.getGlobalContext());
                                        // return from simpleExecute is true
                                        System.out.println("--- Main tank
and pump removed from rete ---");
                                        
                                        t = null;
                                        p = null;
                                        
                                }
                                
                                if ((t2 != null && !t2.isIntact()) ||
i_count > 500)
                                        break;
                        }
                }
                catch (Exception e) {
                        System.out.println("Exception thrown\n" + e);
                        
                }
                System.out.println("DONE");
        }

}



Dan Larner, [EMAIL PROTECTED]
Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA, USA 94304
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