[rules-users] Sudoku Example Errors

[Ming Fang]

Michael,

This is the example in the drools-examples directory,  
org.drools.examples.sudoku.SudokuExample.
I'm running latest code from the repository using Intellij, JDK 1.5  
on OS X.

--ming

On May 25, 2007, at 12:48 AM, Michael Neale wrote:

> Errors like that are not normal, and definitely indicates a bug (ie  
> not a compile error or anything - not something you should have to  
> debug). So some more information is needed like versions, how you  
> are running it, where the example came from etc (as there are a few  
> versions floating around).
>
> On 5/25/07, Ming Fang <mingfang at mac.com> wrote:
> Hi,
> I'm getting many of these errors when running the Sudoku Example
>
> java.lang.NullPointerException
>         at org.drools.reteoo.ReteTuple.get(ReteTuple.java:71)
>         at org.drools.common.InstanceNotEqualsConstraint
> $InstanceNotEqualsConstraintContextEntry.updateFromTuple
> (InstanceNotEqualsConstraint.java:112)
>         at org.drools.common.TripleBetaConstraints.updateFromTuple
> (TripleBetaConstraints.java:146)
>         at org.drools.reteoo.NotNode.assertTuple(NotNode.java:108)
>         at  
> org.drools.reteoo.SingleTupleSinkAdapter.propagateAssertTuple
> (SingleTupleSinkAdapter.java:29)
>         at org.drools.reteoo.NotNode.assertTuple(NotNode.java :121)
>         at  
> org.drools.reteoo.SingleTupleSinkAdapter.propagateAssertTuple
> (SingleTupleSinkAdapter.java:29)
>         at org.drools.reteoo.NotNode.assertTuple(NotNode.java:121)
>         at
> org.drools.reteoo.CompositeTupleSinkAdapter.createAndPropagateAssertTu 
> pl
> e(CompositeTupleSinkAdapter.java:73)
>         at org.drools.reteoo.LeftInputAdapterNode.assertObject
> (LeftInputAdapterNode.java:144)
>         at  
> org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject
> (CompositeObjectSinkAdapter.java:317)
>         at org.drools.reteoo.ObjectTypeNode.assertObject 
> (ObjectTypeNode.java:
> 183)
>         at org.drools.reteoo.Rete.assertObject(Rete.java:121)
>         at org.drools.reteoo.ReteooRuleBase.assertObject  
> (ReteooRuleBase.java:
> 201)
>         at org.drools.reteoo.ReteooWorkingMemory.doAssertObject
> (ReteooWorkingMemory.java:70)
>         at org.drools.common.AbstractWorkingMemory.assertObject
> (AbstractWorkingMemory.java :735)
>         at org.drools.base.DefaultKnowledgeHelper.assertObject
> (DefaultKnowledgeHelper.java:72)
>         at org.drools.base.DefaultKnowledgeHelper.assertObject
> (DefaultKnowledgeHelper.java:66)
>         at
> org.drools.examples.sudoku.Rule_Rule_1__If_a_field_has_the_value_0__it 
> _i
> s_empty__remove_it_and_insert_the_PossibleValues_0.consequence
> (Rule_Rule_1__If_a_field_has_the_value_0__it_is_empty__remove_it_and_i 
> ns
> ert_the_PossibleValues_0.java:8)
>         at
> org.drools.examples.sudoku.Rule_Rule_1__If_a_field_has_the_value_0__it 
> _i
> s_empty__remove_it_and_insert_the_PossibleValues_0ConsequenceInvoker.e 
> va
> luate
> (Rule_Rule_1__If_a_field_has_the_value_0__it_is_empty__remove_it_and_i 
> ns
> ert_the_PossibleValues_0ConsequenceInvoker.java:22)
>         at org.drools.common.DefaultAgenda.fireActivation 
> (DefaultAgenda.java:
> 497)
>         at org.drools.common.DefaultAgenda.fireNextItem 
> (DefaultAgenda.java :461)
>         at org.drools.common.AbstractWorkingMemory.fireAllRules
> (AbstractWorkingMemory.java:372)
>         at org.drools.common.AbstractWorkingMemory.fireAllRules
> (AbstractWorkingMemory.java:353)
>         at org.drools.examples.sudoku.SudokuExample.testWithInput
> (SudokuExample.java:52)
>         at org.drools.examples.sudoku.SudokuExample.main 
> (SudokuExample.java:94)
>
>
> Besides the fact that these errors are naturally bad,
> this points out the issue of Drools being very difficult debug when
> bad things happen.
> Can somebody give some tips of Drool debugging techniques?
>
> Thanks,
> --ming
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