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From "Benjamin McCann (JIRA)" <j...@apache.org>
Subject [jira] Updated: (MATH-290) NullPointerException in SimplexTableau.initialize
Date Tue, 25 Aug 2009 20:43:59 GMT

     [ https://issues.apache.org/jira/browse/MATH-290?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Benjamin McCann updated MATH-290:
---------------------------------

    Attachment: SimplexTableau.patch
                SimplexSolverTest.patch

Thanks for the bug report.  I'm glad to be finding these bugs (hopefully the last of them
:o)  That was the point in open sourcing this, so looks like that was a good decision!
Problem here was that when the constraint's right hand side is negative, we need to flip the
constraint around so that it is positive.  We were doing that too late during the initialization
and it should have been done at the very beginning, so that we only deal with the normalized
version instead of both versions.

> NullPointerException in SimplexTableau.initialize
> -------------------------------------------------
>
>                 Key: MATH-290
>                 URL: https://issues.apache.org/jira/browse/MATH-290
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 2.0
>         Environment: Java 1.6.0_13 on Windows XP 32-bit 
>            Reporter: Andrea
>         Attachments: SimplexSolverTest.patch, SimplexTableau.patch
>
>
> SimplexTableau throws a NullPointerException when no solution can be found instead of
a NoFeasibleSolutionException
> Here is the code that causes the NullPointerException:
> LinearObjectiveFunction f = new LinearObjectiveFunction(new double[] { 1, 5 }, 0 );
> Collection<LinearConstraint> constraints = new ArrayList<LinearConstraint>();
> constraints.add(new LinearConstraint(new double[] { 2, 0 }, Relationship.GEQ, -1.0));
> RealPointValuePair solution = new SimplexSolver().optimize(f, constraints, GoalType.MINIMIZE,
true);
> Note: Tested both with Apache Commons Math 2.0 release and SVN trunk

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