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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 22:28:59 GMT

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

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

    Attachment: SimplexSolverTest.patch
                SimplexTableau.patch

My earlier comments were misleading.  I misread the example provided (I need more sleep!).
 The original patch is sufficient.  I'm attaching a new one that also cleans up some code
formatting (weird spacing in SimplexTableau) and also provides a little bit better test.
Andrea, the correct solution for the example you provided is 0.  You restricted the variables
to be non-negative and are trying to minimize the objective function, so the best you can
do is make both variables 0 for an objective function value of 0.

> 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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