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From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] Created: (MATH-297) Eigenvector computation incorrectly returning vectors of NaNs
Date Sun, 20 Sep 2009 14:33:15 GMT
Eigenvector computation incorrectly returning vectors of NaNs
-------------------------------------------------------------

                 Key: MATH-297
                 URL: https://issues.apache.org/jira/browse/MATH-297
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: 2.0
            Reporter: Phil Steitz
             Fix For: 2.1


As reported by Axel Kramer on commons-dev, the following test case succeeds, but should fail:

{code}
public void testEigenDecomposition() {
    double[][] m = { { 0.0, 1.0, -1.0 }, { 1.0, 1.0, 0.0 }, { -1.0,0.0, 1.0 } };
    RealMatrix rm = new Array2DRowRealMatrix(m);
    assertEquals(rm.toString(),
        "Array2DRowRealMatrix{{0.0,1.0,-1.0},{1.0,1.0,0.0},{-1.0,0.0,1.0}}");
    EigenDecompositionImpl ed = new EigenDecompositionImpl(rm,
        MathUtils.SAFE_MIN);
    RealVector rv0 = ed.getEigenvector(0);
    assertEquals(rv0.toString(), "{(NaN); (NaN); (NaN)}");
  }
{code}

ed.getRealEigenvalues() returns the correct eigenvalues (2, 1, -1), but all three eigenvectors
contain only NaNs.


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