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From "alberto trivellato (JIRA)" <j...@apache.org>
Subject [jira] [Created] (MATH-1176) QRDecomposition does not detect the matrix singularity
Date Thu, 04 Dec 2014 11:20:12 GMT
alberto trivellato created MATH-1176:
----------------------------------------

             Summary: QRDecomposition does not detect the matrix singularity
                 Key: MATH-1176
                 URL: https://issues.apache.org/jira/browse/MATH-1176
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: 3.3
            Reporter: alberto trivellato
            Priority: Minor


QRDecomposition fails this test. The default contructor sets the threshold=0, so we will never
have abs(Rii) <= 0

public void testSimpleRankDeficient() throws Exception {
		double[][] A = new double[][] { 
				{ 1, 2, 3 }, 
				{ 4, 5, 6 },
				{ 7, 8, 9 }};
		//this matrix is singular			
		
		RealMatrix M2 = MatrixUtils.createRealMatrix(A);
		QRDecomposition qr2 = new QRDecomposition(M2);
		assertFalse(qr2.getSolver().isNonSingular());//this fails
}



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