public void DeterminantException()
        {
            MatrixD a = new MatrixD(new double[, ] {
                { 1, 2 }, { 5, 6 }, { 0, 1 }
            });

            LUDecompositionD d   = new LUDecompositionD(a);
            double           det = d.Determinant();
        }
        public void TestSingularMatrix()
        {
            MatrixD a = new MatrixD(new double[, ] {
                { 1, 2, 3 }, { 4, 5, 6 }, { 5, 7, 9 }
            });

            LUDecompositionD d = new LUDecompositionD(a);

            Assert.AreEqual(true, d.IsNumericallySingular);
            Assert.IsTrue(Numeric.IsZero(d.Determinant()));
        }
        public void Determinant()
        {
            MatrixD a = new MatrixD(new double[, ] {
                { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 0, 1, 2, 0 }, { 1, 0, 1, 0 }
            });

            LUDecompositionD d = new LUDecompositionD(a);

            Assert.AreEqual(false, d.IsNumericallySingular);
            Assert.IsTrue(Numeric.AreEqual(-24, d.Determinant()));

            MatrixD aPermuted = d.L * d.U;

            Assert.IsTrue(MatrixD.AreNumericallyEqual(aPermuted, a.GetSubmatrix(d.PivotPermutationVector, 0, 3)));
        }