public void DeterminantTest()
{
double[,] value =
{
{ 6, -1, 2, 1 },
{ -1, 9, -3, -2 },
{ 2, -3, 8, 1 },
{ 1, -2, 1, 7 },
};
var chol = new CholeskyDecomposition(value);
//var L = chol.LeftTriangularFactor;
//var det = L.Determinant();
Assert.IsTrue(chol.IsPositiveDefinite);
Assert.AreEqual(2232, chol.Determinant, 1e-12);
Assert.IsTrue(chol.Nonsingular);
}