@Test
public void testNorm2() throws Exception {

    DenseMatrix matA = DenseMatrix.zeros(4, 5);
    matA.set(0, 0, 1);
    matA.set(0, 4, 2);
    matA.set(1, 2, 3);
    matA.set(3, 1, 2);
    Assert.assertEquals(matA.norm2(), 3., TOL);
}