@Test
public void testRowSum() {

    Matrix x = new Matrix(10, 10);
    x.set(1);
    x.row(0).cumul();
    for (int i = 0; i < 10; ++i) {
        x.column(i).cumul();
    }
    DataBlock rowSum = x.subMatrix().rowSum();
    for (int i = 0; i < 10; ++i) {
        assertTrue(Math.abs(rowSum.get(i) - 55 - i * 10) < 1e-9);
    }
    
}