public void ToArray()
    {
      DoubleMatrix a = new DoubleMatrix(2);
      a[0,0] = 1;
      a[0,1] = 2;
      a[1,0] = 3;
      a[1,1] = 4;

      double[,] b = a.ToArray();

      Assert.AreEqual(a[0,0], b[0,0]);
      Assert.AreEqual(a[0,1], b[0,1]);
      Assert.AreEqual(a[1,0], b[1,0]);
      Assert.AreEqual(a[1,1], b[1,1]);
    }