public void SetDiagonal()
 {
   DoubleMatrix a = new DoubleMatrix(2,2);
   DoubleVector b = new DoubleVector(2);
   b[0] = 1;
   b[1] = 2;
   a.SetDiagonal(b);
   Assert.AreEqual(b[0], a[0,0]);
   Assert.AreEqual(b[1], a[1,1]);
 }