Algorithm 6.5 is not optimal because it attempts to satisfy two constraints alternatively in each iteration.

A better way is to compute an optimal step size  at each step, which satisfies both constraints:

 = arg max



, subject to 0  ¹nº ???? 
˜r L¹¹nºº  C 0    n.

use the KKT conditions to derive a closed-form solution to compute the optimal step size .