Editing Conjugate gradient method (section)

==Conjugate gradient method as optimal feedback controller for double integrator==

The conjugate gradient method can also be derived using [[Optimal control|optimal control theory]].<ref name=":0">[[I. Michael Ross|Ross, I. M.]],  "An Optimal Control Theory for Accelerated Optimization," {{arXiv|1902.09004}}, 2019.</ref> In this approach, the conjugate gradient method falls out as an [[Feedback Control|optimal feedback controller]],<math display="block">u = k(x, v):= -\gamma_a \nabla f(x) - \gamma_b v </math> for the [[Double integrator|double integrator system]],<math display="block">\dot x = v, \quad \dot v = u </math> The quantities <math>\gamma_a</math> and <math>\gamma_b</math> are variable feedback gains.<ref name=":0" />