Class PenaltyBarrierU_quartic

Inheritance Relationships

Base Type

Class Documentation

class Mechatronix::PenaltyBarrierU_quartic : public Mechatronix::PenaltyBarrierU_base

Piecewise cubic penalty.

Public Functions

inline explicit PenaltyBarrierU_quartic(string const &name)

Construct the penalty.

inline virtual void setup(real_type epsilon, real_type tolerance) override

Initialize the penalty internal parameters based on the values of \( h \) and \( \epsilon \)

for \( h \) and vars[name()+"Epsi"] for \( \epsilon \)

Set the internal parameters

\[ H=1-h,\qquad C_0 = \frac{\epsilon}{H^2},\qquad C_1 = \frac{4}{h^4},\qquad C_2 = \frac{12}{h^4},\qquad C_3 = 6h^4 C_0,\qquad C_4 = C_3^{1/3},\qquad C_5 = \frac{C_4}{6}; \]

based on the values of \( h \) and \( \epsilon \)

Parameters
  • epsilon[in] value \( \epsilon \)

  • tolerance[in] value \( h \)

inline virtual real_type eval(real_type x) const override

Compute the penalty

\[\begin{split} p(x) = \epsilon\frac{x^2}{H^2} + \frac{1}{H^4} \begin{cases} (x+H)^4 & x < -1+h \\[1em] 0 & x\in[-H,H] \\[1em] (x-H)^4 & x > 1-h \end{cases} \end{split}\]

where the parameters

\[ H=1-h,\qquad C_0 = \frac{\epsilon}{H^2},\qquad C_1 = \frac{4}{h^4},\qquad C_2 = \frac{12}{h^4},\qquad C_3 = 6h^4 C_0,\qquad C_4 = C_3^{1/3},\qquad C_5 = \frac{C_4}{6}; \]

are precomputed after a call of method setup.

../_images/U_QUARTIC_0.jpeg

inline virtual real_type eval_D(real_type x) const override

First derivative of the penalty

../_images/U_QUARTIC_1.jpeg

inline virtual real_type eval_DD(real_type x) const override

Second derivative of the penalty

../_images/U_QUARTIC_2.jpeg

inline virtual real_type solve(real_type RHS) const override

Solve the problem \( p'(x) = r \)

By setting

\[ R = \frac{r}{2\epsilon},\qquad C_2 = 6\epsilon h^4,\qquad C_1 = (C_2)^{1/3},\qquad A = \left(\sqrt{C_2+(9(|R|-H))^2}+9(|R|-H)\right)^{1/3}, \]
the solution is
\[\begin{split} x = \mathrm{sign}(R) \begin{cases} |R| & |R| < H \\[1em] \frac{C_1}{6}\left(A-\frac{C_1}{A}\right)+H & \mathrm{otherwise} \end{cases} \end{split}\]