* Generalized geometric programming
* Robust stability problem
* Ackermann et al. (1991)

VARIABLES
	 q1  
	 q2  
	 q3  
	 w     stability margin
	 k  
     objval    objective function variable;

FREE VARIABLES    objval;


EQUATIONS
	 f Objective function
	 g1
	 g2
	 b1u  
	 b1l  
	 b2l  
	 b2u  
	 b3l  
	 b3u ;

f  .. objval =e=k;
g1  .. q3 - 4*q1 - q2 - 78*w + 9.625*q1*w + 16*q2*w + 16*POWER(w,2) =e= -12;
g2  .. -19*q1 - 8*q2 - q3 - 24*w + 16*q1*w =e= -44;
b1l  .. -0.25*k - q1 =l= -2.25;
b1u  .. -0.25*k + q1 =l= 2.25;
b2l  .. -0.5*k - q2 =l= -1.5;
b2u  .. -0.5*k + q2 =l= 1.5;
b3l  .. -1.5*k - q3 =l= -1.5;
b3u  .. -1.5*k + q3 =l= 1.5;

* Bounds
w.LO = 0;
w.UP = 10;

* Starting point (global solution)
* q1.L = 2.4544;
* q2.L = 1.9088;
* q3.L = 2.7263;
* k.L = 0.8175;
* w.L = 1.3510;

MODEL test /ALL/;
SOLVE test USING NLP MINIMIZING objval;