* Generalized geometric programming problem
* Robust stability analysis
* Sideris and Sanchez (1988)

VARIABLES
	 q1  
	 q2  
	 q3  
	 k  
     objval    objective function variable;

FREE VARIABLES    objval;


EQUATIONS
	 f Objective function
	 g  
	 b1l  
	 b1u  
	 b2l  
	 b2u  
	 b3l  
	 b3u;  

f  .. objval =e=k;
g  .. POWER(q1,4) * POWER(q2,4) - POWER(q1,4) - POWER(q2,4) * q3 =l= 0;
b1l  .. -0.25 * k - q1 =l= -1.4;
b1u  .. -0.25 * k + q1 =l= 1.4;
b2l  .. -0.2 * k - q2 =l= -1.5;
b2u  .. -0.2 * k + q2 =l= 1.5;
b3l  .. -0.2 * k - q3 =l= -0.8;
b3u  .. -0.2 * k + q3 =l= 0.8;

* Starting point (global solution)
* q1.L = 1.1275;
* q2.L = 1.2820;
* q3.L = 1.0179;
* k.L = 1.089;

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