* NLP literature problem
* Six-hump camelback function, Dixon and Szego (1975)

VARIABLES
	 x  
	 y  
     objval    objective function variable;

FREE VARIABLES    objval;


EQUATIONS
	 f Objective function;

f  .. objval =e=4*POWER(x,2)-(2.1*POWER(x,4))+(1/3)*POWER(x,6)+x*y-(4*POWER(y,2))+4*POWER(y,4);

* Starting point (global solution)
* x.L = 0.08984;
* y.L = -0.71266;

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