function y = colville(x)
% 
% Colville function 
% Matlab Code by A. Hedar (Sep. 29, 2005).
% The number of variables n = 4.
% 
y  = 100*(x(1)^2-x(2))^2+(x(1)-1)^2+(x(3)-1)^2+90*(x(3)^2-x(4))^2+...
10.1*((x(2)-1)^2+(x(4)-1)^2)+19.8*(x(2)^-1)*(x(4)-1);
