function Ackley

dx = 1;
xlimits = [-30 30];
N = floor((xlimits(2) - xlimits(1)) / dx) + 1;
obj = zeros(N, N);
i = 0;
for x = xlimits(1) : dx : xlimits(2)
    i = i + 1;
    k = 0;
    for y = xlimits(1) : dx : xlimits(2)
        k = k + 1;
        sum1 = x^2 + y^2;
        sum2 = cos(2*pi*x) + cos(2*pi*y);
        obj(i,k) = 20 + exp(1) - 20 * exp(-0.2*sqrt(sum1/2)) - exp(sum2/2);
    end
end
close all;
[x, y] = meshgrid(xlimits(1) : dx : xlimits(2));
mesh(x,y,obj);
figure;
contour(x,y,obj); hold;
plot(0,0,'*');
plot(0,0,'o');