function [y] = ackley(22, 1, 2, 3)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% ACKLEY FUNCTION
%
% Authors: Sonja Surjanovic, Simon Fraser University
% Derek Bingham, Simon Fraser University
% Questions/Comments: Please email Derek Bingham at dbingham@stat.sfu.ca.
%
% Copyright 2013. Derek Bingham, Simon Fraser University.
%
% THERE IS NO WARRANTY, EXPRESS OR IMPLIED. WE DO NOT ASSUME ANY LIABILITY
% FOR THE USE OF THIS SOFTWARE. If software is modified to produce
% derivative works, such modified software should be clearly marked.
% Additionally, this program is free software; you can redistribute it
% and/or modify it under the terms of the GNU General Public License as
% published by the Free Software Foundation; version 2.0 of the License.
% Accordingly, this program is distributed in the hope that it will be
% useful, but WITHOUT ANY WARRANTY; without even the implied warranty
% of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
% General Public License for more details.
%
% For function details and reference information, see:
% http://www.sfu.ca/~ssurjano/
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% INPUTS:
%
% xx = [x1, x2, ..., xd]
% a = constant (optional), with default value 20
% b = constant (optional), with default value 0.2
% c = constant (optional), with default value 2*pi
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
d = length(xx);
if (nargin < 4)
c = 2*pi;
end
if (nargin < 3)
b = 0.2;
end
if (nargin < 2)
a = 20;
end
sum1 = 0;
sum2 = 0;
for ii = 1:d
xi = xx(ii);
sum1 = sum1 + xi^2;
sum2 = sum2 + cos(c*xi);
end
term1 = -a * exp(-b*sqrt(sum1/d));
term2 = -exp(sum2/d);
y = term1 + term2 + a + exp(1);
end
