function [x,fval,gfx,output]=hPSO(fitnessfun,nvars,options,varargin)
%Syntax: [x,fval,gfx,output]=hPSO(fitnessfun,nvars,options,varargin)
%___________________________________________________________________
%
% A hybrid Particle Swarm Optimization algorithm for finding the minimum of
% the function 'fitnessfun' in the real space.
%
% x is the scalar/vector of the functon minimum
% fval is the function minimum
% gfx contains the best particle for each flight (columns 2:end) and the
%  corresponding solutions (1st column)
% output structure contains the following information
%   reason : is the reason for stopping
%   flights: the nuber of flights before stopping
%   time   : the total time before stopping
% fitnessfun is the function to be minimized
% nvars is the number of variables of the problem
% options are specified in the file "PSOoptions.m"
%
%
% Reference:
% Kennedy J., Eberhart R.C. (1995): Particle swarm optimization. In: Proc.
% IEEE Conf. on Neural Networks, IV, Piscataway, NJ, pp. 1942