pso.m

%% function pso()
%   Particle Swarm Optimization algorithm implementation

dimension = length(lower_boundary);
best_global = zeros(1,dimension);
iteration = 0;

%% Hyperparams struct
hyperparams.num_particles = num_particles;
hyperparams.lb = lower_boundary;
hyperparams.ub = upper_boundary;
hyperparams.w = 0.9;
hyperparams.phip = 0.6;
hyperparams.phig = 0.8;

if length(hyperparams.lb) ~= length(hyperparams.ub)
    disp("Dimensional error")
end

%% function initialize_particles(num_particles, lb, ub):
clear particles
for i = 1:hyperparams.num_particles
    particles(i) = Particle;
    % random_uniform here operates on arrays
    particles(i).x = random_uniform(hyperparams.lb, hyperparams.ub);
    delta = hyperparams.ub - hyperparams.lb;
    particles(i).v = random_uniform(-delta, delta);
    particles(i).best = zeros(1,length(particles(i).x));
end

%% main loop
while ~check_stopping_condition(iteration, max_iteration)
    disp(num2str(iteration/max_iteration*100, "%.2f") + "%");
    iteration = iteration + 1;
    %[particles, best_iteration] = update_particles(particles,...
    %    best_global, hyperparams);
    
    %% function update_particles(particles, best_global, hyperparams):
    w = hyperparams.w;
    phip = hyperparams.phip;
    phig = hyperparams.phig;
    best_iteration = zeros(1,dimension);
    
    for i = 1:length(particles)
        rp = random_uniform(0.0, 1.0);
        rg = random_uniform(0.0, 1.0);
        particles(i).v = w * particles(i).v + ...
            phip * rp * (particles(i).best - particles(i).x) + ...
            phig * rg * (best_global - particles(i).x);
        particles(i).x = particles(i).x + particles(i).v;
        particles(i).x = min(...
            max(...
                particles(i).x, ...
                hyperparams.lb ...
            ), ...
            hyperparams.ub ...
        );
        if custo(particles(i).x) < custo(particles(i).best)
            particles(i).best = particles(i).x;
            if custo(particles(i).x) < custo(best_iteration)
                best_iteration = particles(i).x;
            end
        end
    end
    
    if custo(best_iteration) < custo(best_global)
        best_global = best_iteration;
    end
end