mutate_pop.m

function popm = mutate_pop(pop, n_mutation, X, Y, Fl)
% mutation operation
    individual.position = [];
    individual.cost = [];
    popm = repmat(individual, n_mutation, 1);
    parfor k = 1:n_mutation

        max_retry = 3;
        for t = 1:max_retry

            p = pop(randi(numel(pop)));
            position = quick_bit_mutate(p.position);

            cost = fitness(X, Y, position);
            if ~is_dominated(cost, Fl)
                break;
            end

        end
        
        % no mutation retry
%         p = pop(randi(numel(pop)));
%         position = quick_bit_mutate(p.position);
%         cost = fitness(X, Y, position);

        popm(k).position = position;
        popm(k).cost = cost;
%         if mod(k, 100) == 0
%             logger(['mutate ', num2str(k), '/', num2str(n_mutation), ', cost = ', num2str(pop(k).cost')]);
%         end
    end
end

function new_position = quick_bit_mutate(position)
    mu = 0.1;
    r = rand;

    index_one = find(position == true);
    index_zero = find(position == false);
    n_one = numel(index_one);
    n_zero = numel(index_zero);

    n_mu = ceil(min(n_one, n_zero) * mu);
    new_position = repmat(position, 1);
    if r > 0.5
        index = randsample(index_one, n_mu);
        new_position(index) = false;
    else
        index = randsample(index_zero, n_mu);
        new_position(index) = true;
    end
end

function b = is_dominated(cost, Fl)
    b = false;
    for i = 1:numel(Fl)
        if dominates(Fl(i).cost, cost)
            b = true;
            break;
        end
    end
end

% function b = inpop(position, pop)
%     b = false;
%     for i = 1:numel(pop)
%         if all(pop(i).position == position)
%             b = true;
%             break;
%         end
%     end
% end