differential_grouping_setting_parameter.cpp

#include <decomposition/differential_grouping.h>
#include <decomposition/optimization_problem.h>
#include <sstream>

using namespace decompose;
using namespace std;

class problem_example : public optimization_problem {
    public:
        using super = optimization_problem;

        explicit problem_example(size_t dimension, vector<scalar> lower_bound,
                                 vector<scalar> upper_bound)
            : super(dimension, std::move(lower_bound), std::move(upper_bound)) {}

        scalar value(const vector<scalar> &x) override {
            scalar sum = 0.0;
            for(size_t i = 0; i < dimension; i++){
                if(i % 3 == 0){
                    sum += pow(x[i], 2) * pow(x[(i+1) % dimension], 2);
                } else{
                    sum += pow(x[i], 2);
                }
            }
            return sum;
        }
};


int main(){
    const size_t dimension = 7;
    const scalar lower_bound = -5.0;
    const scalar upper_bound = 10.0;

    vector<set<size_t>> sub_problems;
    size_t number_seps, number_non_seps;

    problem_example f(dimension, vector<scalar>(dimension, lower_bound), vector<scalar>(dimension, upper_bound));

    criteria criteria_;
    options options_{};
    options_.set_dg_epsilon(0.3);
    differential_grouping method;
    method.decompose(f, options_, criteria_);

    cout << "Differential Grouping Method Example - Setting Epsilon Parameter" << endl;

    sub_problems = f.get_problem_structure();
    cout << " - Number of Function Evaluations: " << criteria_.evaluations << endl;
    number_seps = 0;
    number_non_seps = 0;
    for(auto & sub_problem : sub_problems){
        if(sub_problem.size() > 1){
            number_non_seps += sub_problem.size();
        }
        else{
            number_seps++;
        }
    }

    ostringstream s;
    s << "[";
    for(size_t i = 0; i < sub_problems.size(); i++){
        s << "[";
        auto it = sub_problems[i].begin();
        bool print = true;
        while(print && !sub_problems.empty()){
            s << (*it);
            it++;
            if(it != sub_problems[i].end()){
                s << ", ";
            }else{
                print = false;
            }
        }
        s << "]";
    }
    s << "]";

    cout << " - Number of sub-problems found: " << sub_problems.size() << endl;
    cout << " - Number of separable decision variables: " << number_seps  << endl;
    cout << " - Number of non-separable decision variables: " << number_non_seps  << endl;
    cout << " - Problem Structure Found: " << s.str() << endl;
    cout << endl << endl;

    return 0;
}