The type of problem instance should be class derived from the base class problem.

• Definition
• Registration

Definition

A problem object must:

1. define how to initialize the added data members (e.g., optimal solutions and search domain) in initialize();
2. define a default initialization method for decision variables of a given solution in initialize_solution(s);
3. define how to calculate the objective values and the constraint violation of a given solution in evaluate_(s);
4. define the distance between two decision variables or two solutions in variable_distance(x1, x2) or variable_distance(s1, s2);
5. define how to check whether two solutions are the same in same(s1, s2).

For a combinatorial optimization algorithm, just make it inherited from problem:

class one_max : public problem {
protected:
    optima<variable_vector<int>, real> m_optima;
public:
    void initialize() override ;   // Initialize m_optima
    void initialize_solution(solution_base&) const override;
    evaluation_tag evaluate_(solution_base&, caller, bool, bool) override;
    real variable_distance(const solution_base&, const solution_base&) const override;
    real variable_distance(const variable_base&, const variable_base&) const override;
    bool same(const solution_base&, const solution_base&) const override;

For a continuous optimization problem, it is recommended to make it inherited from continuous or function (which is derived from continuous).

class sphere : public function {
public:
    void initialize() override;   // Initialize m_domain m_optima
    void evaluate_objective(real*, vector<real>&) override;
}

• m_domain and m_optima are added in continuous;
• initialize_solution(s) variable_distance(s1, s2) variable_distance(x1, x2) same(s1, s2) have been given in continuous;
• evaluate_(s) has been given in continuous as a mixture of evaluate_objective(x, obj) and evaluate_obj_nd_con(x, obj, con);

Registration

1. In the file “/run/include_problem.h” include the header file:

   #include "../instance/problem/combination/one_max/one_max.h"
   #include "../instance/problem/continuous/global/classical/sphere.h"
   

2. In the file “/run/user_initialization.cpp”, use the REGISTER(...) macro to register:

   REGISTER(problem, one_max, "ComOP_One_Max", std::set<problem_tag>({ problem_tag::ONEMAX, problem_tag::ComOP }));
   REGISTER(problem, sphere, "GOP_CLASSICAL_sphere", std::set<problem_tag>({ problem_tag::GOP,problem_tag::ConOP }));
   

   • the 3rd parameter is the name string to call the problem in command line arguments;
   • the 4th parameter marks the tags of the problem.