enforced_hill_climbing_search.h

#ifndef SEARCH_ALGORITHMS_ENFORCED_HILL_CLIMBING_SEARCH_H
#define SEARCH_ALGORITHMS_ENFORCED_HILL_CLIMBING_SEARCH_H
 
#include "downward/evaluation_context.h"
#include "downward/open_list.h"
#include "downward/search_algorithm.h"
 
#include <map>
#include <memory>
#include <set>
#include <utility>
#include <vector>
 
namespace enforced_hill_climbing_search {
enum class PreferredUsage { PRUNE_BY_PREFERRED, RANK_PREFERRED_FIRST };
 
/*
  Enforced hill-climbing with deferred evaluation.
 
  TODO: We should test if this lazy implementation really has any benefits over
  an eager one. We hypothesize that both versions need to evaluate and store
  the same states anyways.
*/
class EnforcedHillClimbingSearch : public SearchAlgorithm {
    std::unique_ptr<EdgeOpenList> open_list;
 
    std::shared_ptr<Evaluator> evaluator;
    std::vector<std::shared_ptr<Evaluator>> preferred_operator_evaluators;
    std::set<Evaluator*> path_dependent_evaluators;
    bool use_preferred;
    PreferredUsage preferred_usage;
 
    EvaluationContext current_eval_context;
    int current_phase_start_g;
 
    // Statistics
    std::map<int, std::pair<int, int>> d_counts;
    int num_ehc_phases;
    int last_num_expanded;
 
    void insert_successor_into_open_list(
        const EvaluationContext& eval_context,
        int parent_g,
        OperatorID op_id,
        bool preferred);
    void expand(EvaluationContext& eval_context);
    void reach_state(const State& parent, OperatorID op_id, const State& state);
    SearchStatus ehc();
 
protected:
    virtual void initialize() override;
    virtual SearchStatus step() override;
 
public:
    EnforcedHillClimbingSearch(
        const std::shared_ptr<Evaluator>& h,
        PreferredUsage preferred_usage,
        const std::vector<std::shared_ptr<Evaluator>>& preferred,
        OperatorCost cost_type,
        int bound,
        double max_time,
        const std::string& description,
        utils::Verbosity verbosity);
 
    virtual void print_statistics() const override;
};
} // namespace enforced_hill_climbing_search
 
#endif