ConnectionStrategy.h

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/* Author: James D. Marble */

#ifndef OMPL_GEOMETRIC_PLANNERS_PRM_CONNECTION_STRATEGY_
#define OMPL_GEOMETRIC_PLANNERS_PRM_CONNECTION_STRATEGY_

#include "ompl/datastructures/NearestNeighbors.h"
#include <functional>
#include <memory>
#include <boost/math/constants/constants.hpp>
#include <algorithm>
#include <utility>
#include <vector>

namespace ompl
{
    namespace geometric
    {
        template <class Milestone>
        class KStrategy
        {
        public:
            KStrategy(const unsigned int k, std::shared_ptr<NearestNeighbors<Milestone>> nn) : k_(k), nn_(std::move(nn))
            {
                neighbors_.reserve(k_);
            }

            virtual ~KStrategy() = default;

            void setNearestNeighbors(const std::shared_ptr<NearestNeighbors<Milestone>> &nn)
            {
                nn_ = nn;
            }

            const std::vector<Milestone> &operator()(const Milestone &m)
            {
                nn_->nearestK(m, k_, neighbors_);
                return neighbors_;
            }

        protected:
            unsigned int k_;

            std::shared_ptr<NearestNeighbors<Milestone>> nn_;

            std::vector<Milestone> neighbors_;
        };

        template <class Milestone>
        class KStarStrategy : public KStrategy<Milestone>
        {
        public:
            typedef std::function<unsigned int()> NumNeighborsFn;
            KStarStrategy(const NumNeighborsFn &n, const std::shared_ptr<NearestNeighbors<Milestone>> &nn,
                          const unsigned int d = 1)
              : KStrategy<Milestone>(n(), nn)
              , n_(n)
              , kPRMConstant_(boost::math::constants::e<double>() + (boost::math::constants::e<double>() / (double)d))
            {
            }

            const std::vector<Milestone> &operator()(const Milestone &m)
            {
                KStrategy<Milestone>::k_ = static_cast<unsigned int>(ceil(kPRMConstant_ * log((double)n_())));
                return static_cast<KStrategy<Milestone> &>(*this)(m);
            }

        protected:
            const NumNeighborsFn n_;
            const double kPRMConstant_;
        };

        template <class Milestone>
        class KBoundedStrategy : public KStrategy<Milestone>
        {
        public:
            KBoundedStrategy(const unsigned int k, const double bound,
                             const std::shared_ptr<NearestNeighbors<Milestone>> &nn)
              : KStrategy<Milestone>(k, nn), bound_(bound)
            {
            }

            const std::vector<Milestone> &operator()(const Milestone &m)
            {
                std::vector<Milestone> &result = KStrategy<Milestone>::neighbors_;
                KStrategy<Milestone>::nn_->nearestK(m, KStrategy<Milestone>::k_, result);
                if (result.empty())
                    return result;
                const typename NearestNeighbors<Milestone>::DistanceFunction &dist =
                    KStrategy<Milestone>::nn_->getDistanceFunction();
                if (!KStrategy<Milestone>::nn_->reportsSortedResults())
                    std::sort(result.begin(), result.end(), dist);
                std::size_t newCount = result.size();
                while (newCount > 0 && dist(result[newCount - 1], m) > bound_)
                    --newCount;
                result.resize(newCount);
                return result;
            }

        protected:
            const double bound_;
        };
    }
}

#endif