longestmedian_splitrule.h

// Description: Median-of-longest-side splitting rule

#ifndef PASTELGEOMETRY_LONGESTMEDIAN_SPLITRULE_H
#define PASTELGEOMETRY_LONGESTMEDIAN_SPLITRULE_H

#include "pastel/sys/pointset/pointset_concept.h"
#include "pastel/sys/locator/locator_concept.h"

#include "pastel/geometry/splitrule/splitrule_concept.h"
#include "pastel/geometry/shape/alignedbox.h"

#include <algorithm>
#include <vector>

namespace Pastel
{

    //! Median-of-longest-side splitting rule.
    class LongestMedian_SplitRule
    {
    public:
        template <
            PointSet_Concept PointSet,
            typename Real = PointSet_Real<PointSet>,
            int N = PointSet_Dimension<PointSet>::value
        >
        std::pair<Real, integer> operator()(
            const PointSet& pointSet,
            const AlignedBox<Real, N>& bound) const
        {
            // Split along the longest dimension.

            integer splitAxis = maxIndex(bound.extent());
            Real splitPosition = linear(
                bound.min()[splitAxis], 
                bound.max()[splitAxis], 0.5);

            if (isEmptyRange(pointSet))
            {
                return std::make_pair(splitPosition, splitAxis);
            }

            // Get the positions of the points along the splitting axis.

            std::vector<Real> positionSet;
            positionSet.reserve(rangeSize(pointSet));

            for (auto&& point : pointSet)
            {
                positionSet.emplace_back(
                    pointAxis(point, splitAxis));
            }

            // Get the median of the points on the splitting axis.
            std::sort(positionSet.begin(), positionSet.end());
            splitPosition = positionSet[positionSet.size() / 2];

            return std::make_pair(splitPosition, splitAxis);
        }
    };

}

#endif