rp_tree_mean_split.hpp

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#ifndef MLPACK_CORE_TREE_BINARY_SPACE_TREE_RP_TREE_MEAN_SPLIT_HPP
#define MLPACK_CORE_TREE_BINARY_SPACE_TREE_RP_TREE_MEAN_SPLIT_HPP

#include <mlpack/prereqs.hpp>
#include "rp_tree_max_split.hpp"
#include <mlpack/core/tree/perform_split.hpp>
#include <mlpack/core/math/lin_alg.hpp>

namespace mlpack {
namespace tree  {

template<typename BoundType, typename MatType = arma::mat>
class RPTreeMeanSplit
{
 public:
  typedef typename MatType::elem_type ElemType;
  struct SplitInfo
  {
    arma::Col<ElemType> direction;
    arma::Col<ElemType> mean;
    ElemType splitVal;
    bool meanSplit;
  };

  static bool SplitNode(const BoundType& /* bound */,
                        MatType& data,
                        const size_t begin,
                        const size_t count,
                        SplitInfo& splitInfo);

  static size_t PerformSplit(MatType& data,
                             const size_t begin,
                             const size_t count,
                             const SplitInfo& splitInfo)
  {
    return split::PerformSplit<MatType, RPTreeMeanSplit>(data, begin, count,
        splitInfo);
  }

  static size_t PerformSplit(MatType& data,
                             const size_t begin,
                             const size_t count,
                             const SplitInfo& splitInfo,
                             std::vector<size_t>& oldFromNew)
  {
    return split::PerformSplit<MatType, RPTreeMeanSplit>(data, begin, count,
        splitInfo, oldFromNew);
  }

  template<typename VecType>
  static bool AssignToLeftNode(const VecType& point, const SplitInfo& splitInfo)
  {
    if (splitInfo.meanSplit)
      return arma::dot(point - splitInfo.mean, point - splitInfo.mean) <=
          splitInfo.splitVal;

    return (arma::dot(point, splitInfo.direction) <= splitInfo.splitVal);
  }

 private:

  static ElemType GetAveragePointDistance(MatType& data,
                                          const arma::uvec& samples);

  static bool GetDotMedian(const MatType& data,
                           const arma::uvec& samples,
                           const arma::Col<ElemType>& direction,
                           ElemType& splitVal);

  static bool GetMeanMedian(const MatType& data,
                            const arma::uvec& samples,
                            arma::Col<ElemType>& mean,
                            ElemType& splitVal);
};

} // namespace tree
} // namespace mlpack

// Include implementation.
#include "rp_tree_mean_split_impl.hpp"

#endif // MLPACK_CORE_TREE_BINARY_SPACE_TREE_RP_TREE_MEAN_SPLIT_HPP