KDTreeLinkerTools.h

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#ifndef KDTreeLinkerToolsTemplated_h
#define KDTreeLinkerToolsTemplated_h

#include <algorithm>

// Box structure used to define 2D field.
// It's used in KDTree building step to divide the detector
// space (ECAL, HCAL...) and in searching step to create a bounding
// box around the demanded point (Track collision point, PS projection...).
struct KDTreeBox
{
  float dim1min, dim1max;
  float dim2min, dim2max;
  
  public:

  KDTreeBox(float d1min, float d1max, 
        float d2min, float d2max)
    : dim1min (d1min), dim1max(d1max)
    , dim2min (d2min), dim2max(d2max)
  {}

  KDTreeBox()
    : dim1min (0), dim1max(0)
    , dim2min (0), dim2max(0)
  {}
};

  
// Data stored in each KDTree node.
// The dim1/dim2 fields are usually the duplication of some PFRecHit values
// (eta/phi or x/y). But in some situations, phi field is shifted by +-2.Pi
template <typename DATA>
struct KDTreeNodeInfo 
{
  DATA data;
  float dim[2];
  enum {kDim1=0, kDim2=1};

  public:
  KDTreeNodeInfo()
  {}
  
  KDTreeNodeInfo(const DATA&    d,
         float      dim_1,
         float      dim_2)
    : data(d), dim{dim_1, dim_2}
  {}
};

template <typename DATA>
struct KDTreeNodes {
  std::vector<float> median; // or dimCurrent;
  std::vector<int> right;
  std::vector<float> dimOther;
  std::vector<DATA> data;

  int poolSize;
  int poolPos;

  constexpr KDTreeNodes(): poolSize(-1), poolPos(-1) {}

  bool empty() const { return poolPos == -1; }
  int size() const { return poolPos + 1; }

  void clear() {
    median.clear();
    right.clear();
    dimOther.clear();
    data.clear();
    poolSize = -1;
    poolPos = -1;
  }

  int getNextNode() {
    ++poolPos;
    return poolPos;
  }

  void build(int sizeData) {
    poolSize = sizeData*2-1;
    median.resize(poolSize);
    right.resize(poolSize);
    dimOther.resize(poolSize);
    data.resize(poolSize);
  };

  constexpr bool isLeaf(int right) const {
    // Valid values of right are always >= 2
    // index 0 is the root, and 1 is the first left node
    // Exploit index values 0 and 1 to mark which of dim1/dim2 is the
    // current one in recSearch() at the depth of the leaf.
    return right < 2;
  }

  bool isLeafIndex(int index) const {
    return isLeaf(right[index]);
  }
};

#endif