/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_5_3_13_patch3/src/RecoParticleFlow/PFProducer/interface/KDTreeLinkerBase.h

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#ifndef KDTreeLinkerBase_h
#define KDTreeLinkerBase_h

#include "DataFormats/ParticleFlowReco/interface/PFRecHitFraction.h"
#include "DataFormats/ParticleFlowReco/interface/PFBlockElement.h"

#include <vector>

class KDTreeLinkerBase
{
 public:
  KDTreeLinkerBase();

  virtual ~KDTreeLinkerBase();

  // Get/Set of the maximal size of the cristal (ECAL, HCAL,...) in phi/eta and
  // X/Y. By default, thus value are set for the ECAL cristal.
  void setCristalPhiEtaMaxSize(float size);
  void setCristalXYMaxSize(float size);
  float getCristalPhiEtaMaxSize() const;
  float getCristalXYMaxSize() const;

  // Get/Set phi offset. See bellow in the description of phiOffset_ to understand
  // the application.
  void setPhiOffset(double phiOffset);
  float getPhiOffset() const;

  // Debug flag. 
  void setDebug(bool isDebug);

  // With this method, we create the list of elements that we want to link.
  virtual void insertTargetElt(reco::PFBlockElement             *target) = 0;

  // Here, we create the list of cluster that we want to link. From cluster
  // and fraction, we will create a second list of rechits that will be used to
  // build the KDTree.
  virtual void insertFieldClusterElt(reco::PFBlockElement       *cluster) = 0;  

  // The KDTree building from rechits list.
  virtual void buildTree() = 0;

  // Here we will iterate over all target elements. For each one, we will search the closest
  // rechits in the KDTree, from rechits we will find the associated clusters and after that
  // we will check the links between the target and all closest clusters.
  virtual void searchLinks() = 0;

  // Here, we will store all target/cluster founded links in the PFBlockElement class
  // of each target in the PFmultilinks field.
  virtual void updatePFBlockEltWithLinks() = 0;
  
  // Here we free all allocated structures.
  virtual void clear() = 0;

  // This method calls is the good order buildTree(), searchLinks(), 
  // updatePFBlockEltWithLinks() and clear()
  virtual void process();

 protected:
  // Cristal maximal size. By default, thus value are set for the ECAL cristal.
  float                 cristalPhiEtaMaxSize_;
  float                 cristalXYMaxSize_;

  // Usually, phi is between -Pi and +Pi. But phi space is circular, that's why an element 
  // with phi = 3.13 and another with phi = -3.14 are close. To solve this problem, during  
  // the kdtree building step, we duplicate some elements close enough to +Pi (resp -Pi) by
  // substracting (adding) 2Pi. This field define the threshold of this operation.
  float                 phiOffset_;

  // Debug boolean. Not used until now.
  bool                  debug_;
};


#endif /* !KDTreeLinkerBase_h */