AFPSiClusterBasicNearestNeighbour.cxx

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/*
  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
*/
 
#include "AFP_SiClusterTools/AFPSiClusterBasicNearestNeighbour.h"
#include "AFP_SiClusterTools/AFPSiClusterBasicObj.h"
#include "xAODForward/AFPClusterAlgID.h"
#include "xAODForward/AFPSiHit.h"
 
// STL includes
#include <list>
 
// FrameWork includes
#include "GaudiKernel/IToolSvc.h"
 
AFPSiClusterBasicNearestNeighbour::AFPSiClusterBasicNearestNeighbour(const std::string &type,
                                             const std::string &name,
                                             const IInterface *parent)
    : base_class(type, name, parent) {
}
 
StatusCode AFPSiClusterBasicNearestNeighbour::initialize() {
  return StatusCode::SUCCESS;
}
 
StatusCode AFPSiClusterBasicNearestNeighbour::finalize() {
  return StatusCode::SUCCESS;
}
 
StatusCode AFPSiClusterBasicNearestNeighbour::doClustering (const std::list<const xAOD::AFPSiHit*>& hits, std::list<AFPSiClusterBasicObj>& outputClusters) const
{
  std::list<const xAOD::AFPSiHit*> hitsAboveThreshold;
 
  // select only hits above charge threshold
  for (const xAOD::AFPSiHit* theHit : hits)
    if (theHit->depositedCharge() > m_chargeThreshold)
      hitsAboveThreshold.push_back(theHit);
  
  while (!hitsAboveThreshold.empty()) {
    const xAOD::AFPSiHit* theHit = hitsAboveThreshold.front();
    hitsAboveThreshold.pop_front();        // remove current hit from the list
    
    const int pixelHorizID = theHit->pixelHorizID();
    float horizID = pixelHorizID;         // value used to make cluster may be not integer
    float vertID = theHit->pixelVertID();         // value used to make cluster may be not integer
    float charge = theHit->depositedCharge();
    outputClusters.emplace_back(theHit, xAOD::AFPClusterAlgID::nearestNeighbour);
 
    const std::list<const xAOD::AFPSiHit*>::iterator neighbourEnd = hitsAboveThreshold.end();
    std::list<const xAOD::AFPSiHit*>::iterator neighbourIter = hitsAboveThreshold.begin();
    while (neighbourIter != neighbourEnd) {
      const xAOD::AFPSiHit* neighbour = *neighbourIter;
      // check if pixels are next to each other
      if (abs(neighbour->pixelHorizID()-pixelHorizID) == 1) {
        const float neighbourCharge = neighbour->depositedCharge();
        // charge weighted mean position
        horizID = (horizID*charge + neighbour->pixelHorizID()*neighbourCharge)/(charge + neighbourCharge);
        vertID = (vertID*charge + neighbour->pixelVertID()*neighbourCharge)/(charge + neighbourCharge);
 
        charge += neighbourCharge;
 
        hitsAboveThreshold.erase(neighbourIter);
 
        // update cluster before finishing the loop
        AFPSiClusterBasicObj& theCluster = outputClusters.back();
        theCluster.setHorizID(horizID);
        theCluster.setVertID(vertID);
        theCluster.setCharge(charge);
        theCluster.hits().push_back(neighbour);
        break;
      }
      ++neighbourIter;
    }
    
  }
 
  
  return StatusCode::SUCCESS;
}