CDCCKFPathMerger.h

/**************************************************************************
 * BASF2 (Belle Analysis Framework 2)                                     *
 * Copyright(C) 2017 - Belle II Collaboration                             *
 *                                                                        *
 * Author: The Belle II Collaboration                                     *
 * Contributors:  Nils Braun                                              *
 *                                                                        *
 * This software is provided "as is" without any warranty.                *
 **************************************************************************/
#pragma once
 
#include <tracking/trackFindingCDC/findlets/base/Findlet.h>
#include <tracking/ckf/cdc/entities/CDCCKFPath.h>
 
#include <boost/range/adaptor/reversed.hpp>
#include <boost/functional/hash.hpp>
 
namespace Belle2 {
  class CDCCKFPathMerger : public TrackFindingCDC::Findlet<CDCCKFPath> {
  public:
    void apply(std::vector<CDCCKFPath>& newPaths) override
    {
      std::unordered_map<size_t, CDCCKFPath> hashToPathList;
      for (const CDCCKFPath& path : newPaths) {
        const auto lastHitsHash = lastThreeHitHash(path);
        if (hashToPathList.find(lastHitsHash) != hashToPathList.end()) {
          if (hashToPathList[lastHitsHash].size() < path.size()) {
            hashToPathList[lastHitsHash] = path;
          }
        } else {
          hashToPathList[lastHitsHash] = path;
        }
      }
 
      newPaths.clear();
      for (const auto& hashAndPathList : hashToPathList) {
        const CDCCKFPath& path = hashAndPathList.second;
        newPaths.push_back(path);
      }
    }
 
  private:
    size_t lastThreeHitHash(const CDCCKFPath& path)
    {
      size_t seed = 0;
      unsigned int counter = 0;
 
      for (const CDCCKFState& state : boost::adaptors::reverse(path)) {
        if (counter >= 3) {
          break;
        }
        if (not state.isSeed()) {
          boost::hash_combine(seed, state.getWireHit());
        }
        counter++;
      }
      return seed;
    };
 
  };
}