BestMatchSelector.h

/**************************************************************************
 * BASF2 (Belle Analysis Framework 2)                                     *
 * Copyright(C) 2016 - 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/trackFindingCDC/numerics/WeightComperator.h>
 
#include <tracking/trackFindingCDC/utilities/WeightedRelation.h>
#include <tracking/trackFindingCDC/utilities/Algorithms.h>
 
#include <algorithm>
#include <vector>
 
namespace Belle2 {
  namespace TrackFindingCDC {
    template <class ACollectorItem, class ACollectionItem>
    class BestMatchSelector :
      public Findlet<WeightedRelation<ACollectorItem, const ACollectionItem>> {
    public:
      using WeightedRelationItem = WeightedRelation<ACollectorItem, const ACollectionItem>;
 
      using Super = Findlet<WeightedRelation<ACollectorItem, const ACollectionItem>>;
 
      void apply(std::vector<WeightedRelationItem>& weightedRelations) override
      {
        std::vector<WeightedRelationItem> selectedWeightedRelations;
 
        // Do until there are no more relations left:
        // (1) find the relation with the maximum weight
        // (2) store this and delete all relations, which share a "To" or a "From" item with this maximal relation
        // (3) repeat
        while (not weightedRelations.empty()) {
          // std:min_element is strange... this actually returns the element with the largest weight
          const auto maxElement = *(std::min_element(weightedRelations.begin(), weightedRelations.end(), GreaterWeight()));
          selectedWeightedRelations.push_back(maxElement);
 
          const auto itemSharesFromOrTo = [&maxElement](const WeightedRelationItem & item) {
            return item.getFrom() == maxElement.getFrom() or item.getTo() == maxElement.getTo();
          };
 
          erase_remove_if(weightedRelations, itemSharesFromOrTo);
        }
 
        std::sort(selectedWeightedRelations.begin(), selectedWeightedRelations.end());
        weightedRelations.swap(selectedWeightedRelations);
      }
    };
  }
}