/data/refman/pasoursint/CMSSW_6_1_2_SLHC2_patch1/src/RecoJets/JetAssociationAlgorithms/src/JetSignalVertexCompatibilityAlgo.cc

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#include <functional>
#include <cmath>
#include <map>

#include "DataFormats/Common/interface/RefToBase.h"
#include "DataFormats/TrackReco/interface/Track.h"
#include "DataFormats/VertexReco/interface/Vertex.h"
#include "DataFormats/VertexReco/interface/VertexFwd.h"

#include "TrackingTools/GeomPropagators/interface/AnalyticalImpactPointExtrapolator.h"
#include "TrackingTools/TrajectoryState/interface/TrajectoryStateOnSurface.h"
#include "TrackingTools/TransientTrack/interface/TransientTrack.h"
#include "TrackingTools/TransientTrack/interface/TransientTrackBuilder.h"
#include "TrackingTools/Records/interface/TransientTrackRecord.h"

#include "RecoVertex/VertexPrimitives/interface/ConvertToFromReco.h"

#include "RecoJets/JetAssociationAlgorithms/interface/JetSignalVertexCompatibilityAlgo.h"

using namespace reco;

// helper
template<typename T>
inline bool
JetSignalVertexCompatibilityAlgo::RefToBaseLess<T>::operator()(
        const edm::RefToBase<T> &r1, const edm::RefToBase<T> &r2) const
{ return r1.id() < r2.id() || (r1.id() == r2.id() && r1.key() < r2.key()); }


JetSignalVertexCompatibilityAlgo::JetSignalVertexCompatibilityAlgo(
                                        double cut, double temperature) :
        cut(cut), temperature(temperature)
{}

JetSignalVertexCompatibilityAlgo::~JetSignalVertexCompatibilityAlgo()
{}

double JetSignalVertexCompatibilityAlgo::trackVertexCompat(
                        const Vertex &vtx, const TransientTrack &track)
{
        GlobalPoint point1 = RecoVertex::convertPos(vtx.position());
        AnalyticalImpactPointExtrapolator extrap(track.field());
        TrajectoryStateOnSurface tsos =
                        extrap.extrapolate(track.impactPointState(), point1);

        if (!tsos.isValid())
                return 1.0e6;

        GlobalPoint point2 = tsos.globalPosition();
        ROOT::Math::SVector<double, 3> dir(point1.x() - point2.x(),
                                           point1.y() - point2.y(),
                                           point1.z() - point2.z());
        GlobalError cov = RecoVertex::convertError(vtx.covariance()) +
                          tsos.cartesianError().position();

        return ROOT::Math::Mag2(dir) /
               std::sqrt(ROOT::Math::Similarity(cov.matrix_new(), dir));
}

const TransientTrack&
JetSignalVertexCompatibilityAlgo::convert(const TrackBaseRef &track) const
{
        TransientTrackMap::iterator pos = trackMap.lower_bound(track);
        if (pos != trackMap.end() && pos->first == track)
                return pos->second;

        // the castTo will only work with regular, i.e. no GsfTracks
        // the interface is not intrinsically polymorph...
        return trackMap.insert(pos,
                std::make_pair(track, trackBuilder->build(
                                        track.castTo<TrackRef>())))->second;
}

double JetSignalVertexCompatibilityAlgo::activation(double compat) const
{
        return 1. / (std::exp((compat - cut) / temperature) + 1.);
}

std::vector<float>
JetSignalVertexCompatibilityAlgo::compatibility(
                                const reco::VertexCollection &vertices,
                                const reco::TrackRefVector &tracks) const
{
        std::vector<float> result(vertices.size(), 0.);
        float sum = 0.;

        for(TrackRefVector::const_iterator track = tracks.begin();
            track != tracks.end(); ++track) {
                const TransientTrack &transientTrack =
                                        convert(TrackBaseRef(*track));

                for(unsigned int i = 0; i < vertices.size(); i++) {
                        double compat =
                                trackVertexCompat(vertices[i], transientTrack);
                        double contribution =
                                activation(compat) * (*track)->pt();

                        result[i] += contribution;
                        sum += contribution;
                }
        }

        if (sum < 1.0e-9) {
                for(unsigned int i = 0; i < result.size(); i++)
                        result[i] = 1.0 / result.size();
        } else {
                for(unsigned int i = 0; i < result.size(); i++)
                        result[i] /= sum;
        }

        return result;
}

void JetSignalVertexCompatibilityAlgo::resetEvent(
                                        const TransientTrackBuilder *builder)
{
        trackMap.clear();
        trackBuilder = builder;
}