JMEmatching< RecContainer, GenContainer >

Description

template<typename RecContainer = std::vector<RecJet>, typename GenContainer = std::vector<GenJet>>
class DAS::JMEmatching< RecContainer, GenContainer >

Function that performs matching between an input list of reconstructed level jets and a list of generator level jets, based on their angular distance. The JetMET matching algorithm is used for the procedure.

JetMET matching algorithm (to what we understand):

1. Allow all possible pairs between gen and rec jets
2. Discard pairs with DR larger than R/2
3. Sort by ascending DR (smaller to larger)
4. Keep pairs that are uniquely defined

According to a page on the TWiki, the matching radius should be taken as half of the cone size radius.

#include <JMEmatching.h>

Collaboration diagram for JMEmatching< RecContainer, GenContainer >:

Public Types
using	RecIt = RecContainer::iterator
using	GenIt = GenContainer::iterator
using	Couple = std::pair< RecIt, GenIt >

Public Member Functions
	JMEmatching (RecContainer &recJets, GenContainer &genJets)

Public Attributes
std::vector< RecIt >	fake_its
std::vector< GenIt >	miss_its
std::vector< Couple >	match_its

Static Public Attributes
static float	maxDR = 0.2

Static Private Member Functions
static FourVector	getP4 (const FourVector &p4)
static FourVector	getP4 (const PhysicsObject &phys_obj)

Member Typedef Documentation

Couple

using Couple = std::pair<RecIt, GenIt>

GenIt

using GenIt = GenContainer::iterator

RecIt

using RecIt = RecContainer::iterator

Constructor & Destructor Documentation

JMEmatching()

JMEmatching ( RecContainer &  recJets, GenContainer &  genJets  )

inline

Parameters

recJets	full container of rec jet
genJets	full container of gen jet

    {
        using namespace std;
 
        // 1) get the size of the collections
 
        size_t nRec = distance(recJets.begin(), recJets.end()),
               nGen = distance(genJets.begin(), genJets.end());
 
        // 2) declare a few utilities
 
        using Indices = pair<size_t,size_t>;
 
        auto DeltaR2 = [&recJets,&genJets](const Indices& indices) {
            const FourVector& recJet = getP4(recJets[indices.first ]),
                            & genJet = getP4(genJets[indices.second]);
            return ROOT::Math::VectorUtil::DeltaR2(recJet, genJet);
        };
 
        auto ascending_DR2 = [&DeltaR2](const Indices& l, const Indices& r) {
            return DeltaR2(l) > DeltaR2(r);
        };
 
        // 3) make pair candidates
 
        // https://en.cppreference.com/w/cpp/container/priority_queue
        priority_queue<      Indices,
                      vector<Indices>, decltype(ascending_DR2)>
                                     candidates(ascending_DR2);
        for (size_t iRec = 0; iRec < nRec; ++iRec)
        for (size_t iGen = 0; iGen < nGen; ++iGen) {
            Indices indices {iRec, iGen};
            auto DR2 = DeltaR2(indices);
            const auto maxDR2 = pow(maxDR,2);
            if (DR2 >= maxDR2) continue;
            candidates.emplace( move(indices) );
        }
 
        // 4) keep only the closest pairs (keep track of matched jets to avoid double matching)
 
        vector<bool> matchedRec(nRec, false),
                     matchedGen(nGen, false);
        match_its.reserve(min(nRec,nGen));
        while (!candidates.empty()) {
            auto [iRec, iGen] = candidates.top();
            candidates.pop();
 
            // skip already matched objects
            if (matchedRec.at(iRec)) continue;
            if (matchedGen.at(iGen)) continue;
            matchedRec.at(iRec) = true;
            matchedGen.at(iGen) = true;
 
            RecIt rec_it = recJets.begin();
            GenIt gen_it = genJets.begin();
            advance(rec_it, iRec);
            advance(gen_it, iGen);
 
            match_its.push_back( make_pair(rec_it, gen_it) );
        }
 
        // 5) fill the unmatched entries
 
        fake_its.reserve(nRec);
        for (int iRec = 0; iRec < nRec; ++iRec) {
            if (matchedRec.at(iRec)) continue;
            RecIt fake_it = recJets.begin();
            advance(fake_it, iRec);
            fake_its.push_back(fake_it);
        }
 
        miss_its.reserve(nGen);
        for (int iGen = 0; iGen < nGen; ++iGen) {
            if (matchedGen.at(iGen)) continue;
            GenIt miss_it = genJets.begin();
            advance(miss_it, iGen);
            miss_its.push_back(miss_it);
        }
    }

Member Function Documentation

getP4() [1/2]

static FourVector getP4 ( const FourVector &  p4 )

inlinestaticprivate

    {
        return p4;
    }

getP4() [2/2]

static FourVector getP4 ( const PhysicsObject &  phys_obj )

inlinestaticprivate

    {
        return phys_obj.p4;
    }

Member Data Documentation

fake_its

std::vector<RecIt> fake_its

match_its

std::vector<Couple> match_its

maxDR

float maxDR = 0.2

static

miss_its

std::vector<GenIt> miss_its

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The documentation for this class was generated from the following file:

• /builds/cms-analysis/general/DasAnalysisSystem/Core/Installer/Core/JEC/interface/JMEmatching.h