JetResolutionDemo.cc

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#include <memory>
#include <iomanip>

#include "FWCore/Framework/interface/Frameworkfwd.h"
#include "FWCore/Framework/interface/EDAnalyzer.h"

#include "FWCore/Framework/interface/Event.h"
#include "FWCore/Framework/interface/MakerMacros.h"
#include "FWCore/Framework/interface/EventSetup.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/Framework/interface/ESHandle.h"
#include "JetMETCorrections/Modules/interface/JetResolution.h"

#include "FWCore/ServiceRegistry/interface/Service.h"
#include "CommonTools/UtilAlgos/interface/TFileService.h"

#include <DataFormats/PatCandidates/interface/Jet.h>

#include <TH2.h>

//
// class declaration
//

class JetResolutionDemo : public edm::EDAnalyzer {
    public:
        explicit JetResolutionDemo(const edm::ParameterSet&);
        ~JetResolutionDemo();

    private:
        virtual void analyze(const edm::Event&, const edm::EventSetup&) override;
        virtual void endJob() override;

        edm::EDGetTokenT<std::vector<pat::Jet>> m_jets_token;

        bool m_debug = false;
        bool m_use_conddb = false;

        std::string m_payload;
        std::string m_resolutions_file;
        std::string m_scale_factors_file;

        edm::Service<TFileService> fs;

        TH2* m_res_vs_eta = nullptr;
};
//
//----------- Class Implementation ------------------------------------------
//
//---------------------------------------------------------------------------
JetResolutionDemo::JetResolutionDemo(const edm::ParameterSet& iConfig)
{
    m_jets_token = consumes<std::vector<pat::Jet>>(iConfig.getParameter<edm::InputTag>("jets"));
    m_debug      = iConfig.getUntrackedParameter<bool>("debug", false);
    m_use_conddb = iConfig.getUntrackedParameter<bool>("useCondDB", false);

    if (m_use_conddb)
        m_payload    = iConfig.getParameter<std::string>("payload");
    else {
        m_resolutions_file = iConfig.getParameter<edm::FileInPath>("resolutionsFile").fullPath();
        m_scale_factors_file = iConfig.getParameter<edm::FileInPath>("scaleFactorsFile").fullPath();
    }
}
//---------------------------------------------------------------------------
JetResolutionDemo::~JetResolutionDemo()
{

}

//---------------------------------------------------------------------------
void JetResolutionDemo::analyze(const edm::Event& iEvent, const edm::EventSetup& iSetup)
{

    edm::Handle<std::vector<pat::Jet>> jets;
    iEvent.getByToken(m_jets_token, jets);

    // Access jet resolution and scale factor from the condition database
    // or from text files
    JME::JetResolution resolution;
    JME::JetResolutionScaleFactor res_sf;

    // Two differents way to create a class instance
    if (m_use_conddb) {
        // First way, using the get() static method
        resolution = JME::JetResolution::get(iSetup, m_payload);
        res_sf = JME::JetResolutionScaleFactor::get(iSetup, m_payload);
    } else {
        // Second way, using the constructor
        resolution = JME::JetResolution(m_resolutions_file);
        res_sf = JME::JetResolutionScaleFactor(m_scale_factors_file);
    }

    if (m_debug) {
        // Dump resolution
        resolution.dump();
    }

    if (! m_res_vs_eta) {
        
        // Advanced usage. Create the histogram by retriving the eta binning directly from the JetResolutionObject. This suppose you need that the parametrization only depends on eta.

        // Get the list of bins of this object
        const std::vector<JME::Binning>& bins = resolution.getResolutionObject()->getDefinition().getBins();

        // Check that the first bin is eta
        if ((bins.size()) && (bins[0] == JME::Binning::JetEta)) {
        
            const std::vector<JME::JetResolutionObject::Record> records = resolution.getResolutionObject()->getRecords();
            // Get all records from the object. Each record correspond to a different binning and different parameters
                
            std::vector<float> etas;
            for (const auto& record: records) {
                if (etas.empty()) {
                    etas.push_back(record.getBinsRange()[0].min);
                    etas.push_back(record.getBinsRange()[0].max);
                } else {
                    etas.push_back(record.getBinsRange()[0].max);
                }   
            }

            std::vector<float> res;
            for (std::size_t i = 0; i < 40; i++) {
                res.push_back(i * 0.005);
            }

            m_res_vs_eta = fs->make<TH2F>("res_vs_eta", "res_vs_eta", etas.size() - 1, &etas[0], res.size() - 1, &res[0]);
        }
    }

    for (const auto& jet: *jets) {
        if (m_debug) {
            std::cout << "New jet; pt=" << jet.pt() << "  eta=" << jet.eta() << "  phi=" << jet.phi() << "  e=" << jet.energy() << std::endl;
        }


        // Get resolution for this jet
        // The method to use is getResolution(const JME::JetParameters& parameters) from a JetResolution object
        
        // You *must* now in advance which variables are needed for getting the resolution. For the moment, only pt and eta are needed, but this will
        // probably change in the futur when PU dependency is added. Please keep an eye on the twiki page
        //     https://twiki.cern.ch/twiki/bin/view/CMSPublic/WorkBookJetEnergyResolution
        // to stay up-to-date. All currently supported parameters (ie, 'set' functions) are available here:
        //     https://twiki.cern.ch/twiki/bin/view/CMSPublic/WorkBookJetEnergyResolution#List_of_supported_parameters
        

        // Three way to create a JetParameters object

        // First, using 'set' functions
        JME::JetParameters parameters_1;
        parameters_1.setJetPt(jet.pt());
        parameters_1.setJetEta(jet.eta());

        // You can also chain calls

        JME::JetParameters parameters_2;
        parameters_2.setJetPt(jet.pt()).setJetEta(jet.eta());

        // Second, using the set() function
        JME::JetParameters parameters_3;
        parameters_3.set(JME::Binning::JetPt, jet.pt());
        parameters_3.set({JME::Binning::JetEta, jet.eta()});

        // Or

        JME::JetParameters parameters_4;
        parameters_4.set(JME::Binning::JetPt, jet.pt()).set(JME::Binning::JetEta, jet.eta());
    
        // Third, using a initializer_list
        JME::JetParameters parameters_5 = {{JME::Binning::JetPt, jet.pt()}, {JME::Binning::JetEta, jet.eta()}};

        // Now, get the resolution

        float r = resolution.getResolution(parameters_1);
        if (m_debug) {
            std::cout << "Resolution with parameters_1: " << r << std::endl;
            std::cout << "Resolution with parameters_2: " << resolution.getResolution(parameters_2) << std::endl;
            std::cout << "Resolution with parameters_3: " << resolution.getResolution(parameters_3) << std::endl;
            std::cout << "Resolution with parameters_4: " << resolution.getResolution(parameters_4) << std::endl;
            std::cout << "Resolution with parameters_5: " << resolution.getResolution(parameters_5) << std::endl;

            // You can also use a shortcut to get the resolution
            float r2 = resolution.getResolution({{JME::Binning::JetPt, jet.pt()}, {JME::Binning::JetEta, jet.eta()}});
            std::cout << "Resolution using shortcut   : " << r2 << std::endl;
        }

        m_res_vs_eta->Fill(jet.eta(), r);

        // We do the same thing to access the scale factors
        float sf = res_sf.getScaleFactor({{JME::Binning::JetEta, jet.eta()}});

        // Access up and down variation of the scale factor
        float sf_up = res_sf.getScaleFactor({{JME::Binning::JetEta, jet.eta()}}, Variation::UP);
        float sf_down = res_sf.getScaleFactor({{JME::Binning::JetEta, jet.eta()}}, Variation::DOWN);

        if (m_debug) {
            std::cout << "Scale factors (Nominal / Up / Down) : " << sf << " / " << sf_up << " / " << sf_down << std::endl;
        }
    }
}
//---------------------------------------------------------------------------
void JetResolutionDemo::endJob()
{

}
//---------------------------------------------------------------------------
//define this as a plug-in
DEFINE_FWK_MODULE(JetResolutionDemo);