MCParticleModuloFilter.cc

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// description: select events where the multiplicity of specified particle is a multiple of provided number

// system include files
#include <memory>
#include <string>
#include <cmath>
#include <vector>
#include <algorithm>

// user include files
#include "FWCore/Framework/interface/Frameworkfwd.h"
#include "FWCore/Framework/interface/global/EDFilter.h"
#include "FWCore/Framework/interface/Event.h"
#include "FWCore/Framework/interface/MakerMacros.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "SimDataFormats/GeneratorProducts/interface/HepMCProduct.h"

class MCParticleModuloFilter : public edm::global::EDFilter<> {
    public:
        explicit MCParticleModuloFilter(const edm::ParameterSet&);
        ~MCParticleModuloFilter() override {}

        bool filter(edm::StreamID, edm::Event&, const edm::EventSetup&) const override;

        static void fillDescriptions(edm::ConfigurationDescriptions& descriptions);

    private:
        // member data
        const edm::EDGetTokenT<edm::HepMCProduct> token_;
        std::vector<int> particleIDs_;
        unsigned multipleOf_;
        bool absID_;
        unsigned min_;
        int status_;
};

MCParticleModuloFilter::MCParticleModuloFilter(const edm::ParameterSet& iConfig) :
    token_(consumes<edm::HepMCProduct>(iConfig.getParameter<edm::InputTag>("moduleLabel"))),
    particleIDs_(iConfig.getParameter<std::vector<int>>("particleIDs")),
    multipleOf_(iConfig.getParameter<unsigned>("multipleOf")),
    absID_(iConfig.getParameter<bool>("absID")),
    min_(iConfig.getParameter<unsigned>("min")),
    status_(iConfig.getParameter<int>("status"))
{
    // allow binary search
    std::sort(particleIDs_.begin(),particleIDs_.end());
}

bool MCParticleModuloFilter::filter(edm::StreamID, edm::Event& iEvent, const edm::EventSetup& iSetup) const {
    // get input
    edm::Handle<edm::HepMCProduct> h_evt;
    iEvent.getByToken(token_,h_evt);
    const HepMC::GenEvent * myGenEvent = h_evt->GetEvent();
    
    unsigned sum_part = 0;
    for(auto i_part = myGenEvent->particles_begin(); i_part != myGenEvent->particles_end(); ++i_part){
        int id_part = (*i_part)->pdg_id();
        if(absID_) id_part = std::abs(id_part);
        if(std::binary_search(particleIDs_.begin(),particleIDs_.end(),id_part) and (status_==0 or (*i_part)->status()==status_)) ++sum_part;
    }
    
    return (sum_part % multipleOf_ == 0) and (sum_part >= min_);
}

void MCParticleModuloFilter::fillDescriptions(edm::ConfigurationDescriptions& descriptions) {
    edm::ParameterSetDescription desc;
    desc.add<edm::InputTag>("moduleLabel",edm::InputTag("generator","unsmeared"));
    desc.add<std::vector<int>>("particleIDs",{});
    desc.add<unsigned>("multipleOf",1);
    desc.add<bool>("absID",false);
    desc.add<unsigned>("min",0);
    desc.add<int>("status",0);

    descriptions.add("MCParticleModuloFilter",desc);
}

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