CMSSW Reference Manual

00001 
00008 #include "FWCore/Framework/interface/EDProducer.h"
00009 #include "FWCore/ParameterSet/interface/InputTag.h"
00010 #include "DataFormats/Candidate/interface/CandidateFwd.h"
00011 #include <vector>
00012 
00013 namespace edm { class ParameterSet; }
00014 namespace HepMC { class GenParticle; class GenEvent; }
00015 
00016 class GenEventWeightProducer : public edm::EDProducer {
00017  public:
00019   GenEventWeightProducer( const edm::ParameterSet & );
00020 
00021  private:
00022   void produce( edm::Event& evt, const edm::EventSetup& es );
00023   edm::InputTag src_;
00024 };
00025 
00026 #include "SimDataFormats/HepMCProduct/interface/HepMCProduct.h"
00027 #include "DataFormats/Common/interface/Handle.h"
00028 #include "FWCore/Framework/interface/Event.h"
00029 #include "FWCore/Utilities/interface/EDMException.h"
00030 #include "FWCore/ParameterSet/interface/ParameterSet.h"
00031 using namespace edm;
00032 using namespace std;
00033 using namespace HepMC;
00034 
00035 GenEventWeightProducer::GenEventWeightProducer( const ParameterSet & p ) :
00036   src_( p.getParameter<InputTag>( "src" ) ) {
00037   produces<double>();
00038 }
00039 
00040 
00041 void GenEventWeightProducer::produce( Event& evt, const EventSetup& es ) {
00042   Handle<HepMCProduct> mc;
00043   evt.getByLabel( src_, mc );
00044   const GenEvent * genEvt = mc->GetEvent();
00045   if( genEvt == 0 ) 
00046     throw edm::Exception( edm::errors::InvalidReference ) 
00047       << "HepMC has null pointer to GenEvent" << endl;
00048   auto_ptr<double> weight( new double(1) );
00049   HepMC::WeightContainer wc = genEvt->weights();
00050   if ( wc.size() > 0 )  (*weight) = wc[ 0 ];
00051   evt.put( weight );
00052 }
00053 
00054 #include "FWCore/Framework/interface/MakerMacros.h"
00055 
00056 DEFINE_FWK_MODULE( GenEventWeightProducer );
00057
GenEventWeightProducer.cc
