/data/refman/pasoursint/CMSSW_5_2_9/src/PhysicsTools/FWLite/bin/FWLiteWithPythonConfig.cc

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#include <TH1F.h>
#include <TROOT.h>
#include <TFile.h>
#include <TSystem.h>

#include "DataFormats/FWLite/interface/Event.h"
#include "DataFormats/Common/interface/Handle.h"
#include "FWCore/FWLite/interface/AutoLibraryLoader.h"

#include "DataFormats/FWLite/interface/InputSource.h"
#include "DataFormats/FWLite/interface/OutputFiles.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/PythonParameterSet/interface/MakeParameterSets.h"

#include "DataFormats/MuonReco/interface/Muon.h"
#include "DataFormats/PatCandidates/interface/Muon.h"
#include "PhysicsTools/FWLite/interface/TFileService.h"


int main(int argc, char* argv[]) 
{
  // define what muon you are using; this is necessary as FWLite is not 
  // capable of reading edm::Views
  using reco::Muon;

  // ----------------------------------------------------------------------
  // First Part: 
  //
  //  * enable the AutoLibraryLoader 
  //  * book the histograms of interest 
  //  * open the input file
  // ----------------------------------------------------------------------

  // load framework libraries
  gSystem->Load( "libFWCoreFWLite" );
  AutoLibraryLoader::enable();

  // parse arguments
  if ( argc < 2 ) {
    std::cout << "Usage : " << argv[0] << " [parameters.py]" << std::endl;
    return 0;
  }

  if( !edm::readPSetsFrom(argv[1])->existsAs<edm::ParameterSet>("process") ){
    std::cout << " ERROR: ParametersSet 'process' is missing in your configuration file" << std::endl; exit(0);
  }
  // get the python configuration
  const edm::ParameterSet& process = edm::readPSetsFrom(argv[1])->getParameter<edm::ParameterSet>("process");
  fwlite::InputSource inputHandler_(process); fwlite::OutputFiles outputHandler_(process);


  // now get each parameter
  const edm::ParameterSet& ana = process.getParameter<edm::ParameterSet>("muonAnalyzer");
  edm::InputTag muons_( ana.getParameter<edm::InputTag>("muons") );

  // book a set of histograms
  fwlite::TFileService fs = fwlite::TFileService(outputHandler_.file().c_str());
  TFileDirectory dir = fs.mkdir("analyzeBasicPat");
  TH1F* muonPt_  = dir.make<TH1F>("muonPt"  , "pt"  ,   100,   0.,  300.);
  TH1F* muonEta_ = dir.make<TH1F>("muonEta" , "eta" ,   100,  -3.,    3.);
  TH1F* muonPhi_ = dir.make<TH1F>("muonPhi" , "phi" ,   100,  -5.,    5.);  
  TH1F* mumuMass_= dir.make<TH1F>("mumuMass", "mass",    90,   30., 120.);
  
  // loop the events
  int ievt=0;  
  int maxEvents_( inputHandler_.maxEvents() );
  for(unsigned int iFile=0; iFile<inputHandler_.files().size(); ++iFile){
    // open input file (can be located on castor)
    TFile* inFile = TFile::Open(inputHandler_.files()[iFile].c_str());
    if( inFile ){
      // ----------------------------------------------------------------------
      // Second Part: 
      //
      //  * loop the events in the input file 
      //  * receive the collections of interest via fwlite::Handle
      //  * fill the histograms
      //  * after the loop close the input file
      // ----------------------------------------------------------------------
      fwlite::Event ev(inFile);
      for(ev.toBegin(); !ev.atEnd(); ++ev, ++ievt){
        edm::EventBase const & event = ev;
        // break loop if maximal number of events is reached 
        if(maxEvents_>0 ? ievt+1>maxEvents_ : false) break;
        // simple event counter
        if(inputHandler_.reportAfter()!=0 ? (ievt>0 && ievt%inputHandler_.reportAfter()==0) : false) 
          std::cout << "  processing event: " << ievt << std::endl;
        
        // Handle to the muon collection
        edm::Handle<std::vector<Muon> > muons;
        event.getByLabel(muons_, muons);
        
        // loop muon collection and fill histograms
        for(std::vector<Muon>::const_iterator mu1=muons->begin(); mu1!=muons->end(); ++mu1){
          muonPt_ ->Fill( mu1->pt () );
          muonEta_->Fill( mu1->eta() );
          muonPhi_->Fill( mu1->phi() );   
          if( mu1->pt()>20 && fabs(mu1->eta())<2.1 ){
            for(std::vector<Muon>::const_iterator mu2=muons->begin(); mu2!=muons->end(); ++mu2){
              if(mu2>mu1){ // prevent double conting
                if( mu1->charge()*mu2->charge()<0 ){ // check only muon pairs of unequal charge 
                  if( mu2->pt()>20 && fabs(mu2->eta())<2.1 ){
                    mumuMass_->Fill( (mu1->p4()+mu2->p4()).mass() );
                  }
                }
              }
            }
          }
        }
      }  
      // close input file
      inFile->Close();
    }
    // break loop if maximal number of events is reached:
    // this has to be done twice to stop the file loop as well
    if(maxEvents_>0 ? ievt+1>maxEvents_ : false) break;
  }
  return 0;
}