PileupReweightingProvider.h

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef PILEUPREWEIGHTINGPROVIDER
#define PILEUPREWEIGHTINGPROVIDER
 
#include "AsgAnalysisInterfaces/IPileupReweightingTool.h"
#include "AthenaBaseComps/AthAlgorithm.h"
#include "GaudiKernel/ToolHandle.h"
 
#include "xAODEventInfo/EventInfoAuxContainer.h"
 
#include "PATInterfaces/SystematicRegistry.h"
 
namespace CP {
 
class PileupReweightingProvider : public AthAlgorithm {
 
     public:
      PileupReweightingProvider( const std::string& name, ISvcLocator* svcloc) : AthAlgorithm(name,svcloc),m_tool("CP::PileupReweightingTool/auto") {
         declareProperty("Tool",m_tool,"The configured PileupReweightingTool");
         declareProperty("Input",m_inputKey="","Specify a specific EventInfo object");
         declareProperty("Output",m_outputKey="","Specify an output EventInfo object. If differs from input, will create a clone of EventInfo and decorate that");
         declareProperty("ConfigOutputStream",m_configStream="","Specify the stream to output config file to");
         declareProperty("RunSystematics",m_systematics=true,"Enable systematics during run");
      }
 
      ~PileupReweightingProvider() { }
 
      virtual StatusCode initialize() { 
         CHECK( m_tool.retrieve() ); 
 
         IProperty* myTool = dynamic_cast<IProperty*>(&*m_tool);
         if (!myTool)
           return StatusCode::FAILURE;
         CHECK( myTool->setProperty("ConfigOutputStream",m_configStream) );
 
         //get the list of systematics 
         CP::SystematicRegistry& registry = CP::SystematicRegistry::getInstance();
         m_allSysts = registry.recommendedSystematics();
 
         if(m_configStream!="") ATH_MSG_INFO("Now running config file making .... please be patient! ... ");
 
         return StatusCode::SUCCESS; 
      }
      virtual StatusCode execute(const EventContext& /*ctx*/) {
            const xAOD::EventInfo* evtInfo =0;
 
            if(m_inputKey.length()>0) ATH_CHECK(evtStore()->retrieve(evtInfo,m_inputKey));
            else {
               #ifdef XAOD_STANDALONE
                  ATH_CHECK( evtStore()->retrieve(evtInfo,"") ); //apparently TEvent can't do keyless retrieves!!??
               #else
                  ATH_CHECK(evtStore()->retrieve(evtInfo));
               #endif
            }
 
            //do we need to make a copy??
            if(m_inputKey!=m_outputKey && m_outputKey!="") {
               xAOD::EventInfo* evtInfoCopy = new xAOD::EventInfo( *evtInfo );
               xAOD::EventInfoAuxContainer* aux = new xAOD::EventInfoAuxContainer;
               evtInfoCopy->setStore(aux);
               ATH_CHECK( evtStore()->record( evtInfoCopy , m_outputKey ) );
               ATH_CHECK( evtStore()->record( aux , m_outputKey+"Aux." ) );
               evtInfo = evtInfoCopy;
            }
 
            CHECK( m_tool->apply(*evtInfo) );
 
 
            //here's an example of systematic variations 
            if (m_systematics){
               for(auto& syst : m_allSysts) {
                  ATH_MSG_VERBOSE("Doing systematic : " << syst.name());
                  if(! m_tool->isAffectedBySystematic( syst )) continue;
                  CP::SystematicSet tmp; tmp.insert( syst );
                  if( m_tool->applySystematicVariation( tmp ) != StatusCode::SUCCESS ) continue;
                  CHECK( m_tool->apply(*evtInfo) );
               }
               //make sure we leave the tool in the nominal mode
               if( m_tool->applySystematicVariation( CP::SystematicSet() ) != StatusCode::SUCCESS ) return StatusCode::FAILURE;
            }
 
            return StatusCode::SUCCESS; 
      }
 
   private:
      ToolHandle<IPileupReweightingTool> m_tool;
 
      std::string m_inputKey,m_outputKey,m_configStream;
 
      CP::SystematicSet m_allSysts;
 
      bool m_systematics;
 
}; 
 
} //end of CP namespace
 
#endif