DisplacedJetRankComboHypoTool.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
#include "DisplacedJetRankComboHypoTool.h"
#include "xAODJet/JetContainer.h"
#include "xAODJet/Jet.h"
 
DisplacedJetRankComboHypoTool::DisplacedJetRankComboHypoTool(const std::string& type, const std::string& name, const IInterface* parent): ComboHypoToolBase(type, name, parent) {}
 
StatusCode DisplacedJetRankComboHypoTool::initialize(){
    return StatusCode::SUCCESS;
}
 
StatusCode DisplacedJetRankComboHypoTool::decide(Combo::LegDecisionsMap& passingLegs, const EventContext& /*context*/) const{
    // if no combinations passed, then exit 
    if (passingLegs.size() == 0) {
        return StatusCode::SUCCESS;
    }
 
    std::vector<std::vector<Combo::LegDecision>> legDecisions;
    ATH_CHECK(selectLegs(passingLegs, legDecisions));
 
    //get all the passing jets across all legs valid for this tool
    //also fill a map of jet -> decisions
    //derive ranks for these jets
    //get the list of decision objects which can go on
 
    //need to establish which leg ids come from the displaced jet trigger
    std::unordered_set<TrigCompositeUtils::DecisionID> dispj_leg_ids;
 
    ATH_MSG_DEBUG("Have "<<passingLegs.size()<<" passing legs in");
 
    for(auto legId: legDecisionIds()){
        if(!passingLegs.contains(legId)) continue;
 
        auto decs = passingLegs[legId];
        if(decs.size() == 0) continue;
 
        const TrigCompositeUtils::Decision* decision(*(decs[0]));
        if(decision->hasObjectLink("djtrig_counts")){
            dispj_leg_ids.insert(legId);
        }
    }
 
    ATH_MSG_DEBUG("Have "<<dispj_leg_ids.size()<<" dispjet legs");
 
    std::vector<const xAOD::Jet*> input_jets;
    std::map<const xAOD::Jet*, std::vector<Combo::LegDecision>> jet_decisions;
 
    //populate jet decision map first
    for(const auto& leg_decs : legDecisions){
        for(auto dec_pair : leg_decs){
            const TrigCompositeUtils::Decision* decision(*(dec_pair.second));
 
            //this leg is not a displaced jet leg
            //this tool should ignore it
            if(dispj_leg_ids.count(dec_pair.first) == 0) continue;
 
            //find the jet feature
            std::vector<TrigCompositeUtils::LinkInfo<xAOD::JetContainer>> jet_feature_links = TrigCompositeUtils::findLinks<xAOD::JetContainer>(decision, TrigCompositeUtils::featureString(), TrigDefs::lastFeatureOfType);
            if(jet_feature_links.size() == 0) continue; //verify that we get a jet
            ATH_CHECK(jet_feature_links.size() == 1); //ensure we only have 1 link
            const TrigCompositeUtils::LinkInfo<xAOD::JetContainer> jet_feature_link = jet_feature_links.at(0);
            //verify if the feature link is valid
            ATH_CHECK(jet_feature_link.isValid());
            const xAOD::Jet* jet = *(jet_feature_link.link);
 
            jet_decisions[jet].push_back(dec_pair);
        }
    }
 
    ATH_MSG_DEBUG("Have "<<jet_decisions.size()<<" jets");
 
 
    //fill the input_jets vector
    //filled from the map key which ensures it only gets one entry per jet
    for(const auto & pair: jet_decisions){
        input_jets.push_back(pair.first);
    }
 
    if(input_jets.empty()){
        //reject all legs
        //this should not happen
        ATH_MSG_DEBUG("No input jets, rejecting all legs");
        eraseFromLegDecisionsMap(passingLegs);
        return StatusCode::SUCCESS;
    }
    
    //apply max jet cut to the number of input passing jets
    if(m_maxjets > 0 && input_jets.size() > m_maxjets){
        //max jets cut
        //event fails
        ATH_MSG_DEBUG("Reject event as it has "<<input_jets.size()<<" input passing jets but max jet cut is "<<m_maxjets);
        eraseFromLegDecisionsMap(passingLegs);
        return StatusCode::SUCCESS;
    }
 
 
    //rank jets by pt
    std::sort(input_jets.begin(), input_jets.end(), [](const xAOD::Jet* a, const xAOD::Jet* b) -> bool
        { 
            return a->pt() > b->pt();
        }
    );
 
    //map of legid -> vector of passing decisions
    Combo::LegDecisionsMap accepted_decisions_by_leg;
 
    unsigned int n_jets_passed = 0;
    //make a list of all decisions which are associated with passed jets
    for(size_t i = 0; i<input_jets.size(); i++){
        if(i > m_rankcut) continue; //skip jet as it is outside the rank cut
        n_jets_passed += 1;
 
        //get all the decisions pairs [legId, decision] for this jet
        for(auto leg_dec_pair: jet_decisions.at(input_jets.at(i))){
            accepted_decisions_by_leg[leg_dec_pair.first].push_back(leg_dec_pair.second);
            ATH_MSG_DEBUG("Accepting decision for jet "<<input_jets.at(i)->pt()/1000.0);
        }
    }
 
 
    if(n_jets_passed < input_jets.size()){
        //check that the number of jets has changed
        //this is an optimisation to avoid a needless loop when all jets pass
        //update the legs to only pass the decisions which are associated with passing jets
        for (auto& legIt : passingLegs) {
            if(dispj_leg_ids.count(legIt.first) == 0) continue; //do not do anything with none dispj legs
 
            auto accepted_decisions_on_leg = accepted_decisions_by_leg.find(legIt.first);
 
            if(accepted_decisions_on_leg != accepted_decisions_by_leg.end()){
                //update the list of decisions
                legIt.second = accepted_decisions_on_leg->second;
                ATH_MSG_DEBUG("Updating leg "<<legIt.first<<" with "<<accepted_decisions_on_leg->second.size()<<" decisions");
            }else{
                //no jets pass this leg and the pt rank cut
                //empty the leg
                ATH_MSG_DEBUG("Updating leg "<<legIt.first<<"; clearing decisions");
                legIt.second.clear();
            }
        }
    }
 
    //apply the multiplicity rules
    auto lm = legMultiplicity();
    for(size_t i=0; i<lm.size(); i++){
        auto legId = legDecisionId(i);
 
        if(passingLegs[legId].size() < (size_t)(lm.at(i))){
            //leg has not got enough passes
            //whole event fails as a leg does not pass
            ATH_MSG_DEBUG("Leg "<<legId<<" fails mulitplicity check, rejecting event");
            eraseFromLegDecisionsMap(passingLegs);
            return StatusCode::SUCCESS;
        }
    }
 
    return StatusCode::SUCCESS;
}