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#include "UHHAnalysis/NtupleWriter/interface/Qjets.h"
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Qjets::Qjets(double zcut, double dcut_fctr, double exp_min, double exp_max, double rigidity)
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: _zcut(zcut), _dcut_fctr(dcut_fctr), _exp_min(exp_min), _exp_max(exp_max), _rigidity(rigidity)
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{
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_dcut = -1.;
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_rand_seed_set = false;
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}
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void Qjets::SetRandSeed(unsigned int seed){
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_rand_seed_set = true;
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_seed = seed;
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}
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bool Qjets::JetUnmerged(int num){
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if(count(_merged_jets.begin(), _merged_jets.end(), num) > 0)
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return false;
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return true;
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}
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bool Qjets::JetsUnmerged(jet_distance& jd){
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return JetUnmerged(jd.j1) && JetUnmerged(jd.j2);
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}
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void Qjets::ComputeNewDistanceMeasures(fastjet::ClusterSequence & cs, int new_jet){
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// jet-jet distances
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for(unsigned int i = 0; i < cs.jets().size(); i++)
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if(JetUnmerged(i) && i != (unsigned int) new_jet){
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jet_distance jd;
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jd.j1 = new_jet;
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jd.j2 = i;
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jd.dij = d_ij(cs.jets()[jd.j1], cs.jets()[jd.j2]);
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_distances.push_back(jd);
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}
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}
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void Qjets::ComputeDCut(fastjet::ClusterSequence & cs){
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// assume all jets in cs form a single jet. compute mass and pt
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fastjet::PseudoJet sum(0.,0.,0.,0.);
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for(vector<fastjet::PseudoJet>::const_iterator it = cs.jets().begin(); it != cs.jets().end(); it++)
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sum += (*it);
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_dcut = 2. * _dcut_fctr * sum.m()/sum.perp();
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}
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double Qjets::ComputeMinimumDistance(){
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double dmin(-1.);
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for(list<jet_distance>::iterator it = _distances.begin(); it != _distances.end(); )
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if(JetsUnmerged(*it)){
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if(dmin == -1. || (*it).dij < dmin)
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dmin = (*it).dij;
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it++;
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} else
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it = _distances.erase(it);
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return dmin;
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}
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double Qjets::ComputeNormalization(double dmin){
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double norm(0.);
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for(list<jet_distance>::iterator it = _distances.begin(); it != _distances.end(); )
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if(JetsUnmerged(*it)){
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double inc = 0.;
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/*
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We need to be careful about dmin == 0 which happens for collinear jets.
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(Thanks go to Nhan V Tran for finding this bug)
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*/
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if(dmin == 0.){
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if((*it).dij == 0.)
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inc = 1.;
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else
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inc = 0.;
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} else
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inc = exp(-_rigidity*((*it).dij-dmin)/dmin);
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assert(inc <= 1. && !isnan((float) inc));
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norm += inc;
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it++;
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} else
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it = _distances.erase(it);
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return norm;
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}
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void Qjets::Cluster(fastjet::ClusterSequence & cs){
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ComputeDCut(cs);
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ComputeAllDistances(cs.jets());
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while (!_distances.empty()){
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double dmin = ComputeMinimumDistance();
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double norm = ComputeNormalization(dmin);
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// sometimes if the rigidity is too large the norm is zero. make sure this is not the case
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if(_distances.size() == 0)
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break;
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assert(norm > 0.);
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// Now compute a random number between 0 and 1 and find the corresponding measure
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double rand = Rand();
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double sum = 0.;
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for(list<jet_distance>::iterator it = _distances.begin(); it != _distances.end(); it++){
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/*
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We need to be careful about dmin == 0 which happens for collinear jets.
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(Thanks go to Nhan V Tran for finding this bug)
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*/
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if(dmin == 0.){
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if((*it).dij == 0.)
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sum += 1./norm;
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} else
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sum += exp(-_rigidity*((*it).dij-dmin)/dmin)/norm;
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assert(!isnan((float)sum));
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if(sum > rand){
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if(!Prune((*it),cs)){
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_merged_jets.push_back((*it).j1);
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_merged_jets.push_back((*it).j2);
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int new_jet;
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cs.plugin_record_ij_recombination((*it).j1, (*it).j2, 1., new_jet);
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assert(JetUnmerged(new_jet));
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ComputeNewDistanceMeasures(cs,new_jet);
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} else {
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double j1pt = cs.jets()[(*it).j1].perp();
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double j2pt = cs.jets()[(*it).j2].perp();
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if(j1pt>j2pt){
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_merged_jets.push_back((*it).j2);
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cs.plugin_record_iB_recombination((*it).j2, 1.);
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} else {
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_merged_jets.push_back((*it).j1);
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cs.plugin_record_iB_recombination((*it).j1, 1.);
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}
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}
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break;
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}
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}
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}
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// merge remaining jets with beam
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int num_merged_final(0);
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for(unsigned int i = 0 ; i < cs.jets().size(); i++)
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if(JetUnmerged(i)){
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num_merged_final++;
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cs.plugin_record_iB_recombination(i,1.);
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}
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assert(num_merged_final < 2);
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}
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bool Qjets::Prune(jet_distance& jd,fastjet::ClusterSequence & cs){
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double pt1 = cs.jets()[jd.j1].perp();
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double pt2 = cs.jets()[jd.j2].perp();
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fastjet::PseudoJet sum_jet = cs.jets()[jd.j1]+cs.jets()[jd.j2];
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double sum_pt = sum_jet.perp();
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double z = min(pt1,pt2)/sum_pt;
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double d = sqrt(cs.jets()[jd.j1].plain_distance(cs.jets()[jd.j2]));
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return (d > _dcut) && (z < _zcut);
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}
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void Qjets::ComputeAllDistances(const vector<fastjet::PseudoJet>& inp){
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for(unsigned int i = 0 ; i < inp.size()-1; i++){
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// jet-jet distances
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for(unsigned int j = i+1 ; j < inp.size(); j++){
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jet_distance jd;
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jd.j1 = i;
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jd.j2 = j;
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if(jd.j1 != jd.j2){
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jd.dij = d_ij(inp[i],inp[j]);
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_distances.push_back(jd);
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}
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}
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}
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}
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double Qjets::d_ij(const fastjet::PseudoJet& v1,const fastjet::PseudoJet& v2){
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double p1 = v1.perp();
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double p2 = v2.perp();
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double ret = pow(min(p1,p2),_exp_min) * pow(max(p1,p2),_exp_max) * v1.squared_distance(v2);
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assert(!isnan((float)ret));
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return ret;
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}
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double Qjets::Rand(){
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double ret = 0.;
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if(_rand_seed_set)
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ret = rand_r(&_seed)/(double)RAND_MAX;
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else
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ret = rand()/(double)RAND_MAX;
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return ret;
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}
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