source: git/external/fastjet/contribs/Nsubjettiness/MeasureFunction.cc@ f14bd6a

//  Nsubjettiness Package
//  Questions/Comments?  jthaler@jthaler.net
//
//  Copyright (c) 2011-14
//  Jesse Thaler, Ken Van Tilburg, Christopher K. Vermilion, and TJ Wilkason
//
//  $Id: MeasureFunction.cc 670 2014-06-06 01:24:42Z jthaler $
//----------------------------------------------------------------------
// This file is part of FastJet contrib.
//
// It is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2 of the License, or (at
// your option) any later version.
//
// It is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
// License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this code. If not, see <http://www.gnu.org/licenses/>.
//----------------------------------------------------------------------


#include "MeasureFunction.hh"

FASTJET_BEGIN_NAMESPACE      // defined in fastjet/internal/base.hh

namespace contrib{

///////
//
// Measure Function
//
///////

// Return all of the necessary TauComponents for specific input particles and axes
TauComponents MeasureFunction::result(const std::vector<fastjet::PseudoJet>& particles, const std::vector<fastjet::PseudoJet>& axes) const {
   
   // first find partition
   // this sets jetPartitionStorage and beamPartitionStorage
   PseudoJet beamPartitionStorage;
   std::vector<fastjet::PseudoJet> jetPartitionStorage = get_partition(particles,axes,&beamPartitionStorage);
   
   // then return result calculated from partition
   return result_from_partition(jetPartitionStorage,axes,&beamPartitionStorage);
}

std::vector<fastjet::PseudoJet> MeasureFunction::get_partition(const std::vector<fastjet::PseudoJet>& particles,
                                                               const std::vector<fastjet::PseudoJet>& axes,
                                                               PseudoJet * beamPartitionStorage) const {
   
   std::vector<std::vector<PseudoJet> > jetPartition(axes.size());
   std::vector<PseudoJet> beamPartition;
   
   // Figures out the partiting of the input particles into the various jet pieces
   // Based on which axis the parition is closest to
   for (unsigned i = 0; i < particles.size(); i++) {
      
      // find minimum distance; start with beam (-1) for reference
      int j_min = -1;
      double minRsq;
      if (_has_beam) minRsq = beam_distance_squared(particles[i]);
      else minRsq = std::numeric_limits<double>::max(); // make it large value
      
      // check to see which axis the particle is closest to
      for (unsigned j = 0; j < axes.size(); j++) {
         double tempRsq = jet_distance_squared(particles[i],axes[j]); // delta R distance
         if (tempRsq < minRsq) {
            minRsq = tempRsq;
            j_min = j;
         }
      }
      
      if (j_min == -1) {
         if (_has_beam) beamPartition.push_back(particles[i]);
         else assert(_has_beam);  // this should never happen.
      } else {
         jetPartition[j_min].push_back(particles[i]);
      }
   }
   
   // Store beam partition
   if (beamPartitionStorage) {
      *beamPartitionStorage = join(beamPartition);
   }

   // Store jet partitions
   std::vector<PseudoJet> jetPartitionStorage(axes.size(),PseudoJet(0,0,0,0));
   for (unsigned j = 0; j < axes.size(); j++) {
      jetPartitionStorage[j] = join(jetPartition[j]);
   }
   
   return jetPartitionStorage;
}

// does partition, but only stores index of PseudoJets
std::vector<std::list<int> > MeasureFunction::get_partition_list(const std::vector<fastjet::PseudoJet>& particles,
                                                                 const std::vector<fastjet::PseudoJet>& axes) const {

   std::vector<std::list<int> > jetPartition(axes.size());
   
   // Figures out the partiting of the input particles into the various jet pieces
   // Based on which axis the parition is closest to
   for (unsigned i = 0; i < particles.size(); i++) {
      
      // find minimum distance; start with beam (-1) for reference
      int j_min = -1;
      double minRsq;
      if (_has_beam) minRsq = beam_distance_squared(particles[i]);
      else minRsq = std::numeric_limits<double>::max(); // make it large value
      
      // check to see which axis the particle is closest to
      for (unsigned j = 0; j < axes.size(); j++) {
         double tempRsq = jet_distance_squared(particles[i],axes[j]); // delta R distance
         if (tempRsq < minRsq) {
            minRsq = tempRsq;
            j_min = j;
         }
      }
      
      if (j_min == -1) {
         assert(_has_beam); // consistency check
      } else {
         jetPartition[j_min].push_back(i);
      }
   }
   
   return jetPartition;
}
   

// Uses existing partition and calculates result
// TODO:  Can we cache this for speed up when doing area subtraction?
TauComponents MeasureFunction::result_from_partition(const std::vector<fastjet::PseudoJet>& jet_partition,
                                                     const std::vector<fastjet::PseudoJet>& axes,
                                                     PseudoJet * beamPartitionStorage) const {
   
   std::vector<double> jetPieces(axes.size(), 0.0);
   double beamPiece = 0.0;
   
   double tauDen = 0.0;
   if (!_has_denominator) tauDen = 1.0;  // if no denominator, then 1.0 for no normalization factor
   
   // first find jet pieces
   for (unsigned j = 0; j < axes.size(); j++) {
      std::vector<PseudoJet> thisPartition = jet_partition[j].constituents();
      for (unsigned i = 0; i < thisPartition.size(); i++) {
         jetPieces[j] += jet_numerator(thisPartition[i],axes[j]); //numerator jet piece
         if (_has_denominator) tauDen += denominator(thisPartition[i]); // denominator
      }
   }
   
   // then find beam piece
   if (_has_beam) {
      assert(beamPartitionStorage); // make sure I have beam information
      std::vector<PseudoJet> beamPartition = beamPartitionStorage->constituents();

      for (unsigned i = 0; i < beamPartition.size(); i++) {
         beamPiece += beam_numerator(beamPartition[i]); //numerator beam piece
         if (_has_denominator) tauDen += denominator(beamPartition[i]); // denominator
      }
   }
   return TauComponents(jetPieces, beamPiece, tauDen, _has_denominator, _has_beam);
}

   
   
   
   
} //namespace contrib

FASTJET_END_NAMESPACE