source: HiSusy/trunk/Delphes/Delphes-3.0.9/external/fastjet/plugins/GridJet/GridJetPlugin.cc @ 5

Last change on this file since 5 was 5, checked in by zerwas, 11 years ago

update to Delphes-3.0.9

File size: 6.6 KB
Line 
1//STARTHEADER
2// $Id: GridJetPlugin.cc 859 2012-11-28 01:49:23Z pavel $
3//
4// Copyright (c) 2011, Matteo Cacciari, Gavin Salam and Gregory Soyez
5//
6//----------------------------------------------------------------------
7// This file is part of FastJet.
8//
9//  FastJet is free software; you can redistribute it and/or modify
10//  it under the terms of the GNU General Public License as published by
11//  the Free Software Foundation; either version 2 of the License, or
12//  (at your option) any later version.
13//
14//  The algorithms that underlie FastJet have required considerable
15//  development and are described in hep-ph/0512210. If you use
16//  FastJet as part of work towards a scientific publication, please
17//  include a citation to the FastJet paper.
18//
19//  FastJet is distributed in the hope that it will be useful,
20//  but WITHOUT ANY WARRANTY; without even the implied warranty of
21//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
22//  GNU General Public License for more details.
23//
24//  You should have received a copy of the GNU General Public License
25//  along with FastJet. If not, see <http://www.gnu.org/licenses/>.
26//----------------------------------------------------------------------
27//ENDHEADER
28
29// fastjet stuff
30#include "fastjet/ClusterSequence.hh"
31#include "fastjet/GridJetPlugin.hh"
32
33// other stuff
34#include <vector>
35#include <sstream>
36
37FASTJET_BEGIN_NAMESPACE      // defined in fastjet/internal/base.hh
38
39using namespace std;
40
41//----------------------------------------------------------------------
42GridJetPlugin::GridJetPlugin (double ymax,
43                              double requested_grid_spacing, 
44                              const JetDefinition & post_jet_def) :
45  _ymin(-ymax), _ymax(ymax), 
46  _requested_grid_spacing(requested_grid_spacing) ,
47  _post_jet_def(post_jet_def)
48{
49  setup_grid();
50}
51
52void GridJetPlugin::setup_grid() {
53  // since we've exchanged the arguments of the constructor,
54  // there's a danger of calls with exchanged ymax,spacing arguments --
55  // the following check should catch most such situations.
56  assert(_ymax>0 && _ymax - _ymin >= _requested_grid_spacing);
57
58  double ny_double = (_ymax-_ymin) / _requested_grid_spacing;
59  _ny = int(ny_double+0.49999);
60  _dy = (_ymax-_ymin) / _ny;
61 
62  _nphi = int (twopi / _requested_grid_spacing + 0.5);
63  _dphi = twopi / _nphi;
64
65  // some sanity checking (could throw a fastjet::Error)
66  assert(_ny >= 1 && _nphi >= 1);
67
68  _ntotal = _nphi * _ny;
69}
70
71
72//----------------------------------------------------------------------
73string GridJetPlugin::description () const {
74  ostringstream desc;
75  desc << "GridJetPlugin plugin with ymax = " << _ymax << ", dy = " << _dy << ", dphi = " << _dphi << " (requested grid spacing was " << _requested_grid_spacing << ")";
76  if (_post_jet_def.jet_algorithm() != undefined_jet_algorithm) {
77    desc << ", followed by " << _post_jet_def.description();
78  }
79  return desc.str();
80}
81
82
83//----------------------------------------------------------------------
84double GridJetPlugin::R() const {return sqrt(_dy*_dphi/pi);}
85
86
87//----------------------------------------------------------------------
88int GridJetPlugin::igrid(const PseudoJet & p) const {
89  // directly taking int does not work for values between -1 and 0
90  // so use floor instead
91  // double iy_double = (p.rap() - _ymin) / _dy;
92  // if (iy_double < 0.0) return -1;
93  // int iy = int(iy_double);
94  // if (iy >= _ny) return -1;
95
96  // writing it as below gives a huge speed gain (factor two!). Even
97  // though answers are identical and the routine here is not the
98  // speed-critical step. It's not at all clear why.
99  int iy = int(floor( (p.rap() - _ymin) / _dy ));
100  if (iy < 0 || iy >= _ny) return -1;
101
102  int iphi = int( p.phi()/_dphi );
103  assert(iphi >= 0 && iphi <= _nphi);
104  if (iphi == _nphi) iphi = 0; // just in case of rounding errors
105
106  int igrid_res = iy*_nphi + iphi;
107  assert (igrid_res >= 0 && igrid_res < _ny*_nphi);
108  return igrid_res;
109}
110
111
112//----------------------------------------------------------------------
113void GridJetPlugin::run_clustering(ClusterSequence & cs) const {
114 
115  // we will create a grid;
116  //  * -1 will indicate there is no jet here currently
117  //  * a number >= 0 will mean that particle indicated by the index
118  //    is currently the jet on the grid
119  vector<int> grid(_ntotal, -1);
120 
121  int nparticles = cs.jets().size();
122  double dij_or_diB = 1.0;
123
124  int ngrid_active = 0;
125
126  // combine particles with whatever is in the grid
127  for (int i = 0; i < nparticles; i++) {
128    int igrd = igrid(cs.jets()[i]);
129    //cout << i << " " << cs.jets()[i].rap() << " " << cs.jets()[i].phi()
130    //   << " " << igrd << " " << grid.size() << " " << _ntotal << endl;
131    if (igrd < 0) continue;
132    assert(igrd <= _ntotal);
133    if (grid[igrd] == -1) {
134      grid[igrd] = i; // jet index of initial particle i is i
135      ngrid_active++;
136    } else {
137      int k;
138      cs.plugin_record_ij_recombination(grid[igrd], i, dij_or_diB, k);
139      grid[igrd] = k; // grid takes jet index of new particle
140      //cout << "  res: " << cs.jets()[k].rap() << " " << cs.jets()[k].phi() << endl;
141    }
142  }
143
144  if (_post_jet_def.jet_algorithm() == undefined_jet_algorithm) {
145    // make the final jets via iB recombinations
146    for (unsigned igrd = 0; igrd < grid.size(); igrd++) {
147      if (grid[igrd] != -1) cs.plugin_record_iB_recombination(grid[igrd], 
148                                                              dij_or_diB);
149    }
150  } else {
151    // otherwise post-cluster the grid elements with a normal jet algorithm
152    vector<PseudoJet> inputs;
153    vector<int>       cs_indices;
154    inputs.reserve(ngrid_active);
155    cs_indices.reserve(2*ngrid_active);
156    for (unsigned igrd = 0; igrd < grid.size(); igrd++) {
157      if (grid[igrd] != -1) {
158        inputs.push_back(cs.jets()[grid[igrd]]);
159        cs_indices.push_back(grid[igrd]);
160      }
161    }
162    ClusterSequence post_cs(inputs, _post_jet_def);
163    const vector<ClusterSequence::history_element> & post_history = post_cs.history();
164    const vector<PseudoJet>                        & post_jets = post_cs.jets();
165    for (unsigned ihist = ngrid_active; ihist < post_history.size(); ihist++) {
166      const ClusterSequence::history_element & hist = post_history[ihist];
167      int post_ij1 = post_history[hist.parent1].jetp_index;
168      int ij1 = cs_indices[post_ij1];
169      if (hist.parent2 >= 0) {
170        int post_ij2 = post_history[hist.parent2].jetp_index;
171        int ij2 = cs_indices[post_ij2];
172        int k;
173        cs.plugin_record_ij_recombination(ij1, ij2, hist.dij, post_jets[hist.jetp_index], k); 
174        assert(int(cs_indices.size()) == hist.jetp_index);
175        cs_indices.push_back(k);
176      } else {
177        cs.plugin_record_iB_recombination(ij1, hist.dij);
178      }
179    }
180   
181  }
182}
183
184FASTJET_END_NAMESPACE      // defined in fastjet/internal/base.hh
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