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//FJSTARTHEADER
// $Id: GridJetPlugin.cc 2268 2011-06-20 15:12:26Z salam $
//
// Copyright (c) 2005-2021, Matteo Cacciari, Gavin P. Salam and Gregory Soyez
//
//----------------------------------------------------------------------
// This file is part of FastJet.
//
// FastJet 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.
//
// The algorithms that underlie FastJet have required considerable
// development. They are described in the original FastJet paper,
// hep-ph/0512210 and in the manual, arXiv:1111.6097. If you use
// FastJet as part of work towards a scientific publication, please
// quote the version you use and include a citation to the manual and
// optionally also to hep-ph/0512210.
//
// FastJet 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 FastJet. If not, see <http://www.gnu.org/licenses/>.
//----------------------------------------------------------------------
//FJENDHEADER
// fastjet stuff
#include "fastjet/ClusterSequence.hh"
#include "fastjet/GridJetPlugin.hh"
// other stuff
#include <vector>
#include <sstream>
FASTJET_BEGIN_NAMESPACE // defined in fastjet/internal/base.hh
using namespace std;
//----------------------------------------------------------------------
GridJetPlugin::GridJetPlugin (double ymax,
double requested_grid_spacing,
const JetDefinition & post_jet_def) :
#ifdef FASTJET_GRIDJET_USEFJGRID
RectangularGrid(ymax, requested_grid_spacing), _post_jet_def(post_jet_def) {
}
#else
_ymin(-ymax), _ymax(ymax),
_requested_grid_spacing(requested_grid_spacing) ,
_post_jet_def(post_jet_def)
{
setup_grid();
}
#endif
#ifdef FASTJET_GRIDJET_USEFJGRID
GridJetPlugin::GridJetPlugin (const RectangularGrid & grid,
const JetDefinition & post_jet_def) :
RectangularGrid(grid), _post_jet_def(post_jet_def) {
if (!RectangularGrid::is_initialised())
throw Error("attempt to construct GridJetPlugin with uninitialised RectangularGrid");
}
#endif // FASTJET_GRIDJET_USEFJGRID
#ifndef FASTJET_GRIDJET_USEFJGRID
void GridJetPlugin::setup_grid() {
// since we've exchanged the arguments of the constructor,
// there's a danger of calls with exchanged ymax,spacing arguments --
// the following check should catch most such situations.
assert(_ymax>0 && _ymax - _ymin >= _requested_grid_spacing);
double ny_double = (_ymax-_ymin) / _requested_grid_spacing;
_ny = int(ny_double+0.49999);
_dy = (_ymax-_ymin) / _ny;
_nphi = int (twopi / _requested_grid_spacing + 0.5);
_dphi = twopi / _nphi;
// some sanity checking (could throw a fastjet::Error)
assert(_ny >= 1 && _nphi >= 1);
_ntotal = _nphi * _ny;
}
//----------------------------------------------------------------------
int GridJetPlugin::tile_index(const PseudoJet & p) const {
// directly taking int does not work for values between -1 and 0
// so use floor instead
// double iy_double = (p.rap() - _ymin) / _dy;
// if (iy_double < 0.0) return -1;
// int iy = int(iy_double);
// if (iy >= _ny) return -1;
// writing it as below gives a huge speed gain (factor two!). Even
// though answers are identical and the routine here is not the
// speed-critical step. It's not at all clear why.
int iy = int(floor( (p.rap() - _ymin) / _dy ));
if (iy < 0 || iy >= _ny) return -1;
int iphi = int( p.phi()/_dphi );
assert(iphi >= 0 && iphi <= _nphi);
if (iphi == _nphi) iphi = 0; // just in case of rounding errors
int igrid_res = iy*_nphi + iphi;
assert (igrid_res >= 0 && igrid_res < _ny*_nphi);
return igrid_res;
}
#endif // not FASTJET_GRIDJET_USEFJGRID
//----------------------------------------------------------------------
string GridJetPlugin::description () const {
ostringstream desc;
desc << "GridJetPlugin plugin with ";
#ifndef FASTJET_GRIDJET_USEFJGRID
desc << "ymax = " << _ymax << ", dy = " << _dy << ", dphi = " << _dphi << " (requested grid spacing was " << _requested_grid_spacing << ")";
#else
desc << RectangularGrid::description();
#endif
if (_post_jet_def.jet_algorithm() != undefined_jet_algorithm) {
desc << ", followed by " << _post_jet_def.description();
}
return desc.str();
}
//----------------------------------------------------------------------
double GridJetPlugin::R() const {return sqrt(drap()*dphi()/pi);}
//----------------------------------------------------------------------
void GridJetPlugin::run_clustering(ClusterSequence & cs) const {
// we will create a grid;
// * -1 will indicate there is no jet here currently
// * a number >= 0 will mean that particle indicated by the index
// is currently the jet on the grid
vector<int> grid(n_tiles(), -1);
int nparticles = cs.jets().size();
double dij_or_diB = 1.0;
int ngrid_active = 0;
// combine particles with whatever is in the grid
for (int i = 0; i < nparticles; i++) {
int igrd = tile_index(cs.jets()[i]);
//cout << i << " " << cs.jets()[i].rap() << " " << cs.jets()[i].phi()
// << " " << igrd << " " << grid.size() << " " << _ntotal << endl;
if (igrd < 0) continue;
assert(igrd <= n_tiles());
if (grid[igrd] == -1) {
grid[igrd] = i; // jet index of initial particle i is i
ngrid_active++;
} else {
int k;
cs.plugin_record_ij_recombination(grid[igrd], i, dij_or_diB, k);
grid[igrd] = k; // grid takes jet index of new particle
//cout << " res: " << cs.jets()[k].rap() << " " << cs.jets()[k].phi() << endl;
}
}
if (_post_jet_def.jet_algorithm() == undefined_jet_algorithm) {
// make the final jets via iB recombinations
for (unsigned igrd = 0; igrd < grid.size(); igrd++) {
if (grid[igrd] != -1 && tile_is_good(igrd))
cs.plugin_record_iB_recombination(grid[igrd], dij_or_diB);
}
} else {
// otherwise post-cluster the grid elements with a normal jet algorithm
vector<PseudoJet> inputs;
vector<int> cs_indices;
inputs.reserve(ngrid_active);
cs_indices.reserve(2*ngrid_active);
for (unsigned igrd = 0; igrd < grid.size(); igrd++) {
if (grid[igrd] != -1) {
inputs.push_back(cs.jets()[grid[igrd]]);
cs_indices.push_back(grid[igrd]);
}
}
ClusterSequence post_cs(inputs, _post_jet_def);
const vector<ClusterSequence::history_element> & post_history = post_cs.history();
const vector<PseudoJet> & post_jets = post_cs.jets();
for (unsigned ihist = ngrid_active; ihist < post_history.size(); ihist++) {
const ClusterSequence::history_element & hist = post_history[ihist];
int post_ij1 = post_history[hist.parent1].jetp_index;
int ij1 = cs_indices[post_ij1];
if (hist.parent2 >= 0) {
int post_ij2 = post_history[hist.parent2].jetp_index;
int ij2 = cs_indices[post_ij2];
int k;
cs.plugin_record_ij_recombination(ij1, ij2, hist.dij, post_jets[hist.jetp_index], k);
assert(int(cs_indices.size()) == hist.jetp_index);
cs_indices.push_back(k);
} else {
cs.plugin_record_iB_recombination(ij1, hist.dij);
}
}
}
}
FASTJET_END_NAMESPACE // defined in fastjet/internal/base.hh
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