Loading...
Searching...
No Matches
11-filter.cc
Go to the documentation of this file.
//----------------------------------------------------------------------
/// \file
/// \page Example11 11 - use of filtering
///
/// fastjet example program to illustrate the use of the
/// fastjet::Filter class
///
/// We apply different filter examples to either the hardest jet of
/// the given event, or to the composition of the two hardest jets:
///
/// - two examples of a filter keeping a fixed number of subjets (as
/// in arXiv:0802.2470)
/// - a "trimmer" i.e. a filter keeping subjets carrying at least a given
/// fraction of the pt of the jet (arXiv:0912.1342).
/// - two examples of filter in combination with background subtraction
///
/// run it with : ./11-filter < data/single-event.dat
///
/// Source code: 11-filter.cc
//----------------------------------------------------------------------
//STARTHEADER
// $Id$
//
// Copyright (c) 2005-2018, 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 and are described in hep-ph/0512210. If you use
// FastJet as part of work towards a scientific publication, please
// include a citation to the FastJet paper.
//
// 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/>.
//----------------------------------------------------------------------
//ENDHEADER
#include <fastjet/PseudoJet.hh>
#include <fastjet/ClusterSequence.hh>
#include <fastjet/Selector.hh>
#include <iostream>
#include "fastjet/tools/Filter.hh"
// the following includes are only needed when combining filtering with subtraction
#include "fastjet/tools/GridMedianBackgroundEstimator.hh"
#include "fastjet/ClusterSequenceArea.hh"
#include "fastjet/tools/Subtractor.hh"
#include <cstdio> // needed for io
using namespace fastjet;
using namespace std;
// a function returning
// min(Rmax, deltaR_factor * deltaR(j1,j2))
// where j1 and j2 are the 2 subjets of j
// if the jet does not have 2 exactly pieces, Rmax is used.
class DynamicRfilt : public FunctionOfPseudoJet<double>{
public:
// default ctor
DynamicRfilt(double Rmax, double deltaR_factor) : _Rmax(Rmax), _deltaR_factor(deltaR_factor){}
// action of the function
double result(const PseudoJet &j) const{
if (! j.has_pieces()) return _Rmax;
vector<PseudoJet> pieces = j.pieces();
if (pieces.size() != 2) return _Rmax;
double deltaR = pieces[0].delta_R(pieces[1]);
return min(_Rmax, _deltaR_factor * deltaR);
}
private:
double _Rmax, _deltaR_factor;
};
/// an example program showing how to use Filter in FastJet
int main(){
// read in input particles
//----------------------------------------------------------
vector<PseudoJet> input_particles;
double px, py , pz, E;
while (cin >> px >> py >> pz >> E) {
// create a PseudoJet with these components and put it onto
// back of the input_particles vector
input_particles.push_back(PseudoJet(px,py,pz,E));
}
// get the resulting jets ordered in pt
//----------------------------------------------------------
JetDefinition jet_def(cambridge_algorithm, 1.2);
// the use of a ClusterSequenceArea (instead of a plain ClusterSequence)
// is only needed because we will later combine filtering with area-based
// subtraction
ClusterSequenceArea clust_seq(input_particles, jet_def,
AreaDefinition(active_area_explicit_ghosts));
vector<PseudoJet> inclusive_jets = sorted_by_pt(clust_seq.inclusive_jets(5.0));
// label the columns
printf("%5s %15s %15s %15s\n","jet #", "rapidity", "phi", "pt");
// print out the details for each jet
for (unsigned int i = 0; i < inclusive_jets.size(); i++) {
printf("%5u %15.8f %15.8f %15.8f\n",
i, inclusive_jets[i].rap(), inclusive_jets[i].phi(),
inclusive_jets[i].perp());
}
// simple test to avoid that the example below crashes:
// make sure there is at least 3 jets above our 5 GeV
if (inclusive_jets.size()<3){
cout << "Please provide an event with at least 3 jets above 5 GeV" << endl;
return 1;
}
// the sample PseudoJet that we will filter
// - the hardest jet of the event
// - the composition of the second and third hardest jets
/// (this shows that the Filter can also be applied to a composite jet)
//----------------------------------------------------------
vector<PseudoJet> candidates;
candidates.push_back(inclusive_jets[0]);
candidates.push_back(join(inclusive_jets[1],inclusive_jets[2]));
// create 5 filters
//----------------------------------------------------------
vector<Filter> filters;
// 1.
// the Cambridge/Aachen filter with Rfilt=0.3 (simpliefied version of arXiv:0802.2470)
filters.push_back(Filter(JetDefinition(cambridge_algorithm, 0.3), SelectorNHardest(3)));
// 2.
// the Cambridge/Aachen filter with Rfilt=min(0.3, 0.5*Rbb) as in arXiv:0802.2470
SharedPtr<DynamicRfilt> dynamic_Rfilt(new DynamicRfilt(0.3, 0.5));
filters.push_back(Filter(dynamic_Rfilt.get(), SelectorNHardest(3)));
// 3.
// Filtering with a pt cut as for trimming (arXiv:0912.1342)
filters.push_back(Filter(JetDefinition(kt_algorithm, 0.2), SelectorPtFractionMin(0.03)));
// 4.
// First example of filtering with subtraction of the background: provide rho
// First, estimate the background for the given event
GridMedianBackgroundEstimator bkgd(4.5, 0.55); // uses particles up to |y|=4.5
bkgd.set_particles(input_particles);
double rho = bkgd.rho();
// Then, define the filter
filters.push_back(Filter(JetDefinition(cambridge_algorithm, 0.3), SelectorNHardest(3), rho));
// 5.
// Second example of filtering with subtraction of the background: set a subtractor
// First, define a subtractor from a background estimator
Subtractor subtractor(&bkgd);
// Then, define the filter
Filter filt(JetDefinition(cambridge_algorithm, 0.3), SelectorNHardest(3));
// Finally, tell the filter about the subtractor
filt.set_subtractor(&subtractor);
filters.push_back(filt);
// apply the various filters to the test PseudoJet
// and show the result
//----------------------------------------------------------
// print out original jet candidates
cout << "\nOriginal jets that will be filtered: " << endl;
for (vector<PseudoJet>::iterator jit=candidates.begin(); jit!=candidates.end(); jit++){
const PseudoJet & c = *jit;
cout << " rap = " << c.rap() << ", phi = " << c.phi() << ", pt = " << c.perp()
<< " [" << c.description() << "]" << endl;
}
// loop on filters
for (vector<Filter>::iterator it=filters.begin(); it!=filters.end(); it++){
const Filter & f = *it;
cout << "\nUsing filter: " << f.description() << endl;
// loop on jet candidates
for (vector<PseudoJet>::iterator jit=candidates.begin(); jit!=candidates.end(); jit++){
const PseudoJet & c = *jit;
// apply filter f to jet c
PseudoJet j = f(c);
// access properties specific to the Filter
//
// We first make sure that the jet indeed has a structure
// compatible with the result of a Filter (using
// has_structure_of()), and then retrieve the pieces rejected by the
// filter (using structure_of())
assert(j.has_structure_of<Filter>());
const Filter::StructureType & fj_struct = j.structure_of<Filter>();
// write out result
cout << " rap = " << j.rap() << ", phi = " << j.phi() << ", pt = " << j.perp()
<< " [kept: " << j.pieces().size() << ", rejected: "
<< fj_struct.rejected().size() << "]" << endl;
}
}
return 0;
}
main
int main()
an example program showing how to use Filter in FastJet
Definition 11-filter.cc:90
fastjet::AreaDefinition
class that holds a generic area definition
Definition AreaDefinition.hh:82
fastjet::ClusterSequenceArea
General class for user to obtain ClusterSequence with additional area information.
Definition ClusterSequenceArea.hh:51
fastjet::ClusterSequence::inclusive_jets
std::vector< PseudoJet > inclusive_jets(const double ptmin=0.0) const
return a vector of all jets (in the sense of the inclusive algorithm) with pt >= ptmin.
Definition ClusterSequence.cc:916
fastjet::FilterStructure::rejected
const std::vector< PseudoJet > & rejected() const
returns the subjets that were not kept during the filtering procedure (subtracted if the filter reque...
Definition Filter.hh:228
fastjet::Filter
Class that helps perform filtering (Butterworth, Davison, Rubin and Salam, arXiv:0802....
Definition Filter.hh:97
fastjet::Filter::set_subtractor
void set_subtractor(const FunctionOfPseudoJet< PseudoJet > *subtractor_in)
Set a subtractor that is applied to all individual subjets before deciding which ones to keep.
Definition Filter.hh:144
fastjet::Filter::description
virtual std::string description() const
class description
Definition Filter.cc:50
fastjet::FunctionOfPseudoJet
base class providing interface for a generic function of a PseudoJet
Definition FunctionOfPseudoJet.hh:48
fastjet::GridMedianBackgroundEstimator
Background Estimator based on the median pt/area of a set of grid cells.
Definition GridMedianBackgroundEstimator.hh:69
fastjet::GridMedianBackgroundEstimator::set_particles
void set_particles(const std::vector< PseudoJet > &particles) override
tell the background estimator that it has a new event, composed of the specified particles.
Definition GridMedianBackgroundEstimator.cc:43
fastjet::GridMedianBackgroundEstimator::rho
double rho() const override
returns rho, the median background density per unit area
Definition GridMedianBackgroundEstimator.cc:158
fastjet::JetDefinition
class that is intended to hold a full definition of the jet clusterer
Definition JetDefinition.hh:250
fastjet::PseudoJet
Class to contain pseudojets, including minimal information of use to jet-clustering routines.
Definition PseudoJet.hh:68
fastjet::PseudoJet::rap
double rap() const
returns the rapidity or some large value when the rapidity is infinite
Definition PseudoJet.hh:138
fastjet::PseudoJet::structure_of
const TransformerType::StructureType & structure_of() const
this is a helper to access any structure created by a Transformer (that is, of type Transformer::Stru...
Definition PseudoJet.hh:1122
fastjet::PseudoJet::phi
double phi() const
returns phi (in the range 0..2pi)
Definition PseudoJet.hh:123
fastjet::PseudoJet::perp
double perp() const
returns the scalar transverse momentum
Definition PseudoJet.hh:158
fastjet::PseudoJet::has_structure_of
bool has_structure_of() const
check if the PseudoJet has the structure resulting from a Transformer (that is, its structure is comp...
Definition PseudoJet.hh:1112
fastjet::PseudoJet::has_pieces
virtual bool has_pieces() const
returns true if a jet has pieces
Definition PseudoJet.cc:783
fastjet::PseudoJet::description
std::string description() const
return a string describing what kind of PseudoJet we are dealing with
Definition PseudoJet.cc:517
fastjet::PseudoJet::pieces
virtual std::vector< PseudoJet > pieces() const
retrieve the pieces that make up the jet.
Definition PseudoJet.cc:792
fastjet::SharedPtr
An implementation of shared pointers that is broadly similar to C++11 shared_ptr (https://en....
Definition SharedPtr.hh:341
fastjet::SharedPtr::get
T * get() const
get the stored pointer
Definition SharedPtr.hh:473
fastjet::Subtractor
Class that helps perform jet background subtraction.
Definition Subtractor.hh:62
fastjet::SelectorNHardest
Selector SelectorNHardest(unsigned int n)
select the n hardest objects
Definition Selector.cc:1074
fastjet::SelectorPtFractionMin
Selector SelectorPtFractionMin(double fraction)
select objects that carry at least a fraction "fraction" of the reference jet.
Definition Selector.cc:1365
fastjet
the FastJet namespace
Definition AreaDefinition.cc:37
fastjet::cambridge_algorithm
@ cambridge_algorithm
the longitudinally invariant variant of the cambridge algorithm (aka Aachen algoithm).
Definition JetDefinition.hh:142
fastjet::kt_algorithm
@ kt_algorithm
the longitudinally invariant kt algorithm
Definition JetDefinition.hh:139
fastjet::sorted_by_pt
vector< PseudoJet > sorted_by_pt(const vector< PseudoJet > &jets)
return a vector of jets sorted into decreasing kt2
Definition PseudoJet.cc:882