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 // $Id: RecursiveSoftDrop.hh 1444 2024-12-09 18:15:56Z salam $
 //
 // Copyright (c) 2014-, Gavin P. Salam, Gregory Soyez, Jesse Thaler,
 // Kevin Zhou, Frederic Dreyer
 //
 //----------------------------------------------------------------------
 // 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/>.
 //----------------------------------------------------------------------
 
 #ifndef __RECURSIVESOFTDROP_HH__
 #define __RECURSIVESOFTDROP_HH__
 
 #include "fastjet/config.h"
 
 // we'll use the native FJ class for reculstering if available
 #if FASTJET_VERSION_NUMBER >= 30100
 #include "fastjet/tools/Recluster.hh"
 #else
 #include "Recluster.hh"
 #endif
 #include "SoftDrop.hh"
 #include "fastjet/WrappedStructure.hh"
 
 #include <iostream>
 #include <queue>
 #include <vector>
 
 FASTJET_BEGIN_NAMESPACE
 
 namespace contrib{
 
 //------------------------------------------------------------------------
 /// \class RecursiveSoftDrop
 /// An implementation of the RecursiveSoftDrop.
 ///
 /// Recursive Soft Drop will recursively groom a jet, removing
 /// particles that fail the criterion
 /// \f[
 ///     z > z_{\rm cut} (\theta/R0)^\beta
 /// \f]
 /// until n subjets have been found.
 ///
 /// Several variants are supported:
 ///  - set_fixed_depth_mode() switches to fixed depth on all branches
 ///    of the clustering tree
 ///  - set_dynamical_R0() switches to dynamical R0 implementation of
 ///    RSD
 ///  - set_hardest_branch_only() switches to following only the
 ///    hardest branch (e.g. for Iterated Soft Drop)
 ///  - set_min_deltaR_square(val) sets a minimum angle considered for
 ///    substructure (e.g. for Iterated Soft Drop)
 ///
 /// Notes:
 ///
 ///  - Even though the calls to "set_tagging_mode()" or
 ///    "set_grooming_mode(false)" are allowed, they should not be used
 ///    with n=-1, and the default grooming_mode has to remain
 ///    untouched (except for beta<0 and finite n).
 ///
 //----------------------------------------------------------------------
 class RecursiveSoftDrop : public SoftDrop {
 public:
   /// Simplified constructor. This takes the value of the "beta"
   /// parameter and the symmetry cut (applied by default on the
   /// scalar_z variable, as for the mMDT). It also takes an optional
   /// subtractor.
   ///
   /// n is the number of times we require the SoftDrop condition to be
   /// satisfied. n=-1 means infinity, i.e. we recurse into the jet
   /// until individual constituents
   ///
   /// If the (optional) pileup subtractor can be supplied, then see
   /// also the documentation for the set_input_jet_is_subtracted() member
   /// function.
   ///
   /// \param beta               the value of the beta parameter
   /// \param symmetry_cut       the value of the cut on the symmetry measure
   /// \param n                  the requested number of iterations
   /// \param R0                 the angular distance normalisation [1 by default]
   RecursiveSoftDrop(double beta,
                     double symmetry_cut,
                     int n = -1,
                     double R0 = 1,
                     const FunctionOfPseudoJet<PseudoJet> * subtractor = 0) : 
     SoftDrop(beta, symmetry_cut, R0, subtractor), _n(n) { set_defaults(); }
 
   /// Full constructor, which takes the following parameters:
   ///
   /// \param beta               the value of the beta parameter
   /// \param symmetry_cut       the value of the cut on the symmetry measure
   /// \param symmetry_measure   the choice of measure to use to estimate the symmetry
   /// \param n                  the requested number of iterations
   /// \param R0                 the angular distance normalisation [1 by default]
   /// \param mu_cut             the maximal allowed value of mass drop variable mu = m_heavy/m_parent 
   /// \param recursion_choice   the strategy used to decide which subjet to recurse into
   /// \param subtractor         an optional pointer to a pileup subtractor (ignored if zero)
   RecursiveSoftDrop(double           beta,
                     double           symmetry_cut, 
                     SymmetryMeasure  symmetry_measure,
                     int              n = -1,
                     double           R0 = 1.0,
                     double           mu_cut = std::numeric_limits<double>::infinity(), 
                     RecursionChoice  recursion_choice = larger_pt,
                     const FunctionOfPseudoJet<PseudoJet> * subtractor = 0) : 
     SoftDrop(beta, symmetry_cut, symmetry_measure, R0, mu_cut, recursion_choice, subtractor),
     _n(n) { set_defaults(); }
 
   /// default destructor
   virtual ~RecursiveSoftDrop(){}
 
   //----------------------------------------------------------------------
   // access to class info
   int n() const { return _n; }
   
   //----------------------------------------------------------------------
   // on top of the tweaks that we inherit from SoftDrop (via
   // RecursiveSymmetryBase):
   //  - set_verbose_structure()
   //  - set_subtractor()
   //  - set_input_jet_is_subtracted()
   // we provide several other knobs, given below
 
   /// initialise all the flags below to their default value
   void set_defaults();
   
   /// switch to using the "same depth" variant where instead of
   /// recursing from large to small angles and requiring n SD
   /// conditions to be met (our default), we recurse simultaneously in
   /// all the branches found during the previous iteration, up to a
   /// maximum depth of n.
   /// default: false
   void set_fixed_depth_mode(bool value=true) { _fixed_depth = value; }
   bool fixed_depth_mode() const { return _fixed_depth; }
   
   /// switch to using a dynamical R0 (used for the normalisation of
   /// the symmetry measure) set by the last deltaR at which some
   /// substructure was found.
   /// default: false
   void set_dynamical_R0(bool value=true) { _dynamical_R0 = value; }
   bool use_dynamical_R0() const { return _dynamical_R0; }
 
   /// when finding some substructure, only follow the hardest branch
   /// for the recursion
   /// default: false (i.e. recurse in both branches)
   void set_hardest_branch_only(bool value=true) { _hardest_branch_only = value; }
   bool use_hardest_branch_only() const { return _hardest_branch_only; }
 
   /// set the minimum angle (squared) that we should consider for
   /// substructure
   /// default: -1.0 (i.e. no minimum)
   void set_min_deltaR_squared(double value=-1.0) { _min_dR2 = value; }
   double   min_deltaR_squared() const { return _min_dR2; }
 
   /// description of the tool
   virtual std::string description() const;
 
   //----------------------------------------------------------------------
   /// action on a single jet with RecursiveSoftDrop.
   ///
   /// uses "result_fixed_tags" by default (i.e. recurse from R0 to
   /// smaller angles until n SD conditions have been met), or
   /// "result_fixed_depth" where each of the previous SD branches are
   /// recirsed into down to a depth of n.
   virtual PseudoJet result(const PseudoJet &jet) const;
 
   /// this routine applies the Soft Drop criterion recursively on the
   /// CA tree until we find n subjets (or until it converges), and
   /// adds them together into a groomed PseudoJet
   PseudoJet result_fixed_tags(const PseudoJet &jet) const;
 
   /// this routine applies the Soft Drop criterion recursively on the
   /// CA tree, recursing into all the branches found during the previous iteration
   /// until n layers have been found (or until it converges)
   PseudoJet result_fixed_depth(const PseudoJet &jet) const;
     
 protected:  
   /// return false if we reached desired layer of grooming _n
   bool continue_grooming(int current_n) const {
     return ((_n < 0) or (current_n < _n));
   }
   
 private:
   int    _n;            ///< the value of n
 
   // behaviour tweaks
   bool _fixed_depth;         ///< look in parallel into each all branches until depth n
   bool _dynamical_R0;        ///< when true, use the last deltaR with substructure as D0
   bool _hardest_branch_only; ///< recurse only in the hardest branch
                              ///  when substructure is found
   double _min_dR2;           ///< the min allowed angle to search for substructure
 };
 
 // helper to get the (linear) list of prongs inside a jet resulting
 // from RecursiveSoftDrop. This would avoid having amnually to go
 // through the successive pairwise compositeness
 std::vector<PseudoJet> recursive_soft_drop_prongs(const PseudoJet & rsd_jet);
 
 }
 
 FASTJET_END_NAMESPACE      // defined in fastjet/internal/base.hh
 #endif // __RECURSIVESOFTDROP_HH__

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