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 #ifndef __FASTJET_NNFJN2TILED_HH__
 #define __FASTJET_NNFJN2TILED_HH__
 
 //FJSTARTHEADER
 // $Id$
 //
 // Copyright (c) 2016-2021, 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
 
 #include "fastjet/NNBase.hh"
 #include "fastjet/internal/TilingExtent.hh"
 
 FASTJET_BEGIN_NAMESPACE      // defined in fastjet/internal/base.hh
 
 //----------------------------------------------------------------------
 /// @ingroup advanced_usage
 /// \class NNFJN2Tiled
 ///
 /// Helps solve closest pair problems with factorised interparticle
 /// and beam distances (ie satisfying the FastJet lemma) that are on
 /// a cylindrical geometry and allow tiling.
 ///
 /// (see NNBase.hh for an introductory description)
 ///
 /// This variant provides an implementation based on the N2Tiled
 /// clustering strategy in FastJet. As for the NNFJN2Plain case, the
 /// interparticle and beam distances should be of the form
 ///
 /// \code
 ///   dij = min(mom_factor(i), mom_factor(j)) * geometrical_distance(i,j)
 ///   diB = mom_factor(i) * geometrical_beam_distance(i)
 /// \endcode
 ///
 /// Additionally, the NNFJN2Tiled class takes a tile_size parameter
 /// that controls the size of the tiles. It must be such that, for any
 /// two points in non-neighbouring (and non-identical) tiles, the
 /// geometrical distance between the 2 points is larger than the
 /// geometrical beam distance of each of the 2 points.
 ///
 /// It is templated with a BJ (brief jet) class and can be used with or
 /// without an extra "Information" template, i.e. NNFJN2Tiled<BJ> or
 /// NNFJN2Tiled<BJ,I>
 ///
 /// For the NNFJN2Tiled<BJ> version of the class to function, BJ must provide 
 /// three member functions
 ///  
 /// \code
 ///   void   BJ::init(const PseudoJet & jet);                   // initialise with a PseudoJet
 ///   double BJ::geometrical_distance(const BJ * other_bj_jet); // distance between this and other_bj_jet (geometrical part)
 ///   double BJ::geometrical_beam_distance();                   // distance to the beam (geometrical part)
 ///   double BJ::momentum_factor();                             // extra momentum factor
 /// \endcode
 ///
 /// For the NNFJN2Tiled<BJ,I> version to function, the BJ::init(...) member
 /// must accept an extra argument
 ///
 /// \code
 ///   void BJ::init(const PseudoJet & jet, I * info);   // initialise with a PseudoJet + info
 /// \endcode
 ///
 /// NOTE: THE DISTANCE MUST BE SYMMETRIC I.E. SATISFY
 /// \code
 ///     a.geometrical_distance(b) == b.geometrical_distance(a)
 /// \endcode
 ///
 /// Finally, the BJ class needs to provide access to the variables used
 /// for the rectangular tiling:
 ///
 /// \code
 ///   double BJ::rap(); // rapidity-like variable
 ///   double BJ::phi(); // azimutal-angle-like variable (should be > -2pi)
 /// \endcode
 ///
 /// Note that you are strongly advised to add the following lines
 /// to your BJ class to allow it to be used also with NNH:
 ///
 /// \code
 ///   /// make this BJ class compatible with the use of NNH
 ///   double BJ::distance(const BJ * other_bj_jet){
 ///     double mom1 = momentum_factor();
 ///     double mom2 = other_bj_jet->momentum_factor();
 ///     return (mom1<mom2 ? mom1 : mom2) * geometrical_distance(other_bj_jet);
 ///   }
 ///   double BJ::beam_distance(){
 ///     return momentum_factor() * geometrical_beam_distance();
 ///   }
 /// \endcode
 ///
 template<class BJ, class I = _NoInfo> class NNFJN2Tiled : public NNBase<I> {
 public:
 
   /// constructor with an initial set of jets (which will be assigned indices
   /// `0...jets.size()-1`)
   NNFJN2Tiled(const std::vector<PseudoJet> & jets, double requested_tile_size)
     : NNBase<I>(),     _requested_tile_size(requested_tile_size) {start(jets);}
   NNFJN2Tiled(const std::vector<PseudoJet> & jets, double requested_tile_size, I * info)
     : NNBase<I>(info), _requested_tile_size(requested_tile_size) {start(jets);}
   
   void start(const std::vector<PseudoJet> & jets);
 
   /// return the dij_min and indices iA, iB, for the corresponding jets.
   /// If iB < 0 then iA recombines with the beam
   double dij_min(int & iA, int & iB);
 
   /// remove the jet pointed to by index iA
   void remove_jet(int iA);
 
   /// merge the jets pointed to by indices A and B and replace them with
   /// jet, assigning it an index jet_index.
   void merge_jets(int iA, int iB, const PseudoJet & jet, int jet_index);
 
   /// a destructor
   ~NNFJN2Tiled() {
     delete[] briefjets;
     delete[] diJ;
   }
     
 private:
   class TiledJet; // forward declaration
   class Tile;
   class diJ_plus_link;
 
   // Set up the tiles:
   void _initialise_tiles(const std::vector<PseudoJet> & particles);
 
   // return the full distance of a particle to its NN
   inline double _compute_diJ(const TiledJet * const jet) const {
     double mom_fact = jet->momentum_factor();
     if (jet->NN != NULL) {
       double other_mom_fact = jet->NN->momentum_factor();
       if (other_mom_fact < mom_fact) {mom_fact = other_mom_fact;}
     }
     return jet->NN_dist * mom_fact;
   }
 
   // reasonably robust return of tile index given irap and iphi, in particular
   // it works even if iphi is negative
   inline int _tile_index (int irap, int iphi) const {
     // note that (-1)%n = -1 so that we have to add _n_tiles_phi
     // before performing modulo operation
     return (irap-_tiles_irap_min)*_n_tiles_phi
                   + (iphi+_n_tiles_phi) % _n_tiles_phi;
   }
 
   int  _tile_index(const double rap, const double phi) const;
   void _tiledjet_set_jetinfo ( TiledJet * const tiled_jet, const PseudoJet &jet, int index);
   void _bj_remove_from_tiles(TiledJet * const jet);
   void _initialise_tiles();
   void _print_tiles(TiledJet * briefjets ) const;
   void _add_neighbours_to_tile_union(const int tile_index, int & n_near_tiles) const;
   void _add_untagged_neighbours_to_tile_union(const int tile_index, int & n_near_tiles);
 
 
   /// contains the briefjets
   TiledJet * briefjets;
 
   /// semaphores for the current extent of our structure
   TiledJet * head;
 
   /// currently active number of jets
   int n;
 
   /// where_is[i] contains a pointer to the jet with index i
   std::vector<TiledJet *> where_is;
 
   /// helper to keep tracks of tiles to be checked for updates
   std::vector<int> tile_union;
 
   /// a table containing all the (full) distances to each object's NN
   diJ_plus_link * diJ;
 
   /// tiling information
   std::vector<Tile> _tiles;
   double _requested_tile_size;
   double _tiles_rap_min, _tiles_rap_max;
   double _tile_size_rap, _tile_size_phi;
   int    _n_tiles_phi,_tiles_irap_min,_tiles_irap_max;
   
   /// a class that wraps around the BJ, supplementing it with extra information
   /// such as pointers to neighbours, etc.
   class TiledJet : public BJ {
   public:
     void init(const PseudoJet & jet, int index_in) {
       BJ::init(jet);
       other_init(index_in);
     }
     void init(const PseudoJet & jet, int index_in, I * info) {
       BJ::init(jet, info);
       other_init(index_in);
     }
     void other_init(int index_in) {
       _index = index_in;
       NN_dist = BJ::geometrical_beam_distance();
       NN = NULL;
     }
     int jet_index() const {return _index;}
     
     double NN_dist;
     TiledJet * NN, *previous, * next;
     int tile_index, diJ_posn;
     // routines that are useful in the minheap version of tiled
     // clustering ("misuse" the otherwise unused diJ_posn, so as
     // to indicate whether jets need to have their minheap entries
     // updated).
     inline void label_minheap_update_needed() {diJ_posn = 1;}
     inline void label_minheap_update_done()   {diJ_posn = 0;}
     inline bool minheap_update_needed() const {return diJ_posn==1;}
     
   private:
     int _index;
   };
 
   /// number of neighbours that a tile will have (rectangular geometry
   /// gives 9 neighbours).
   static const int n_tile_neighbours = 9;
   //----------------------------------------------------------------------
   /// The fundamental structures to be used for the tiled N^2 algorithm
   /// (see CCN27-44 for some discussion of pattern of tiling)
   class Tile {
   public:
     /// pointers to neighbouring tiles, including self
     Tile *   begin_tiles[n_tile_neighbours]; 
     /// neighbouring tiles, excluding self
     Tile **  surrounding_tiles; 
     /// half of neighbouring tiles, no self
     Tile **  RH_tiles;  
     /// just beyond end of tiles
     Tile **  end_tiles; 
     /// start of list of BriefJets contained in this tile
     TiledJet * head;    
     /// sometimes useful to be able to tag a tile
     bool     tagged;    
   };
 
   // structure that holds the real, full, distance (as well as a pointer to the corresponding TiledJet)
   class diJ_plus_link {
   public:
     double     diJ; // the distance
     TiledJet * jet; // the jet (i) for which we've found this distance
                     // (whose NN will the J).
   };
 
 };
 
 
 
 //----------------------------------------------------------------------
 template<class BJ, class I> void NNFJN2Tiled<BJ,I>::start(const std::vector<PseudoJet> & jets) {
 
   _initialise_tiles(jets);
 
   n = jets.size();
 
   briefjets = new TiledJet[n];
   where_is.resize(2*n);
 
   TiledJet * jetA = briefjets, * jetB;
 
   // will be used quite deep inside loops, but declare it here so that
   // memory (de)allocation gets done only once
   tile_union.resize(3*n_tile_neighbours);
   
   // initialise the basic jet info 
   for (int i = 0; i< n; i++) {
     _tiledjet_set_jetinfo(jetA, jets[i], i);
     where_is[i] = jetA;
     jetA++; // move on to next entry of briefjets
   }
 
   head = briefjets; // a nicer way of naming start
 
   // set up the initial nearest neighbour information
   typename std::vector<Tile>::const_iterator tile;
   for (tile = _tiles.begin(); tile != _tiles.end(); tile++) {
     // first do it on this tile
     for (jetA = tile->head; jetA != NULL; jetA = jetA->next) {
       for (jetB = tile->head; jetB != jetA; jetB = jetB->next) {
     double dist = jetA->geometrical_distance(jetB);
     if (dist < jetA->NN_dist) {jetA->NN_dist = dist; jetA->NN = jetB;}
     if (dist < jetB->NN_dist) {jetB->NN_dist = dist; jetB->NN = jetA;}
       }
     }
     // then do it for RH tiles
     for (Tile ** RTile = tile->RH_tiles; RTile != tile->end_tiles; RTile++) {
       for (jetA = tile->head; jetA != NULL; jetA = jetA->next) {
     for (jetB = (*RTile)->head; jetB != NULL; jetB = jetB->next) {
       double dist = jetA->geometrical_distance(jetB);
       if (dist < jetA->NN_dist) {jetA->NN_dist = dist; jetA->NN = jetB;}
       if (dist < jetB->NN_dist) {jetB->NN_dist = dist; jetB->NN = jetA;}
     }
       }
     }
     // no need to do it for LH tiles, since they are implicitly done
     // when we set NN for both jetA and jetB on the RH tiles.
   }
   
   diJ = new diJ_plus_link[n];
   jetA = head;
   for (int i = 0; i < n; i++) {
     diJ[i].diJ = _compute_diJ(jetA); // kt distance * R^2
     diJ[i].jet = jetA;  // our compact diJ table will not be in      
     jetA->diJ_posn = i; // one-to-one corresp. with non-compact jets,
                         // so set up bi-directional correspondence here.
     jetA++; // have jetA follow i 
   }
 }
 
 
 //----------------------------------------------------------------------
 template<class BJ, class I> double NNFJN2Tiled<BJ,I>::dij_min(int & iA, int & iB) {
   // find the minimum of the diJ on this round
   diJ_plus_link * best, *stop; // pointers a bit faster than indices
                                // could use best to keep track of diJ
                                // min, but it turns out to be
                                // marginally faster to have a separate
                                // variable (avoids n dereferences at
                                // the expense of n/2 assignments).
   double diJ_min = diJ[0].diJ; // initialise the best one here.
   best = diJ;                  // and here
   stop = diJ+n;
   for (diJ_plus_link * here = diJ+1; here != stop; here++) {
     if (here->diJ < diJ_min) {best = here; diJ_min  = here->diJ;}
   }
 
   // return information to user about recombination
   TiledJet * jetA = best->jet;
   iA = jetA->jet_index();
   iB = jetA->NN ? jetA->NN->jet_index() : -1;
   return diJ_min;
 }
 
 
 //----------------------------------------------------------------------
 // remove jetA from the list
 template<class BJ, class I> void NNFJN2Tiled<BJ,I>::remove_jet(int iA) {
   TiledJet * jetA = where_is[iA];
 
   _bj_remove_from_tiles(jetA);
 
   // first establish the set of tiles over which we are going to
   // have to run searches for updated and new nearest-neighbours --
   // basically a combination of vicinity of the tiles of the two old
   // and one new jet.
   int n_near_tiles = 0;
   _add_untagged_neighbours_to_tile_union(jetA->tile_index, n_near_tiles);
 
   // now update our nearest neighbour info and diJ table
   // first reduce size of table
   n--;
   // then compactify the diJ by taking the last of the diJ and copying
   // it to the position occupied by the diJ for jetA
   diJ[n].jet->diJ_posn = jetA->diJ_posn;
   diJ[jetA->diJ_posn] = diJ[n];
 
   // updating other particles' NN.
   // Run over all tiles in our union 
   for (int itile = 0; itile < n_near_tiles; itile++) {
     Tile * tile_ptr = &_tiles[tile_union[itile]];
     tile_ptr->tagged = false; // reset tag, since we're done with unions
     // run over all jets in the current tile
     for (TiledJet * jetI = tile_ptr->head; jetI != NULL; jetI = jetI->next) {
       // see if jetI had jetA or jetB as a NN -- if so recalculate the NN
       if (jetI->NN == jetA) {
         jetI->NN_dist = jetI->geometrical_beam_distance();
         jetI->NN      = NULL;
         // now go over tiles that are neighbours of I (include own tile)
         for (Tile ** near_tile  = tile_ptr->begin_tiles; 
              near_tile != tile_ptr->end_tiles; near_tile++) {
           // and then over the contents of that tile
           for (TiledJet * jetJ  = (*near_tile)->head; jetJ != NULL; jetJ = jetJ->next) {
             double dist = jetI->geometrical_distance(jetJ);
             if (dist < jetI->NN_dist && jetJ != jetI) {
               jetI->NN_dist = dist; jetI->NN = jetJ;
             }
           }
         }
         diJ[jetI->diJ_posn].diJ = _compute_diJ(jetI); // update diJ kt-dist
       }
     }
   }
 
 }
 
 
 //----------------------------------------------------------------------
 template<class BJ, class I> void NNFJN2Tiled<BJ,I>::merge_jets(int iA, int iB, 
                     const PseudoJet & jet, int index) {
 
   TiledJet * jetA = where_is[iA];
   TiledJet * jetB = where_is[iB];
 
   // jet-jet recombination
   // If necessary relabel A & B to ensure jetB < jetA, that way if
   // the larger of them == newtail then that ends up being jetA and 
   // the new jet that is added as jetB is inserted in a position that
   // has a future!
   if (jetA < jetB) {std::swap(jetA,jetB);}
 
   // what was jetB will now become the new jet
   _bj_remove_from_tiles(jetA);
   TiledJet oldB = * jetB;  // take a copy because we will need it...
   _bj_remove_from_tiles(jetB);
   _tiledjet_set_jetinfo(jetB, jet, index); // cause jetB to become _jets[nn]
                                            // (also registers the jet in the tiling)
   where_is[index] = jetB;
   
   // first establish the set of tiles over which we are going to
   // have to run searches for updated and new nearest-neighbours --
   // basically a combination of vicinity of the tiles of the two old
   // and one new jet.
   int n_near_tiles = 0;
   _add_untagged_neighbours_to_tile_union(jetA->tile_index, n_near_tiles);
   if (jetB->tile_index != jetA->tile_index) {
     _add_untagged_neighbours_to_tile_union(jetB->tile_index, n_near_tiles);
   }
   if (oldB.tile_index != jetA->tile_index && 
       oldB.tile_index != jetB->tile_index) {
     _add_untagged_neighbours_to_tile_union(oldB.tile_index, n_near_tiles);
   }
 
   // now update our nearest neighbour info and diJ table
   // first reduce size of table
   n--;
   // then compactify the diJ by taking the last of the diJ and copying
   // it to the position occupied by the diJ for jetA
   diJ[n].jet->diJ_posn = jetA->diJ_posn;
   diJ[jetA->diJ_posn] = diJ[n];
 
   // Initialise jetB's NN distance as well as updating it for 
   // other particles.
   // Run over all tiles in our union 
   for (int itile = 0; itile < n_near_tiles; itile++) {
     Tile * tile_ptr = &_tiles[tile_union[itile]];
     tile_ptr->tagged = false; // reset tag, since we're done with unions
     // run over all jets in the current tile
     for (TiledJet * jetI = tile_ptr->head; jetI != NULL; jetI = jetI->next) {
       // see if jetI had jetA or jetB as a NN -- if so recalculate the NN
       if ((jetI->NN == jetA) || (jetI->NN == jetB)) {
         jetI->NN_dist = jetI->geometrical_beam_distance();
         jetI->NN      = NULL;
         // now go over tiles that are neighbours of I (include own tile)
         for (Tile ** near_tile  = tile_ptr->begin_tiles; near_tile != tile_ptr->end_tiles; near_tile++) {
           // and then over the contents of that tile
           for (TiledJet * jetJ  = (*near_tile)->head; jetJ != NULL; jetJ = jetJ->next) {
             double dist = jetI->geometrical_distance(jetJ);
             if (dist < jetI->NN_dist && jetJ != jetI) {
               jetI->NN_dist = dist; jetI->NN = jetJ;
             }
           }
         }
         diJ[jetI->diJ_posn].diJ = _compute_diJ(jetI); // update diJ kt-dist
       }
       // check whether new jetB is closer than jetI's current NN and
       // if jetI is closer than jetB's current (evolving) nearest
       // neighbour. Where relevant update things
       double dist = jetI->geometrical_distance(jetB);
       if (dist < jetI->NN_dist) {
         if (jetI != jetB) {
           jetI->NN_dist = dist;
           jetI->NN = jetB;
           diJ[jetI->diJ_posn].diJ = _compute_diJ(jetI); // update diJ...
         }
       }
       if (dist < jetB->NN_dist) {
         if (jetI != jetB) {
           jetB->NN_dist = dist;
           jetB->NN      = jetI;}
       }
     }
   }
 
   // finally, register the updated kt distance for B
   diJ[jetB->diJ_posn].diJ = _compute_diJ(jetB);
 }
 
 
 //----------------------------------------------------------------------
 /// Set up the tiles:
 ///  - decide the range in eta
 ///  - allocate the tiles
 ///  - set up the cross-referencing info between tiles
 ///
 /// The neighbourhood of a tile is set up as follows
 ///
 ///           LRR
 ///           LXR
 ///           LLR
 ///
 /// such that tiles is an array containing XLLLLRRRR with pointers
 ///                                         |   \ RH_tiles
 ///                                         \ surrounding_tiles
 ///
 /// with appropriate precautions when close to the edge of the tiled
 /// region.
 ///
 template <class BJ, class I>
 void NNFJN2Tiled<BJ,I>::_initialise_tiles(const std::vector<PseudoJet> &particles) {
 
   // first decide tile sizes (with a lower bound to avoid huge memory use with
   // very small R)
   double default_size = _requested_tile_size>0.1 ? _requested_tile_size : 0.1;
   _tile_size_rap = default_size;
   // it makes no sense to go below 3 tiles in phi -- 3 tiles is
   // sufficient to make sure all pair-wise combinations up to pi in
   // phi are possible
   _n_tiles_phi   = int(floor(twopi/default_size));
   if (_n_tiles_phi<3) _n_tiles_phi = 3;
   _tile_size_phi = twopi / _n_tiles_phi; // >= _Rparam and fits in 2pi
 
   TilingExtent tiling_analysis(particles);
   _tiles_rap_min = tiling_analysis.minrap();
   _tiles_rap_max = tiling_analysis.maxrap();
 
   // now adjust the values
   _tiles_irap_min = int(floor(_tiles_rap_min/_tile_size_rap));
   _tiles_irap_max = int(floor( _tiles_rap_max/_tile_size_rap));
   _tiles_rap_min = _tiles_irap_min * _tile_size_rap;
   _tiles_rap_max = _tiles_irap_max * _tile_size_rap;
 
   // allocate the tiles
   _tiles.resize((_tiles_irap_max-_tiles_irap_min+1)*_n_tiles_phi);
 
   // now set up the cross-referencing between tiles
   for (int irap = _tiles_irap_min; irap <= _tiles_irap_max; irap++) {
     for (int iphi = 0; iphi < _n_tiles_phi; iphi++) {
       Tile * tile = & _tiles[_tile_index(irap,iphi)];
       // no jets in this tile yet
       tile->head = NULL; // first element of tiles points to itself
       tile->begin_tiles[0] =  tile;
       Tile ** pptile = & (tile->begin_tiles[0]);
       pptile++;
       //
       // set up L's in column to the left of X
       tile->surrounding_tiles = pptile;
       if (irap > _tiles_irap_min) {
     // with the itile subroutine, we can safely run tiles from
     // idphi=-1 to idphi=+1, because it takes care of
     // negative and positive boundaries
     for (int idphi = -1; idphi <=+1; idphi++) {
       *pptile = & _tiles[_tile_index(irap-1,iphi+idphi)];
       pptile++;
     }   
       }
       // now set up last L (below X)
       *pptile = & _tiles[_tile_index(irap,iphi-1)];
       pptile++;
       // set up first R (above X)
       tile->RH_tiles = pptile;
       *pptile = & _tiles[_tile_index(irap,iphi+1)];
       pptile++;
       // set up remaining R's, to the right of X
       if (irap < _tiles_irap_max) {
     for (int idphi = -1; idphi <= +1; idphi++) {
       *pptile = & _tiles[_tile_index(irap+1,iphi+idphi)];
       pptile++;
     }   
       }
       // now put semaphore for end tile
       tile->end_tiles = pptile;
       // finally make sure tiles are untagged
       tile->tagged = false;
     }
   }
 
 }
 
 //----------------------------------------------------------------------
 /// return the tile index corresponding to the given rap,phi point
 template <class BJ, class I>
 int NNFJN2Tiled<BJ,I>::_tile_index(const double rap, const double phi) const {
   int irap, iphi;
   if      (rap <= _tiles_rap_min) {irap = 0;}
   else if (rap >= _tiles_rap_max) {irap = _tiles_irap_max-_tiles_irap_min;}
   else {
     //irap = int(floor((rap - _tiles_rap_min) / _tile_size_rap));
     irap = int(((rap - _tiles_rap_min) / _tile_size_rap));
     // following needed in case of rare but nasty rounding errors
     if (irap > _tiles_irap_max-_tiles_irap_min) {
       irap = _tiles_irap_max-_tiles_irap_min;} 
   }
   // allow for some extent of being beyond range in calculation of phi
   // as well
   //iphi = (int(floor(phi/_tile_size_phi)) + _n_tiles_phi) % _n_tiles_phi;
   // with just int and no floor, things run faster but beware
   iphi = int((phi+twopi)/_tile_size_phi) % _n_tiles_phi;
   return (iphi + irap * _n_tiles_phi);
 }
 
 //----------------------------------------------------------------------
 template <class BJ, class I>
 void NNFJN2Tiled<BJ,I>::_bj_remove_from_tiles(TiledJet * const jet) {
   Tile * tile = & _tiles[jet->tile_index];
 
   if (jet->previous == NULL) {
     // we are at head of the tile, so reset it.
     // If this was the only jet on the tile then tile->head will now be NULL
     tile->head = jet->next;
   } else {
     // adjust link from previous jet in this tile
     jet->previous->next = jet->next;
   }
   if (jet->next != NULL) {
     // adjust backwards-link from next jet in this tile
     jet->next->previous = jet->previous;
   }
 }
 
 
 //----------------------------------------------------------------------
 // overloaded version which additionally sets up information regarding the
 // tiling
 template <class BJ, class I>
 inline void NNFJN2Tiled<BJ,I>::_tiledjet_set_jetinfo(TiledJet * const tile_jet,
                                                    const PseudoJet &jet, 
                                                    int index) {
   // the this-> in the next line is required by standard compiler
   // see e.g. http://stackoverflow.com/questions/10639053/name-lookups-in-c-templates
   this->init_jet(tile_jet, jet, index); 
 
   // Then do the setup specific to the tiled case.
 
   // Find out which tile it belonds to
   tile_jet->tile_index = _tile_index(tile_jet->rap(), tile_jet->phi());
 
   // Insert it into the tile's linked list of jets
   Tile * tile = &_tiles[tile_jet->tile_index];
   tile_jet->previous   = NULL;
   tile_jet->next       = tile->head;
   if (tile_jet->next != NULL) {tile_jet->next->previous = tile_jet;}
   tile->head      = tile_jet;
 }
 
 //----------------------------------------------------------------------
 /// Add to the vector tile_union the tiles that are in the neighbourhood
 /// of the specified tile_index, including itself -- start adding
 /// from position n_near_tiles-1, and increase n_near_tiles as
 /// you go along (could have done it more C++ like with vector with reserved
 /// space, but fear is that it would have been slower, e.g. checking
 /// for end of vector at each stage to decide whether to resize it)
 template <class BJ, class I>
 void NNFJN2Tiled<BJ,I>::_add_neighbours_to_tile_union(const int tile_index, 
                                                     int & n_near_tiles) const {
   for (Tile * const * near_tile = _tiles[tile_index].begin_tiles; 
        near_tile != _tiles[tile_index].end_tiles; near_tile++){
     // get the tile number
     tile_union[n_near_tiles] = *near_tile - & _tiles[0];
     n_near_tiles++;
   }
 }
 
 //----------------------------------------------------------------------
 /// Like _add_neighbours_to_tile_union, but only adds neighbours if 
 /// their "tagged" status is false; when a neighbour is added its
 /// tagged status is set to true.
 ///
 /// Note that with a high level of warnings (-pedantic -Wextra -ansi,
 /// gcc complains about tile_index maybe being used uninitialised for
 /// oldB in ClusterSequence::_minheap_faster_tiled_N2_cluster(). We
 /// have explicitly checked that it was harmless so we could disable
 /// the gcc warning by hand using the construct below
 ///
 ///  #pragma GCC diagnostic push
 ///  #pragma GCC diagnostic ignored "-Wpragmas"
 ///  #pragma GCC diagnostic ignored "-Wuninitialized"
 ///  #pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
 ///    ...
 ///  #pragma GCC diagnostic pop
 ///
 /// the @GCC diagnostic push/pop directive was only introduced in
 /// gcc-4.6, so for broader usage, we'd need to insert #pragma GCC
 /// diagnostic ignored "-Wpragmas" at the top of this file
 template <class BJ, class I>
 inline void NNFJN2Tiled<BJ,I>::_add_untagged_neighbours_to_tile_union(
                const int tile_index, 
            int & n_near_tiles)  {
   for (Tile ** near_tile = _tiles[tile_index].begin_tiles; 
        near_tile != _tiles[tile_index].end_tiles; near_tile++){
     if (! (*near_tile)->tagged) {
       (*near_tile)->tagged = true;
       // get the tile number
       tile_union[n_near_tiles] = *near_tile - & _tiles[0];
       n_near_tiles++;
     }
   }
 }
 
 
 
 FASTJET_END_NAMESPACE      // defined in fastjet/internal/base.hh
 
 
 #endif // __FASTJET_NNFJN2TILED_HH__

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