fastjet::Dnn2piCylinder Class Reference

class derived from DynamicNearestNeighbours that provides an implementation for the surface of cylinder (using one DnnPlane object spanning 0--2pi). More...

#include <Dnn2piCylinder.hh>

Inheritance diagram for fastjet::Dnn2piCylinder:

[legend]Collaboration diagram for fastjet::Dnn2piCylinder:

[legend]List of all members.


Public Member Functions
	Dnn2piCylinder ()
	empty initaliser
	Dnn2piCylinder (const std::vector< EtaPhi > &, const bool &ignore_nearest_is_mirror=false, const bool &verbose=false)
	Initialiser from a set of points on an Eta-Phi plane, where eta can have an arbitrary ranges and phi must be in range 0 <= phi < 2pi;.
int	NearestNeighbourIndex (const int &ii) const
	Note: one of the difficulties of the 0--2pi mapping is that a point may have its mirror copy as its own nearest neighbour (if no other point is within a distance of 2pi).
double	NearestNeighbourDistance (const int &ii) const
	Returns the distance to the nearest neighbour of point labelled by index ii (assumes ii is valid).
bool	Valid (const int &index) const
	Returns true iff the given index corresponds to a point that exists in the DNN structure (meaning that it has been added, and not removed in the meantime).
void	RemoveAndAddPoints (const std::vector< int > &indices_to_remove, const std::vector< EtaPhi > &points_to_add, std::vector< int > &indices_added, std::vector< int > &indices_of_updated_neighbours)
	remove the points labelled by the std::vector indices_to_remove, and add the points specified by the std::vector points_to_add (corresponding indices will be calculated automatically); the idea behind this routine is that the points to be added will somehow be close to the one or other of the points being removed and this can be used by the implementation to provide hints for inserting the new points in whatever structure it is using.
	~Dnn2piCylinder ()
Private Member Functions
EtaPhi	_remap_phi (const EtaPhi &point)
	given a phi value in the 0--pi range return one in the 2pi--3pi range; whereas if it is in the pi-2pi range then remap it to be inthe range (-pi)--0.
void	_RegisterCylinderPoint (const EtaPhi &cylinder_point, std::vector< EtaPhi > &plane_points)
	Actions here are similar to those in the Dnn3piCylinder::_RegisterCylinderPoint case, however here we do NOT create the mirror point -- instead we initialise the structure as if there were no need for the mirror point.
void	_CreateNecessaryMirrorPoints (const std::vector< int > &plane_indices, std::vector< int > &updated_plane_points)
	For each plane point specified in the vector plane_indices, establish whether there is a need to create a mirror point according to the following criteria:.
Private Attributes
bool	_verbose
bool	_ignore_nearest_is_mirror
std::vector< MirrorVertexInfo >	_mirror_info
std::vector< int >	_cylinder_index_of_plane_vertex
DnnPlane *	_DNN
Static Private Attributes
static const int	INEXISTENT_VERTEX = -3
Classes
struct	MirrorVertexInfo

Detailed Description

class derived from DynamicNearestNeighbours that provides an implementation for the surface of cylinder (using one DnnPlane object spanning 0--2pi).

Definition at line 46 of file Dnn2piCylinder.hh.

Constructor & Destructor Documentation

fastjet::Dnn2piCylinder::Dnn2piCylinder ( ) [inline]

empty initaliser

Definition at line 49 of file Dnn2piCylinder.hh.

00049 {}

fastjet::Dnn2piCylinder::Dnn2piCylinder	(	const std::vector< EtaPhi > &	,
		const bool &	ignore_nearest_is_mirror = `false`,
		const bool &	verbose = `false`
	)

Initialiser from a set of points on an Eta-Phi plane, where eta can have an arbitrary ranges and phi must be in range 0 <= phi < 2pi;.

NB: this class is more efficient than the plain Dnn4piCylinder class, but can give wrong answers when the nearest neighbour is further away than 2pi (in this case a point's nearest neighbour becomes itself, because it is considered to be a distance 2pi away). For the kt-algorithm (e.g.) this is actually not a problem (the distance need only be accurate when it is less than R), so we can tell the routine to ignore this problem -- alternatively the routine will crash if it detects it occurring (only when finding the nearest neighbour index, not its distance).

fastjet::Dnn2piCylinder::~Dnn2piCylinder ( ) [inline]

Definition at line 259 of file Dnn2piCylinder.hh.

References _DNN.

00259                                        {
00260   delete _DNN; 
00261 }

Member Function Documentation

int fastjet::Dnn2piCylinder::NearestNeighbourIndex ( const int & current ) const [inline, virtual]

Note: one of the difficulties of the 0--2pi mapping is that a point may have its mirror copy as its own nearest neighbour (if no other point is within a distance of 2pi).

This does not matter for the kt_algorithm with reasonable values of radius, but might matter for a general use of this algorithm -- depending on whether or not the user has initialised the class with instructions to ignore this problem the program will detect and ignore it, or crash.

Implements fastjet::DynamicNearestNeighbours.

Definition at line 214 of file Dnn2piCylinder.hh.

References _cylinder_index_of_plane_vertex, _DNN, _ignore_nearest_is_mirror, _mirror_info, INEXISTENT_VERTEX, fastjet::DnnPlane::NearestNeighbourDistance(), and fastjet::DnnPlane::NearestNeighbourIndex().

00214                                                                           {
00215   int main_index = _mirror_info[current].main_index;
00216   int mirror_index = _mirror_info[current].mirror_index;
00217   int plane_index;
00218   if (mirror_index == INEXISTENT_VERTEX ) {
00219     plane_index = _DNN->NearestNeighbourIndex(main_index);
00220   } else {
00221     plane_index = (
00222         _DNN->NearestNeighbourDistance(main_index) < 
00223         _DNN->NearestNeighbourDistance(mirror_index)) ? 
00224       _DNN->NearestNeighbourIndex(main_index) : 
00225       _DNN->NearestNeighbourIndex(mirror_index) ; 
00226   }
00227   int this_cylinder_index = _cylinder_index_of_plane_vertex[plane_index];
00228   // either the user has acknowledged the fact that they may get the
00229   // mirror copy as the closest point, or crash if it should occur
00230   // that mirror copy is the closest point.
00231   assert(_ignore_nearest_is_mirror || this_cylinder_index != current);
00232   //if (this_cylinder_index == current) {
00233   //  cerr << "WARNING point "<<current<<
00234   //    " has its mirror copy as its own nearest neighbour"<<endl;
00235   //}
00236   return this_cylinder_index;
00237 }

double fastjet::Dnn2piCylinder::NearestNeighbourDistance ( const int & ii ) const [inline, virtual]

Returns the distance to the nearest neighbour of point labelled by index ii (assumes ii is valid).

Implements fastjet::DynamicNearestNeighbours.

Definition at line 239 of file Dnn2piCylinder.hh.

References _DNN, _mirror_info, INEXISTENT_VERTEX, and fastjet::DnnPlane::NearestNeighbourDistance().

00239                                                                                 {
00240   int main_index = _mirror_info[current].main_index;
00241   int mirror_index = _mirror_info[current].mirror_index;
00242   if (mirror_index == INEXISTENT_VERTEX ) {
00243     return _DNN->NearestNeighbourDistance(main_index);
00244   } else {
00245     return (
00246         _DNN->NearestNeighbourDistance(main_index) < 
00247         _DNN->NearestNeighbourDistance(mirror_index)) ? 
00248       _DNN->NearestNeighbourDistance(main_index) : 
00249       _DNN->NearestNeighbourDistance(mirror_index) ; 
00250   }
00251  
00252 }

bool fastjet::Dnn2piCylinder::Valid ( const int & index ) const [inline, virtual]

Returns true iff the given index corresponds to a point that exists in the DNN structure (meaning that it has been added, and not removed in the meantime).

Implements fastjet::DynamicNearestNeighbours.

Definition at line 254 of file Dnn2piCylinder.hh.

References _DNN, _mirror_info, and fastjet::DnnPlane::Valid().

00254                                                          {
00255   return (_DNN->Valid(_mirror_info[index].main_index));
00256 }

void fastjet::Dnn2piCylinder::RemoveAndAddPoints	(	const std::vector< int > &	indices_to_remove,
		const std::vector< EtaPhi > &	points_to_add,
		std::vector< int > &	indices_added,
		std::vector< int > &	indices_of_updated_neighbours
	)			`[virtual]`

remove the points labelled by the std::vector indices_to_remove, and add the points specified by the std::vector points_to_add (corresponding indices will be calculated automatically); the idea behind this routine is that the points to be added will somehow be close to the one or other of the points being removed and this can be used by the implementation to provide hints for inserting the new points in whatever structure it is using.

In a kt-algorithm the points being added will be a result of a combination of the points to be removed -- hence the proximity is (more or less) guaranteed.

Implements fastjet::DynamicNearestNeighbours.

EtaPhi fastjet::Dnn2piCylinder::_remap_phi ( const EtaPhi & point ) [inline, private]

given a phi value in the 0--pi range return one in the 2pi--3pi range; whereas if it is in the pi-2pi range then remap it to be inthe range (-pi)--0.

Definition at line 164 of file Dnn2piCylinder.hh.

References fastjet::EtaPhi::first, fastjet::pi, fastjet::EtaPhi::second, and twopi.

00164                                                  {
00165     double phi = point.second;
00166     if (phi < pi) { phi += twopi ;} else {phi -= twopi;}
00167     return EtaPhi(point.first, phi);}

void fastjet::Dnn2piCylinder::_RegisterCylinderPoint	(	const EtaPhi &	cylinder_point,
		std::vector< EtaPhi > &	plane_points
	)			`[private]`

Actions here are similar to those in the Dnn3piCylinder::_RegisterCylinderPoint case, however here we do NOT create the mirror point -- instead we initialise the structure as if there were no need for the mirror point.

ADDITIONALLY push the cylinder_point onto the vector plane_points.

void fastjet::Dnn2piCylinder::_CreateNecessaryMirrorPoints	(	const std::vector< int > &	plane_indices,
		std::vector< int > &	updated_plane_points
	)			`[private]`

For each plane point specified in the vector plane_indices, establish whether there is a need to create a mirror point according to the following criteria:.

. phi < pi . mirror does not already exist . phi < NearestNeighbourDistance (if this is not true then there is no way that its mirror point could have a nearer neighbour).

If conditions all hold, then create the mirror point, insert it into the _DNN structure, adjusting any nearest neighbours, and return the list of plane points whose nearest neighbours have changed (this will include the new neighbours that have just been added)