fastjet::Dnn3piCylinder Class Reference

class derived from DynamicNearestNeighbours that provides an implementation for the surface of cylinder (using one DnnPlane object spanning 0--3pi). More...

#include <Dnn3piCylinder.hh>

Inheritance diagram for fastjet::Dnn3piCylinder:

[legend]Collaboration diagram for fastjet::Dnn3piCylinder:

[legend]List of all members.


Public Member Functions
	Dnn3piCylinder ()
	empty initaliser
	Dnn3piCylinder (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--3pi 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.
	~Dnn3piCylinder ()
Private Member Functions
EtaPhi	_remap_phi (const EtaPhi &point)
	given a phi value in the 0--2pi range return one in the pi--3pi range.
void	_RegisterCylinderPoint (const EtaPhi &cylinder_point, std::vector< EtaPhi > &plane_points)
	What on earth does this do?
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--3pi).

Definition at line 45 of file Dnn3piCylinder.hh.

Constructor & Destructor Documentation

fastjet::Dnn3piCylinder::Dnn3piCylinder ( ) [inline]

empty initaliser

Definition at line 48 of file Dnn3piCylinder.hh.

00048 {}

fastjet::Dnn3piCylinder::Dnn3piCylinder	(	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::Dnn3piCylinder::~Dnn3piCylinder ( ) [inline]

Definition at line 249 of file Dnn3piCylinder.hh.

References _DNN.

00249                                        {
00250   delete _DNN; 
00251 }

Member Function Documentation

int fastjet::Dnn3piCylinder::NearestNeighbourIndex ( const int & current ) const [inline, virtual]

Note: one of the difficulties of the 0--3pi 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 204 of file Dnn3piCylinder.hh.

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

00204                                                                           {
00205   int main_index = _mirror_info[current].main_index;
00206   int mirror_index = _mirror_info[current].mirror_index;
00207   int plane_index;
00208   if (mirror_index == INEXISTENT_VERTEX ) {
00209     plane_index = _DNN->NearestNeighbourIndex(main_index);
00210   } else {
00211     plane_index = (
00212         _DNN->NearestNeighbourDistance(main_index) < 
00213         _DNN->NearestNeighbourDistance(mirror_index)) ? 
00214       _DNN->NearestNeighbourIndex(main_index) : 
00215       _DNN->NearestNeighbourIndex(mirror_index) ; 
00216   }
00217   int this_cylinder_index = _cylinder_index_of_plane_vertex[plane_index];
00218   // either the user has acknowledged the fact that they may get the
00219   // mirror copy as the closest point, or crash if it should occur
00220   // that mirror copy is the closest point.
00221   assert(_ignore_nearest_is_mirror || this_cylinder_index != current);
00222   //if (this_cylinder_index == current) {
00223   //  std::cerr << "WARNING point "<<current<<
00224   //    " has its mirror copy as its own nearest neighbour"<<endl;
00225   //}
00226   return this_cylinder_index;
00227 }

double fastjet::Dnn3piCylinder::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 229 of file Dnn3piCylinder.hh.

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

00229                                                                                 {
00230   int main_index = _mirror_info[current].main_index;
00231   int mirror_index = _mirror_info[current].mirror_index;
00232   if (mirror_index == INEXISTENT_VERTEX ) {
00233     return _DNN->NearestNeighbourDistance(main_index);
00234   } else {
00235     return (
00236         _DNN->NearestNeighbourDistance(main_index) < 
00237         _DNN->NearestNeighbourDistance(mirror_index)) ? 
00238       _DNN->NearestNeighbourDistance(main_index) : 
00239       _DNN->NearestNeighbourDistance(mirror_index) ; 
00240   }
00241  
00242 }

bool fastjet::Dnn3piCylinder::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 244 of file Dnn3piCylinder.hh.

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

00244                                                          {
00245   return (_DNN->Valid(_mirror_info[index].main_index));
00246 }

void fastjet::Dnn3piCylinder::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::Dnn3piCylinder::_remap_phi ( const EtaPhi & point ) [inline, private]

given a phi value in the 0--2pi range return one in the pi--3pi range.

Definition at line 162 of file Dnn3piCylinder.hh.

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

00162                                                  {
00163     double phi = point.second;
00164     if (phi < pi) { phi += twopi ;}
00165     return EtaPhi(point.first, phi);}

void fastjet::Dnn3piCylinder::_RegisterCylinderPoint	(	const EtaPhi &	cylinder_point,
		std::vector< EtaPhi > &	plane_points
	)			`[private]`

What on earth does this do?

Example: last true "cylinder" index was 15 last plane index was 23

Then: _cylinder_index_of_plane_vertex.size() = 24 and _mirror_info.size() = 16

IF cylinder_point's phi < pi then create: _mirror_info[16] = (main_index = 24, mirror_index=25) _cylinder_index_of_plane_vertex[24] = 16 _cylinder_index_of_plane_vertex[25] = 16 ELSE create: _mirror_info[16] = (main_index = 24, mirror_index=INEXISTENT..) _cylinder_index_of_plane_vertex[24] = 16

ADDITIONALLY push the cylinder_point (and if it exists the mirror copy) onto the vector plane_points.