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Schwarzschild Modelling Interactive expLoratory Environment
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smile::CPotentialNB Class Reference

frozen N-body potential calculated by tree-code algorithm (based on hackcode1.c) More...

#include <potential.h>

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Classes

struct  cell
 CELL: structure used to represent internal nodes of tree. More...
 
struct  node
 NODE: data common to BODY and CELL structures. More...
 

Public Member Functions

 CPotentialNB ()
 default (empty) initialization
 
template<typename NumT >
 CPotentialNB (double _eps, double _tol, const CPointMassSet< NumT > &points)
 Initialize from a list of particles;. More...
 
virtual CPotential * clone () const
 Return a pointer to a copy of this instance of potential. More...
 
virtual POTENTIALTYPE PotentialType () const
 enumerable potential type
 
virtual const char * PotentialName () const
 string representation of potential type
 
virtual SYMMETRYTYPE symmetry () const
 returns symmetry type of this potential
 
virtual double Phi (double X, double Y, double Z, double t=0) const
 Return potential at a given spatial point (possibly a time-varying one). More...
 
virtual double Rho (double X, double Y, double Z, double t=0) const
 returns density at given coordinates, this should obviously be overriden in derivative classes
 
virtual void Force (const double xyz[N_DIM], const double t, double *force, double *forceDeriv=NULL) const
 Compute forces and, optionally, force derivatives at a given point. More...
 
virtual double Mass (const double r) const
 reimplement the mass estimate by counting bodies inside given radius
 
size_t bodyNum () const
 return number of particles
 
template<typename NumT >
CPosPoint< NumT > bodyPos (size_t index) const
 return the position of a given particle
 
double bodyMass (size_t index) const
 return the mass of a given particle
 
- Public Member Functions inherited from smile::CDensity
virtual double totalMass () const
 returns estimated M(r=infinity) or -1 if mass is infinite
 
double getRadiusByMass (const double m) const
 solves for Mass(r)=m
 
void getRadiiByMass (const vectord &masses, vectord *radii) const
 solves for Mass(r)=m for an array of sorted values of m (more efficient than doing it one-by-one)
 
bool checkMassMonotonic () const
 safety measure: check (roughly) that mass is increasing with radius
 
bool checkDensityNonzero () const
 another safety measure: check that density doesn't drop to zero along any of three axes (important to assess spherical-harmonic approximation quality)
 
virtual double getGamma () const
 returns inner density slope estimate (only used in BSE potential expansion for the automatic selection of shape parameter Alpha)
 

Static Public Member Functions

static const char * myName ()
 

Private Types

enum  NODETYPE { BODY, CELL }
 tree contains nodes of two kinds: individual particles and child cells More...
 
enum  WALKOP { CALCPHI, CALCACC }
 operation to perform during the tree-walk More...
 
typedef double vec3 [N_DIM]
 
typedef double matrix3 [N_DIM][N_DIM]
 
typedef node * nodeptr
 
typedef node body
 BODY: data structure used to represent particles.
 
typedef node * bodyptr
 
typedef cell * cellptr
 

Private Member Functions

void maketree ()
 initialize tree for the constructor
 
bool expandbox (const size_t b)
 expand bounding box (aka root cell) if particle does not fit into existing one
 
bool appendtree (const size_t b)
 append particle to the tree
 
bool intcoord (int xp[N_DIM], const vec3 rp) const
 calculate integerized coords
 
int subindex (const int x[N_DIM], const int l) const
 determine subcell that a given position belongs to (l is cell level)
 
void centerofmass (const nodeptr q, const vec3 corner, const double cellsize, int l)
 recursive calculation of cell center-of-mass
 
void assigneps (const nodeptr q, const double epsparent, const double cellsize)
 recursive initialization of individual softening radii of cells More...
 
void propagateeps (const nodeptr q)
 recursively assign epsilon to tree cells from underlying nodes
 
void walktree (const nodeptr p, const double dsq, const vec3 pos0, const WALKOP operation, double data[]) const
 recursive computation of potential or forces from tree node/cell p at position pos0
 
void walktreedens (const nodeptr p, const double dsq, const double searchradsq, const vec3 pos0, const int xp[N_DIM], const int lev, vectorpd *data) const
 recursive search of particles in node/cell p which are closer to pos0 than sqrt{dsq). More...
 

Private Attributes

const double eps
 potential softening parameter; negative value means position-dependent softening proportional to local density^{-1/3}
 
const double tol
 accuracy parameter (opening angle): 0 means exact N^2 force calculation (don't ever try!)
 
std::vector< body > bodytab
 list of all particles
 
std::vector< cell > celltab
 list of all tree cells
 
nodeptr troot
 pointer to the root cell of the tree
 
vec3 rmin
 lower-left corner of coordinate box
 
double rsize
 side-length of integerized coordinate box
 

Static Private Attributes

static const int IMAX =(1 << (8 * sizeof(int) - 2))
 max integer coordinate
 
static const unsigned int NSUB =(1 << N_DIM)
 subcells per cell (2^3)
 

Additional Inherited Members

- Public Types inherited from smile::CDensity
enum  POTENTIALTYPE {
  PT_UNKNOWN, PT_DIRECT, PT_COMPOSITE, PT_COEFS,
  PT_NB, PT_BSE, PT_BSECOMPACT, PT_SPLINE,
  PT_CYLSPLINE, PT_LOG, PT_HARMONIC, PT_SCALEFREE,
  PT_SCALEFREESH, PT_SPHERICAL, PT_DEHNEN, PT_MIYAMOTONAGAI,
  PT_FERRERS, PT_PLUMMER, PT_ISOCHRONE, PT_PERFECTELLIPSOID,
  PT_NFW, PT_SERSIC, PT_EXPDISK, PT_ELLIPSOIDAL,
  PT_MGE
}
 list of all existing types of density or density/potential models, each of them implemented in its own class More...
 
enum  SYMMETRYTYPE {
  ST_NONE = 0, ST_REFLECTION = 1, ST_PLANESYM = 2, ST_ZROTSYM = 4,
  ST_SPHSYM = 8, ST_TRIAXIAL = ST_REFLECTION | ST_PLANESYM, ST_AXISYMMETRIC = ST_TRIAXIAL | ST_ZROTSYM, ST_SPHERICAL = ST_AXISYMMETRIC | ST_SPHSYM,
  ST_DEFAULT = ST_TRIAXIAL
}
 Type of symmetry. More...
 

Detailed Description

frozen N-body potential calculated by tree-code algorithm (based on hackcode1.c)

Member Enumeration Documentation

enum smile::CPotentialNB::NODETYPE
private

tree contains nodes of two kinds: individual particles and child cells

Enumerator
BODY 

one particle

CELL 

tree cell containing up to 8 child nodes

enum smile::CPotentialNB::WALKOP
private

operation to perform during the tree-walk

Enumerator
CALCPHI 

compute potential

CALCACC 

compute acceleration(3d)

Constructor & Destructor Documentation

template<typename NumT >
smile::CPotentialNB::CPotentialNB ( double  _eps,
double  _tol,
const CPointMassSet< NumT > &  points 
)

Initialize from a list of particles;.

Template Parameters
NumT= double or float

Member Function Documentation

void smile::CPotentialNB::assigneps ( const nodeptr  q,
const double  epsparent,
const double  cellsize 
)
private

recursive initialization of individual softening radii of cells

recursive assign of softening length: compute the number density of points in a given cell and average it with the parent cell, repeat process for the entire tree is scanned several times to perform back and forth averaging over parent/daughter nodes.

eps_i = |eps| * n^{-1/3}, where eps is the global softening parameter and n is the average number density in the vicinity of the node. epsparent is the softening length of the parent cell (zero on the first iteration).

virtual CPotential* smile::CPotentialNB::clone ( ) const
inlinevirtual

Return a pointer to a copy of this instance of potential.

A standard copy constructor or assignment is disabled because of different amount of data needed to be copied in different derived classes).

Implements smile::CPotential.

void smile::CPotentialNB::Force ( const double  xyz[N_DIM],
const double  t,
double *  force,
double *  forceDeriv = NULL 
) const
virtual

Compute forces and, optionally, force derivatives at a given point.

Parameters
[in]xyz- coordinates of the point to compute forces (array of 3 numbers)
[in]t- time to compute forces (matters only if potential is time-dependent)
[out]force- computed values of -d Phi/d x_i; output array must exist and contain N_DIM values.
[out]forceDeriv- if not NULL, then also compute the second derivatives of potential (which is a symmetric matrix of size N_DIM^2, thus the array must be of size N_DIM*(N_DIM+1)/2 ): first 3 values contain $ -d^2 \Phi/d x_i^2 $, second three contain mixed derivatives $ -d^2 \Phi/d x_1 d x_2, -d^2 \Phi/d x_2 d x_3, -d^2 \Phi/d x_3 d x_1 $.

Implements smile::CPotential.

double smile::CPotentialNB::Phi ( double  X,
double  Y,
double  Z,
double  t = 0 
) const
virtual

Return potential at a given spatial point (possibly a time-varying one).

Implements smile::CPotential.

void smile::CPotentialNB::walktreedens ( const nodeptr  p,
const double  dsq,
const double  searchradsq,
const vec3  pos0,
const int  xp[N_DIM],
const int  lev,
vectorpd *  data 
) const
private

recursive search of particles in node/cell p which are closer to pos0 than sqrt{dsq).

the list of such particles is stored in data and then used to compute density via kernel estimate

The documentation for this class was generated from the following files:
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