Multipole approximation of distance particle. More...

#include <BarnesHut.h>

Inheritance diagram for BarnesHut:

Classes
class	NodeTask

struct	TreeWalkResult

struct	TreeWalkState
	Data passed into each node during treewalk. More...

Public Member Functions
	BarnesHut (const Float theta, const MultipoleOrder order, const Size leafSize=25, const Size maxDepth=50, const Float gravityConstant=Constants::gravity)
	Constructs the Barnes-Hut gravity assuming point-like particles (with zero radius). More...

	BarnesHut (const Float theta, const MultipoleOrder order, GravityLutKernel &&kernel, const Size leafSize=25, const Size maxDepth=50, const Float gravityConstant=Constants::gravity)
	Constructs the Barnes-Hut gravity with given smoothing kernel. More...

virtual void	build (IScheduler &pool, const Storage &storage) override
	Masses of particles must be strictly positive, otherwise center of mass would be undefined. More...

virtual void	evalAll (IScheduler &pool, ArrayView< Vector > dv, Statistics &stats) const override
	Evaluates the gravitational acceleration concurrently. More...

virtual Vector	eval (const Vector &r0) const override
	Evaluates the gravitational acceleration at given point. More...

virtual Float	evalEnergy (IScheduler &scheduler, Statistics &stats) const override
	Computes the total potential energy of the particles. More...

virtual RawPtr< const IBasicFinder >	getFinder () const override
	Optionally returns a finder used by the gravity implementation. More...

MultipoleExpansion< 3 >	getMoments () const
	Returns the multipole moments computed from root node. More...

Public Member Functions inherited from Polymorphic
virtual	~Polymorphic ()

Protected Member Functions
Vector	evalImpl (const Vector &r0, const Size idx) const
	Evaluates the gravity at a single point in space. More...

void	evalNode (IScheduler &scheduler, ArrayView< Vector > dv, const Size nodeIdx, TreeWalkState data, TreeWalkResult &result) const
	Performs a recursive treewalk evaluating gravity for all particles. More...

void	evalParticleList (const LeafNode< BarnesHutNode > &leaf, ArrayView< Size > particleList, ArrayView< Vector > dv) const

void	evalNodeList (const LeafNode< BarnesHutNode > &leaf, ArrayView< Size > nodeList, ArrayView< Vector > dv) const

Vector	evalExact (const LeafNode< BarnesHutNode > &node, const Vector &r0, const Size idx) const

void	buildLeaf (BarnesHutNode &node)

void	buildInner (BarnesHutNode &node, BarnesHutNode &left, BarnesHutNode &right)

Protected Attributes
ArrayView< const Vector >	r
	View of a position buffer in the storage. More...

Array< Float >	m
	Particle masses multiplied by gravitational constant. More...

KdTree< BarnesHutNode >	kdTree
	K-d tree storing gravitational moments. More...

GravityLutKernel	kernel
	Kernel used to evaluate gravity of close particles. More...

Float	thetaInv
	Inverted value of the opening angle for multipole approximation (in radians) More...

MultipoleOrder	order
	Order of multipole approximation. More...

Size	maxDepth
	Maximum depth at which the nodes evaluation is parallelized. More...

Float	gravityConstant = Constants::gravity
	Gravitational constant in the selected unit system. More...

Detailed Description

Multipole approximation of distance particle.

Definition at line 43 of file BarnesHut.h.

Constructor & Destructor Documentation

◆ BarnesHut() [1/2]

BarnesHut::BarnesHut	(	const Float	theta,
		const MultipoleOrder	order,
		const Size	leafSize = `25`,
		const Size	maxDepth = `50`,
		const Float	gravityConstant = `Constants::gravity`
	)

Constructs the Barnes-Hut gravity assuming point-like particles (with zero radius).

Parameters

theta	Opening angle; lower value means higher precision, but slower computation
order	Order of multipole approximation
leafSize	Maximum number of particles in a leaf
maxDepth	Maximum parallel depth for tree contruction and evaluation

Definition at line 17 of file BarnesHut.cpp.

◆ BarnesHut() [2/2]

BarnesHut::BarnesHut	(	const Float	theta,
		const MultipoleOrder	order,
		GravityLutKernel &&	kernel,
		const Size	leafSize = `25`,
		const Size	maxDepth = `50`,
		const Float	gravityConstant = `Constants::gravity`
	)

Constructs the Barnes-Hut gravity with given smoothing kernel.

Parameters

theta	Opening angle; lower value means higher precision, but slower computation
order	Order of multipole approximation
kernel	Precomputed gravity smoothing kernel
leafSize	Maximum number of particles in a leaf
maxDepth	Maximum parallel depth for tree contruction and evaluation

Definition at line 34 of file BarnesHut.cpp.

Member Function Documentation

◆ build()

void BarnesHut::build	(	IScheduler &	pool,
		const Storage &	storage
	)

overridevirtual

Masses of particles must be strictly positive, otherwise center of mass would be undefined.

Todo:: sequential needed because TBB cannot wait on child tasks yet

Implements IGravity.

Definition at line 49 of file BarnesHut.cpp.

◆ buildInner()

void BarnesHut::buildInner	(	BarnesHutNode &	node,
		BarnesHutNode &	left,
		BarnesHutNode &	right
	)

protected

Definition at line 413 of file BarnesHut.cpp.

◆ buildLeaf()

void BarnesHut::buildLeaf ( BarnesHutNode & node )

protected

Definition at line 351 of file BarnesHut.cpp.

◆ eval()

Vector BarnesHut::eval ( const Vector & r0 ) const

overridevirtual

Evaluates the gravitational acceleration at given point.

The point must NOT correspond to any particle, as this case could formally lead to infinite acceleration if no smoothing kernel is used.

Parameters

r0	Point where the gravity is evaluated.

Implements IGravity.

Definition at line 99 of file BarnesHut.cpp.

◆ evalAll()

void BarnesHut::evalAll	(	IScheduler &	scheduler,
		ArrayView< Vector >	dv,
		Statistics &	stats
	)		const

overridevirtual

Evaluates the gravitational acceleration concurrently.

The function is blocking, it must exit after the gravity is evaluated.

Parameters

scheduler	Scheduler used for parallelization.
dv	Acceleration values; it may already contain some accelerations computed by other code components, gravity should add acceleration instead of replacing the current values.
stats	Output statistics of the gravitational solver.

Implements IGravity.

Definition at line 83 of file BarnesHut.cpp.

◆ evalEnergy()

Float BarnesHut::evalEnergy	(	IScheduler &	scheduler,
		Statistics &	stats
	)		const

overridevirtual

Computes the total potential energy of the particles.

The zero point is implementation-specific; it is not required that the energy is strictly negative.

Parameters

scheduler	Scheduler used for parallelization.
stats	Output statistics of the gravitational solver.

Implements IGravity.

Definition at line 103 of file BarnesHut.cpp.

◆ evalExact()

Vector BarnesHut::evalExact	(	const LeafNode< BarnesHutNode > &	node,
		const Vector &	r0,
		const Size	idx
	)		const

protected

Definition at line 339 of file BarnesHut.cpp.

◆ evalImpl()

Vector BarnesHut::evalImpl	(	const Vector &	r0,
		const Size	idx
	)		const

protected

Evaluates the gravity at a single point in space.

Definition at line 107 of file BarnesHut.cpp.

◆ evalNode()

void BarnesHut::evalNode	(	IScheduler &	scheduler,
		ArrayView< Vector >	dv,
		const Size	evaluatedNodeIdx,
		TreeWalkState	data,
		TreeWalkResult &	result
	)		const

protected

Performs a recursive treewalk evaluating gravity for all particles.

Treewalk starts at given node and subsequently calls evalNode for children nodes. Function moves nodes from checkList into interaction lists and in case the node is a leaf, gravity is computed using constructed interaction lists.

Parameters

scheduler	Scheduler used for (potential) parallelization
dv	Output thread-local buffer where computed accelerations are stored
nodeIdx	Index of the first node evaluated by the function
data	Checklist nad interaction lists of he node
result	Statistics incremented by the node. Cannot be return value, the type is not moveable.

Todo:: try different containers; we need fast inserting & deletion

Todo:: ASSERT FIRED !

Definition at line 185 of file BarnesHut.cpp.

◆ evalNodeList()

void BarnesHut::evalNodeList	(	const LeafNode< BarnesHutNode > &	leaf,
		ArrayView< Size >	nodeList,
		ArrayView< Vector >	dv
	)		const

protected

Definition at line 325 of file BarnesHut.cpp.

◆ evalParticleList()

void BarnesHut::evalParticleList	(	const LeafNode< BarnesHutNode > &	leaf,
		ArrayView< Size >	particleList,
		ArrayView< Vector >	dv
	)		const

protected

Definition at line 288 of file BarnesHut.cpp.

◆ getFinder()

RawPtr< const IBasicFinder > BarnesHut::getFinder ( ) const

overridevirtual

Optionally returns a finder used by the gravity implementation.

If the gravity uses an acceleration structure that implements the IBasicFinder interface, this function allows the user to obtain the object and re-use in other parts of the code. Finder is assumed to be initialized after build is called.

If the gravity does not use any such structure or it simply does not implement the IBasicFinder interface, the function returns nullptr.

Implements IGravity.

Definition at line 470 of file BarnesHut.cpp.

◆ getMoments()

MultipoleExpansion< 3 > BarnesHut::getMoments ( ) const

Returns the multipole moments computed from root node.

Mostly for testing purposes.

Definition at line 465 of file BarnesHut.cpp.

Member Data Documentation

◆ gravityConstant

Float BarnesHut::gravityConstant = Constants::gravity

protected

Gravitational constant in the selected unit system.

In SI, this is simply Constants::gravity.

Todo:: generalize

Definition at line 72 of file BarnesHut.h.

◆ kdTree

KdTree<BarnesHutNode> BarnesHut::kdTree

protected

K-d tree storing gravitational moments.

Definition at line 52 of file BarnesHut.h.

◆ kernel

GravityLutKernel BarnesHut::kernel

protected

Kernel used to evaluate gravity of close particles.

Definition at line 55 of file BarnesHut.h.

◆ m

Array<Float> BarnesHut::m

protected

Particle masses multiplied by gravitational constant.

Definition at line 49 of file BarnesHut.h.

◆ maxDepth

Size BarnesHut::maxDepth

protected

Maximum depth at which the nodes evaluation is parallelized.

Child nodes are then evaluated serially on the same thread.

Definition at line 66 of file BarnesHut.h.

◆ order

MultipoleOrder BarnesHut::order

protected

Order of multipole approximation.

Definition at line 61 of file BarnesHut.h.

◆ r

ArrayView<const Vector> BarnesHut::r

protected

View of a position buffer in the storage.

Definition at line 46 of file BarnesHut.h.

◆ thetaInv

Float BarnesHut::thetaInv

protected

Inverted value of the opening angle for multipole approximation (in radians)

Definition at line 58 of file BarnesHut.h.

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

/home/pavel/projects/astro/sph/src/core/gravity/BarnesHut.h
/home/pavel/projects/astro/sph/src/core/gravity/BarnesHut.cpp

Classes

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ BarnesHut() [1/2]

◆ BarnesHut() [2/2]

Member Function Documentation

◆ build()

◆ buildInner()

◆ buildLeaf()

◆ eval()

◆ evalAll()

◆ evalEnergy()

◆ evalExact()

◆ evalImpl()

◆ evalNode()

◆ evalNodeList()

◆ evalParticleList()

◆ getFinder()

◆ getMoments()

Member Data Documentation

◆ gravityConstant

◆ kdTree

◆ kernel

◆ m

◆ maxDepth

◆ order

◆ r

◆ thetaInv