orrery::solvers::BarnesHutSolver Class Reference

The Barnes-Hut solver described above. More...

#include <orrery/solvers/barnes_hut_solver.hpp>

Inheritance diagram for orrery::solvers::BarnesHutSolver:

Public Member Functions
	BarnesHutSolver (TreeParameters parameters={}) noexcept
	A solver over exact point masses, evaluated on the calling thread.
	BarnesHutSolver (TreeParameters parameters, core::Softening softening) noexcept
	A solver softening at the given length.
	BarnesHutSolver (TreeParameters parameters, core::Softening softening, backend::Executor &executor) noexcept
	A softened solver evaluated through executor.
void	evaluate (core::Vec3Span< const core::Real > positions, std::span< const core::Real > masses, core::Vec3Span< core::Real > accelerations) override
	Write the acceleration at each position into accelerations.
std::string_view	name () const noexcept override
	The solver's name, for benchmark tables and test messages.
core::Softening	softening () const noexcept override
	The softening this solver applies.
InteractionCount	interaction_count () const noexcept override
	The work done since construction or since the last reset.
void	reset_interaction_count () noexcept override
	Set every counter back to zero.
const TreeParameters &	parameters () const noexcept
	The parameters in force, which are the ones asked for after correction.
const Octree &	tree () const noexcept
	The tree the last evaluation built, empty before the first.
const EvaluationTimings &	timings () const noexcept
	Where the last evaluation's time went.
const backend::Executor *	executor () const noexcept
	The executor this solver evaluates through, or null if it runs on the calling thread.
void	select_kernel (KernelKind kind) noexcept
	Ask for a particular kernel for the pairs at the leaves, and settle for the scalar one if this machine cannot run it.
KernelKind	kernel () const noexcept
	The kernel this solver will use at the leaves.
Public Member Functions inherited from orrery::solvers::ForceSolver
	~ForceSolver () override=default
	Public and virtual, the second by inheritance from AccelerationField.

Additional Inherited Members
Protected Member Functions inherited from orrery::solvers::ForceSolver
	ForceSolver (const ForceSolver &)=default
	ForceSolver (ForceSolver &&)=default
ForceSolver &	operator= (const ForceSolver &)=default
ForceSolver &	operator= (ForceSolver &&)=default
Protected Member Functions inherited from orrery::integrators::AccelerationField
	AccelerationField (const AccelerationField &)=default
	AccelerationField (AccelerationField &&)=default
AccelerationField &	operator= (const AccelerationField &)=default
AccelerationField &	operator= (AccelerationField &&)=default

Detailed Description

The Barnes-Hut solver described above.

Constructor & Destructor Documentation

BarnesHutSolver() [1/2]

orrery::solvers::BarnesHutSolver::BarnesHutSolver ( TreeParameters parameters = {} )

inlineexplicitnoexcept

A solver over exact point masses, evaluated on the calling thread.

The parameters are corrected on the way in, so a solver constructed with an opening angle of two reports one and behaves accordingly.

BarnesHutSolver() [2/2]

orrery::solvers::BarnesHutSolver::BarnesHutSolver ( TreeParameters parameters, core::Softening softening, backend::Executor & executor )

inlinenoexcept

A softened solver evaluated through executor.

The executor is referred to rather than owned and must outlive the solver, for the reason DirectSolver gives: a pool of threads is a machine-wide resource and a solver that owned one could not be created inside a loop.

Member Function Documentation

evaluate()

void orrery::solvers::BarnesHutSolver::evaluate ( core::Vec3Span< const core::Real > positions, std::span< const core::Real > masses, core::Vec3Span< core::Real > accelerations )

overridevirtual

Write the acceleration at each position into accelerations.

The three views must describe the same particles in the same order and have the same length, as AccelerationField requires.

Safe to call with no particles.

Implements orrery::integrators::AccelerationField.

name()

std::string_view orrery::solvers::BarnesHutSolver::name ( ) const

inlinenodiscardoverridevirtualnoexcept

The solver's name, for benchmark tables and test messages.

Implements orrery::solvers::ForceSolver.

softening()

core::Softening orrery::solvers::BarnesHutSolver::softening ( ) const

inlinenodiscardoverridevirtualnoexcept

The softening this solver applies.

Exposed so that a caller measuring energies asks the solver what it softened with rather than carrying a second copy of the value alongside it. Two copies of a number that must agree are how they come to disagree, and a potential energy computed with a different softening from the force kernel turns the project's headline conservation result into a measurement of the mismatch (ADR-0008).

Implements orrery::solvers::ForceSolver.

interaction_count()

InteractionCount orrery::solvers::BarnesHutSolver::interaction_count ( ) const

inlinenodiscardoverridevirtualnoexcept

The work done since construction or since the last reset.

Cheap: solvers accumulate this as they go and this call only reads it.

Implements orrery::solvers::ForceSolver.

reset_interaction_count()

void orrery::solvers::BarnesHutSolver::reset_interaction_count ( )

inlineoverridevirtualnoexcept

Set every counter back to zero.

A benchmark counts the work of the measured region rather than of the warm-up that preceded it, and the two are otherwise indistinguishable once they have been added together.

Implements orrery::solvers::ForceSolver.

tree()

const Octree & orrery::solvers::BarnesHutSolver::tree ( ) const

inlinenodiscardnoexcept

The tree the last evaluation built, empty before the first.

Exposed so that a test can assert what the tree is and a benchmark can report its shape beside its timing. A depth or a leaf count is the first thing to look at when a tree costs more than it should, and recovering either from outside would mean building a second tree.

select_kernel()

void orrery::solvers::BarnesHutSolver::select_kernel ( KernelKind kind )

inlinenoexcept

Ask for a particular kernel for the pairs at the leaves, and settle for the scalar one if this machine cannot run it.

The same knob DirectSolver offers and for the same callers: the accuracy test comparing kernels and the benchmark timing them. It matters more here than it looks. A tree solver's leaves are short ranges, so the vector kernel is called with a few dozen sources rather than a few thousand, and how much of Phase 7's speedup survives that is a measurement rather than a deduction.

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

• orrery/solvers/barnes_hut_solver.hpp