orrery::core::Diagnostics Struct Reference

Every conserved quantity of a configuration, measured at one instant. More...

#include <orrery/core/diagnostics.hpp>

Public Member Functions
constexpr Real	total_energy () const noexcept
constexpr Real	virial_ratio () const noexcept
	The virial ratio 2T / |U|.

Public Attributes
Real	kinetic_energy {}
Real	potential_energy {}
Vec3	linear_momentum {}
Vec3	angular_momentum {}

Detailed Description

Every conserved quantity of a configuration, measured at one instant.

An aggregate, because it is a record of measurements with no invariant relating them. The two derived quantities are member functions rather than fields so that they cannot be stale.

Member Function Documentation

virial_ratio()

Real orrery::core::Diagnostics::virial_ratio ( ) const

inlinenodiscardconstexprnoexcept

The virial ratio 2T / |U|.

One for a self-gravitating system in equilibrium, by the virial theorem. Below one the system is colder than equilibrium and will collapse before settling; above one it is hotter and will expand. It is the standard check that a sampled configuration is in the state its model claims, and it is how the Plummer sampler is validated.

The convention differs between authors: some write the same statement as -2T/U, which is identical for a bound system, and some as T/|U|, which is a half where this is one. This project quotes 2T/|U| throughout.

A configuration whose particles do not interact has no potential energy and no virial statement to make. The division then returns an infinity or a quiet NaN rather than a plausible number, which is the intended behaviour: a nonsense question should give a visibly nonsense answer.

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

• orrery/core/diagnostics.hpp