Struct SplinedPotential 

pub struct SplinedPotential { /* private fields */ }

A splined version of any isotropic twobody potential.

Provides O(1) evaluation via cubic spline interpolation. Supports three grid types:

• PowerLaw(p): Power-law spacing with denser sampling at short range (default, p=2.0)
• UniformR: Uniform spacing in r
• UniformRsq: Uniform spacing in r² (legacy, not recommended)

The splined potential is type-erased after construction—it stores only the precomputed coefficients, not the original potential.

Implementations

impl SplinedPotential

pub fn coefficients(&self) -> &[SplineCoeffs]

Returns a reference to the spline coefficients for all grid intervals.

pub const fn f_at_rmin(&self) -> f64

Returns the force at r_min, used for linear extrapolation below the grid.

pub const fn r_min(&self) -> f64

Returns the minimum distance of the spline grid.

pub const fn r_max(&self) -> f64

Returns the maximum distance of the spline grid.

pub const fn grid_type(&self) -> GridType

Returns the grid type used for construction.

pub const fn n_points(&self) -> usize

Returns the number of grid points.

pub const fn inv_delta(&self) -> f64

Returns the inverse grid spacing.

pub const fn delta(&self) -> f64

Returns the grid spacing.

pub fn new<P: IsotropicTwobodyEnergy + Cutoff>( potential: &P, config: SplineConfig, ) -> Self

Create a new splined potential from an analytical potential with a Cutoff.

Arguments

• potential - The analytical potential to tabulate (must implement Cutoff)
• config - Configuration for the spline table

Panics

Panics if n_points < 4, if rsq_min >= rsq_max, or if cutoff is infinite

pub fn with_cutoff<P: IsotropicTwobodyEnergy + Cutoff>( potential: &P, cutoff: f64, config: SplineConfig, ) -> Self

Create a new splined potential with an explicit cutoff distance.

Use this for potentials that have infinite cutoff, or when you want to override the potential’s native cutoff.

Arguments

• potential - The analytical potential to tabulate
• cutoff - The cutoff distance (must be finite and positive)
• config - Configuration for the spline table

Panics

Panics if n_points < 4, if rsq_min >= rsq_max, or if cutoff is not finite/positive

impl SplinedPotential

pub const fn cutoff_squared(&self) -> f64

Get the squared cutoff distance.

pub fn stats(&self) -> SplineStats

Get table statistics for debugging.

pub fn validate<P: IsotropicTwobodyEnergy>( &self, potential: &P, n_test: usize, ) -> ValidationResult

Validate spline accuracy against the original potential.

impl SplinedPotential

pub fn energies_batch(&self, rsq_values: &[f64], out: &mut [f64])

Evaluate energy for multiple distances at once (scalar loop).

pub fn evaluate_batch( &self, rsq_values: &[f64], energies: &mut [f64], forces: &mut [f64], )

Evaluate energy and force for multiple distances (scalar loop).

pub fn to_simd(&self) -> SplineTableSimd

Convert to SIMD-friendly SoA layout for batch evaluation (f64).

pub fn to_simd_f32(&self) -> SplineTableSimdF32

Convert to single-precision (f32) SIMD layout for faster evaluation.

Uses architecture-optimal SIMD width: f32x8 on x86_64, f32x4 on aarch64. Provides ~2x memory efficiency at the cost of reduced precision.

Trait Implementations

impl Clone for SplinedPotential

fn clone(&self) -> SplinedPotential

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Cutoff for SplinedPotential

fn cutoff(&self) -> f64

Cutoff distance (upper)

fn cutoff_squared(&self) -> f64

Squared cutoff distance

fn lower_cutoff(&self) -> f64

Cutoff distance (lower)

fn is_finite(&self) -> bool

Test if cutoff is finite

impl Debug for SplinedPotential

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl IsotropicTwobodyEnergy for SplinedPotential

fn isotropic_twobody_energy(&self, distance_squared: f64) -> f64

Evaluate energy at squared distance using cubic spline interpolation.

Returns 0.0 if rsq >= cutoff². For rsq < rsq_min, linearly extrapolates using the slope at r_min to maintain repulsive behavior.

fn isotropic_twobody_force(&self, distance_squared: f64) -> f64

Evaluate force at squared distance using cubic spline interpolation.

Returns 0.0 if rsq >= cutoff². Below r_min, scales as f(r_min) * r_min / r to stay consistent with the linear energy extrapolation in real-force space.