interatomic 0.5.0

Library for calculating inter-particle interactions
Documentation 
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// InverseRsq spline evaluation for GPU pair potentials
//
// Grid mapping: t = (1/r² - w_min) * inv_delta

struct SplineParams {
    r_min: f32,
    r_max: f32,
    n_coeffs: u32,
    coeff_offset: u32,
    inv_delta: f32,
    w_min: f32,       // 1/r_max²
    f_at_rmin: f32,
    _pad0: f32,
}

struct SplineCoeffs {
    u: vec4<f32>,  // energy coefficients [A0, A1, A2, A3]
    f: vec4<f32>,  // force coefficients  [B0, B1, B2, B3]
}

// Compute spline grid index and fractional epsilon for distance r
fn spline_index_eps(params: SplineParams, r: f32) -> vec2<f32> {
    let rsq = clamp(r * r, params.r_min * params.r_min, params.r_max * params.r_max);
    let w = 1.0 / rsq;
    let t = (w - params.w_min) * params.inv_delta;
    let i = floor(t);
    return vec2<f32>(min(i, f32(params.n_coeffs - 2u)), t - i);
}

struct AngleSplineParams {
    angle_min: f32,
    angle_max: f32,
    n_coeffs: u32,
    coeff_offset: u32,
    inv_delta: f32,
    _pad0: f32,
    _pad1: f32,
    _pad2: f32,
}

// Compute angle spline grid index and fractional epsilon
fn angle_spline_index_eps(params: AngleSplineParams, angle: f32) -> vec2<f32> {
    let clamped = clamp(angle, params.angle_min, params.angle_max);
    let t = (clamped - params.angle_min) * params.inv_delta;
    let i = floor(t);
    return vec2<f32>(min(i, f32(params.n_coeffs - 2u)), t - i);
}