Struct SampleCache 

pub(crate) struct SampleCache<const N: usize> {
    radials: Vec<Option<Complex>>,
    harmonics: [Option<(usize, Vec<Complex>)>; 2],
    spherical: Option<((usize, usize, i32, i32), [VectorWave; 2])>,
    cylindrical: Option<((usize, usize, i32, u64), [[Jet<N>; 3]; 2])>,
}

Work shared by the waves of one sample point: scaled radial functions per (position, wavenumber, order), and the last spherical parts or cylindrical components, which the adjacent polarization of the same mode reuses. Every entry is keyed by all of its inputs, so any mode order is evaluated exactly as without the cache. N is the derivative level (VALUES, SPATIAL_AND_K or WITH_AXIAL).

Fields

radials: Vec<Option<Complex>>

harmonics: [Option<(usize, Vec<Complex>)>; 2]

Only the current centre for each wavenumber, bounding table storage by lmax rather than the number of centres. Each entry packs the value and gradient, followed by the row-major Hessian only above VALUES.

spherical: Option<((usize, usize, i32, i32), [VectorWave; 2])>

cylindrical: Option<((usize, usize, i32, u64), [[Jet<N>; 3]; 2])>