Enum NcdVariant 

pub enum NcdVariant {
    Vitanyi,
    SymVitanyi,
    Cons,
    SymCons,
}

—–– NCD (Normalized Compression Distance) ——

NCD is a parameter-free similarity metric based on Kolmogorov complexity. Since Kolmogorov complexity K(x) is uncomputable, we approximate it using the compressed size C(x) provided by a real-world compressor (here, ZPAQ).

The general form is: NCD(x,y) = (C(xy) - min(C(x), C(y))) / max(C(x), C(y))

Different variants handle normalization and symmetry differently.

Variants

Vitanyi

Standard Vitanyi NCD: NCD(x,y) = (C(xy) - min(C(x), C(y))) / max(C(x), C(y)) Note: C(xy) denotes compressing the concatenation of x and y.

SymVitanyi

Symmetric Vitanyi NCD: NCD_sym(x,y) = (min(C(xy), C(yx)) - min(C(x), C(y))) / max(C(x), C(y)) Takes the best compression of xy or yx to ensure symmetry even if the compressor is not symmetric.

Cons

Conservative NCD: NCD_cons(x,y) = (C(xy) - min(C(x), C(y))) / C(xy) Normalizes by the joint compressed size instead of the max marginal.

SymCons

Symmetric Conservative NCD: NCD_sym_cons(x,y) = (min(C(xy), C(yx)) - min(C(x), C(y))) / min(C(xy), C(yx))

Trait Implementations

impl Clone for NcdVariant

fn clone(&self) -> NcdVariant

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for NcdVariant

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

Formats the value using the given formatter.

impl PartialEq for NcdVariant

fn eq(&self, other: &NcdVariant) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for NcdVariant

impl Eq for NcdVariant

impl StructuralPartialEq for NcdVariant