Struct CoverOptions 

pub struct CoverOptions {
    pub k: u32,
    pub d: u32,
    pub steps: u32,
    pub split_point: f64,
    pub shrink: Option<u32>,
}

Available on crate feature dict-builder only.

Tuning for COVER training, the knobs of the reference’s ZDICT_cover_params_t.

The defaults are those zstd --train-cover starts from: d of 8, a search over k in four steps, every sample both building and scoring.

Fields

k: u32

Segment size in bytes. Zero searches 50..=2000 when optimizing.

d: u32

Dmer size in bytes, at most k. Zero searches 6 and 8 when optimizing.

steps: u32

How many values of k the search tries; zero is 40.

split_point: f64

Share of the samples dictionaries are built from, in (0, 1]; the rest score them. At 1 every sample does both. Zero or below is the trainer’s default: 1 for COVER, 0.75 for FastCOVER.

shrink: Option<u32>

Try the content’s last 256, 512, 1024, … bytes, each finalized into a dictionary of its own, and keep the first whose scoring samples compress to at most this many percent more than with the whole content (upstream zstd COVER_selectDict). A dictionary so found is its header plus that tail, so none is smaller than the header plus 256 bytes. A search cuts its winner down this way; the parameters it chooses are unchanged.

Trait Implementations

impl Clone for CoverOptions

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for CoverOptions

impl Debug for CoverOptions

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

Formats the value using the given formatter.

impl Default for CoverOptions

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for CoverOptions

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for CoverOptions