Struct HLL

pub struct HLL { /* private fields */ }

The HLL struct stores the underlying registers of the HyperLogLog, with m many registers.

The value for m is derived from the desired error of the estimation. The error is considered to be 1.04 / sqrt(2 ^ bits). So, given a desired 1% error rate, we result in around 12 bits per register, producing an underlying M of 2^12 bits (i.e. 4kb).

Implementations

impl HLL

pub fn one_hundred_twenty_eight() -> HLL

Convenience function to produce a HLL with one hundred and twenty eight registers.

pub fn new(error: f64) -> HLL

Create a new HLL with the desired standard error. Some examples might be:

     bits    size    error
     12      4096    0.0163
     13      8192    0.0115
     14      16384   0.0081

The error must be between 0.0 and 1.0. Beware using a stupidly small error size will grow beyond e.g. isize at less than 0.03 (if you need something that isn’t an estimate probably don’t use a hyperloglog).

pub fn insert<T: Hash>(&mut self, val: &T) -> bool

Add an element into the hyperloglog estimate. We require the type of value to be able to be hashed. Returns whether the insertion altered the hyperloglog

pub fn count(&self) -> f64

Return the estimated cardinality of the observed set of elements.

pub fn registers(&self) -> Vec<u8>

Access a copy of the underlying registers (this is mainly here just for debugging/testing… its unlikely you’ll need this access typically).

pub fn empty() -> HLL

A completely zeroed HLL. Not particularly useful except as an identity element in Add.

pub fn into_vec(self) -> Vec<u8>

pub fn from_vec(data: Vec<u8>) -> HLL

Trait Implementations

impl<'a> Add for &'a HLL

Adding together two HLLs produces a new HLL where the larger value of each register has been selected.

type Output = HLL

The resulting type after applying the + operator.

fn add(self, other: &'a HLL) -> HLL

Performs the + operation.

impl Clone for HLL

fn clone(&self) -> HLL

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for HLL

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

Formats the value using the given formatter.

impl Display for HLL

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

Formats the value using the given formatter.

impl PartialEq for HLL

fn eq(&self, other: &HLL) -> 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 Eq for HLL

impl StructuralPartialEq for HLL