Struct CountMinSketch 

pub struct CountMinSketch { /* private fields */ }

Count-Min Sketch for approximate frequency queries.

Answers “how many times did item X appear?” with bounded over-estimation. Mergeable across shards: element-wise addition of tables.

Implementations

impl CountMinSketch

pub fn new() -> Self

Create a sketch with default parameters (width=1024, depth=4).

Error ≤ e/1024 ≈ 0.27% of total count, confidence ≥ 1 − e^(−4) ≈ 98.2%.

pub fn with_params(width: usize, depth: usize) -> Self

Create with custom width and depth.

• width — number of counters per row (controls accuracy; larger = less error)
• depth — number of hash functions/rows (controls confidence; larger = higher)

pub fn add(&mut self, item: u64)

Add an item occurrence.

pub fn add_count(&mut self, item: u64, count: u64)

Add an item with a specified count.

pub fn add_batch(&mut self, items: &[u64])

Add a batch of items (each with count 1).

pub fn estimate(&self, item: u64) -> u64

Estimate the frequency of an item.

Returns the minimum count across all hash rows (point query). This is always ≥ the true count and ≤ true_count + ε·N.

pub fn total(&self) -> u64

Total number of items added.

pub fn merge(&mut self, other: &CountMinSketch)

Merge another sketch (element-wise addition).

Both sketches must have the same width and depth.

pub fn memory_bytes(&self) -> usize

Memory usage in bytes.

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

Serialize the table as a flat byte array (row-major, little-endian u64).

pub fn from_table_bytes(data: &[u8], width: usize, depth: usize) -> Self

Reconstruct from serialized table bytes.

Trait Implementations

impl Debug for CountMinSketch

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

Formats the value using the given formatter.

impl Default for CountMinSketch

fn default() -> Self

Returns the “default value” for a type.