Crate hyperminhash

Very fast, constant memory-footprint cardinality approximation, including intersection and union operation. A straight port of Hyperminhash.

use hyperminhash::Sketch;

// A `Sketch` can approximate the unique count of elements it has seen over it's lifetime.
let mut sk = Sketch::default();

// After initialization, a `Sketch` will never allocate.

// Elements added to Sketch need to implement `std::hash::Hash`
sk.add("foobar");
sk.add(1);
sk.add(2);
sk.add(vec![3, 4, 5]);
for i in 0..5000 {
    sk.add(i);
}
// There will be some error in the count
assert!(sk.cardinality() > 4_900.0 && sk.cardinality() < 5_100.0);


// Using `std::iter::FromIterator`
let sketch1 = (0..10_000).collect::<Sketch>();
let sketch2 = (5_000..15_000).collect::<Sketch>();
assert!(sketch1.cardinality() > 9_800.0 && sketch1.cardinality() < 10_200.0);
assert!(sketch2.cardinality() > 9_800.0 && sketch2.cardinality() < 10_200.0);

// The intersection of two sketches yields the approximate number of unique
// elements that are in both sets.
let i = sketch1.intersection(&sketch2);
assert!(i > 4_800.0 && i < 5_200.0);

// Merge sketch1 with sketch2
let mut sketch1 = sketch1;
sketch1.union(&sketch2);
assert!(sketch1.cardinality() > 14_800.0 && sketch1.cardinality() < 15_200.0);

Structs

Sketch

Records the approximate number of unique elements it has seen over it's lifetime.