wavelet-matrix 0.3.0

A wavelet matrix implementation. Supports various near-O(1) queries on large number of symbols or integers.
Documentation

wavelet-matrix crate for the Rust language

The Wavelet Matrix is a space-efficient variant of Wavelet Tree data structure.

Usage

Add to Cargo.toml:

[dependencies]
wavelet-matrix = "0.2.0"

Add to lib.rs or main.rs

extern crate wavelet_matrix; // Note: underscore is used here

Example

Add to main.rs:

use wavelet_matrix::*;

fn main() {
    let vec = vec![1, 2, 4, 5, 1, 0, 4, 6, 2, 9, 2, 0];

    let wm = WaveletMatrix::new(vec);
    assert_eq!(wm.len(), 12);
    assert_eq!(wm.lookup(7), 6);
    assert_eq!(wm.rank(5, 1), 2);
    assert_eq!(wm.select(2, 2), Some(10));

    println!("Worked as expected!");
}

Features

Basic/Classical WaveletMatrix operations

Given unsigned integer sequence A, it provides the following queries:

  • .len(): returns the length of A.
  • .lookup(pos): returns the value at the position pos of A, A[pos].
  • .rank(pos, value): counts value included in A[0..pos].
    • Note: pos is exclusive. When pos is 0, .rank() always returns 0.
  • .select(rank, value): return the position of the (rank+1)-th value
    • Note: When found nothing, it returns .len() instead of None.

Advanced queries

  • to be added

Releases

v0.3.0

  • [INCOMPATIBLE] .select() now returns .len() instead of None.

TODO

  • Implement .top_n for WaveletMatrix

  • Add prefix queries like .prefix_rank() and .prefix_select(). They will be much faster and useful for IPv4 prefix search (eg. searching for 192.168.12.0/24).

  • Add less_than queries like .rank_less_than() and the variations with the other operators such as equal, greater_than

  • Add ranged queries like .ranged_rank() and .ranged_select().

  • We may need to come up with the better name for those queries, though.

  • impl SpaceUsage for WaveletMatrix

  • Add Benchmark.

    • Implement same queries using trivial algorithm
    • Compare wm's queries against trivial one.
    • Make a nice plot.

  • Profiling

  • Optimize underlying rsdic structure.

  • Add travis CI.

  • Add u128 support or arbitrary-length integer support

  • The fastest implementation on the planet

Credits