mode89 / fdtrie-js

Persistent data structures with fast diff

fdtrie-js

Persistent data structures with fast diff.

Usage

Installation

npm install fdtrie

Import

import {PHashMap} from "fdtrie";

Create an empty persistent hash map

const m0  = PHashMap.blank();

Add entry into the map (returns new map object)

const m1 = m0.assoc("some-key", "some-value");

Remove entry from the map (returns new map object)

const m2 = m1.dissoc("some-key");

Get value by key (returns undefined if key not found)

const someValue = m1.get("some-key");

Get value by key and return notFound if key not found

const notFound = {};
const anotherValue = m1.get("another-value", notFound);

Count entries

const n = m1.count();

Iterate through key-value pairs (returns generator object)

for (const e of m1.entries()) {
    console.log(e.key, e.value);
}

Reduce difference between two maps by calling one of the callbacks (remove, change, add) on each of the differing entries

const accInit = 0;
const acc = m1.reduceDifference(m2, accInit, {
    remove: (m1Entry, acc) => acc + m1Entry.key + m1Entry.value,
    change: (m1Entry, m2Entry, acc) =>
        acc + m1Entry.key + m1Entry.value + m2Entry.value,
    add: (m2Entry, acc) => acc + m2Entry.key + m2Entry.value,
});

Calculate difference (returns a map that holds key-value pairs of the first map, which don't present in the second map)

const m3 = m1.difference(m0);

Testing

Run unit tests

npm test

Run property-based tests

npm run test-props

Benchmarking

Run benchmarks

npm run bench

Results:

CPU: Intel Core i5-9400F
RAM: 16 GB
Linux kernel: 5.19.12
Node v18.10.0

Associate a key with a value
  PHashMap: 51 ms
  ImmutableJS: 51 ms
  Mori: 49 ms
  Native: 8 ms

Get a value by a key
  PHashMap: 13 ms
  ImmutableJS: 12 ms
  Mori: 8 ms
  Native: 1 ms

Delete a key
  PHashMap: 48 ms
  ImmutableJS: 49 ms
  Mori: 54 ms
  Native: 0 ms

Single key difference
  PHashMap: 949 ns
  ImmutableJS: 8545869 ns
  Mori: 5904032 ns

All keys difference
  PHashMap: 10 ms
  ImmutableJS: 43 ms
  Mori: 27 ms

Reduce difference (single key)
  PHashMap: 458 ns
  ImmutableJS: 18070695 ns
  Mori: 11168898 ns

Reduce difference (all keys)
  PHashMap: 7 ms
  ImmutableJS: 23 ms
  Mori: 15 ms