Demonstration of uniformly allocating integers into a fixed number of hash buckets

hash-buckets.js

import * as math from 'mathjs'

const MINUTES_PER_DAY = 1440
const REFRESH_MINUTES = 1
const HASH_BUCKETS = MINUTES_PER_DAY / REFRESH_MINUTES

const MAX_IDS = 291554

main()

function main () {
  let buckets = new Array(HASH_BUCKETS)
  for (let i = 0; i < HASH_BUCKETS; i++) {
    buckets[i] = []
  }

  for (let i = 0; i < MAX_IDS; i++) {
    const bucket = jenkinsHash(i, HASH_BUCKETS)
    buckets[bucket].push(i)
  }

  var counts = []
  for (let i = 0; i < HASH_BUCKETS; i++) {
    counts.push(buckets[i].length)
  }
  console.log(`mean=${math.mean(counts)}, std=${math.std(counts)}, min=${math.min(counts)}, max=${math.max(counts)}`)
}

function jenkinsHash (key, intervalSize) {
  key = '' + key
  let hash = 0
  for (let i = 0; i < key.length; ++i) {
    hash += key.charCodeAt(i)
    hash += (hash << 10)
    hash ^= (hash >> 6)
  }
  hash += (hash << 3)
  hash ^= (hash >> 11)
  hash += (hash << 15)

  // Make unsigned and modulo intervalSize
  return (hash >>> 0) % intervalSize
}