Created
March 11, 2021 14:54
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Test for hash collisions
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const { crc32 } = require('@node-rs/crc32'); | |
const randomString = require('random-string'); | |
const murmur = require('murmur2js'); | |
//const siphash = require('siphash'); | |
//const sipkey = siphash.string16_to_key(randomString({length: 16})); | |
const values = 16000000; | |
let collisions = 0; | |
const map = new Map(); | |
const t1 = new Date().getTime(); | |
for (let i = 1; i <= values; i++) { | |
const str = randomString({length: 16}); | |
const crc32Hash = crc32(str); | |
//const murmurHash = murmur(str); | |
//const hash = ((crc32Hash & 0xfffff) * 2 ** 32) + murmurHash; | |
//const hash = siphash.hash_uint(sipkey, str); | |
const hash = crc32Hash; | |
if (map.has(hash)) { | |
collisions++; | |
//console.log(`Collision: hash(${str}) = hash(${map.get(hash)})!`); | |
} | |
map.set(hash, str); | |
if (!(i % 100000)) { | |
if (collisions) | |
console.log(`Added ${i} values, one collision for ${ Math.round(i / collisions) } elements`); | |
else | |
console.log(`Added ${i} values, still no collisions!`); | |
} | |
} | |
const t2 = new Date().getTime(); | |
console.log(`Total values: ${values}, collisions: ${collisions} in ${(t2-t1)/1000} seconds`); |
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