deterministic random sequence

A function that returns a sequence of deterministic random numbers. Given the same seed the function will return the same order of random numbers.

This uses the MurmurHash3 hashing function and the sfc32 (Simple Fast Counter) which is part of the PractRand random number testing suite (which it passes of course). sfc32 has a 128-bit state and is very fast in JS.

usage

npm i deterministic-random-sequence

or

npm i -D deterministic-random-sequence

const drs = require("deterministic-random-sequence");

const rand = drs("hello");  // "hello" seed, optional (will seed with "" if not set)
const first = rand();       // 0.6173389465548098 
const second = rand();      // 0.8618584796786308
const third = rand();       // 0.18602279876358807

// creates the same sequence from same initial conditions.
const rand2 = drs("hello");
const fourth = rand2();     // 0.6173389465548098 
const fifth = rand2();      // 0.8618584796786308
const sixth = rand2();      // 0.18602279876358807

performance and randomness

Stats for generating 10 million numbers eg.

const drs = require("deterministic-random-sequence");
const rand = drs("hello");

const calls = () => {
    const time = Date.now();
    for(let j = 0; j < 10000000; j++){
        rand();
    }
    return Date.now() - time;
}

const callsPushedToArray = () => {
    const time = Date.now();
    const arr = [];
    for(let j = 0; j < 10000000; j++){
        arr.push(rand());
    }
    return Date.now() - time;
}

// 10 million calls to the rand() function, averaged of 100 times
let averageTimeCalls = 0;
for(let k = 0; k < 100; k++){
    averageTimeCalls += calls();
}
averageTimeCalls /= 100;

// 10 million calls to the rand() function, pushed to an array, averaged of 100 times
let averageTimeCallsPushedToArray = 0;
for(let k = 0; k < 100; k++){
    averageTimeCallsPushedToArray += callsPushedToArray();
}
averageTimeCallsPushedToArray /= 100;

// distribution of randomness
let average = 0;
const dist = {};
for(let j = 0; j < 10000000; j++){
    const r = rand();
    const key = Math.floor(r * 100)/100;
    const keyName = key.toFixed(2) + "-" + (key + 0.01).toFixed(2);
    if(dist[keyName]){
        dist[keyName] = dist[keyName] + 1;
    }else{
        dist[keyName] = 1;
    }
    average += r;
}
average /= 10000000;

console.log({
    averageTimeCalls,
    averageTimeCallsPushedToArray,
    dist,
    average
});

results

10 million calls (Macbook pro 2017, 16Gb ram, i5 processor), Average of 100 runs.

{ 
  averageTimeCalls: 35.53,               // 0.03553 seconds
  averageTimeCallsPushedToArray: 219.99, // 0.21999 seconds
  dist: { 
    '0.72-0.73': 99958,
    '0.83-0.84': 100553,
    '0.52-0.53': 100063,
    '0.56-0.57': 99678,
    '0.60-0.61': 100292,
    '0.87-0.88': 99739,
    '0.78-0.79': 99939,
    '0.46-0.47': 99975,
    '0.21-0.22': 99731,
    '0.97-0.98': 100231,
    '0.27-0.28': 100091,
    '0.62-0.63': 100112,
    '0.67-0.68': 99869,
    '0.11-0.12': 100378,
    '0.59-0.60': 99819,
    '0.70-0.71': 99457,
    '0.61-0.62': 100117,
    '0.99-1.00': 99615,
    '0.43-0.44': 100276,
    '0.19-0.20': 99686,
    '0.44-0.45': 100114,
    '0.17-0.18': 99790,
    '0.65-0.66': 99896,
    '0.73-0.74': 99668,
    '0.03-0.04': 100539,
    '0.89-0.90': 99506,
    '0.49-0.50': 99549,
    '0.71-0.72': 100020,
    '0.68-0.69': 99928,
    '0.12-0.13': 100131,
    '0.98-0.99': 100378,
    '0.16-0.17': 100245,
    '0.39-0.40': 99734,
    '0.93-0.94': 100071,
    '0.13-0.14': 100331,
    '0.80-0.81': 100200,
    '0.28-0.29': 99987,
    '0.47-0.48': 99730,
    '0.53-0.54': 100218,
    '0.35-0.36': 100209,
    '0.31-0.32': 100039,
    '0.06-0.07': 100321,
    '0.66-0.67': 100058,
    '0.76-0.77': 100152,
    '0.37-0.38': 99835,
    '0.00-0.01': 100340,
    '0.55-0.56': 99886,
    '0.88-0.89': 100105,
    '0.25-0.26': 99727,
    '0.58-0.59': 99819,
    '0.30-0.31': 99575,
    '0.18-0.19': 100106,
    '0.26-0.27': 99859,
    '0.85-0.86': 99875,
    '0.75-0.76': 99762,
    '0.94-0.95': 99846,
    '0.33-0.34': 99944,
    '0.38-0.39': 99790,
    '0.48-0.49': 100566,
    '0.74-0.75': 99909,
    '0.24-0.25': 100012,
    '0.20-0.21': 99633,
    '0.92-0.93': 99684,
    '0.15-0.16': 100058,
    '0.42-0.43': 100269,
    '0.41-0.42': 99463,
    '0.02-0.03': 99448,
    '0.07-0.08': 100346,
    '0.95-0.96': 100466,
    '0.04-0.05': 99505,
    '0.69-0.70': 99883,
    '0.81-0.82': 99587,
    '0.08-0.09': 100137,
    '0.50-0.51': 99707,
    '0.90-0.91': 100206,
    '0.54-0.55': 100296,
    '0.51-0.52': 99838,
    '0.09-0.10': 100034,
    '0.64-0.65': 99765,
    '0.32-0.33': 100026,
    '0.77-0.78': 99239,
    '0.84-0.85': 99884,
    '0.57-0.58': 100010,
    '0.45-0.46': 100505,
    '0.34-0.35': 99567,
    '0.86-0.87': 99842,
    '0.05-0.06': 100256,
    '0.23-0.24': 100428,
    '0.63-0.64': 99648,
    '0.82-0.83': 100151,
    '0.79-0.80': 100216,
    '0.01-0.02': 100072,
    '0.29-0.30': 100377,
    '0.91-0.92': 100296,
    '0.36-0.37': 100220,
    '0.40-0.41': 99927,
    '0.10-0.11': 100350,
    '0.22-0.23': 100491,
    '0.96-0.97': 100347,
    '0.14-0.15': 100474 
  },
  average: 0.4998805594122014 
}