xorshift

What is xorshift?

The xorshift npm package is a JavaScript implementation of the xorshift family of pseudorandom number generators (PRNGs). It is designed to provide fast and high-quality random number generation suitable for various applications such as simulations, games, and procedural content generation.

What are xorshift's main functionalities?

Basic Random Number Generation

This feature allows you to generate a basic random number using the xorshift algorithm. The `random` method returns a floating-point number between 0 and 1.

const xorshift = require('xorshift');
const rng = xorshift.create();
console.log(rng.random());

Seeded Random Number Generation

This feature allows you to initialize the random number generator with a specific seed. This is useful for reproducible results in simulations or tests.

const xorshift = require('xorshift');
const seed = [1, 2, 3, 4];
const rng = xorshift.create(seed);
console.log(rng.random());

Random Integer Generation

This feature allows you to generate a random integer. The `randomint` method returns a 32-bit integer.

const xorshift = require('xorshift');
const rng = xorshift.create();
console.log(rng.randomint());

Random Number Generation in a Range

This feature allows you to generate a random number within a specified range. The `randomInRange` function demonstrates how to use the `random` method to achieve this.

const xorshift = require('xorshift');
const rng = xorshift.create();
function randomInRange(min, max) {
  return min + Math.floor(rng.random() * (max - min + 1));
}
console.log(randomInRange(1, 100));

Other packages similar to xorshift

seedrandom

The seedrandom package provides a seeded random number generator that can be used to create reproducible random sequences. It supports multiple algorithms including Alea, XOR128, and Tychei. Compared to xorshift, seedrandom offers more flexibility in terms of algorithms and seeding options.

random-js

The random-js package is a versatile random number generator library that supports multiple PRNG algorithms including Mersenne Twister and native Math.random. It provides a rich set of features for generating random numbers, integers, and booleans, as well as shuffling arrays. Compared to xorshift, random-js offers a broader range of algorithms and utilities.

chance

The chance package is a comprehensive library for generating random data in JavaScript. It includes functions for generating random numbers, strings, dates, and even entire objects. While xorshift focuses on efficient random number generation, chance provides a wide array of random data generation utilities.

README

xorshift

Pseudorandom number generator using xorshift128+

Installation

npm install xorshift

Example

var xorshift = require('xorshift');

for (var i = 0; i < 10; i++) {
  console.log(xorshift.random()); // number in range [0, 1)
}

Documentation

This module exports a default pseudo random generator. This generators seed have already been set (using Date.now()). If this is not suitable a custom generator can be initialized using the constructor function xorshift.constructor. In both cases random numbers can be generated using the two methods .random and .randomint.

var xorshift = require('xorshift');

xorshift.random()

This method returns a random 64-bit double, with its value in the range [0, 1). That means 0 is inclusive and 1 is exclusive. This is equivalent to Math.random().

console.log(xorshift.random()); // number between 0 and 1

This method will serve most purposes, for instance to randomly select between 2, 3 and 4, this function can be used:

function uniformint(a, b) {
  return Math.floor(a + xorshift().random() * (b - a));
}

console.log(uniformint(2, 4));

xorshift.randomint()

This method returns a random 64-bit integer. Since JavaScript doesn't support 64-bit integers, the number is represented as an array with two elements in big-endian order.

This method is useful if high precision is required, the xorshift.random() method won't allow you to get this precision since a 64-bit IEEE754 double only contains the 52 most significant bits.

var bview = require('binary-view');
console.log(bview( new Uint32Array(xorshift.randomint()) ));

xorshift.constructor

This method is used to construct a new random generator, with a specific seed. This is useful when testing software where random numbers are involved and getting consistent results is important.

var XorShift = require('xorshift').constructor;
var rng1 = new XorShift([1, 0, 2, 0]);
var rng2 = new XorShift([1, 0, 2, 0]);

assert(rng1.random() === rng2.random());

A XorShift instance have both methods random and randomint. In fact the xorshift module is an instance of the XorShift constructor.

The constructor can also be accessed as require('xorshift').XorShift, which is useful when using the import syntax.

import { XorShift } from 'xorshift'

Reference

This module implements the xorshift128+ pseudo random number generator.

This is the fastest generator passing BigCrush without systematic errors, but due to the relatively short period it is acceptable only for applications with a very mild amount of parallelism; otherwise, use a xorshift1024* generator. – http://xorshift.di.unimi.it

This source also has a reference implementation for the xorshift128+ generator. A wrapper around this implementation has been created and is used for testing this module. To compile and run it:

gcc -O2 reference.c -o reference
./reference <numbers> <seed0> <seed1>

• <numbers> can be any number greater than zero, and it will be the number of random numbers written to stdout. The default value is 10.
• <seed0> and <seed1> forms the 128bit seed that the algorithm uses. Default is [1, 2].

License

This software is licensed under "MIT"

Copyright (c) 2014 Andreas Madsen & Emil Bay

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.