pringle

Fast pseudorandom number generator

JavaScript adaptation of the pseudorandom number generator from the 2008 research paper Evolving Sub-Grid Turbulence for Smoke Animation [PDF] by H. Schechter and R. Bridson of the The University of British Columbia, Canada. which in turn uses the research paper Wavelet Noise [PDF] by Robert L. Cook Tony DeRose of Pixar Animation Studios for the PRNG.

This algorithm is small, fast and in most cases random enough.

PRNG

A PRNG (pseudorandom number generator) always generates the same sequence of random numbers. You can change the sequence by supplying a different seed. This is very useful if you always want the same sequence of random numbers.

Install

To install, type in the console:

npm install pringle

Import

Preferred: load pringle as a JavaScript module using a bundler like webpack or Rollup:

import { Prng } from "pringle";

Load pringle dynamically as a JavaScript module (no bundler needed, like in demo.js):

const {Prng} = await import( "./pringle.js" );

API

prng = new Prng(seed);

Initialise Prng with a seed (any number).

const r = prng.rand();

Returns a floating point number 0 and 1.

This is including 0, excluding 1, so prng.rand() can return 0, but will never return 1.

const r = prng.rand(max);

Returns a floating point number between 0 and max.

const r = prng.rand(min, max);

Returns a floating point number between min and max.

const i = prng;

prng can be used as an endless iterator of random numbers.

let count = 5;
for (const r of prng) {
    doSomething(r);
    if (count-- == 0) {
        break;
    }
}

const i = prng.iter(count);

Returns an iterable returning count random numbers between 0 and 1.

You can use the iterable in a for loop like this:

for (const r of prng.iter(5)) {
    doSomething(r);
}

Another example of using the iterator is generating an array of 5 random integers between 0 and 10:

const arr = Array.from(prng.iter(5), (r) => Math.floor(r * 10));

const r = prng.prng();

Returns the raw value of the generator, a 32 bit signed integer (between -2,147,483,648 and 2,147,483,647, inclusive).

Normally, you use prng.rand() instead of this function.

Demo

In the file demo.js, you can see examples of using the API.

You can run it in the console by typing:

npm run demo

Naming

Pringle is named after the American actress Aileen Pringle (1895-1989). It's unrelated to some brand of potato-based crisps.

License

Copyright 2022 Edwin Martin and released under the MIT license.