borilla/fast-random

Simple fast seedable pseudo-random number generator

fast-random

Simple fast seedable pseudo-random number generator

Purpose

Returns a single factory function that creates a new pseudo-random number generator (PRNG) based on the provided seed value. The generator returns 32-bit pseudo-random integers using the Lehmer/Park-Miller generator. This is a circular generator, which will cycle through all 2147483646 possible values before repeating

While not the most robust of PRNGs, the code has a very small footprint, is extremely quick and produces results good enough for many purposes. It has been written to work both within Node.js and in the browser

Installation

npm install --save fast-random

API Summary

Get a new random number generator

const random = require('fast-random');

const seed = 12345;
const generator = random(seed);

The returned generator contains the following functions

• seed(SEED_VALUE): set the current seed value (SEED_VALUE is an integer)
• nextInt(): get the next integer value (1 <= x <= 2147483646)
• nextFloat(): get the next float value (0 <= x < 1)

Examples

General use

const random = require('fast-random');

// create a new generator
const seed = 12345;
const r = random(seed);

// produce some integer values
for (let i = 0; i < 8; ++i) {
	console.log(r.nextInt());
}

// reset the seed
r.seed(seed);

// produce some floating point values
for (let j = 0; j < 8; ++j) {
	console.log(r.nextFloat());
}

Set seed from current time

const random = require('fast-random');

const seed = Date.now();
const r = random(seed);

Get integers in a given range

const random = require('fast-random');

const seed = 12345;
const r = random(seed);

// get random number between a and b inclusive, ie (a <= x <= b)
function getRandomBetween(a, b) {
	return a + r.nextInt() % (b - a + 1);
}

More information

• https://en.wikipedia.org/wiki/Lehmer_random_number_generator
• http://www.firstpr.com.au/dsp/rand31/
• http://lab.polygonal.de/2007/04/21/a-good-pseudo-random-number-generator-prng/

fast-random's Issues

fast random as class

Thanks for the code. I made small changed, I hope it will be helpful:

var RandomGenerator = function(seed) {
  this.seed = function(seed) {
    if (seed === undefined)
      seed = (new Date()).getTime();
    if ((seed_value = seed % 2147483647) <= 0)
      seed_value += 2147483646;
  }
    
  this.random_int = function() {
    return seed_value = seed_value * 48271 % 2147483647;
  }
  
  this.random_float = function() {
    return (this.random_int() - 1) / 2147483646;
  }
  
  this.random_int_in_range = function(min, max) {
    return min + this.random_int() % (max - min + 1);  
  }
  
  this.seed(seed);
}
    
var generator = new RandomGenerator(12345);
for (var i=1; i<10; i++)
  console.log(generator.random_int() % 4);
  
generator.seed(12345);
for (var i=1; i<10; i++)
  console.log(generator.random_int_in_range(0, 3));

generator.seed();
for (var i=1; i<10; i++)
  console.log(generator.random_float());

Thanks