xorshift.js/README.md

xorshift* / xorshift+ generators

#xorshift.js

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> Pseudorandom number generator using [xorshift](http://xorshift.di.unimi.it/) (xorshift128+ and xorshift1024*)

This package is based on [xorshift](https://www.npmjs.com/package/xorshift) [[github](https://github.com/AndreasMadsen/xorshift)] with fixed `random` and added `randomBytes` & `XorShift1024Star`.

## Installation

```shell
npm install xorshift.js
```

## Example

```js
var xorshift = require('xorshift.js')

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

## API

This module exports a default PRNG created from `XorShift128Plus` with seed that have been set from `Date.now` and `Math.random`.

#### XorShift128Plus(seed)

Construct xorshift128+ with specific seed.

```js
var XorShift128Plus = require('xorshift.js').XorShift128Plus
var prng1 = new XorShift128Plus([1, 0, 2, 0])
var prng2 = new XorShift128Plus('000000010000000000000002')

assert(prng1.random() === prng2.random())
```

#### XorShift1024Star(seed, p)

Construct xorshift1024* with specific seed (longer period, but slower).

```js
var XorShift128Plus = require('xorshift.js').XorShift128Plus
var seed = [ 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3,
             0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3]
var prng1 = new XorShift1024Star(seed, 1)
var prng2 = new XorShift1024Star(seed, 1)

assert(prng1.random() === prng2.random())
```

#### randomInt64()

This method returns a random 64-bit integer represented as array with two 32-bit numbers.

```js
var XorShift128Plus = require('xorshift.js').XorShift128Plus
var prng = new XorShift128Plus([1, 0, 2, 0])
console.log(prng.randomInt64()) // [ 8388677, 32896 ]
```

#### random()

This method returns a floating-point, pseudo-random number in the range [0, 1). Like `Math.ramdom`.

```js
var XorShift128Plus = require('xorshift.js').XorShift128Plus
var prng = new XorShift128Plus([1, 0, 2, 0])
console.log(prng.random()) // 0.0019531410653161885
```

#### randomBytes(size)

Generates pseudo-random data. The size argument is a number indicating the number of bytes to generate.

```js
var XorShift128Plus = require('xorshift.js').XorShift128Plus
var prng = new XorShift128Plus([1, 0, 2, 0])
console.log(prng.randomBytes(10).toString('hex')) // 00800045000080800200
```

## License

MIT