README.md

PCG-32: A Seedable 32-bit PRNG

A WebAssembly port of the PCG Random Number Generator, Minimal C Edition.

Usage

import * as pcg from '@alisey/pcg32';

pcg.setState(0x0123456789ABCDEFn);

console.log(pcg.randomInt(10)); // ⇒ 5
console.log(pcg.random());      // ⇒ 0.3697000732146962

API

randomInt(bound: number): number

Returns a uniformly distributed 32-bit unsigned random integer in the range [0, bound), where bound is a number from 1 to 2³².

random(): number

Returns a uniformly distributed floating point number in the range [0, 1) that has been rounded down to the nearest multiple of 2⁻⁵³.

setState(state: bigint): void

Updates the internal state of the generator. The generator has 2⁶⁴ possible internal states, and iterates through all of them. state is a 64-bit unsigned BigInt.

getState(): bigint

Returns a 64-bit unsigned BigInt representing the internal state of the generator.

seed(value?: bigint): void

Seeds the generator with a 64-bit BigInt. If the value is not provided, uses a value based on Math.random().

Performance

As of 2021, in V8 pcg.randomInt() is as fast as Math.floor(Math.random() * n), but doesn't introduce bias. pcg.random() is 2 times slower than Math.random().

In SpiderMonkey and JavaScriptCore both functions are 10 times slower than native equivalents.

Working With This Repo

1. npm install
2. npm run build
3. npm run test
4. npm run demo
5. npm run perf

Links

• PCG: A Family of Better Random Number Generators
• PCG: Using the Minimal C Implementation