@alisey/pcg32

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

• npm install
• npm run build
• npm run test
• npm run demo
• npm run perf

Links

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