Destructuring performance

[mikecann]

I was wondering about the performance of destructuring within systems so I decided to run some tests:

import { World } from "miniplex";
import { Entity } from "./miniplex";

const count = 1_000_000;
const iterations = 10;

const world = new World<Entity>();

const positions = world.archetype("position");

const profile = <T>(name: string, fn: () => T) => {
  const before = Date.now();
  const result = fn();
  const after = Date.now();
  console.log(`${name} took ${after - before}ms`);
  return result;
};

const createEntities = () => {
  const entities: Entity[] = [];

  for (let i = 0; i < count; i++)
    entities.push(world.createEntity({ position: { x: 0, y: i, z: 0 }, age: i }));

  return entities;
};

it(`works`, () => {
  profile(`create`, createEntities);

  profile(`destructured`, () => {
    for (let iter = 0; iter < iterations; iter++)
      for (const { position } of positions.entities) position.x += Math.random();
  });

  profile(`not-destructured`, () => {
    for (let iter = 0; iter < iterations; iter++)
      for (const entity of positions.entities) entity.position.x += Math.random();
  });

  profile(`simple for`, () => {
    for (let iter = 0; iter < iterations; iter++)
      for (let i = 0; i < positions.entities.length; i++)
        positions.entities[i]!.position.x += Math.random();
  });
});

Results are:

  console.log
    create took 1794ms

  console.log
    destructured took 2363ms

  console.log
    not-destructured took 1502ms

  console.log
    simple for took 1473ms

So it looks like destructuring has quite a large impact.. having said that tho there could be some CPU vectorization / JIT'ing going on here that might cause oddness.

[NateTheGreatt]

pretty interesting results @mikecann! i have experimented with similar benchmarks. the results can vary wildly between each javascript engine. did you mean to create this issue in the miniplex repo, or just sharing info that may apply to bitECS as well?

[mikecann]

whoops! hahhaha I did indeed mean to post this to miniplex, sorry about that, very embarrassing!