Async Generator Performance

async_generator_perf.js

const C = 20_000_000;

async function* AG() {
  const ret = [];
  for (let i = 0; i < C; i++) {
    ret.push(i);
  }
  for (const item of ret) {
    yield item;
  }
}

function* SG() {
  const ret = [];
  for (let i = 0; i < C; i++) {
    ret.push(i);
  }
  for (const item of ret) {
    yield item;
  }
}

function LG() {
  const ret = [];
  for (let i = 0; i < C; i++) {
    ret.push(i);
  }
  return ret;
}

let t0 = Date.now();
let s = 0;
for await (const i of AG()) {
  s += (i - 100) / 17;
  s = s * s;
}
console.log("AsyncGenerator Await", Date.now() - t0);

t0 = Date.now();
s = 0;
for (const i of LG()) {
  s += (i - 100) / 17;
  s = s * s;
}
console.log("Loop Loop", Date.now() - t0);

t0 = Date.now();
s = 0;
for await (const i of LG()) {
  s += (i - 100) / 17;
  s = s * s;
}
console.log("Loop Await", Date.now() - t0);

t0 = Date.now();
s = 0;
for await (const i of SG()) {
  s += (i - 100) / 17;
  s = s * s;
}
console.log("SyncGenetator Await", Date.now() - t0);

t0 = Date.now();
s = 0;
for (const i of SG()) {
  s += (i - 100) / 17;
  s = s * s;
}
console.log("SyncGenerator  Loop", Date.now() - t0);

// AsyncGenerator Await 2613
// Loop Loop 368
// Loop Await 2109
// SyncGenetator Await 2475
// SyncGenerator  Loop 731