findL1CacheSize.js

// CPU L2 cache size
function ASMModule1(stdlib, foreign, heap) {
  "use asm";
  var memory = new stdlib.Uint32Array(heap);
  function loop(c) {
    c = c | 0;
    var k = 0;
    var j = 0;
    for (j = c; (j | 0) != 0; j = (j - 1) | 0) {
      k = memory[k >> 2] << 2;
    }
    return 0;
  }
  return {loop: loop};
}
function findCacheSize() {
  "use strict";
  function shuffle(array, n) {
    // https://en.wikipedia.org/wiki/Fisher–Yates_shuffle#Modern_method
    for (let i = n - 1; i >= 1; i--) {
      const j = Math.floor(Math.random() * (i + 1));
      const e = array[j];
      array[j] = array[i];
      array[i] = e;
    }
  }
  let base = 0;
  const m = 19;
  const heap = new ArrayBuffer(2**m * 4);
  const memory = new Uint32Array(heap);
  const loop = ASMModule1(globalThis, null, heap).loop;
  let result = 0;
  for (let e = 13; e <= m; e += 1) {
    const n = 2**e;
    for (let i = 0; i < n; i++) {
      memory[i] = i;
    }
    shuffle(memory, n);
    const start = performance.now();
    const c = 2**m * 4;
    loop(c);
    const end = performance.now();
    const f = (end - start) / (c) / base;
    if (base === 0) {
      base = (end - start) / (c);
    } else {
      console.log(n * 4, (f).toFixed(3));
    }
    if (f < 4) {
      result = n * 4;
    }
  }
  return result;
}

setTimeout(() => {
  console.time();
  console.log(findCacheSize());
  console.timeEnd();
}, 1000);