why is the performance of javascript bitwise operations unstable All In One

why is the performance of javascript bitwise operations unstable All In One

为什么 javascript 位运算的性能不稳定 ?

性能优化/性能测试

demos

~~ double not bitwise

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2022-07-22
 * @modified 2022-09-27
 * @modified 2023-02-25
 *
 * @description js performance.now / console.time & console.timeEnd
 * @description js 高精度时间戳 / 性能优化 / 性能测试
 * @difficulty Easy
 * @time_complexity O(n)
 * @space_complexity O(n)
 * @augments
 * @example
 * @link https://www.cnblogs.com/xgqfrms/p/16736458.html
 * @link https://www.cnblogs.com/xgqfrms/p/13360113.html
 * @solutions
 *
 * @best_solutions
 *
 */

// export {};

// const log = console.log;

function math(n) {
  const nums = [];
  let startTime = performance.now();
  for (let i = 0; i < n; i++) {
    nums.push(Math.floor(Math.random()));
  }
  let endTime = performance.now();
  console.log(`🐌 Math.floor cost time is ${endTime - startTime} ms`, n);
  return endTime - startTime;
}

function bitwise(n) {
  const nums = [];
  let startTime = performance.now();
  for (let i = 0; i < n; i++) {
    nums.push(~~Math.random());
  }
  let endTime = performance.now();
  console.log(`🚀 double not bitwise cost time is ${endTime - startTime} ms`, n);
  return endTime - startTime;
}

// test cases
const arr = [...``.padEnd(8, `_`)].map((_, i) => i + 1);


let mathCost;
let bitwiseCosts;

for (const n of arr) {
  console.log(`\n n =`, n);
  mathCost = math(10**n);
  bitwiseCosts = bitwise(10**n);
  if(mathCost > bitwiseCosts) {
    console.log(`🚀 bitwiseCosts performance ✅`, `${mathCost - bitwiseCosts} ms`);
  } else {
    console.log(`🚀 bitwiseCosts performance ❌`, `${bitwiseCosts - mathCost} ms`);
  }
}

test env

// Chrome DevTools
// Version 109.0.5414.119 (Official Build) (x86_64)

$ node -v
# v18.12.0
$ node ./bitwise.js

$ npx ts-node -v
# v10.9.1
$ npx ts-node ./bitwise.js

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refs

https://gist.github.com/xgqfrms/b5cc537ecfeac1b1e64e4f5a82d8776e

https://github.com/microsoft/TypeScript/issues/52929

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