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Array performance quiz
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| // Which iteration in the fastest? | |
| // each number is in range [0 .. 255] | |
| import { bench, run } from 'mitata'; | |
| var arr1 = []; // array of { rand: number } objects | |
| var arr2 = []; // array of numbers | |
| var arr3 = []; // array of numbers, iterated with forEach | |
| var arr4 = []; // array of numbers packed into 4-byte integers | |
| var arr5; // Uint8Array | |
| var arr6 = []; // array of numbers, iterated with for .. of | |
| var MAX_LEN = 20000000; | |
| for (var i = 0; i < MAX_LEN; i++) { | |
| var rand = Math.floor(Math.random() * 256); | |
| arr1.push({ rand }); | |
| arr2.push(rand); | |
| arr3.push(rand); | |
| arr6.push(rand); | |
| if (i % 4 === 3) { | |
| arr4.push(arr2[i-3] << 24 | arr2[i-2] << 16 | arr2[i-1] << 8 | arr2[i]); | |
| } | |
| } | |
| arr5 = new Uint8Array(arr2); | |
| var sum, len; | |
| // Benchmark starts here | |
| bench('1. array of { rand: number } objects', () => { | |
| sum = 0; | |
| for (var i = 0; i < MAX_LEN; i++) { | |
| sum += arr1[i].rand; | |
| } | |
| }); | |
| bench('2. array of numbers', () => { | |
| sum = 0; | |
| for (var i = 0; i < MAX_LEN; i++) { | |
| sum += arr2[i]; | |
| } | |
| }); | |
| bench('3. array of numbers, iterated with forEach', () => { | |
| sum = 0; | |
| arr2.forEach(function (val) { | |
| sum += val; | |
| }); | |
| }); | |
| bench('4. array of numbers packed into 4-byte integers', () => { | |
| sum = 0; | |
| len = arr4.length; | |
| for (var i = 0; i < MAX_LEN; i++) { | |
| if (i >= len) continue; // keeping the same amount of iterations, just for fun | |
| sum += (arr4[i] >>> 24) + ((arr4[i] >>> 16) & 0xff) + ((arr4[i] >>> 8) & 0xff) + (arr4[i] & 0xff); | |
| } | |
| }); | |
| bench('5. Uint8Array', () => { | |
| sum = 0; | |
| len = arr5.length; | |
| for (var i = 0; i < len; i++) { | |
| sum += arr5[i]; | |
| } | |
| }); | |
| bench('6. array of numbers, iterated with for .. of', () => { | |
| sum = 0; | |
| len = arr6.length; | |
| for (var val of arr6) { | |
| sum += val; | |
| } | |
| }); | |
| await run({}); |
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