Benchmark: Computing the running sum of an array

Computing the running sum of an array (version: 2)

The main difference between these loops is that the second loop increments i mid-loop so it can avoid a subtraction to get the previous element. This is the kind of operation you would do to get an integral image so the array size is set to the same amount of pixels as a 720p image.

Comparing performance of: `Normal way vs Mid-iteration increment (post) vs Mid-iteration increment (pre)`

Created: one year ago by: Registered User

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HTML Preparation code:

<!--your preparation HTML code goes here-->

Script Preparation code:

var array1 = new Uint16Array(1280 * 720);
for (let i = array1.length; i > 0; i--) {
	array1[i] = Math.round(Math.random() * 3);
}
var array2 = Uint16Array.from(array1);
var array3 = Uint16Array.from(array1);

Tests:

Normal way
const length = array1.length; for (let i = 1; i < length; i++) { array1[i] += array1[i - 1]; }
Mid-iteration increment (post)
const length = array2.length - 1; for (let i = 0; i < length;) { const last = array2[i++]; array2[i] += last; }
Mid-iteration increment (pre)
const length = array3.length - 1; for (let i = 0; i < length;) { const last = array3[i]; array3[++i] += last; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Normal way
Mid-iteration increment (post)
Mid-iteration increment (pre)

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:142.0) Gecko/20100101 Firefox/142.0

Browser/OS: Firefox 142 on Linux

View result in a separate tab

Mid-iteration increment (post)

469/s

Mid-iteration increment (pre)

465/s

Normal way

464/s

View exact numbers

Test name	Executions per second
✓ Mid-iteration increment (post)	469 Ops/sec
Mid-iteration increment (pre)	465 Ops/sec
Normal way	464 Ops/sec