Run results for: Fast approx. atan2 vs Math.atan2 vs cached atan2 (v8 optimization buster + local scope) 2

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/146.0.0.0 Safari/537.36

Browser: Chrome 146

Operating system: Linux

Device Platform: Desktop

Date tested: 4 months ago

fast approx. atan2

12.6M/s

cached Math.atan2

9.0M/s

Math.atan2

8.7M/s

View exact numbers

Test name	Executions per second
✓ fast approx. atan2	12,607,587 Ops/sec
cached Math.atan2	8,955,988 Ops/sec
Math.atan2	8,668,834 Ops/sec

Script Preparation code:

const ONEQTR_PI = Math.PI / 4;
const THRQTR_PI = (3 * Math.PI) / 4;

// https://gist.github.com/volkansalma/2972237#file-atan2_approximation-c-L29
const fastAtan2 = (y, x) => {
	const abs_y = Math.abs(y) + 1e-10; // kludge to prevent 0/0 condition
	let angle, r;
	if (x < 0) {
		r = (x + abs_y) / (abs_y - x);
		angle = THRQTR_PI;
	} else {
		r = (x - abs_y) / (x + abs_y);
		angle = ONEQTR_PI;
	}
	angle += (0.1963 * r * r - 0.9817) * r;
	return y < 0 ? -angle : angle;
};
var atan2 = Math.atan2;

Tests:

Math.atan2
eval(''); var k = [1, .23, 0.12, 929, 8172, 9.2, 21.2].map(e => Math.atan2(e, .5));
fast approx. atan2
eval(''); var k = [1, .23, 0.12, 929, 8172, 9.2, 21.2].map(e => fastAtan2(e, .5));
cached Math.atan2
eval(''); var k = [1, .23, 0.12, 929, 8172, 9.2, 21.2].map(e => atan2(e, .5));