Run results for: Fast Sqrt 2

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36

Browser: Chrome 86

Operating system: Mac OS X 10.15.6

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
Math.sqrt	3274.0 Ops/sec
Quakes fast inverse sqrt.	3144.8 Ops/sec

Script Preparation code:

var i;
var r;
var v = 2 ** 16;

function test1() {
    for (i = 0; i < 1000; ++i) {
        r = Math.sqrt(v);
    }
}

function test2() {
    for (i = 0; i < 1000; ++i) {
        r = Q_rsqrt(v) * v;
    }
}

//Based on the fast inverse square root function
// https://en.wikipedia.org/wiki/Fast_inverse_square_root
// Some original comments preserved for humor value
// Designed to try to mimic the original as closely as possible
const bytes = new ArrayBuffer(Float32Array.BYTES_PER_ELEMENT);
const floatView = new Float32Array(bytes);
const intView = new Uint32Array(bytes);
const threehalfs = 1.5;

function Q_rsqrt(number) {
    const x2 = number * 0.5;
    floatView[0] = number;
    intView[0] = 0x5f3759df - (intView[0] >> 1);
    let y = floatView[0];
    y = y * (threehalfs - (x2 * y * y));

    return y;
}

Tests:

Math.sqrt
test1();
Quakes fast inverse sqrt.
test2();

Run results for: Fast Sqrt 2

Compare Quakes fast inverse squareroot

Math.sqrt

Quakes fast inverse sqrt.