Run results for: Quake InvertSqrt

Run details:

User agent: Mozilla/5.0 (Linux; arm_64; Android 11; SM-N770F) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.164 YaBrowser/21.6.1.128.00 SA/3 Mobile Safari/537.36

Browser: Yandex Browser 21

Operating system: Android

Device Platform: Mobile

Date tested: 2 years ago

Test name	Executions per second
Math.sqrt	1167.0 Ops/sec
Quake InvertSqrt	1505.2 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;
  }
}

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()
Quake InvertSqrt
test2()