Run results for: Math.sqrt() vs Fast inverse sqrt

Run details:

User agent: Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/132.0.0.0 Mobile Safari/537.36

Browser: Chrome Mobile 132

Operating system: Android

Device Platform: Mobile

Date tested: one year ago

1 / Math.sqrt()

919K/s

Fast inverse sqrt

6K/s

View exact numbers

Test name	Executions per second
✓ 1 / Math.sqrt()	919,037 Ops/sec
Fast inverse sqrt	5,572 Ops/sec

Script Preparation code:

let v = 123.75;

function test1() {
  let r;
  for(let i = 0; i < 2000; ++i)
    r = 1 / Math.sqrt(v);
}

function test2() {
  let r;
  for(let i = 0; i < 2000; ++i)
    r = Q_sqrt(v);
}

function Q_sqrt(num) {
  let i = [];
  let y = [];
  
  y[0] = num;
  i[0] = 0x5f375a86 - (i[0] >> 1);
  
  y[0] = y[0] * (1.5 * ((num * 0.5) * y[0] * y[0]));
  
  return y[0];
}

Tests:

1 / Math.sqrt()
test1();
Fast inverse sqrt
test2();