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

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:147.0) Gecko/20100101 Firefox/147.0

Browser: Firefox 147

Operating system: Linux

Device Platform: Desktop

Date tested: 6 months ago

1 / Math.sqrt()

1.4M/s

Fast inverse sqrt

34K/s

View exact numbers

Test name	Executions per second
✓ 1 / Math.sqrt()	1,361,738 Ops/sec
Fast inverse sqrt	34,188 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();