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

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:84.0) Gecko/20100101 Firefox/84.0

Browser: Firefox 84

Operating system: Windows

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
1 / Math.sqrt()	244829.1 Ops/sec
Fast inverse sqrt	28050.9 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();

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

1 / Math.sqrt()

Fast inverse sqrt