Math.round vs hack

JavaScript performance comparison

Revision 15 of this test case created by

Preparation code

<script>
  var somenum = -500 + (Math.random() * 1000);
  var rounded;
  
  var util = {
   round: function( n ) {
  if ( n < 0 ) {
      return ( n - 0.5 ) << 0;
  } else {
      return ( n + 0.5 ) << 0;
  }
  }
  };
  function round( n ) {
      return ( n + 0.5 ) << 0;
  }
</script>
    

Test runner

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
"proper" rounding
rounded = Math.round(somenum);
pending…
Hack rounding
rounded = ~~ (0.5 + somenum);
pending…
Proper hack rounding
rounded = ~~ (somenum + (somenum > 0 ? .5 : -.5));
pending…
Hack with bitwise OR
rounded = (0.5 + somenum) | 0;
pending…
Hack with bitwise shift
rounded = (0.5 + somenum) << 0;
pending…
hack with bitwise shift func
rounded = util.round( somenum );
pending…

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Revisions

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