Float32Array interactions

Benchmark created by Paul Evans on

Description

Find the fastest way of scaling members of a Float32 array. Untyped array just used as comparison point.

The assumption was that assigning something that was stored in a Float32 to a var and only used with other Float32s that the Javascript engine could surmise this and store it as a Float32 rather than a Float64 / double - thus skip any casting between different precisions.

This theory seems to be disproven!

Setup

var vector = [1.0, 2.0, 3.0];
    var len = 9000;
    var arr = new Array(len);
    for (var i = 0; i < arr.length; ++i)
      arr[i] = vector[i % 3];
    var float32array = new Float32Array(arr);
    var float64array = new Float64Array(arr);
    var float32arrayHalf = new Float32Array([0.5]);
    var float32 = float32arrayHalf[0];
    
    function scaleArray(arr) {
      for (var i = 0; i < len; i = i + 3) {
        arr[i] = arr[i] * 0.5;
        arr[1 + i] = arr[1 + i] * 0.5;
        arr[2 + i] = arr[2 + i] * 0.5;
      }
    };
    
    function scaleArrayFloat32(arr) {
      for (var i = 0; i < len; i = i + 3) {
        arr[i] = arr[i] * 0.5;
        arr[1 + i] = arr[1 + i] * 0.5;
        arr[2 + i] = arr[2 + i] * 0.5;
      }
    };
    
    function scaleArrayFloat32Array(arr) {
      for (var i = 0; i < len; i = i + 3) {
        arr[i] = arr[i] * float32arrayHalf[0];
        arr[1 + i] = arr[1 + i] * float32arrayHalf[0];
        arr[2 + i] = arr[2 + i] * float32arrayHalf[0];
      }
    };
    
    function scaleArrayFloat32Inst(arr) {
      for (var i = 0; i < len; i = i + 3) {
        arr[i] = arr[i] * float32;
        arr[1 + i] = arr[1 + i] * float32;
        arr[2 + i] = arr[2 + i] * float32;
      }
    };

Test runner

Ready to run.

Testing in
TestOps/sec
Untyped
scaleArray(arr);
ready
Float32
scaleArrayFloat32(arr);
ready
Float32Array
scaleArrayFloat32Array(arr);
ready
Float32Array elem in var
scaleArrayFloat32Inst(arr);
ready

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.

  • Revision 1: published by Paul Evans on