Comments on: Notes: Math Optimizations

By: gabriel

gabriel — Thu, 28 Jan 2010 14:27:13 +0000

Thanks, I’ll make that clarification.

By: J

Thu, 28 Jan 2010 10:03:35 +0000

Same for Math.abs

// Slower 1572ms
var value:Number = -0.5;
var test:Number = value;
var nn:Number = Math.abs(test);
trace(nn);

// Faster 76ms
test = value;
if (test > 31)) – (test >> 31); // FALSE
trace(nn);

// OUTPUT :
0.5
0.5
0

By: J

Thu, 28 Jan 2010 09:58:22 +0000

When you use bitwise for multiplication and division, take care that the result is not a float. So your comments a not exact :

var value:Number = 12.5;

//Slowest 152ms
var n:Number = value / 2; // Divide by 2
trace(n);
n = value / 4; // Divide by 4
trace(n);
//Faster 112ms
n = value * .5; // Divide by 2
trace(n);
n = value * .25; // Divide by 4
trace(n);
//Fastest 63ms
n = value >> 1; // Divide by 2 -> FALSE
trace(n);
n = value >> 2; // Divide by 4 -> FALSE
trace(n);

// OUTPUT :
6.25
3.125
6.25
3.125
6
3

Bye :)