Johan van Mol .org - x*x is faster than Math.pow(x, 2) in ActionScript

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x*x is faster than Math.pow(x, 2) in ActionScript

Wednesday, 07 February 2007

Just found out that x*x is about 78% faster than Math.pow(x, 2) in ActionScript (Flash 8, Windows)

In case you want to test it for yourself, here's some sample code:

var sq;
var t0, t1, tt, tp;

t0 = getTimer()
for (var i = 0; i < 100000; i++){
sq = i*i;
}
t1 = getTimer()
tt = t1-t0;
trace ("* : "+ tt);

t0 = getTimer()
for (var i = 0; i < 100000; i++){
sq = Math.pow(i, 2);
}
t1 = getTimer()
ts = t1-t0;
trace ("^ : "+ ts);
trace ("*/^ : "+ (tt/ts*100) + "%");

Comments

this is not surprise. Math.pow uses a generic algorithm that works for any exponent, including non-integers etc.
Posted by michal, on Wednesday, 07 February 2007 at 3:17

You're right :). But in my case ( f8 and Windows, too ) it is about 65-67 % faster. How about that?
Posted by sema, Whose homepage is http://szemraj.eu on Wednesday, 07 February 2007 at 3:19

Some C/C++ compilers do all kinds of optimization for you. I was kinda hoping Flash would do that too. But I guess not.
Posted by Johan van Mol, on Wednesday, 07 February 2007 at 4:37

For Math.pow() to support variable powers, it has to use logarithmic functions, which are way slower than multiplication functions.
Posted by Randy Edmunds, on Wednesday, 07 February 2007 at 11:28

You mean 22% right.

if x*x takes 366msec and Math.pow takes 477msec. then x*x must be 22% faster than Math.pow

x*x use only 78% of the time that Math.pow uses
Posted by Klaus, on Friday, 28 September 2007 at 3:42

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