Is it faster to reset a collection of properties or create a new instance?

actionscript-3, recycle

Solution

I think reusing the same instance of `Matrix` is more efficient than creating a new one every time.

In fact, creating a new instance is a relatively heavy operation and that's why caches are used: to create a few instances and reuse them instead of creating a high number of instances.

I run a little benchmark and it confirms my answer:

var t:Number;
var i:int;
var N:int = 10000000;

t = getTimer();
for (i = 0; i < N; i++) {
    _matrix = new Matrix();
}
trace(getTimer()-t); // 7600


t = getTimer();
for (i = 0; i < N; i++) {
    _matrix.a = 1;
    _matrix.b = 0;
    _matrix.c = 0;
    _matrix.d = 1;
    _matrix.tx = 0;
    _matrix.ty = 0;
}
trace(getTimer()-t); // 4162

Finally, note that the difference is not that much great and that creating `10000000` new instances takes only `7600 ms`, so unless you are creating thousands of matrices per frame, either approach wouldn't have a noticeable impact on performance.

EDIT:

Using the method `identity` will have the advantages of both approaches (simplicity and performance):

t = getTimer();
for (i = 0; i < N; i++) {
    _matrix.identity();
}
trace(getTimer()-t); // 4140

Problem

I have a `Matrix` which I recycle and use for drawing `DisplayObject` instances onto a `Bitmap`. At the moment, I reset the `Matrix` before I render each item, like this: ``` _matrix.a = 1; _matrix.b = 0; _matrix.c = 0; _matrix.d = 1; _matrix.tx = 0; _matrix.ty = 0; ``` Would it be better to do the above, or to simply do this?: ``` _matrix = new Matrix(); ``` Generally I would say the former, however I'm unsure if in the case of `Matrix` there is some heavy stuff going on for each of those properties that I reset (mathematically).

Original source