Emanuele Feronato

Talking about Actionscript 3 and Flash.

Not so long ago we discussed about the fastest way to find the distance between two points.

In that case, it was a challenge between Euclidean and Manhattan distance. By the way, AS3 provides geom.Point class which comes with built in methods to deal with distances, such as distance and polar. Refer to the official docs for more information.

Will these methods allow faster computation of the distance between two points? Look at this script:

package {
	import flash.display.Sprite;
	import flash.geom.Point;
	import flash.utils.Timer;
	import flash.utils.getTimer;
	public class pointvstrig extends Sprite {
		public function pointvstrig() {
			var p1:Point=new Point(10,20);
			var p2:Point=new Point(20,30);
			var res:Number;
			var begin,end:Number;
			var i:int;
			begin=getTimer();
			for (i=0; i<1000000; i++) {
				res=pow_euclidian(p1,p2);
			}
			end=getTimer();
			trace("Euclidian with Math.pow: "+(end-begin));
			begin=getTimer();
			for (i=0; i<1000000; i++) {
				res=mul_euclidian(p1,p2);
			}
			end=getTimer();
			trace("Euclidian with multiplication: "+(end-begin));
			begin=getTimer();
			for (i=0; i<1000000; i++) {
				res=point_distance(p1,p2);
			}
			end=getTimer();
			trace("Point.distance: "+(end-begin));
		}
		private function pow_euclidian(p1:Point, p2:Point):Number {
			return Math.sqrt(Math.pow((p1.x-p2.x),2)+Math.pow((p1.y-p2.y),2));
		}
		private function mul_euclidian(p1:Point, p2:Point):Number {
			return Math.sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));
		}
		private function point_distance(p1:Point, p2:Point):Number {
			return Point.distance(p1,p2);
		}
	}
}

It calculates the distance in three ways: in the Euclidian way using Math.pow method, in the Euclidian way using the good old multiplication and using Point.distance method.

After a million calculations, these are the results:

Euclidian with Math.pow: 269ms
Euclidian with multiplication: 140ms
Point.distance: 687ms

The good old multiplication, the most basic way to calculate the power, is the fastest way to return the distance between two points. Point.distance is absolutely slow.

But I wanted to give Point class another try, calculating a point at a specified angle and distance from another point (in this case the origin).

Looks at this script:

package {
	import flash.display.Sprite;
	import flash.geom.Point;
	import flash.utils.Timer;
	import flash.utils.getTimer;
	public class pointvstrig extends Sprite {
		public function pointvstrig() {
			var distance:Number=100;
			var angle:Number=-0.5*Math.PI;
			var p:Point;
			var begin,end:Number;
			var i:int;
			begin=getTimer();
			for (i=0; i<1000000; i++) {
				p=Point.polar(distance,angle);
			}
			end=getTimer();
			trace("Moving point with Point.polar: "+(end-begin));
			trace(p);
			begin=getTimer();
			for (i=0; i<1000000; i++) {
				p=new Point(distance*Math.cos(angle),distance*Math.sin(angle));
			}
			end=getTimer();
			trace("Moving point with trigonometry: "+(end-begin));
			trace(p);
		}
	}
}

It calculates the point in two ways: using trigonometry and using Point.polar method. This time it's not just a matter of speed, I also want a good approximation of the result that should be as close as possible to (x=0, y=-100).

After a million iterations, these are the results:

Moving point with Point.polar: 705ms
(x=6.123031769111886e-15, y=-100)
Moving point with trigonometry: 536ms
(x=6.123031769111886e-15, y=-100)

As you can see, Point class is slower again, while the results are identical.

In the end, we can say trigonometry is faster than Point class.