Combining Strings and variables—yet another performance test

 

I’ve been doing a ton of performance testing lately. It’s important to know which methods are the fastest, especially if you’ve been using some of the slowest methods all your life—I’m a victim. Getting in the mindset of “performance first” starts the snowball in improving your apps. This time I’m testing methods for combining Strings, with the hope that I can save a few milliseconds.

Taking a step back to look at memory, Strings are surprisingly heavy. It’s such a commonly used class, you’d think they would be the lightest of them all, but nope. The String class is THE heaviest class in DestroyTwitter, accounting for 40% of its memory usage. The Class class comes in second with 39% and TextField in third with a measly 4%. I always thought BitmapData took the crown, but it limps in fifth with 1.5% just behind the Function class.

Back to speed, we have three of the fastest String combination methods facing off. There’s String+String, String+=String, and String.concat(). I really wish AS3 handled String combination like PHP, allowing embedded variables without multiple Strings or slow methods like StringUtil.substitute(). Because of this, combining Strings and variables involve a ton of quotes and plus signs or a slower String.concat() method. Here are the results followed by the code:

[SWF] Application.swf - 392,771 bytes after decompression
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
+ (100000 iterations)
Player version: MAC 10,0,32,18 (debug)
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
+                                                           336     0.00
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
 
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
+= (100000 iterations)
Player version: MAC 10,0,32,18 (debug)
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
+=                                                          369     0.00
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
 
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
concat (100000 iterations)
Player version: MAC 10,0,32,18 (debug)
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
method...................................................ttl ms...avg ms
concat                                                      496     0.00
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
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package app.test {
	import com.gskinner.utils.PerformanceTest;
 
	import flash.display.Sprite;
	import flash.utils.setTimeout;
 
	public class Test extends Sprite {
		public var p:PerformanceTest;
 
		public var string:String = "";
		public var firstname:String = "Jonnie";
		public var lastname:String = "Hallman";
		public var adjective:String = "fun";
		public var noun:String = "guy";
 
		public function Test()
		{
			p = PerformanceTest.getInstance();
 
			setTimeout(run, 1000);
		}
 
		public function run ():void {
			var it:uint = 100000;
 
			p.testFunction(stringAddition, it, "+");
			p.testFunction(stringAdditionEquals, it, "+=");
			p.testFunction(stringConcat, it, "concat");
		}
 
		public function stringAddition ():void {
			string = "" +
				firstname +
				lastname +
				"is" +
				"a" +
				adjective +
				noun +
				"to" +
				"be" +
				"around."
		}
		public function stringAdditionEquals ():void {
			string = "";
			string += firstname;
			string += lastname;
			string += "is";
			string += "a";
			string += adjective;
			string += noun;
			string += "to";
			string += "be";
			string += "around.";
		}
		public function stringConcat ():void {
			string = "";
			string.concat(
				firstname,
				lastname,
				"is",
				"a",
				adjective,
				noun,
				"to",
				"be",
				"around.");
		}
	}
}
11.21.2009
6 comments comments
 

6 replies

  1. Not too surprising though; you have to take in that += does a assign a new value to the variable, which does take some time as well. It’s actually quite fast considering that. And String.concat is a method, so it’s slow by definition :D

    Thanks for the test (and all others), they are really helpful :)

    Patrick W.  Nov 21  9:19 pm

  2. I’m also not so surprised. I’d add that String.concat is not just a method but a var args method, so even slower as I show here. Actually, I’d have expected it to be even slower than it is. Lastly, you don’t need to start out your assignment version with the empty string since it isn’t contributing to the result. This would yield the same result:

    string = firstname +
				lastname +
				"is" +
				"a" +
				adjective +
				noun +
				"to" +
				"be" +
				"around."

    That’s totally a nit pick though. I doubt it’d change much in your results. Thanks for the test!

    Jackson Dunstan  Nov 21  11:48 pm

  3. @Jackson — I added the “” at the beginning of both the String+String and String+=String functions so it didn’t give the String.concat() function an unfair disadvantage since it requires an empty starting string. I thought you would say something. :)

    Jonnie  Nov 22  12:07 am

  4. How come you’re only testing in the debug player?

    dVyper  Nov 23  6:06 am

  5. But in the end? There are no-way to resolve this String “speed”?

    NoriSte  Dec 22  8:38 am

  6. @NoriSte — Unfortunately not. The improvements would have to come from the runtime internals.

    Jonnie  Dec 22  4:45 pm

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