Android Performance (Object Pools)

This is the second part of my series of post about avoiding some performance hit caused by dalvik GC, first entry is here:

Object factories are quite useful in this context as they avoid object to be GC’ed and also avoid allocating new memory which also incurs in some overhead.

In java this is done quite easily. For our objects to be poolable we need them to conform to an interface:

public interface Poolable {
   public void initializeFromPool();
   public void finalizeFromPool();

We also need to create a pool which allocates new objects if needed, and keeps the pool moving. The soruce code can be best viewed at GitHub here:

There is one drawback with this implementation, we need one pool for each kind (or type) of object we want to be poolable. With some more code we can have a jack-of-all-trades pool which can create any kind of object. ShadingZen has an specialized pool that creates rendering task of any type (assuming they inherit from RenderTask), the code can also be found here.

A 3d rendering engine is huge loop creating and destroying objects, thus reusing some of them will make a huge difference on mobile platforms.

Happy coding!

Android Game Development Tips&Tricks

Kill the bugs

Kill the bugs

It has been several months since I first thought I should post here some of basic tips and tricks on android development, specifically game development. Sadly I have almost no free nowadays. But here it is, a new blog entry I hope I can expand into a little series. Everything posted here comes from my own experience developing ShadingZen, an open source 3D Engine for Android

This is all about java, dalvik and you. We well talk about java development and what little tricks you can do to make your game shine (ok maybe not shine, that depends on your graphics people, but to go faster and avoid slow downs). If you follow me on twitter you may recall me saying dalvik GC is slow…oh well, I was wrong, it is not dalvik but the mobile environment what is slow. If you don’t believe me, create a jni example and put a delete inside a loop, then profile.

Lastest versions of dalvik have done a huge leap towards a good-performance-all-around-vm. For gaming it was critical to release a non blocking garbage collector, prior to version 2.3 (Gingerbread) used to pause the whole application for more than 10ms. Let’s do some simple math: for a 30fps animation you need to rendering one frame in 33ms aprox. If the garbage collectors hits in, your animation will suffer.

Ok, so the garbage collector works as intended. so why do still need to use tricks and put more thoughts on the whole thing? Well….it is a mobile, all those Hires bitmaps need to be deleted and created during your application, if you do this very often, it is going to be slow, no matter what. This leads us to the number one tip, don’t allocate memory if you don’t need to.

1. Measure

A claim that something is slow need some proof. You need to start benchmarking your gameloop from day 0 of development and be sure nothing breaks your desired frame rate. A good resource for benchmarking is Caliper.

2. Avoid Allocating Memory

This tip may look like too simple, but it is true, you don’t have many spare memory, don’t allocate objects that you really don’t or have a more basic counterpart that would do the job.

3. Don’t release memory

– What?! – Yes, don’t release memory, it is slow, and furthermore, you will probably need to use it again, or a partial copy of it. Avoid having a huge for lop with hundred of iterations where you code creates and discards objects, that’s going to hurt you later, when the GC starts collecting that memory.

There is a very smart way to condense tip 2 and tip 3 into just one big idea, object factories. This will be may next tip, for the second part of this blog entries series. I will post some code for you all (although you can go right now to ShadingZen repository at GitHub and start taking a look!).


– There is great talk by Google’s Advocate Chris Pruett on some basic ideas, take a look at them: Writting Real-Time Games for Android

– Caliper. A benchmarking tool.