Oleg Andreev

Yesterday you had many great ways to create and digitally distribute your content. First, you could make a website with gorgeous latest web-technologies which is perfectly accessible with every modern browser on all major computer platforms. Or create an ebook based on the open standard Epub, also supported by all major reading software and devices. Third option is to make a movie (encoded in a couple of wildly supported video formats: from FLV to H.264 and Ogg). Finally, you could write a native app for Windows, Mac, iOS, Android etc.

Every platform vendor: Microsoft, Apple, Google, Facebook, Adobe and others work hard every day to give you better ways to create and communicate with people.

Today Apple released three apps: iBooks 2, iBooks Author and iTunes U. Every app is available for free. iBooks now runs interactive books created with iBooks Author and iTunes U integrates books and apps with video materials in a very useful UI.

So today you have one more wonderful option in addition to those listed above. Yet, some people start screaming about “lock in”, how Apple does not care enough about education to make everything open; about many evils of proprietary formats, proprietary apps, proprietary operating systems and proprietary devices.

These people are fantasizing a world where everything is right, cheap and every good is available in an infinite number of options. And at least one of those options is exactly what is right for them (and there must also be a right one for any other person too for fairness’ sake).

Guess what. This is the world we are living in. And everybody has her own idea of the perfect world order and while we are not enslaving or destroying ourselves, our world indeed moves towards better ways to live a life. Nothing is 100% right for you, but it is so for everybody. And this is why we all are working together everyday to make us happier.

Today’s Apple announcement is just one more achievement of human civilization, in addition to iPad, Android, Windows XP, World Wide Web, printing press and alphabet. Choose what you like in any combination and go do something great with it.

I have a single-core chip on iPhone 4 and an app with OpenGL rendering controlled by touch events.

This morning the app was rendering graphics on the main thread. 90% of CPU time was spent on graphics, 10% on gesture recognition and related computations. Overall CPU utilization was about 30%.

These 30% were noticeable: touch events were processed with delays and frame rate was low and not very stable.

In order to make app snappier, I moved the OpenGL rendering into separate serial dispatch queue. Now event loop was much less loaded, and I expected overall improvement. Not a higher framerate, but more stable one and with more accurate touch recognition.

In reality, the rendering was indeed slightly smoother, but touches were still delayed.

Profiler was showing now that 70% of CPU time was spent on graphics (in background thread) and 30% was spent on gesture recognition. Also, overall CPU usage increased up to 50%.

In terms of raw performance of algorithms nothing was changed at all. Threading code that was added is a simple dispatch_async() call consuming almost no time.

Now, I have a theory that explains this. Since the main event loop became 90% less loaded after moving graphics to background thread, it was able to process more touch events per second. Gesture recognition computations increased load on a single CPU core making graphics rendering slower than expected.

In result, framerate was not improved, but became more stable and touches didn’t get much smoother because of the increased pressure on CPU and main thread.

It turns out that rearranging stuff on a single core does not really help unless it is accompanied by actual performance improvements.