This post originated from an RSS feed registered with Java Buzz by dion. Original Post: John Carmack finds Mobile Java Feed Title: techno.blog(Dion) Feed URL: http://feeds.feedburner.com/dion Feed Description: blogging about life the universe and everything tech Latest Java Buzz Posts Latest Java Buzz Posts by dion Latest Posts From techno.blog(Dion)

John Carmack, the creator of Doom to Quake to Doom 3, and plenty others... has found the pleasure that is Mobile Java. It is really quite interesting to listen in to such a low level guy, as he learns the issues that are inherent in the Java platform.

He starts off quite positively:

I wrote a couple java programs several years ago, and I was left with a generally favorable impression of the language. I dug out my old “java in a nutshell” and started browsing around on the web for information on programming for cell phones. After working my way through the alphabet soup of J2ME, CLDC, and MIDP, I’ve found that writing for the platform is pretty easy.

In fact, I think it would be an interesting environment for beginning programmers to learn on. I started programming on an Apple II a long time ago, when you could just do an “hgr” and start drawing to the screen, which was rewarding. For years, I’ve had misgivings about people learning programming on Win32 (unix / X would be even worse), where it takes a lot of arcane crap just to get to the point of drawing something on the screen and responding to input. I assume most beginners wind up with a lot of block copied code that they don’t really understand.

All the documentation and tools needed are free off the web, and there is an inherent neatness to being able to put the program on your phone and walk away from the computer. I wound up using the latest release of NetBeans with the mobility module, which works pretty well. It certainly isn’t MSDev, but for a free IDE it seems very capable. On the downside, MIDP debugging sessions are very flaky, and there is something deeply wrong when text editing on a 3.6 ghz processor is anything but instantaneous.

Unfortunately, when he gets to do real work on the platform he runs into problems:

It turns out that I’m a lot less fond of Java for resource-constrained work. I remember all the little gripes I had with the Java language, like no unsigned bytes, and the consequences of strong typing, like no memset, and the inability to read resources into anything but a char array, but the frustrating issues are details down close to the hardware.

The biggest problem is that Java is really slow. On a pure cpu / memory / display / communications level, most modern cell phones should be considerably better gaming platforms than a Game Boy Advanced. With Java, on most phones you are left with about the CPU power of an original 4.77 mhz IBM PC, and lousy control over everything.

I spent a fair amount of time looking at java byte code disassembly while optimizing my little rendering engine. This is interesting fun like any other optimization problem, but it alternates with a bleak knowledge that even the most inspired java code is going to be a fraction the performance of pedestrian native C code.

Even compiled to completely native code, Java semantic requirements like range checking on every array access hobble it. One of the phones (Motorola i730) has an option that does some load time compiling to improve performance, which does help a lot, but you have no idea what it is doing, and innocuous code changes can cause the compilable heuristic to fail.

And he has even found the fun in the so called Write Once Run Anywhere:

Write-once-run-anywhere. Ha. Hahahahaha. We are only testing on four platforms right now, and not a single pair has the exact same quirks. All the commercial games are tweaked and compiled individually for each (often 100+) platform. Portability is not a justification for the awful performance.

Cool to see John jumping aboard. I have a sneaky suspition the Vodaphone guy who shows up at JavaOne turned up at Camp id Software. "Hey, I keep telling these Java programmers that they can make millions based on the huge install base of phones vs. computers. If they can make millions, you guys can make BILLIONS!"

Thanks a lot for your thoughts, John