Re:There is something magical about Firefox OS
by azakai on Thursday September 13, 2012 @05:13PM
(#4518654)
> Well, I could agree if I saw any computational-heavy JS application (and not a microbenchmark) doing well compared to native counterpart, especially on multicore.
For example, BananaBread compiles 120,000 lines of code of a C++ 3D game engine, including AI and physics and so forth. It also uses 3 cores during startup processing
The difference between JavaScript and C++ is less than one order of magnitude, and note that this is a hard case to optimize for JS engines since LLVM inlining creates huge functions that JS engines just give up on optimizing currently. So that the game ends up still running as fast as it does in JS is a nice surprise.
There are also lots of other compiled examples of real-world code, like Box2D and Bullet. Typically the speed of JS compared to C is 5X-10X slower, again, much of it because of large functions not being fully optimized.
While JIT is getting better over time, you are soon going to hit the law of diminishing returns - the JIT is already extremely sophisticated, but still being a few times slower on average even than JVM. And JVM has it much easier, because it has full explicit type information, while JS has to first figure it out. So I wouldn't expect miracles here.