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Asm.js Gets Faster
mikejuk writes "Asm.js is a subset of standard JavaScript that is simple enough for JavaScript engines to optimize. Now Mozilla claims that with some new improvements it is at worst only 1.5 times slower than native code. How and why? The problem with JavaScript as an assembly language is that it doesn't support the range of datatypes that are needed for optimization. This is good for human programmers because they can simply use a numeric variable and not worry about the difference between int, int32, float, float32 or float64. JavaScript always uses float64 and this provides maximum precision, but not always maximum efficiency. The big single improvement that Mozilla has made to its SpiderMonkey engine is to add a float32 numeric type to asm.js. This allows the translation of float32 arithmetic in a C/C++ program directly into float32 arithmetic in asm.js. This is also backed up by an earlier float32 optimization introduced into Firefox that benefits JavaScript more generally. Benchmarks show that firefox f32 i.e. with the float32 type is still nearly always slower than native code, it is now approaching the typical speed range of native code. Mozilla thinks this isn't the last speed improvement they can squeeze from JavaScript. So who needs native code now?"
Umm, anyone who wants their code to not run substantially slower. Seriously, do you front end programmers really think nobody does numerical simulations or other performance-sensitive work? In my line of work, I'd kill for the opportunity to make my code 1.5 times faster!
I get pissed when you hear programmers say "Oh memory is cheap, we don't need to optimize!" Yes you do. In the server world these days we don't run things on physical hardware usually, we run it in a VM. The less resources a given VM uses, the more VMs we can pack on a system. So if you have some crap code that gobbles up tons of memory that is memory that can't go to other things.
It is seriously like some programmers can't think out of the confines of their own system/setup. They have 16GB of RAM on their desktop so they write some sprawling mess that uses 4GB. They don't think this is an issue after all "16GB was super cheap!" Heck, they'll look at a server and see 256GB in it and say "Why are you worried!" I'm worried because your code doesn't get its own 256GB server, it gets to share that with 100, 200, or even more other things. I want to pack in services as efficient as possible.
The less CPU, memory, disk, etc a given program uses, the more a system can do. Conversely, the less powerful a system needs to be. In terms of a single user system, like maybe an end user computer, well it would always be nice is we could make them less powerful because that means less power hungry. If we could make everything run 1.5 times as fast, what that would really mean is we could cut CPU power by that amount and not affect the user experience. That means longer battery life, less heat, less waste, smaller devices, etc, etc.