Re: [PLUG] Android Forums

[Toby DiPasquale <toby@cbcg.net>]

On Tue, Nov 20, 2007 at 11:13:22PM -0500, Matthew Rosewarne wrote:
> On Tuesday 20 November 2007, Josh Goldstein wrote:
> > I agree it isn't, but I wasn't talking about bytecode.
> > Java has had a JIT compiler for years now, that generates machine code.
> > Check out these results:
> > http://shootout.alioth.debian.org/gp4/benchmark.php?test=all???=all Unless
> > I'm misreading that chart, Java looks like it's doing better than a _lot_
> > of other languages.
> 
> Clearly, there needs to be machine code at some point.  JIT is just the 
> technique the Java VM uses to transform its bytecode into executable machine 
> code.  There aren't really any other good ways to do what Java does, but 
> compiling bytecode at runtime carries with it a considerable overhead.  The 
> code the JIT compiler generates may be as good as an equivalent C compiler, 
> but that generation still needs to happen, so more resources will be used 
> overall.

Which, of course, completely ignores the benefits that a JIT bytecode VM
can acheive that compiled C++ cannot easily replicate, e.g. dynamic
optimization, reflective dispatching, etc. Not to mention the portability
aspect of bytecode and a bytecode VM. Its far easier to port a bytecode VM
to a new platform once than to port every program written with Qt; witness
how many Java programs I can run on my Mac (all of them) versus how many
Qt programs I can run (???, but certainly not anywhere near all of them).

 The tradeoff is very often worth the slightly additional overhead, and 
lets be clear: it is *slight* these days. C++ is no longer that much faster 
than Java, if at all, depending on what you're doing. Given the fact that 
the Java language is a far better language than C++, built-in GC, a 
fantastic bytecode VM with an orders-of-magnitude higher level of 
portability right out of the box, you'd have to be a fool to choose C++ 
over Java at this point unless it was strictly warranted (speaking purely 
on a C++ vs. Java basis, I'm not a tremendous fan of Java in the absolute).

-- 
Toby DiPasquale
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