Re: JIT-compilation for OCaml?

[Markus Mottl <mottl@miss.wu-wien.ac.at>]

On Tue, 02 Jan 2001, Mattias Waldau wrote:
> Why do you want JIT?

I don't need it currently, but I can imagine applications that greatly
benefit from it.

> Do you use Java for regular development? It is a pain,

No, I don't use it at all, but I believe you that it must be very
painful ;)

> the reason is
> 
> 1. Slow, slow
> 2. Big, big

Maybe that's because the Java JIT-compilers were not written by Xavier? ;)

> and the reason that Java gets away with it, is the JIT-compiler. That mean
> that after enormous start-time, the program might achieve resonable
> performance after a couple of minutes. However, at that time, it still needs
> 10-20 extra megs, since the compiler is still loaded into memory.

It shouldn't be too difficult to come up with a protocol that informs
the interpreter whether it should actually use JIT-compilation or not
and if yes, how it should compile the code for optimum performance, etc.

This meta information could be generated by passing options to the byte
code compiler or maybe even by some kind of pragmas in the source. Or
maybe by a magnificent program analysis tool that finds the "hot spots"
automatically.

> The beatty of Ocaml are the fast compilers, the optimizing compiler is
> faster than javac, which only produces bytecode.

But the JIT-compiled/interpreted byte code seems to be pretty fast: I have
tried it with a few mini-benchmarks to see whether this JIT-technology
is of any worth. Really not bad...

> It is sad that so few
> other programming language developers realizes that the speed of the
> development environment matters.

Certainly! I definitely don't want to replace the normal byte code
interpreter with a purely JIT-one. My motivation was rather portability +
speed rather than speed alone. For the latter "ocamlopt" is more than
good enough, and for portability we have the byte code compiler. But
if you want to have portability with reasonable speed for demanding
applications...

> The only thing Ocaml can learn from Java is its libraries. If I would invent
> a programming language with a library today, I would just copy Java's
> interface. Libraries are much harder to learn than programming languages,
> thus standards are needed.

I haven't tried the Java-libraries so far. The OCaml-ones are quite
usable, but if you can tell us what Java has that OCaml is missing,
just tell us (in time! ;)

- Markus Mottl

-- 
Markus Mottl, mottl@miss.wu-wien.ac.at, http://miss.wu-wien.ac.at/~mottl