From: Rick DeNatale <rick.denatale@...>
Date: 2007-03-31T23:42:31+09:00
Subject: Re: compiler for ruby

On 3/30/07, n/a <na@nomail.invalid> wrote:

>
> I meant under windows and/or Linux environments.
>
> And source code to machine code.
>
> I had done a search of this group but I guess didn't download enough
> headers to see the previous threads.
>
> I see there are various forms of compilers that work at different levels of
> code, e.g. XRuby to Java Bytecode, etc.

Yes there are a variety of approaches to compiling Ruby to either Java
bytecodes (e.g. XRuby) or bytecodes more specifically tuned to Ruby
semantics (e.g. YARV which is now in Ruby 1.9).  I think most people
these days think that bytecode == Java bytecode, but the idea preceded
Java.

As of today YARV seems to be the best performing, at least according
to the benchmarks I've seen.

As for compiling directly to machine code, it could be done I suppose,
but it's not clear that it would be the best approach. Why?

   * The dynamic nature of Ruby means that methods can be dynamically
created at run-time and would therefore need to be compiled at
run-time.  Additional bookkeeping would be required to make all the
semantic effects on the compiled code would be properly implemented.

  * Previous experience with compiling dynamic OO languages has shown
that the much smaller code representation of byte codes compared to
machine code can actually lead to better performance on machines with
virtual memory (almost all machines these days) due to the smaller
working set.  Digitalk tried direct compilation of Smalltalk to
machine code, because they were sick of getting blasted for being
'interpreted' and found that the byte coded stuff ran significantly
faster. The practice these days is to do two-stage compilation, first
to byte-codes, and then to machine code for selected code when the
run-time detects that that code is frequently executed.

-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/