what's the point of rpython?

Kay Schluehr kay.schluehr at gmx.net
Tue Jan 20 07:55:33 CET 2009


On 17 Jan., 01:37, "Brendan Miller" <catph... at catphive.net> wrote:

> Is this going anywhere or is this just architecture astronautics?
>
> The RPython project seems kind of interseting to me and I'd like to
> see more python implementations, but looking at the project I can't
> help but think that they haven't really explained *why* they are doing
> the things they are doing.

Remember that the original objective of PyPy was to improve the JIT.
Psyco is limited by the fact that the whole runtime is implemented in
C. The infamous "faster than C" actually refers to work on program
specializers on C code i.e. treating C as a language that is JIT
compiled on a fine grained level ( block structure - whole function
JIT compilation wouldn't obviously yield any advantages ).

So it is not just the application level Python code that shall run
through the JIT but also the interpreter level code. So why not equate
them and think about interpreter level code as Python as well? This
might be the idea. But then the problem of bootstrapping comes up:
there is no interpreter level code with the required properties. Hence
RPython that can serve as a foundation.

I'm also not sure I like the approach. Rather than designing a whole
new runtime for having a fully reflective system I'd model C in Python
( call it CiPy ) and create a bijection between CiPy code and C code.
Once this has been established one can study other translations of
CiPy or Python into CiPy ( not unlike Pyrex/Cython ) doing systematic
refactorings on CiPy code in Python, study properties using runtime
reflection, experiment with macro systems etc. All of this is done in
PyPy as well but sometimes it seems the team has created more new
problems than they solved.

> Anyway, I can tell this is the sort of question that some people will
> interpret as rude. Asking hard questions is never polite, but it is
> always necessary :)

I think it is a good question.



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