[pypy-dev] Roadmap draft

holger krekel holger at merlinux.de
Thu Dec 20 11:50:20 CET 2007

Dear Martijn, all, 

I am aware that you have initiated and participated in various 
successful open source communities and i know that you have experience 
and advises to share.  But the roadmap files are currently not 
about release planning or strategies and ASFAIK no active developer
has asked for a public discussion about such topics.  
I ask you and everybody to respect that.  If neccessary 
please only write brief mails. 

FWIW, i think i understand and share your main point that 
next-release goals do not neccessarily need to focus around 
a PyPy's CPython-replacing interpreter.   Btw, did you see that Anto 
has added his drafts of a "goal_jython_ironpython_replacement.txt"? 

best & cheers, 


On Thu, Dec 20, 2007 at 10:04 +0100, Martijn Faassen wrote:
> Hey,
> The most important point I want to make is this one. The current 
> discussion is about a roadmap towards CPython replacement (or other 
> interpreter replacements). This is a *different* goal from having PyPy 
> being useful in *some* production settings. The latter is a more modest 
> goal. It also shifts the focus: instead of aiming for parity with 
> CPython, you aim to be *better* than CPython at *some* things, while not 
> having parity in other areas.
> So, you could have an interpreter that is not yet a full replacement for 
> CPython being very useful for some tasks. This is where my primarily 
> interest lies right now: it'll take a while before I can use a 
> PyPy-derived interpreter instead of CPython for many tasks, but I'm 
> interested in using it for at least *some* tasks.
> Being better at some things than existing interpreters in production 
> will validate the project in the minds of many, and should increase the 
> mindshare of PyPy tremendously and attract enough contributors to reach 
> the final goal of being better at *everything*. I don't want to detract 
> from that goal of parity with existing interpreters (and beyond). I 
> don't want to take away from that. I just want to frame the discussion 
> in a different light, and highlight other goals. You don't need parity 
> in all respects in order to go beyond existing interpreters in some.
> I'll first note one way in which PyPy is already better than existing 
> interpreters: flexibility. Unfortunately this benefit by itself is not 
> going to be very useful in production itself. The idea is to exploit 
> this flexibility. Flexibility is a goal of the project, but it's only a 
> means, not a goal, of a production-interpreter project.
> As to the goal of being a CPython replacement, one important realisation 
> is that you might in fact reach replacement of CPython through a 
> completely other route than the one sketched out. Who is to say that a 
> CPython replacement has to be run through a C compiler, after all? The 
> only requirement is for it to run Python code. If that Python code runs 
> on top of .NET or JVM, so be it, as long as it runs, right? Of course as 
> an *end* goal you might want third-party library support, but you could 
> get quite far as a replacement of CPython in other ways without covering 
> those.
> So, what intermediate goals could you set that would make PyPy better 
> than other interpreters in production settings? These are the main 
> routes that I can see right now:
> You could aim for compliance with CPython (and library support) - but 
> then actually replacing CPython is a goal you can't compete on soon! 
> Your compliance will shine the most on other backends, like .NET or JVM, 
> and the feature would be access to libraries on those platforms, so 
> integration features would be the most important. Any performance or 
> JIT-related task is less important on the near term, while integration 
> tasks are most important.
> You could make compliance less important and aim for performance. In 
> this case you could complete with CPython right away, even if your 
> compliance and library support isn't perfect yet. You might only support 
> Python 2.4 features and implement a limited set of libraries, and 
> limited extension facilities, and still attract people. Performance and 
> JIT related tasks are the most important.
> You could also target one specialist platform (some embedded 
> architecture, or some dedicated VM architecture, like the Google Android 
> platform). You could make PyPy work way better than any competition on 
> that. (Multi)platform support beyond Linux, OS/X and Windows becomes way 
> more important then.
> What your initial focus is would influence which tasks you focus on 
> first a lot. I think this is important to keep in mind during the 
> roadmap discussions. I'd of course also be curious to find out which 
> ones you're most interested in as initial goals. Saying "all of them, 
> right now" is not good enough. :)
> Regards,
> Martijn
> _______________________________________________
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