[Cython] [cython-users] GSoC 2012

Vitja Makarov vitja.makarov at gmail.com
Mon Apr 2 14:14:20 CEST 2012

2012/4/2 Stefan Behnel <stefan_ml at behnel.de>:
> Vitja Makarov, 11.03.2012 09:51:
>> 2012/3/11 Stefan Behnel:
>>> mark florisson, 11.03.2012 07:44:
>>>> - better type inference, that would be enabled by default and again
>>>> handle thing like reassignments of variables and fallbacks to the
>>>> default object type. With entry caching Cython could build a database
>>>> of types ((extension) classes, functions, variables) used in the
>>>> modules and functions that are compiled (also def functions), and
>>>> infer the types used and specialize on those. Maybe a switch should be
>>>> added to cython to handle circular dependencies, or maybe with the
>>>> distutils preprocessing it can run all the type inference first and
>>>> keep track of unresolved entries, and try to fill those in after
>>>> building the database. For bonus points the user can be allowed to
>>>> write plugins to aid the process.
>>> That would be my favourite. We definitely need control flow driven type
>>> inference, local type specialisation, variable renaming, etc. Maybe even
>>> whole program (or at least module) analysis, like ShedSkin and PyPy do for
>>> their restricted Python dialects. Any serious step towards that goal would
>>> be a good outcome of a GSoC.
>> I think we should be careful here and try to avoid making Cython code
>> more complicated.
> I agree that WPA is probably way out of scope. However, control flow driven
> type inference would allow us to infer the type of a variable in a given
> block, e.g. for code like this:
>  if isinstance(x, list):
>      ...
>  else:
>      ...
> or handle cases like this:
>  def test(x):
>      x = list(x)
>      # ... do read-only stuff with x below this point ...
> Here, we currently infer that x is an unknown object that is being assigned
> to twice, even though it's obviously a list in all interesting parts of the
> function.

What to do if an entry is of PyObject type in some block and of some
C-type in another?

Should it be splitten into two different entries?


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