On May 25, 2010, at 2:50 PM, Charles R Harris wrote:



On Tue, May 25, 2010 at 1:37 PM, Travis Oliphant <oliphant@enthought.com> wrote:

Hi everyone,

There has been some talk about re-factoring NumPy to separate out the
Python C-API layer and make NumPy closer to a C-library.   I know
there are a few different ideas about what this means, and also that
people are very busy.  I also know there is a NumPy 2.0 release that
is in the works.

I'm excited to let everyone know that we (at Enthought) have been able
to find resources (about 3 man months) to work on this re-factoring
project and Scott and Jason (both very experienced C and Python
programmers) are actively pursuing it.    My hope is that NumPy 2.0
will contain this re-factoring (which should be finished just after
SciPy 2010 --- where I'm going to organize a Sprint on NumPy which
will include at least date-time improvements and re-factoring work).

While we have specific goals for the re-factoring, we want this
activity to be fully integrated with the NumPy community and Scott and
Jason want to interact with the community as much as feasible as they
suggest re-factoring changes (though they both have more experience
with phone-conversations to resolve concerns than email chains and so
some patience from everybody will be appreciated).

Because Jason and Scott are new to this mailing list (but not new to
NumPy),  I wanted to introduce them so they would feel more
comfortable posting questions and people would have some context as to
what they were trying to do.

Scott and Jason are both very proficient and skilled programmers and I
have full confidence in their abilities.   That said, we very much
want the input of as many people as possible as we pursue the goal of
grouping together more tightly the Python C-API interface layer to
NumPy.

I will be involved in some of the discussions, but am currently on a
different project which has tight schedules and so I will only be able
to provide limited "mailing-list" visibility.


I think 2.0 would be a bit early for this. Is there any reason it couldn't be done in 2.1? What is the planned policy with regards to the visible interface for extensions? It would also be nice to have a rough idea of how the resulting code would be layered, i.e., what is the design for this re-factoring. Simply having a design would be a major step forward.

The problem with doing it in 2.1 is that this re-factoring will require extensions to be re-built.   The visible interface to extensions will not change, but there will likely be ABI incompatibility.    It seems prudent to do this in NumPy 2.0.   Perhaps we can also put in place the ABI-protecting indirection approaches that David C. was suggesting earlier.  

Some aspects of the design are still being fleshed out, but the basic idea is to separate out a core library that is as independent of the Python C-API as possible.    There will likely be at least some dependency on the Python C-API (reference counting and error handling and possibly others) which any interface would have to provide in a very simple Python.h -- equivalent, for example.  

Our purpose is to allow NumPy to be integrated with other languages or other frameworks systems without explicitly relying on CPython.    There are a lot of questions as to how this will work, and so much of that is being worked out.   Part of the reason for this mail is to help ensure that as much of this discussion as possible takes place in public.  

-Travis



In any case, I think the primary goal for 2.0 should remain the python3k port.

Chuck

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Travis Oliphant
Enthought Inc.
1-512-536-1057