[SciPy-Dev] Cython as build dependency, file/dll size and current issues

Ralf Gommers ralf.gommers@googlemail....
Thu Jul 5 13:25:48 CDT 2012

Hi all,

On https://github.com/scipy/scipy/pull/261 the problem with large size of
generated C files from Cython came up again, and Matthew suggested to add
Cython as a build time dependency. He also pointed out that this was
discussed before, with most people being in favor:
We discussed the same issue on
https://github.com/scipy/scipy/pull/211recently, and also the size of
the binary.

This is probably also the right moment to point out other recent Cython
issues we've had:
1. A memoryview issue with Python 2.4, either a Cython or Numpy bug:
2. We had to manually patch the generated C files when using Cython 0.16,
to make them work with MinGW: http://projects.scipy.org/scipy/ticket/1673
3. According to Ray, there's also an indexing bug in Cython 0.16 which
requires to use 0.17-dev for https://github.com/scipy/scipy/pull/261

I think it's clear that PR's like #261 above (Ray's ndimage.label rewrite)
are in principle a good thing: faster and more general code which is easier
to maintain. Now the question is what to do though. Here's some options
that I see:

a) Keep things as is for now. Accept large file/binary sizes. Manually
patch the generated C if necessary.
b) Keep things as is for now. Either go back to Cython 0.15, or bump
required numpy version to latest dev version to not have to manually patch
the generated C files.
c) Keep things as they are now, without accepting too large file/binary
sizes. To be defined what too large. Means we can't get the full benefits
of fused types for example.
d) Move to Cython as a build dependency. Write down the required versions
and incompatibilities in the docs.
e) Include a Cython version in the scipy git repo, patch it to solve the
above issues 2 and 3 (and any other ones that come along).
f) Some combination of the above.
g) Any other options?

Anyone have an opinion on which way to go?

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