[SciPy-dev] Inclusion of cython code in scipy

Anne Archibald peridot.faceted@gmail....
Tue Apr 22 18:19:57 CDT 2008


Hi,

What do people think about including cython code in scipy?

Pros:
* Easy way to write faster code
* Convenient way to interface to compiled code

Cons:
* Yet another interfacing setup
* Yet another language readers of the code need to understand
* Additional dependency for developers
* cython is in flux and drastic improvements in its handling of numpy
arrays are hoped for
* Requires support in build tools (distutils/makefiles/scons magic)

For one data point, a quick and nasty cythonization of my polynomial
interpolation code got something like a 4x speedup for large arrays of
evaluation points. This is a big improvement but far from the 20-100x
cython claims for raw python. I can't judge the behaviour for shorter
arrays without doing a more reasonable job of converting to cython,
but by looking at the (horrible) generated C code, the inner loops are
raw C with no python objects at all. (The 4x figure also uses gcc's
-march and -O options.) I take this as evidence that numpy's arrays
are doing a fairly good job of handing off the heavy lifting to
compiled code.

I can definitely see that if a little work went into cython's support
of numpy arrays specifically the code could get a lot cleaner: things
like c[i*k+j] could become c[i,k] with support for arbitrary strides
and (possibly) type conversion. So maybe it doesn't make sense to
start producing lots of cython code until that happens.

Anne


More information about the Scipy-dev mailing list