[SciPy-dev] fftpack: building all backends and setting them at runtime (was dropping djbfft)

[David Cournapeau]

Hi,

    After some more work, I have modified scipy.fftpack such as backends 
are truely independent code-wise, and can be selected at runtime. I hope 
it adresses all remarks comments made in the previous thread:

http://projects.scipy.org/scipy/scipy/browser/branches/refactor_fft/

Concretely:
    - all fftw/fftw3/djbfft/mkl code has been put in 
scipy/fftpack/backends directory.
    - fftpack is always build and used by default for all functions
    - for each backend, if the corresponding libraries are available, 
the module is built (so if you have mkl, fftw, fftw3 and djbfft, all 
backends will always be built)
    - fftpack module now uses some magic to set up functions from one 
backend or the other (scipy/fftpack/common.py). Basically, the functions 
are defined at runtime depending on which backend is selected. If the 
function is not available, the default backend is used as a fallback.

TODO:
    - I have not implemented any registration method, because I was not 
sure how to do it (config file, monkey patching, import magic ?).
    - The convolution module is not done yet.
    - I have not implemented djbfft backend yet (all the other ones 
should work), because it needs a bit more logic, but nothing serious.
    - All module .pyf files are almost duplication, but since we want to 
have them independent, I am not sure how to do better.

It should be possible to put all the code in backends out of scipy once 
the registration system is in place.

cheers,

David