[Cython] gsoc: array expressions

I just resended this email as it was rejected by the mailing list. So
I subscribed to it.

Hi,

Sorry for the delay, I had some schedule change.

thanks for adding me. Should I subscribe to cython-dev? How much email
daily there is? I didn't found this on the archives. Fell free to add
me in CC again when you think it is appropriate.

I'll reply here to all email at the same time. Do you prefer that I
reply to each email individually if this happen again? I'll try to
reply faster next time.

- About pickling theano, we currently can't pick Theano function. It
could be made to work in some cases, but not for all cases as there is
hardware dependent optimization in the Theano function. Currently it
is mostly CPU vs GPU operation. So if we stay on the CPU, we could do
some pickling, but we should make sure that the compiled c code into
python module are still there when we unpickle or recompile them.

- I think it make sense to make a theano graph from cython ast,
optimize and redo a cython ast from the optimized graph. This would
allow using Theano optimizations.

- It also make sense to do the code generation in Theano and reuse it
in Cython. But this would make the Theano dependency much stronger.
I'm not sure you want this.