weave replacement for Python 3

[thesamovar]

As noted in #1073 and #1074 Cython (the only low level codegen target for Python 3) is very slow to compile. It would be good to have a replacement. Some options are:

• Update weave for Python 3. This is potentially a lot of work (unsure, didn't check)
• Find an alternative library, like http://pyinline.sourceforge.net
• Write our own library
• Switch to having numba as our default codegen target (although this would require some benchmarking, and I'm in general a bit unsure about this option)
• Build on Cython but generating a C++ file and just using Cython to wrap it (which presumably means the Cython code generation step would be very lightweight?).

I think I would probably favour the last option - thoughts?

[tapaswenipathak]

Hello @thesamovar, interested in doing this, can I work on this?

[mstimberg]

Hi @tapaswenipathak , sorry for taking for getting back to you about this. I think this issue is a really big one and still needs some discussion, it's probably not a good starting point for an external contributor at the moment.

[thesamovar]

Another option to consider is pybind11 and cppimport. Here's an example of how that looks: https://gist.github.com/thesamovar/707fb4c66471bdd7ccb8af8109957a49

[thesamovar]

Here's what it looks like doing it with Cython (probably not canonical way of doing it): https://gist.github.com/thesamovar/750d8b668470af27a41b4bab059513b9

Generates 7,500 line intermediate file, so may not be great for compilation speed.

[mstimberg]

I don't think it will be useful for us, but look at the sheer madness/brilliance of abusing the codec definition: https://github.com/georgek42/inlinec

[thesamovar]

I saw that! :-) We probably don't want to do that, but might be some useful bits for how to auto build an extension in there.