Pip / Conda Packaging Draft PR

[georgiastuart]

This is still very much a rough draft, but I wanted to get this PR open for discussion and iteration!

The aim here is to enable installation via pip, per discussion with @The9Cat . There's also some work on conda packaging, but that's not in working form. The pip installation method does work, but I think I did too much manipulation of the existing CMakeLists.txt for this to be a viable PR.

What this PR achieves:

• creates the pip install structure for EXP as three packages: EXP-libraries, EXP-nbody, and pyEXP. The first two can be installed independently of pyEXP.

Side effects:

• Mostly impacts the current CMake build files since I needed greater separation between the component parts.

Things that need to be done here:

• Add a pypi package for the util executables
• revisit how CMakeLists.txt was altered to remove the impact on the standard build system
• add a lot more documentation on how the pip packages are built
• CICD for building the pip packages for hosting on github or elsewhere
• Either complete or remove the conda additions for another PR

[michael-petersen]

I'm happy to be a 'standard build' test subject for this PR! I ran my native build script on a fresh pull of this fork, and am working through some kinks.

[michael-petersen]

For my standard build, this line addition is a problem. Perhaps it needs to be inside some if statement?

CMake Error at CMakeLists.txt:248 (find_package):
  By not providing "Findyaml-cpp.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "yaml-cpp",
  but CMake did not find one.

  Could not find a package configuration file provided by "yaml-cpp" with any
  of the following names:

    yaml-cppConfig.cmake
    yaml-cpp-config.cmake

  Add the installation prefix of "yaml-cpp" to CMAKE_PREFIX_PATH or set
  "yaml-cpp_DIR" to a directory containing one of the above files.  If
  "yaml-cpp" provides a separate development package or SDK, be sure it has
  been installed.

[georgiastuart]

Ah! I think it should only use find_package for yaml-cpp if USE_SUBMODULES=OFF, so I'll fix that. Merging in the latest updates and fixing up any oddities.

[michael-petersen]

Thanks for working on this! The good news is that the continuous integration is now triggering for this PR, and is replicating what I'm seeing on my machine, so there is now a whole traceback. Perhaps pybind11 also needs a USE_SUBMODULES=OFF trigger? I'm also happy to tinker if helpful.

[georgiastuart]

I've got some changes in progress to fix the nbody pip packaging after pulling in the updates. I'll push those up tonight or tomorrow, then I think we can fix up the standard build! I just don't want to clobber your fixes while I'm still making changes.

[georgiastuart]

Main exe works now! Fixing up pyexp and then it should pass the tests.