JuliaCall

[mjohnson541]

I took a couple hours and dug into the PythonCall.jl julia-python interface framework.
My assessment:

• ~2 PRs merged every month...seems to be much better maintained than pyjulia
• Works specifically with conda environments
• Has separate conda/python-julia interface infrastructure from PyCall.jl and Conda.jl
• JuliaCall syntax specifically is significantly clunkier than pyjulia which makes the julia code feel like a python module...but we don't need to write that much code in it
• PythonCall.jl syntax looks mostly the same or at least very similar to PyCall.jl...unsure if automatic conda installs would be as clean as in PyCall.jl...
• JuliaCall loads julia separately from the individual packages unlike how we currently load pyrms...so we could load julia on start up (fast), but wait to load ReactionMechanismSimulator.jl until it needs to run a simulation with RMS
• JuliaCall automatically finds julia and creates the environment in an isolated julia project
• Right now juliacall is a pip package, but there isn't a conda package
• It claims in the documentation that you can use PythonCall.jl and PyCall.jl infrastructure all at once...but I'm suspicious of this after playing with it...

I played with it in a fresh environment, although in hindsight I kind of wish I had started out in an rmg_env. The python-julia linking was very automatic. I successfully built a julia environment with RMS + PythonCall.jl although I needed to get it to install PythonCall.jl second...which took a bit of effort. I tested important a set of different julia packages, packages seem to import fine unless they are dependent on PyCall.jl in which case I got a malloc error, which suggests to me that JuliaCall doesn't actually play nicely with PyCall.jl.

I think the next step in testing would likely be to make a branch of RMS replacing the PyCall.jl and Conda.jl infrastructure with PythonCall.jl and CondaPkg.jl which should mostly mean swapping out lines of code in the module file (src/ReactionMechanismSimulator.jl) and build file and then swapping the packages out in the project.toml in RMS. With that we can pip install juliacall in a built rmg_env, install that branch of RMS inside the juliacall julia project and attempt to import RMS with juliacall.