PythonCall extension

[tjjarvinen]

This removes PyCall and adds PythonCall as an extension. #51

To use sklearn you need to load both ACEfit and PythonCall

using ACEfit
using PythonCall

There is no need to install sklearn, as that is taken care automatically when PythonCall is loaded.

Notes:

• Extension does not work with earlier Julia version and probably cause them to fail. We need to disscuss shall we remove support for previous version or try some hacks to get it to work - please let CI to run fully to see if there are errors with old versions.
• I updated CI a little bit. It still used the old MolSim registry

[cortner]

Thank you, @tjjarvinen !

@wcwitt -- how do you feel about moving our entire software stack to J1.9? I see no reason at the moment not to. (I want to use the extensions mechanism in other packages as well.)

Teemu - can you think of potential downsides?

[tjjarvinen]

In my opinnion we should go for v1.9. It seem to be general consensus that all packages will switch to it eventually just because of extensions. It is also easier to got for it now that ACEfit is not in general registry.

[wcwitt]

Thanks @tjjarvinen! I don't fully understand J1.9 extensions yet, but I've switched to 1.9 and I have no problem requiring it. Do you want to update the Project.toml and CI accordingly? I don't think I can modify this PR

[tjjarvinen]

I pushed an update for v1.9 and CI for this PR

[wcwitt]

Thanks. Tests pass now - shall I merge?

[cortner]

I guess this would be breaking and require 0.2? It shall we close our eyes for a moment and tag it as 0.1.1?

[wcwitt]

I vote 0.1.1 for now.

[tjjarvinen]

I vote for 0.1.1 too. Only thing that changed is that now you need to load PythonCall instead of PyCall. All else works as it was before, except that you need to have Julia v1.9 or newer.

[cortner]

great, I will merge and tag.

[cortner]

this is now registered as 0.1.1

[wcwitt]

@tjjarvinen, I just realized that src/solvers_pycall.jl still exists. Is this something we should delete now that ext/ACEfit_PythonCall_ext.jl exists?

[wcwitt]

Or maybe we just need to change the name to src/solvers_pythoncall.jl?

[tjjarvinen]

Ye, I forgot to rename that file.

Basicly you need to define the solver structs for sklearn there, so that you can use the extension to overload solve. I think the best option is to rename the file to something like sklearn_structs etc. That should make it clear for future use.

[wcwitt]

I think I would vote to keep the filename analogy with solvers.jl. Happy with either solvers_pythoncall.jl or solvers_sklearn.jl. And we add a comment pointing to the extension?

Edit: actually could we just move them back to solvers.jl and there have the comment about the extension?

[wcwitt]

I have done the latter in 9f4e744

[cortner]

anything for me to do here? test and tag another version?

[wcwitt]

You are welcome to tag a new version if you like, but its just a name change so I'm also fine holding off for now