Native rust API documentation?

[vlovich]

What is the expected enhancement?

All the docs reference this as a replacement for the python networkx library. Is there a pure Rust interface available free of Python dependencies? If so some documentation about it would be helpful. If not, then this would be semi-related to #33 to add a native Rust interface.

[mtreinish]

I'm not sure if there is a use case for retworkx without python. All the payloads for graphs in retworkx are python objects. You could probably leverage some of the code and functions purely from rust, but the you'd need to rely on PyO3 to set for weights/payloads for nodes and edges in the graph. For example of what I mean, you could look at the random gnp functions that are used to generate graphs: https://github.com/Qiskit/retworkx/blob/master/src/lib.rs#L1183-L1241 That is rust code being used to generate the retworkx PyGraph objects which then gets returned to python. You could use retworkx in a manner like this but at the end of the day it would probably need python.

So I guess it depends on what you're looking to accomplish with potential rust interface documentation. If you're just looking for a rust graph library most of what's being used inside retworkx today is based on petgraph and that's probably where I'd go for that. But if it's about writing a rust python extension that interacts with retworkx over a native interface than I agree there is a documentation gap. I actually hadn't thought of this before and it's something that shouldn't be hard to add docs and better support for since most of the functions and structs that exist today should be callable directly from rust.

The idea I had in mind when I opened #33 was to have a native defined stable interface for other python extensions to leverage retworkx (similar to numpy's C API). This use case probably already works for other rust python extensions (although I haven't tried this from an external project), but for that issue I was thinking of some applications with existing C/C++ (or cython) extensions that would probably want to interface with retworkx natively instead of going through python.

[vlovich]

I was actually asking about a rust graph library. I googled a bunch but didn't come across petgraph so it looks like your SEO is better :). Might be worth calling out in the readme that you're wrapping petgraph. Might help other people like me trying to find that.

Glad the bug report helped you ideate documenting how to invoke from other Rust Python extensions 👍 . Please feel free to close out or adjust the bug however you need.

[mtreinish]

Having documentation on this is blocked on: PyO3/pyo3#1444 once we have a good pattern for sharing graph objects between crates then we can document how to do it.

[jlapeyre]

I also think it's a shame that retworkx only works with Python. I guess you are saying it's sort of because of

type StablePyGraph<Ty> = StableGraph<PyObject, PyObject, Ty>;

Is it not possible to write routines in a generic way?

For example in betweenness centrality, I intentionally separated the python from core of the implementation of the algorithm.