Add regular path query algorithm

[georgiy-belyanin]

This patch adds an implementation of the regular path query algorithm based on linear-algebra graph processing approach. The algorithm finds a set of nodes in a edge-labelled directed graph. These nodes are reachable by paths starting from one of source nodes and having edges labels conform a word from the specified regular language.

This algorithm is based on the bread-first-search algorithm over the adjacency matrices. Regular languages are defined by non-deterministic finite automaton. The algorithm considers the paths on which "label words" are accepted by the specified NFA.

Algorithm is used with the following inputs:

• A regular automaton adjacency matrix decomposition.
• A graph adjacency matrix decomposition.
• An array of the starting node indices.

It results with a vector, having v[i] = 1 iff the node is reachable by a path satisfying the provided regular constraints.

Full description of the algorithm is available at:
https://arxiv.org/abs/2412.10287

[georgiy-belyanin]

Points for discussion:

• I suppose the paper should be published somewhere, like on Arxiv, to add it to the algorithm description
• Probably, I'll add more tests/change the format of the matrices in it.

Thus, the PR is draft yet.

[georgiy-belyanin]

Currently, I am working on a benching utility for the algorithm. It's WIP.

I guess we can add it to the organization when it's ready.

See: https://github.com/georgiy-belyanin/RPQ-bench/pulls.

[georgiy-belyanin]

@gsvgit Thank you for reviewing! I appreciate the details you've mentioned.

@vkutuev please, take a look on the details of the implementation when you can.

[georgiy-belyanin]

The patch is almost OK except it lacks of Arxiv paper.

[georgiy-belyanin]

Merged to stable and opened GraphBLAS#261