Graph Library Proposal for the C++ Standard

This library is in the alpha stage that may include significant changes to the interface. It is not recommended for general use.

Overview

This library designed to provide a useful set of algorithms, views and container(s) for graphs. It also defines a core Graph Container Interface that provide the basis of interacting with an abstract adjacency list graph, and to provide easy integration with external adjacency list graphs.

• bi-partite and n-partite graphs are under investigation.
• Hyper-graphs are outside the scope of this project.
• Comments and questions are welcome and can be directed to GitHub discussions or issues.

Purpose

This prototype library is an implementation of the proposed Graph Library for ISO Standard C++ as described in P1709. It has gone through major revisions since it was first introduced in 2019. While we are comfortable of the core design, there is still plenty of activity being done and refinements made in its design and implementation. Experimenting with this library is encouraged, keeping in mind that breaking changes are expected.

Goals

The goals of the library include:

1. Support creation of high-performance, state-of-the-art algorithms.
2. Syntax that is simple, expressive and easy to understand when writing algorithms.
3. Define useful concepts and traits that can be used by algorithms to describe their requirements.
4. Support views for graph traversal commonly used by algorithms.
5. Support optional, user-defined value_types for an edge, vertex and graph.
6. Easy integration of existing graph containers.
7. Have an open design to allow for extensions in the future:
   1. Support for partite (partitioned) graphs. This requires extending (changing?) the Graph Container Interface. This is under investigation.
   2. Support the incoming edges on a vertex (e.g. bidirectional graphs).
   3. Investigate features that might make the Interface useful outside P1709, such as sparse vertex_ids. This can help validate the existing design and guide decisions for the future.

Getting Started

This is being actively developed with the latest releases of MSVC (VS2022) on Windows and gcc (11) on Linux/MacOS. Other releases or compilers may or may not work.

Prerequesites

• C++20 compliant compiler that fully supports concepts and ranges.
• CMake 20 or later (for CMake Presets)

Quick Start Guide (Linux, WSL, MacOS)

git clone https://github.com/stdgraph/graph-v2.git
cd graph-v2
mkdir build && cd build
cmake ..
make -j8

Editor/IDE Configuration (Windows)

You'll need to assure CMake Presets are enabled in your IDE or other development tool. See https://docs.microsoft.com/en-us/cpp/build/cmake-presets-vs?view=msvc-170 for configuring Microsoft tools.

Description

In the following tables, P1709 identifies that the feature is in the P1709 proposal. A value of "TBD" indicates that it is being considered, subject to the size of the proposal and other priorities.

Graph Algorithms

Algorithm	P1709	Status
Dijkstra Shortest Paths	Yes	dijkstra_clrs: needs review
Bellman-Ford Shortest Paths	Yes	needs implementation
Connected Components	Yes	needs implementation
Strongly Connected Components	Yes	needs implementation
Bi-Connected Components	Yes	needs implementation
Articulation Points	Yes	needs implementation
Minimum Spanning Tree	Yes	needs implementation
Page Rank	TBD	needs implementation
Betweenness Centrality	TBD	needs implementation
Triangle Count	TBD	needs implementation
Subgraph Isomorphism	TBD	needs implementation
Kruskell Minimum Spanning Tree	TBD	needs implementation
Prim Minimum Spanning Tre	TBD	needs implementation
Louvain (Community Detection)	TBD	needs implementation
Label propagation (Comm. Detection)	TBD	needs implementation

Graph Views

View	Done?	Description
vertexlist	Yes	Iterates over vertices
incidence	Yes	Iterates over outgoing edges of a vertex
neighbors	Yes	Iterates over outgoing neighbor vertices of a vertex
edgelist	Yes	Iterates over edges of a graph
depth_first_search	Yes	Iterates over vertices or edges of a seed vertex in depth-first order
breadth_first_search	Yes	Iterates over vertices or edges of a seed vertex in breadth-first order
topological_sort	No	Iterates over vertices or edges of a seed vertex in topological sort order

Graph Containers

Container	P1709	Description
compressed_graph	Yes	Compresed Sparse Row graph. High performance, static structure.
dynamic_graph	No	Easy to use different containers for vertices and edges.

Acknowledgments

• The NWGraph team for all their collaborations and support, along with providing the algorithm implementations NWGraph Library
• Numerous comments and support from the Machine Learning study group (SG19) in the ISO C++ Standards Committee (WG21).
• Bob Steagal for his gcc-builder & clang-builder scripts
• Jason Turner for his cpp_starter_project
• Vincent La for his cvs-parser
• The ISO C++ Standards Committee (WG21) for C++