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FAQ.md

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Frequently Asked Questions

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Can I use my own graph type?

Yes. graph-v3 is built on Customization Point Objects (CPOs) — the same mechanism the C++ standard library uses for std::ranges. Any type that satisfies the graph concepts (e.g. a vector<vector<int>>) works automatically. For types that don't model the concepts out of the box, you can specialize the CPOs.

See CPO Reference for the full list of customization points.

How do I add edge weights?

Edge weights are modeled as edge values. You can attach values to edges in several ways:

  • Use a container that stores values directly (e.g. vector<vector<pair<int, double>>>)
  • Provide an edge value function (EVF) to views and algorithms
  • Use dynamic_graph with an edge value template parameter

See Edge Value Concepts for the concept definitions.

What's the difference between views and algorithms?

Views are lazy ranges — they don't compute anything until you iterate. They adapt the graph into a different traversal order (BFS, DFS, topological sort) or projection (vertexlist, edgelist, neighbors, incidence). You can chain them with | pipe syntax.

Algorithms eagerly compute a result — shortest paths, connected components, MST, etc. They typically take output parameters (distance vectors, predecessor maps) and return upon completion.

Why descriptors instead of iterators?

Descriptors are lightweight value types that identify a vertex or edge. Compared to iterators:

Descriptors Iterators
Size Typically one index or pointer Often two pointers
Stability Remain valid across many mutations Invalidated by container mutations
Composability Easy to store, pass, return Tied to a specific range
Concept count Enabled reducing from 18 to 9 concepts Required separate sourced/unsourced variants

See Architecture for the design rationale.

How does this compare to Boost.Graph?

graph-v3 Boost.Graph
C++ standard C++20 (concepts, ranges) C++98/03 origins
Interface CPOs (like std::ranges) Property maps + traits classes
Container support Works with vector<vector<int>>, maps, etc. Requires adjacency_list<> or custom adaptors
Library type Header-only Some compiled components

graph-v3 is designed for modern C++ codebases that want standard-library-style ergonomics. Boost.Graph remains a mature, battle-tested choice with a larger algorithm catalog.

Which container should I use?

Start here:

  1. Read-only, high-performance? → compressed_graph (CSR layout, minimal memory)
  2. Mutable, general-purpose? → dynamic_graph (26 vertex×edge container combinations)
  3. Undirected with frequent edge removal? → undirected_adjacency_list (O(1) edge removal)
  4. Already have a vector<vector<T>>? → Use it directly — no container needed

See Containers for the full selection guide and trait matrix.

Does this work on Windows/macOS?

Yes. Supported compilers:

Compiler Minimum Version Platform Status
GCC 10+ Linux Tested
Clang 10+ Linux, macOS Tested
MSVC 2019+ Windows Tested

CMake presets are provided for all platforms — see the README or Getting Started.

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