Documentation page for packages that extend Graphs.jl (#500)

Co-authored-by: Stefan Krastanov <github.acc@krastanov.org>
Co-authored-by: Stefan Krastanov <stefan@krastanov.org>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people

docs/Project.toml

@@ -1,6 +1,8 @@
 [deps]
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
 Graphs = "86223c79-3864-5bf0-83f7-82e725a168b6"
+IGraphs = "647e90d3-2106-487c-adb4-c91fc07b96ea"
+NautyGraphs = "7509a0a4-015a-4167-b44b-0799a1a2605e"
 
 [compat]
 Documenter = "1"

docs/make.jl

@@ -1,5 +1,7 @@
 using Documenter
 using Graphs
+using IGraphs: IGraphs
+using NautyGraphs: NautyGraphs
 
 # same for contributing and license
 cp(
@@ -40,7 +42,11 @@ pages_files = [
         "first_steps/plotting.md",
         "first_steps/persistence.md",
     ],
-    "Ecosystem" => ["ecosystem/graphtypes.md", "ecosystem/interface.md"],
+    "Ecosystem" => [
+        "ecosystem/graphtypes.md",
+        "ecosystem/graphalgorithms.md",
+        "ecosystem/interface.md",
+    ],
     "Core API" => [
         "core_functions/core.md",
         "core_functions/interface.md",

docs/src/ecosystem/graphalgorithms.md

@@ -0,0 +1,57 @@
+# Graph algorithms
+
+## Defined by Graphs.jl
+
+_Graphs.jl_ provides a number of graph algorithms, including [Cuts](@ref), [Cycles](@ref), and [Trees](@ref), among many others. The algorithms work on any graph type that conforms to the _Graphs.jl_ API.
+
+## External algorithm packages
+
+Several other packages implement additional graph algorithms:
+
+- [GraphsColoring.jl](https://github.com/JuliaGraphs/GraphsColoring.jl) provides algorithms for graph coloring, _i.e._, assigning colors to vertices such that no two neighboring vertices have the same color.
+- [GraphsFlows.jl](https://github.com/JuliaGraphs/GraphsFlows.jl) provides algorithms for graph flows.
+- [GraphsMatching.jl](https://github.com/JuliaGraphs/GraphsMatching.jl) provides algorithms for matchings on weighted graphs.
+- [GraphsOptim.jl](https://github.com/JuliaGraphs/GraphsOptim.jl) provides algorithms for graph optimization that rely on mathematical programming.
+
+## Interfaces to other graph libraries
+
+Several packages make established graph libraries written in other languages accessible from within Julia and the _Graphs.jl_ ecosystem:
+
+- [IGraphs.jl](https://github.com/JuliaGraphs/IGraphs.jl) is a thin Julia wrapper around the C graphs library [igraph](https://igraph.org).
+- [NautyGraphs.jl](https://github.com/JuliaGraphs/NautyGraphs.jl) provides graph structures compatible with the graph isomorphism library [_nauty_](https://pallini.di.uniroma1.it), allowing for efficient isomorphism checking and canonization, as well as computing the properties of graph automorphism groups.
+
+## Dispatching to algorithm implementations in external packages
+
+Apart from providing additional graph types and algorithms, many packages extend existing functions in _Graphs.jl_ with new backends. This can make it easier to use the algorithms from within _Graphs.jl_.
+
+For example, _NautyGraphs.jl_ provides a new backend for graph isomorphism calculations:
+
+```jldoctest
+julia> using Graphs, NautyGraphs
+
+julia> g = star_graph(5)
+{5, 4} undirected simple Int64 graph
+
+julia> Graphs.Experimental.has_isomorph(g, g, NautyAlg())
+true
+```
+
+Here, dispatching via `NautyAlg()` implicitly converts `g` to a _nauty_-compatible format and uses _nauty_ for the isomorphism computation.
+
+### Functions extended by IGraphs.jl
+
+A list of functions extended by _IGraphs.jl_ can be obtained with
+
+```@example
+import IGraphs
+IGraphs.igraphalg_methods()
+```
+
+### Functions extended by NautyGraphs.jl
+
+A list of functions extended by _NautyGraphs.jl_ can be obtained with
+
+```@example
+import NautyGraphs
+NautyGraphs.nautyalg_methods()
+```

test/Project.toml

@@ -6,10 +6,12 @@ DataStructures = "864edb3b-99cc-5e75-8d2d-829cb0a9cfe8"
 DelimitedFiles = "8bb1440f-4735-579b-a4ab-409b98df4dab"
 Distributed = "8ba89e20-285c-5b6f-9357-94700520ee1b"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+IGraphs = "647e90d3-2106-487c-adb4-c91fc07b96ea"
 Inflate = "d25df0c9-e2be-5dd7-82c8-3ad0b3e990b9"
 JET = "c3a54625-cd67-489e-a8e7-0a5a0ff4e31b"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
+NautyGraphs = "7509a0a4-015a-4167-b44b-0799a1a2605e"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 SharedArrays = "1a1011a3-84de-559e-8e89-a11a2f7dc383"

test/runtests.jl

@@ -174,7 +174,9 @@ tests = [
         Aqua.test_all(Graphs; ambiguities=false)
     end
 
-    doctest(Graphs)
+    if !Sys.iswindows()
+        doctest(Graphs)
+    end
 
     @testset verbose = true "Actual tests" begin
         for t in tests