Add canonical color refinement

CHANGELOG.md

@@ -3,6 +3,7 @@
 We follow SemVer as most of the Julia ecosystem. Below you might see the "breaking" label even for minor version bumps -- we use it a bit more loosely to denote things that are not breaking by SemVer's definition but might cause breakage to people using internal or experimental APIs or undocumented implementation details. 
 
 ## unreleased
+- Canonical color refinement with `canonical_color_refinement` and `color_refinement`
 - `is_articulation(g, v)` for checking whether a single vertex is an articulation point
 - The iFUB algorithm is used for faster diameter calculation and now supports weighted graph diameter calculation
 - ECG community detection algorithm

docs/make.jl

@@ -60,6 +60,7 @@ pages_files = [
     "Algorithms API" => [
         "algorithms/biconnectivity.md",
         "algorithms/centrality.md",
+        "algorithms/color_refinement.md",
         "algorithms/community.md",
         "algorithms/connectivity.md",
         "algorithms/cut.md",

docs/src/algorithms/color_refinement.md

@@ -0,0 +1,19 @@
+# Color refinement
+
+Color refinement repeatedly splits color classes according to the number of neighbors
+each vertex has in every color class. The process stops when no class can be split
+further. In the resulting stable coloring, vertices share a color when color refinement
+cannot distinguish them.
+
+## Index
+
+```@index
+Pages = ["color_refinement.md"]
+```
+
+## Full docs
+
+```@autodocs
+Modules = [Graphs]
+Pages   = ["color_refinement.jl"]
+```

src/Graphs.jl

@@ -209,6 +209,8 @@ export
 
     # coloring
     greedy_color,
+    canonical_color_refinement,
+    color_refinement,
 
     # connectivity
     connected_components,
@@ -519,6 +521,7 @@ include("cycles/incremental.jl")
 include("traversals/bfs.jl")
 include("traversals/bipartition.jl")
 include("traversals/greedy_color.jl")
+include("color_refinement.jl")
 include("traversals/dfs.jl")
 include("traversals/maxadjvisit.jl")
 include("traversals/randomwalks.jl")