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Add reverse Cuthill-McKee ordering for graphs #37053

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Merged
merged 2 commits into from
Jan 22, 2024
Merged

Add reverse Cuthill-McKee ordering for graphs #37053

merged 2 commits into from
Jan 22, 2024

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dcoudert
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Fixes #13583.

We add the reverse Cuthill-McKee (RCM) ordering for graphs. We already had Cuthill-McKee and King.

sage: from sage.graphs.base.boost_graph import bandwidth_heuristics
sage: bandwidth_heuristics(graphs.PathGraph(10))
(1, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
sage: bandwidth_heuristics(graphs.GridGraph([3,3]))
(3, [(0, 0), (1, 0), (0, 1), (2, 0), (1, 1), (0, 2), (2, 1), (1, 2), (2, 2)])
sage: bandwidth_heuristics(graphs.GridGraph([3,3]), algorithm='reverse_cuthill_mckee')
(3, [(2, 2), (1, 2), (2, 1), (0, 2), (1, 1), (2, 0), (0, 1), (1, 0), (0, 0)])
sage: bandwidth_heuristics(graphs.GridGraph([3,3]), algorithm='king')
(3, [(0, 0), (1, 0), (0, 1), (2, 0), (1, 1), (0, 2), (2, 1), (1, 2), (2, 2)])

If needed, we can also expose methods bandwidth and bandwidth_heuristics in graphs.

📝 Checklist

  • The title is concise, informative, and self-explanatory.
  • The description explains in detail what this PR is about.
  • I have linked a relevant issue or discussion.
  • I have created tests covering the changes.
  • I have updated the documentation accordingly.

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@dcoudert dcoudert self-assigned this Jan 13, 2024
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Documentation preview for this PR (built with commit beb275a; changes) is ready! 🎉

tscrim
tscrim approved these changes Jan 18, 2024
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LGTM.

@dcoudert
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Thank you.

@vbraun vbraun merged commit 1251ff6 into sagemath:develop Jan 22, 2024
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@tscrim tscrim tscrim approved these changes

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c: graph theory t: enhancement
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Add rcm to graphs/graph.py
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@dcoudert @tscrim @vbraun @mkoeppe