This is much more focused version of this question:

Are there good implementations for easy subclasses of NP-hard graph problems

Computing the graph-crossing number $cr(G)$ for a simple graph is known to be NP-complete. A quick literature review shows some suggested algorithms for computing if $cr(G)<k$. Are they any active implementations available?

Already checked: SAGE, CGAL_Boost, networkx, graph_tool

  • $\begingroup$ Depending on the definition of "available". Check webcompute.ae.uni-jena.de $\endgroup$
    – someone
    Commented May 18, 2014 at 12:35
  • $\begingroup$ @someone this link is broken unfortunately $\endgroup$
    – a3nm
    Commented Nov 14, 2023 at 19:53
  • 1
    $\begingroup$ Looks like it might have moved to: crossings.uos.de $\endgroup$
    – a3nm
    Commented Jan 16 at 8:14

1 Answer 1


A slow brute-force implementation of the graph crossing number was added to Sage in

which was closed 2018-01-05, and merged in Sage 8.2.beta3.

  • 1
    $\begingroup$ This is great, thanks! For completeness, it looks like they implemented the algorithm in arxiv.org/pdf/1612.03854.pdf $\endgroup$
    – Hooked
    Commented Apr 24, 2019 at 15:30

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