Low Dimensional Topology

May 24, 2016

SnapPy 2.4 released

Filed under: 3-manifolds,Computation and experiment,Hyperbolic geometry,Knot theory — Nathan Dunfield @ 6:11 pm

A new version of SnapPy, a program for studying the topology and geometry of 3-manifolds, is available.  Added features include a census of Platonic manifolds, rigorous computation of cusp translations, and substantial improvements to its link diagram component.


  1. Wow, this has lots of really useful new features. I just had a question about the isometry_signature function when the flag of_link=True is set. Am I correct in assuming that Snappy 2.4 is just specifying a choice of a set of ordered bases for the peripheral groups of a cusped manifold? So while this is might be most convenient for link tabulation, it actually applies more generally to all (framed) cusped manifolds?

    Comment by Neil R Hoffman — May 24, 2016 @ 7:52 pm | Reply

    • Yes, the “of_link” flag can be used for any cusped manifold. It corresponds to taking the decorated triangulation isosig of the canonical triangulation with the flags “ignore_cusp_ordering = True” and “ignore_curve_orientations = True”. You can see the docs for “triangulation_isosig” for more details, but in particular the latter flag means that the cusp framings [(1, 0), (0, -1)] and [(1,0), (0, 1)] are regarded as equivalent.

      Comment by Nathan Dunfield — May 24, 2016 @ 8:48 pm | Reply

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