StandardError: CGAL ERROR: assertion violation!

[Nico Schlömer]

Sometimes, creating a ball mesh à la

h = 0.5**(k+2)
c = mshr.Sphere(dolfin.Point(0., 0., 0.), 1.0, int(2*pi / h))
m = mshr.generate_mesh(c, 2.0 / h)

gives me

    m = mshr.generate_mesh(c, 2.0 / h)
File "/usr/lib/python2.7/dist-packages/mshr.py", line 567, in generate_mesh
    _generate(m, geometry, resolution, backend)
StandardError: CGAL ERROR: assertion violation!
File: /build/mshr-W2Doqy/mshr-1.6.0/debian/build-python2.7/CGAL-4.6-installdir/include/CGAL/Mesh_3/Refine_facets_3.h

See, e.g., here.

This is with mshr 1.6.0. Perhaps this is already fixed in CGAL 4.8.1 though (current mshr master).

[Benjamin Dam Kehlet]

Do you always get this error or only now and then?

[Nico Schlömer]

Only now and then.

[Nico Schlömer]

The problem here is mostly that tests are failing randomly, and that quite annoying. Deterministic mesh generation à la https://bitbucket.org/fenics-project/mshr/issues/18/deterministic-mesh-creation would help. Not sure if that's provided for by CGAL.

[Benjamin Dam Kehlet]

I totally agree. It is very annoying that bugs like this are not easyli reproducible. I remember I did try to use a fixed seed for random generator in CGAL, but that didn't help. I'll take another look at it when I find time (probably not until next week).