Status of support for mixed quad/tri elements in dolfinx?

What is the status of support for meshes having both quad/tri elements in dolfinx? It appears that the goal is to support this in dolfinx, and there are a few issues/PRs that appear to refer to this, but I can’t find more details about the status. Is mixed element support implemented, or not yet? If it is implemented, how should such a mesh be defined (e.g. in .xdmf format)?

As a potential workaround, I tried defining my triangular elements as quads with having one repeated vertex–i.e. connectivity of 0 1 2 2–(degenerated triangular filler elements are an option in some commercial FEA software) but this leads to errors in dolfinx at present.

It’s not supported yet. My estimate is that it will be supported by the end of the year. It requires a careful design to maintain performance.

@garth can I ask about the status of this again? I haven’t seen anything on GitHub indicating that this support has been added in the last year but perhaps I missed it…

Some preliminary steps are in We have someone who will work on this after the summer.

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@garth Greetings!
May I know if dolfinx can now handle both tri/quad elements mesh?
I have a .msh file, Can you suggest how I can import this mixed mesh in dolfinx. Thanks

As far as I’m aware this is still under development and highly experimental. See, for example, dolfinx/cpp/demo/mixed_topology/main.cpp at main · FEniCS/dolfinx · GitHub.

@dokken may be able to provide more details.

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Chris Richardson has made quite some progress, and has a demo with prism and hex elements working (somewhere). the code is not in the main branch yet, but he could probably provide an estimate as to a timeline


Yes, it is coming soon, I hope. There are definitely some issues to be ironed out in the User Interface, but if you are happy to work at a low level, you can alredy create a mesh with multiple cell types.
I will try to get an example in the next few weeks.