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

dolfinx
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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.

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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.

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@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…

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Some preliminary steps are in https://github.com/FEniCS/dolfinx/pull/2597. 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

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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

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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.

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Just curious if there have been any updates on this over the last few months @Chris_Richardson? Thanks

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It’s getting very close. We’re aiming for a brief sprint to push it over the line in the coming month.

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