Hi! I’m trying to export a function from a DG function space to XDMF but obtain the following error: File "/home/remidm/festimx/mwe.py", line 14, in <module> xdmf_file.write_function(u) File "/home/remidm/miniconda3/envs/dolfinx/lib/python3.11/site-packages/dolfinx/io/utils.py", line 235, …

[image] RemDelaporteMathurin: V = fem.FunctionSpace(msh, ("DG", 1)) u = fem.Function(V) xdmf_file = XDMFFile(MPI.COMM_WORLD, "u.xdmf", "w") xdmf_file.write_mesh(msh) xdmf_file.write_function(u) This is an explicit change to highlight the limitations of the XDMF file format, as in comparison…

Understood! I suppose we would need a write_checkpoint method for this then?

We are not aiming for long term support of XDMF, as it is no longer actively developed ( Xdmf / Xdmf · GitLab , no commit in three years), and thus we are not aiming to add checkpointing to it. I was working on an ADIOS2 based checkpoint/visualization code, but hit some speed-bumps, such as: …

Gotcha. I’ll stick with VTXWriter for now then. Not sure how to read it with paraview though. Is there any demo available?

VTXWriter created a .bp folder, that you can open in paraview. It should then Give you the option og fides or VTX (choose Vtx)

Hm I have the folder but it’s not opening in paraview 5.11.1, just hangs forever. This is how I export it, does it seem right? from dolfinx import mesh, fem from mpi4py import MPI from dolfinx.io import XDMFFile from dolfinx.io import VTXWriter msh = mesh.create_unit_square(MPI.COMM_WORLD, 8, 8) …

[image] RemDelaporteMathurin: with VTXWriter(msh.comm, "out.bp", [u]) as vtx: vtx.write(0.0) Try with VTXWriter(msh.comm, "out.bp", [u], engine="BP4") as vtx: vtx.write(0.0) after removing the old directory. Paraview doesn’t support BP5 yet, Which is the default engine for adios2

Progress: now Paraview doesn’t hang anymore but I have this error ERROR: In vtkADIOS2CoreImageReader.cxx, line 648 vtkADIOS2CoreImageReader (000002A5F7ABD6D0): Can not use the dimension of array NumberOfEntities to set the dimension of image data. Its size is neither 2 nor 3

There should be another reader there (that is not image data). Do you Get the option: ADIOS2VTXReader ( paraview.simple.ADIOS2VTXReader — ParaView/Python 5.8.0-RC3-1-g56631fdd9a documentation )

Hm, I wasn’t offered the choice of reader. This is the list of readers I find when going in OpenFile : [image]

That is strange. How did you install paraview and what kind of system are you using?

Cannot write function to XDMF with DG elements

General

RemDelaporteMathurin October 12, 2023, 11:02pm 18

It would seem it has to do with needing the MPI version

Is this the MPI version?

Imposing a discontinuity at interface using DG method

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Cannot write function to XDMF with DG elements

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