Hi Vachan, I don't think you need to use RPE plane. My guess is that you can use VectorTools::point_values(), which internally uses PRE (see https://github.com/dealii/dealii/blob/e413cbf8ac77606cf4a04e1e2fa75232c08533b4/include/deal.II/numerics/vector_tools_evaluate.h#L230-L343). Here you could collect the support points from the new DoFHandler, let VT::point_values() do the work and finally set the values at the support points.
Further resources are: - the test folder https://github.com/dealii/dealii/tree/master/tests/remote_point_evaluation (in particular https://github.com/dealii/dealii/blob/master/tests/remote_point_evaluation/vector_tools_evaluate_at_points_01.cc; here, the solution is interpolated between non-matching grids) - the usage of RPE and VT::point_values() in DataOutResample (https://github.com/dealii/dealii/blob/master/source/numerics/data_out_resample.cc) - the usage in the two-phase solver adaflo (https://github.com/kronbichler/adaflo/blob/master/include/adaflo/sharp_interface_util.h) PM On Tuesday, 3 August 2021 at 09:03:02 UTC+2 vachanpo...@gmail.com wrote: > Dr. Wolfgang, > > Thank you for still taking interest in this thread :) > > This becomes a very difficult data transfer problem because you want to >> evaluate the solution at a point that the current process may know nothing >> about. In essence, you will have to ask all of the other processes about >> who >> owns a part of the mesh on which a given interpolation point is located, >> and >> then that process has to send you the value of the function at that >> point. You >> have to do that for all points. This is going to be an expensive >> operation. >> You might want to check out the Utilities::MPI::RemotePointEvaluation >> class in >> the latest (9.3) release for help with this. > > I understand that the approach I had mentioned is inefficient. I only need > to do this once, to start a simulation, so I thought it might be okay. > > I had a look at Utilities::MPI::RemotePointEvaluation. This is how I > think it can be used (correct me if wrong) > > 1. Call reinit() with the dof locations, along with the corresponding > triangulation and mapping, where I want to evaluate FEFieldFunction (I > suppose the triangulation and mapping here are not of the > FEFieldFunction?). > 2. Call evaluate_and_process() by passing in the FEFieldFunction. > > I have a few questions. > > 1. What is the "buffer" argument in evaluate_and_process()? > 2. The documentation for this function says get_point_ptrs() must be > used to "process" the output in case the point-cell map is not one-one. I > will surely encounter such cases. How can I use the data returned by > get_point_ptrs() and how exactly should I "process" the output? > > I couldn't find this used in any examples. Any clarifications would be > greatly helpful. > > On Tue, 3 Aug 2021 at 04:47, Wolfgang Bangerth <bang...@colostate.edu> > wrote: > >> On 7/5/21 11:04 PM, vachan potluri wrote: >> > >> > So is your fine mesh a refinement of the coarse one? If not, you >> may want to >> > look at FEFieldFunction. >> > >> > Yes, it is. But the "refinement" is done by the meshing >> software, outside >> > dealii. Is there any simplification possible in such a case? >> >> Not really. If deal.II has no knowledge about the relationship between >> cells >> on the two meshes, then it is in essence the interpolation from one >> unstructured grid to another unstructured grid. >> >> >> > Otherwise, I think FEFieldFunction would be a safe choice. Since I want >> to use >> > it with p::d::Triangulation, will setting all dofs as relevant do the >> job? >> > This way the partitioning can also be different. >> >> This becomes a very difficult data transfer problem because you want to >> evaluate the solution at a point that the current process may know >> nothing >> about. In essence, you will have to ask all of the other processes about >> who >> owns a part of the mesh on which a given interpolation point is located, >> and >> then that process has to send you the value of the function at that >> point. You >> have to do that for all points. This is going to be an expensive >> operation. >> >> You might want to check out the Utilities::MPI::RemotePointEvaluation >> class in >> the latest (9.3) release for help with this. >> >> Best >> W. >> >> >> -- >> ------------------------------------------------------------------------ >> Wolfgang Bangerth email: bang...@colostate.edu >> www: http://www.math.colostate.edu/~bangerth/ >> >> -- >> The deal.II project is located at http://www.dealii.org/ >> For mailing list/forum options, see >> https://groups.google.com/d/forum/dealii?hl=en >> --- >> You received this message because you are subscribed to the Google Groups >> "deal.II User Group" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to dealii+un...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/dealii/61601d83-856e-dd27-dc78-3653bd45ec2f%40colostate.edu >> . >> > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. 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