Dear deal.II users,
I am trying to mix step-12 and step-31 for my project.
I have two coupled equations (named eq1 and eq2) that I am solving in
parallel just like in step-31 but for one of them I am using the
discontinuous Galerkin method like in step-12 (eq1) and for the other one I
use standard Galerkin (eq2). I also have two dof_handler like in step-31
one for each equation. It looks like this :
* FESystem<dim> fe_eq1; //FE element for equation
1 FESystem<dim> fe_eq2; //FE element for equation
2 DoFHandler<dim> dof_handler_eq1; DoFHandler<dim>
dof_handler_eq2;template <int dim> DG_FEM<dim>::DG_FEM (): fe_eq1
(FE_DGQ<dim>(1),10), fe_eq2 (FE_Q<dim>(1), 1), dof_handler_eq1
(triangulation), dof_handler_eq2 (triangulation) {}*
*The problem :*
My issue is with the *MeshWorker::mesh_loop*. Like in step-12, I am looping
over cells, faces and boundaries with workers for eq1 like this :
*using Iterator = typename DoFHandler<dim>::active_cell_iterator;auto
cell_worker = [&](const Iterator & cell, ScratchData<dim> &scratch_data,
CopyData & copy_data) {//my code here needs data from eq2 as well
}MeshWorker::mesh_loop(dof_handler_eq1.begin_active(),
dof_handler_eq1.end(), ,/*other
arguments*/, cell_worker, /*other workers*/);*
However, since my two equations are coupled, I need to access data from eq2
(solution at former time step) but I cannot do it with this iterator here
since it is linked only to dof_handler_eq1.
Idealy, I would like to loop using two iterators, one for dof_handler_eq1
and one for dof_handler_eq2.
I know how to do that "traditionnally", I would have something like
*auto eq1_cell = dof_handler_eq1.begin_active();const auto
end1 = dof_handler_eq1.end();auto eq2_cell =
dof_handler_eq2.begin_active();const auto end2 =
dof_handler_eq2.end();for (; eq1_cell != end1 && eq2_cell != end2 ; ++
eq1_cell , ++ eq2_cell ){//my code here}*
but with the cell_worker, I do not know.
*Question:*
How can I modify the cells worker loop (on dof1) initialisation to have a
second iterator linked with a second dof_handler looping at the same time ?
or how can I add a concurrentely running for loop to the cell_worker with a
different iterator ?
I checked in step 16 and 47 as well as in the doc for MeshWorkers and I did
not find a solution to this problem. I hope the question is clear enough,
do not hesitate to inquires more details if I am missing something
important.
Best regards,
Sylvain Mathonnière
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