Dear Subramanya,
The actual cells associated with the integer indices 'cell' (that are
batches in case of SIMD vectorization) are not necessarily the same if
you create two separate MatrixFree objects and initialize each with the
respective DoFHandler for the two fields. If you intend to use coupled
problems like the thermal-stress problem you describe, you should use
the MatrixFree::reinit function that takes both DoFHandler objects as
the arguments to an std::vector<DoFHandler*> and respectively for the
affine constraints. Then, you can initialize FEEvaluation objects using
the 'dof_no' argument in the constructor:
https://www.dealii.org/developer/doxygen/deal.II/classFEEvaluation.html#ade40e452949cbefd4f7e6d5580af81c8
- it is the second argument next to MatrixFree.
You can also try to run with separate MatrixFree objects, but then you
need to manually link the two objects and one FEEvaluation needs to be
initialized with an array of cells (that you constructed manually). I
have done that in some applications, and there is at least one code
inside deal.II that does this:
https://github.com/dealii/dealii/blob/8f97fd0dca1eb878bc7ae9922ac89430cab800db/include/deal.II/multigrid/mg_transfer_global_coarsening.templates.h#L4041-L4068
- but it is much less obvious, so I really recommend the first variant.
I hope this helps!
Best regards,
Martin
Am 03.01.25 um 17:14 schrieb subramanya gautam:
I am trying to implement a staggered thermal-elastic solver using the
matrix-free multigrid solver approach from step-37. I got an
elasticity solver and a thermal solver working and now I am trying to
associate the two. I have a shared triangulation, with two separate
dof_handlers for the thermal and stress problems. The question I have
is when I do the assembly loop, does the cell refer to the same cell
for both the thermal and elastic problems?
So from step-37, can I just call phi_temp.reinit(cell), and
phi_stress.reinit(cell), and have cell refer to the same physical cell
in the triangulation?
for (unsigned int cell = 0;
cell < system_matrix.get_matrix_free()->n_cell_batches();
++cell)
{
phi.reinit(cell);
for (const unsigned int q : phi.quadrature_point_indices())
phi.submit_value(make_vectorized_array
<https://www.dealii.org/current/doxygen/deal.II/vectorization_8h.html#ad7d7e08942faeecf438c75a254e06cbe><double>(1.0),
q);
phi.integrate(EvaluationFlags::values
<https://www.dealii.org/current/doxygen/deal.II/namespaceEvaluationFlags.html#a9b7c6d689cb76386839d0d13640f59aeaf9825c682f693a6a200094641a0d6a58>);
phi.distribute_local_to_global(system_rhs);
}
Thanks!
Subramanya.
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