Sorry for messing up the topic. I should be Understanding loops in
matrix-free. I wanted to insert a figure of the source code rather than the
google groups formatting and it didn't work for some reason.
David schrieb am Samstag, 6. Februar 2021 um 19:15:07 UTC+1:
> Hi there,
>
> I'm currently trying to pack my cell operations into one of the
> matrix-free loop functions.
> In my first version, I implemented the loops manually by using (sorry for
> the odd formatting):
> ```
> local_apply_cell(*matrix_free,
> system_rhs,
> source_vector,
> std::make_pair(0,
>
> matrix_free->n_cell_batches()));
> local_apply_boundary_face(
> *matrix_free,
> system_rhs,
> source_vector,
> std::make_pair(mf_data_reference->n_inner_face_batches(),
> mf_data_reference->n_inner_face_batches() +
>
> mf_data_reference->n_boundary_face_batches()));
> ```
> which works as desired. I don't have any operations on internal faces and
> ghost exchange/compression doesn't matter for the rest of the question.
>
> In a second step, I replaced the manually implemented loops by the
> matrix-free loop in the following way:
> ```
> matrix_free->template loop<VectorType, VectorType>(
> [&](const auto &data,
> auto & dst,
> const auto &src,
> const auto &cell_range) {
> local_apply_cell(data, dst, src, cell_range);
> },
> [](const auto &, auto &, const auto &, const auto &) {},
> [&](const auto &data,
> auto & dst,
> const auto &src,
> const auto &face_range) {
> local_apply_boundary_face(data, dst, src, face_range);
> },
> system_rhs,
> source_vector,
> true,
> MatrixFree<dim, Number,
> VectorizedArrayType>::DataAccessOnFaces::
> none,
> MatrixFree<dim, Number,
> VectorizedArrayType>::DataAccessOnFaces::
> none);
> ```
>
> However, the system starts diverging after a time (as opposed to the
> 'manual' loop), i.e., the result is different.
>
> I should probably add as a comment that I use sorted boundary condition
> according to the boundary cell batches so that I apply the first set of
> data to the first boundary face batch and the second one to the second...
> Though, I checked the ordering manually and the loop-function seems to work
> in the same order on the batches as the manual loop.
>
> I also tried to set the vector zeroing on the destination vector to
> 'false' (I use continuous elements) but it doesn't make any difference.
> According to my understanding of the loop function, both implementations
> should be equivalent. I probably miss something here.
>
> Maybe anyone else has an idea about the differences.
> Thanks in advance and best regards,
> David
>
>
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