Dear community,
I have found a way to implement the case of multiple constraints that was
mentioned in my previous discussion. I am sharing it here, in case of use.
Basically, it seems to me that all affine constraints should be merged
before constructing the sparsity pattern. Differently than before, I build
the affine constraint m_interfaces_constraints
as
*for (auto tie_table_ii : tie_table ){ if ( tie_table_ii.first <
tie_table_ii.second ) { m_interfaces_constraints.add_line(
tie_table_ii.first ); m_interfaces_constraints.add_entry(
tie_table_ii.first, tie_table_ii.second, 1 ); }}*
and then I merged it with the hanging_node_constraints
*this->hanging_node_constraints.merge( this->m_interfaces_constraints );*
from that point on, nothing changes,
*this->hanging_node_constraints.distribute_local_to_global(cell_matrix,
cell_rhs,*
*
local_dof_indices,*
*
this->system_matrix, this->system_rhs);*
is all I need. It works, but I did not make any test on mesh refinement so
far.
Thanks!
In developing those ideas, I found the .print method of AffineConstraints
particularly useful.
Alberto
Il giorno martedì 10 agosto 2021 alle 06:52:40 UTC+2 Alberto Salvadori ha
scritto:
> Dear community
>
> I am asking your help today about imposing affine constraints. I
> understood well example 6, but when it comes to apply it to sparse MPI
> matrices I get lost. I am not sure if example 27 is of help for my case.
>
> What would I like to simulate? Take two separate domains, with conformal
> meshes. I want to impose that two sets of nodes share the same solution,
> i.e. the solution field is continuous. To this aim, the dofs to be tied
> have been collected in a set of pairs (which has been verified, it is OK).
> Hence, say the set is named tie_table, the dof tie_table.first shall be
> equal to tie_table.second .
>
> So far so good, but from now on it blurs to me. I figured out that I shall
> build the affine constraint (say it is named m_interfaces_constraints) and
> update the sparsity pattern (say it is named dsp).
>
> The dsp has been created after the hanging node constraints
>
> DoFTools::make_flux_sparsity_pattern( this->dof_handler,
> dip,
> this->hanging_node_constraints,
> /*keep constrained dofs*/ false);
>
> and it has been updated afterwards like that:
>
> for (auto tie_table_ii : tie_table )
> {
>
> if ( tie_table_ii.first < tie_table_ii.second )
>
> // we shall make sure not to impose a tie twice ...
>
> {
> dsp->add( tie_table_ii.first, tie_table_ii.second ) ;
> dsp->add( tie_table_ii.second, tie_table_ii.first ) ;
> m_interfaces_constraints.add_line( tie_table_ii.first );
> m_interfaces_constraints.add_entry( tie_table_ii.first,
> tie_table_ii.second, 1 );
> }
> }
>
> m_interfaces_constraints.close();
>
>
> Is the above reasonable to build the m_interfaces_constraints? Am I
> missing something? At this point how shall I proceed in distributing the
> cell matrix into the system matrix in the assembly phase? The following
> code does not seem to work.
>
> ... make entries in cell_matrix, cell_rhs ...
> cell->get_dof_indices (local_dof_indices);
>
> this->hanging_node_constraints.distribute_local_to_global(cell_matrix,
> cell_rhs,
>
> local_dof_indices,
>
> this->system_matrix, this->system_rhs);
>
> this->m_interfaces_constraints.distribute_local_to_global(cell_matrix,
> cell_rhs,
>
> local_dof_indices,
>
> this->system_matrix, this->system_rhs);
>
> specifically, the instruction
> this->m_interfaces_constraints.distribute_local_to_global generates the
> following error:
>
>
> --------------------------------------------------------
> An error occurred in line <1683> of file
> </var/folders/py/_sybqp9s7pn6y633bs_bqyp00000gn/T/albertosalvadori/spack-stage/spack-stage-dealii-9.2.0-ujawazz34bb5ybgxwfovovdrwaem4ymj/spack-src/source/lac/trilinos_sparse_matrix.cc>
>
> in function
> void dealii::TrilinosWrappers::SparseMatrix::add(const
> dealii::TrilinosWrappers::SparseMatrix::size_type, const
> dealii::TrilinosWrappers::SparseMatrix::size_type, const
> dealii::TrilinosWrappers::SparseMatrix::size_type *, const
> dealii::TrilinosScalar *, const bool, const bool)
> The violated condition was:
> ierr == 0
> Additional information:
> An error with error number 2 occurred while calling a Trilinos function
> --------------------------------------------------------
>
> Finally, shall I call this function? What does it do?
>
> m_interfaces_constraints.condense(*dsp);
>
> I appreciate your help, very much.
>
> Alberto
>
>
>
>
>
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