Dear Franck,
> I am looking at step-43 using different method. I do a semi discretization
> in space and end up with an ode for the saturation and use different
> technique for time integration for the saturation.
>
> For this I will need to assemble the matrix H after solving for the
> velocity in the darcy system. Individual entries of H are given by:
>
> \mathbf{H}_{ij} & = - \Delta t^{(n)}_c \Big( F\left(S^{(n-1)}\right)
> \mathbf{v}_i,\nabla\phi_j\Big)_{\Omega}
>
>
> I am struggling with sparsity pattern that I have to define for this
> matrix. I try this:
>
> assemble_matrix_H.clear();
> DynamicSparsityPattern dsp (n_s, n_u);
> DoFTools::make_sparsity_pattern (saturation_dof_handler,
> darcy_dof_handler, dsp,
> saturation_constraints, false);
> ssemble_matrix_H.reinit(dsp);
>
>
>
> dealii is complaining and is saying
>
> /home/franckm/apps/candi/deal.II-toolchain/deal.II-v8.4.0/include/deal.II/dofs/dof_tools.h:563:3:
>
> note: template<class DoFHandlerType, class SparsityPatternType> void
> dealii::DoFTools::make_sparsity_pattern(const DoFHandlerType&, const
> DoFHandlerType&, SparsityPatternType&)
> make_sparsity_pattern (const DoFHandlerType &dof_row,
> ^
> /home/franckm/apps/candi/deal.II-toolchain/deal.II-v8.4.0/include/deal.II/dofs/dof_tools.h:563:3:
>
> note: template argument deduction/substitution failed:
> /home/franckm/candi-examples/step-43b/step-43b.cc:918:68: note:
> candidate expects 3 arguments, 5 provided
> saturation_constraints, false);
> ^
> make[3]: *** [CMakeFiles/step-43b.dir/step-43b.cc.o] Error 1
>
The error is not surprising as there isn't a variant of
DoFTools::make_sparsity_pattern that takes two DoFHandlers.
> How one define a sparsity pattern for assembling H in the above scenario?
>
What you can do, is to consider all the blocks of your system and use
\widetilde{H}=[0 H;0 0] instead. In this case your DoFHandler would have to
have two blocks and
you can use the variant [1] instead with an appropriate coupling.
A different approach is to build the SparsityPattern yourself by simulating
assembling the matrix. This means that instead of using
ConstraintMatrix.distribute_local_to_global
you would call SparsityPattern.add [2].
The question is if H really is the matrix you want to assemble. How does
the equation you are considering really look like?
Best,
Daniel
[1]
https://www.dealii.org/8.4.1/doxygen/deal.II/group__constraints.html#ga33ec1ee2ac7c86b16700022b704b69c8
[2]
https://www.dealii.org/8.4.0/doxygen/deal.II/classSparsityPattern.html#aa8dd1f7f393272cc5ae7789ac6be3413
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