Hello everyone, I looked in the forum, in the documentation and in the tutorials but I couldn't find a way to solve this problem in the way I need. I would appreciate a lot any help you could provide me.
I would like to have Dirichlet BCs applied to faces with some boundary id. This id is not changing (i.e., the constrained faces are always the same), and the mesh, elastic properties etc. are also constant throughout the program. The function used to define these BCs has always the same shape, the only thing that is changing is the value of the Dirichlet BCs (e.g., imagine that first you constrain the displacement of a face with a spatially-constant value of 1.0 through the face, and in the next solution step to 2.0 and so on). I need to solve this system many times, each time with a different value of the Dirichlet BCs. To do this efficiently, I would like to precalculate as much as possible, for example, assembling the system matrix only once etc. Now my question is, given that the sparsity pattern is not changing (as the constrained nodes are the same), is there a way to solve this in a manner such that only the solution and rhs are changing from one step to the next? If the answer is that the system matrix must necessarily change, which should be the strategy to reassemble only the changing cells (and avoiding thus reassembling the whole matrix)? In summary, what's the most efficient way to repeatedly solve a system in which the only changes from step to step are the value (not the region over which they are applied) of the Dirichlet BCs? About my current implementation: I don't have hanging nodes, and I'm using PETScWrappers::MPI:: SparseMatrix and PETScWrappers::MPI::Vector. I assemble the matrix with void distribute_local_to_global <https://dealii.org/8.4.1/doxygen/deal.II/classConstraintMatrix.html#aaa155d7c8fcd10b7c417bfabd2698744> (const FullMatrix <https://dealii.org/8.4.1/doxygen/deal.II/classFullMatrix.html>< typename MatrixType::value_type > &local_matrix, const std::vector< size_type <https://dealii.org/8.4.1/doxygen/deal.II/classConstraintMatrix.html#a71b13eb29cd43c9e87abebf2bf78b2a3> > &local_dof_indices, MatrixType &global_matrix) const and apply the BCs with void interpolate_boundary_values <https://dealii.org/8.4.1/doxygen/deal.II/namespaceVectorTools.html#a0e84d0721e3780394e7d854b7ec878cf> (const DoFHandlerType &dof, const types::boundary_id <https://dealii.org/8.4.1/doxygen/deal.II/namespacetypes.html#a685c06c8ba84120df596d9e56f5510e2> boundary_component, const Function <https://dealii.org/8.4.1/doxygen/deal.II/classFunction.html>< DoFHandlerType::space_dimension, double > &boundary_function, std::map< types::global_dof_index <https://dealii.org/8.4.1/doxygen/deal.II/namespacetypes.html#a3bf9e493f1aab00b04933b81856144c4>, double > &boundary_values, const ComponentMask <https://dealii.org/8.4.1/doxygen/deal.II/classComponentMask.html> &component_mask=ComponentMask <https://dealii.org/8.4.1/doxygen/deal.II/classComponentMask.html>()) void apply_boundary_values <https://dealii.org/8.4.1/doxygen/deal.II/namespaceMatrixTools.html#a26b81352fcf862218943831dbb38f0a0> (const std::map< types::global_dof_index <https://dealii.org/8.4.1/doxygen/deal.II/namespacetypes.html#a3bf9e493f1aab00b04933b81856144c4>, double > &boundary_values, PETScWrappers::MPI::SparseMatrix <https://dealii.org/8.4.1/doxygen/deal.II/classPETScWrappers_1_1MPI_1_1SparseMatrix.html> &matrix, PETScWrappers::MPI::Vector <https://dealii.org/8.4.1/doxygen/deal.II/classPETScWrappers_1_1MPI_1_1Vector.html> &solution, PETScWrappers::MPI::Vector <https://dealii.org/8.4.1/doxygen/deal.II/classPETScWrappers_1_1MPI_1_1Vector.html> &right_hand_side, const bool eliminate_columns=true) P.S.: I tried to simply repeat the process to re-apply the BCs with a new value using the same matrix, but I get always the first BCs I apply (I think because once I apply it, the matrix knows it has been already condensed and ignores the next calls). -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
