Hi Michal, any chance that you post or send me a small runnable test program.
By the way, there is an open PR (https://github.com/dealii/dealii/pull/9343) for the computation of the diagonal in a matrix-free manner. Once this is merged, I will work the matrix-free assembly of sparse matrices. Thanks, Peter On Monday, 9 March 2020 15:26:10 UTC+1, Michał Wichrowski wrote: > > Dear all, > I've got matrix-free multigrid solver for Stokes problem. The main > bottleneck is solution of coarse problem, so I tried to assemble the > regular sparse matrix and use direct solver. Since the coarse problem is > (relatively) small, I used vmults by unit vector to obtain columns of the > matrix. This is my code: > > > setup_matrix(); // generates sparsity patters and reinits matrices > > LinearAlgebra::distributed::BlockVector<LevelNumber> dst; > LinearAlgebra::distributed::BlockVector<LevelNumber> src; > > src.reinit(2); > for (unsigned int b = 0; b < 2; ++b) > stokes_matrix.get_matrix_free()->initialize_dof_vector( > src.block(b), b); > src.collect_sizes(); > src =0; > > > dst.reinit(2); > dst.block(0).reinit(owned_dofs_u, relevant_dofs_u, MPI_COMM_WORLD); > dst.block(1).reinit(owned_dofs_p, relevant_dofs_p, MPI_COMM_WORLD); > dst.collect_sizes(); > > for(types::global_dof_index i =0; i< owned_dofs_u.size(); ++i){ > src=0; > dst=0; > if(owned_dofs_u.is_element(i) ) > src.block(0)(i)=1; > > src.compress(VectorOperation::insert); > stokes_matrix.vmult(dst, src); > > dst.update_ghost_values(); > > for(IndexSet::ElementIterator index_iter =owned_dofs_u.begin(); > index_iter != owned_dofs_u.end(); > ++index_iter){ > if(dst.block(0)(*index_iter)!=0 ) > block_A->set(*index_iter,i, dst.block(0)(*index_iter) ); > } > > } > > block_A->compress(VectorOperation::unknown); > > Without constrains the matrix matches the matrix-free operator, but with > constrains present it does not. What is the proper way to assemble the > matrix with vmult? > > Best, > Michał Wichrowski > > > > -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/11de6867-e589-439c-8aa1-e56d808a0345%40googlegroups.com.
