Would that work together with the GMG-preconditioner? Will test it there as
soon as my problem in my second question could be solved.
There I have the following code:
SolverControl coarse_solver_control(1000, 1e-10, false, false);
SolverGMRES<vector_t> coarse_solver(coarse_solver_control);
PreconditionIdentity id;
MGCoarseGridIterativeSolver<vector_t,
SolverGMRES<vector_t>,
matrix_t,
PreconditionIdentity>
coarse_grid_solver(coarse_solver, coarse_matrix, id);
using Smoother = LA::MPI::PreconditionJacobi;
MGSmootherPrecondition<matrix_t, Smoother, vector_t> mg_smoother;
mg_smoother.initialize(mg_matrices, Smoother::AdditionalData(0.5));
mg_smoother.set_steps(2);
mg::Matrix<vector_t> mg_matrix(mg_matrices);
mg::Matrix<vector_t> mg_interface_up(mg_interface_matrices);
mg::Matrix<vector_t> mg_interface_down(mg_interface_matrices);
Multigrid<vector_t> mg(mg_matrix, coarse_grid_solver, mg_transfer,
mg_smoother, mg_smoother);
mg.set_edge_matrices(mg_interface_down, mg_interface_up);
PreconditionMG<dim, vector_t, MGTransferPrebuilt<vector_t>>
preconditioner(dof_handler,
mg,
mg_transfer);
and here I intent to replace all occurences of matrix_t with my custom
LinearOperator (if that makes sense).
Am Freitag, 19. Juli 2019 17:51:10 UTC+2 schrieb Wolfgang Bangerth:
>
> On 7/19/19 9:47 AM, 'Maxi Miller' via deal.II User Group wrote:
> > What I did was the replacement of system_matrix with a function,
> providing a
> > vmult()-function. Now I would like to add a preconditioner based on that
> > function to reduce the necessary GMRES-iterations. But until now most of
> the
> > preconditioners require a matrix for initialization. Thus I wanted to
> replace
> > that matrix with my LinearOperator, if that is possible?
>
> Yes, as I already said, this is possible. Have you tried?
>
> I think you should also be able to look at step-20 (and maybe 22) for
> examples.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
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