vmult (VectorType &dst,
const VectorType &src) const
{
- SolverControl solver_control (src.size(), 5e-8*src.l2_norm());
+ SolverControl solver_control (src.size(), 1e-7*src.l2_norm());
SolverCG<VectorType> cg (solver_control);
dst = 0;
temperature_constraints);
temperature_constraints.close ();
}
-
+
std::vector<unsigned int> stokes_dofs_per_block (2);
DoFTools::count_dofs_per_block (stokes_dof_handler, stokes_dofs_per_block,
stokes_sub_blocks);
// need to tell the AMG setup that we use
// quadratic basis functions for the
// velocity matrix (this implies more
- // nonzero elements in the matrix, so that
- // a more rubust algorithm needs to be
- // chosen internally). Moreover, we want to
- // be able to control how the coarsening
- // structure is build up. The way AMG does
- // this is to look which matrix entries are
- // of similar size as the diagonal entry in
- // order to algebraically build a
- // coarse-grid structure. By setting the
- // parameter
+ // nonzero elements in the matrix, so
+ // that a more rubust algorithm needs to
+ // be chosen internally). Moreover, we
+ // want to be able to control how the
+ // coarsening structure is build up. The
+ // way the Trilinos smoothed aggregation
+ // AMG does this is to look which matrix
+ // entries are of similar size as the
+ // diagonal entry in order to
+ // algebraically build a coarse-grid
+ // structure. By setting the parameter
// <code>aggregation_threshold</code> to
- // 0.05, we specify that all entries that
- // are more than five precent of size of
- // some diagonal pivots in that row should
- // form one coarse grid point. This
- // parameter is rather ad-hoc, and some
- // fine-tuning of it can influence the
- // performance of the preconditioner. As a
- // rule of thumb, larger values of
- // <code>aggregation_threshold</code> will
- // decrease the number of iterations, but
- // increase the costs per iteration. A look
- // at the Trilinos documentation will
- // provide more information on these
- // parameters. With this data set, we then
- // initialize the preconditioner with the
- // matrix we want it to apply to.
+ // 0.02, we specify that all entries that
+ // are more than two precent of size of
+ // some diagonal pivots in that row
+ // should form one coarse grid
+ // point. This parameter is rather
+ // ad-hoc, and some fine-tuning of it can
+ // influence the performance of the
+ // preconditioner. As a rule of thumb,
+ // larger values of
+ // <code>aggregation_threshold</code>
+ // will decrease the number of
+ // iterations, but increase the costs per
+ // iteration. A look at the Trilinos
+ // documentation will provide more
+ // information on these parameters. With
+ // this data set, we then initialize the
+ // preconditioner with the matrix we want
+ // it to apply to.
//
// Finally, we also initialize the
// preconditioner for the inversion of
// object.
amg_data.elliptic = true;
amg_data.higher_order_elements = true;
- amg_data.aggregation_threshold = 5e-2;
+ amg_data.smoother_sweeps = 2;
+ amg_data.aggregation_threshold = 0.02;
Amg_preconditioner->initialize(stokes_preconditioner_matrix.block(0,0),
amg_data);
projects / dealii-svn.git / commitdiff