I rewrote example 15 for a MPI-environment using Trilinos, and solve it with
IndexSet solution_relevant_partitioning(dof_handler.n_dofs());
DoFTools::extract_locally_relevant_dofs(dof_handler,
solution_relevant_partitioning);
LinearAlgebraTrilinos::MPI::Vector completely_distributed_solution(
dof_handler.locally_owned_dofs(), mpi_communicator);
LinearAlgebraTrilinos::MPI::Vector completely_distributed_update(
dof_handler.locally_owned_dofs(), mpi_communicator);
completely_distributed_solution = present_solution;
SolverControl solver_control (dof_handler.n_dofs(),
(system_rhs.l2_norm() > 0) ? 1e-6 *
system_rhs.l2_norm() : 1e-6);
LinearAlgebraTrilinos::SolverGMRES solver (solver_control);
LinearAlgebraTrilinos::MPI::PreconditionAMG preconditioner;
LinearAlgebraTrilinos::MPI::PreconditionAMG::AdditionalData data;
print_status_update("Initializing system matrix with
preconditioner\n");
preconditioner.initialize(system_matrix, data);
print_status_update("Solving\n");
solver.solve (system_matrix, completely_distributed_update,
system_rhs,
preconditioner);
print_status_update("Solving done\n");
hanging_node_constraints.distribute (completely_distributed_update);
print_status_update("Adding to newton\n");
newton_update = completely_distributed_update;
newton_update.compress(VectorOperation::insert);
const double alpha = determine_step_length();
completely_distributed_solution.add (alpha,
completely_distributed_update);
present_solution = completely_distributed_solution;
which works fine. Now, as next step I wanted to test if I could introduce
an offset, i.e. the resulting surface is not located at z=0, but rather at
z=OFFSET, with OFFSET a double value set at the beginning. Thus I also
initialize the solution accordingly with
template <int dim>
class InitialValues : public Function<dim>
{
public:
InitialValues () : Function<dim>() {}
virtual double value(const Point<dim> &p, const unsigned int
component) const;
};
template <int dim>
double InitialValues<dim>::value(const Point<dim> &p, const unsigned int
component) const
{
return OFFSET;
}
//In run-function
LinearAlgebraTrilinos::MPI::Vector local_solution;
local_solution.reinit(dof_handler.locally_owned_dofs(),
mpi_communicator);
VectorTools::project (dof_handler,
boundary_constraints,
QGauss<dim>(fe.degree+2),
InitialValues<dim>(),
local_solution);
//boundary_constraints.distribute(local_solution);
present_solution = local_solution;
Now I notice that if my offset goes above a certain level, I have to reduce
the step length, else I get the error
An error occurred in line <522> of file </home/roland/Downloads/dealii/
source/lac/trilinos_solver.cc> in function
void dealii::TrilinosWrappers::SolverBase::do_solve(const Preconditioner
&) [with Preconditioner = dealii::TrilinosWrappers::PreconditionBase]
The violated condition was:
false
Additional information:
AztecOO::Iterate error code -3: loss of precision
I do not understand the reason why that happens. Is it a mathematical
problem? Or rather a problem in my code? Afaik the gradients should not
depend on the offset, thus I do not know where to look for the problem here.
Thanks!
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