Hello team,
I am running a 3D simulation with periodicity in all 3 directions.
I have defined the periodic boundary conditions using (similarly in the
other 2 directions) -
*DoFTools::make_periodicity_constraints(dof_handler,
/*b_id*/ 0, /*b_id*/
1, /*direction*/
0, constraints);*
and the deformation of the box using -
*IndexSet selected_dofs_x; std::set< types::boundary_id >
boundary_ids_x= std::set<types::boundary_id>();
boundary_ids_x.insert(0);
DoFTools::extract_boundary_dofs(dof_handler,
fe.component_mask(y_displacement),
selected_dofs_x,
boundary_ids_x); unsigned int nb_dofs_face_x =
selected_dofs_x.n_elements(); IndexSet::ElementIterator dofs_x =
selected_dofs_x.begin(); double relative_displacement_x = 0.0;
if(timestep<=020) relative_displacement_x = 5e-4; else
if(timestep%02==0) relative_displacement_x = 2e-4; else
relative_displacement_x = 0.0; for(unsigned int i = 0; i <
nb_dofs_face_x; i++) { constraints.add_line (*dofs_x);
constraints.set_inhomogeneity(*dofs_x, (apply_dirichlet_bc ?
relative_displacement_x : 0.0)); dofs_x++; }*
This works fine when run using a single process. But when increased to 2
processes, it pauses after few time steps without any error message. When
used more than 2 processes, it does not converge in the first time step
itself. I am not sure what is causing the problem.
I also tested it with step-45. It works fine with 1 and 2 processes. But
when 4 processes are used, it gives out the following error:
[100%] Built target step-45
Refinement cycle 0
Assembling...
Computing preconditioner...
Solving...
----------------------------------------------------
Exception on processing:
----------------------------------------------------
Exception on processing:
--------------------------------------------------------
An error occurred in line <457> of file
</usr/include/deal.II/lac/solver_cg.h> in function
void dealii::SolverCG<VectorType>::solve(const MatrixType&,
VectorType&, const VectorType&, const PreconditionerType&) [with MatrixType
= Step45::SchurComplement<dealii::TrilinosWrappers::PreconditionJacobi>;
PreconditionerType = dealii::TrilinosWrappers::PreconditionAMG; VectorType
= dealii::TrilinosWrappers::MPI::Vector]
The violated condition was:
false
Additional information:
Iterative method reported convergence failure in step 65. The residual in
the last step was 4.56146e-06.
This error message can indicate that you have simply not allowed a
sufficiently large number of iterations for your iterative solver to
converge. This often happens when you increase the size of your problem. In
such cases, the last residual will likely still be very small, and you can
make the error go away by increasing the allowed number of iterations when
setting up the SolverControl object that determines the maximal number of
iterations you allow.
The other situation where this error may occur is when your matrix is not
invertible (e.g., your matrix has a null-space), or if you try to apply the
wrong solver to a matrix (e.g., using CG for a matrix that is not symmetric
or not positive definite). In these cases, the residual in the last
iteration is likely going to be large.
I would appreciate any pointers on the possible mistakes I might be making.
Best regards,
Raghunandan.
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