I switched to the block AMG Stokes solver and re-ran the case. It successfully passed timestep 470; however, the simulation terminated at timestep 568 with an error. I’ve attached the relevant log snippet for reference.
The initial residual was: -nan
The final residual is: -nan
The required residual for convergence is: 3.924943e-07
See output-Brittle_thrust_wedge_exp2_amg/solver_history.txt for the
full convergence history.
The solver reported the following error:
--------------------------------------------------------
An error occurred in line <2092> of file
</home/deal.II-v9.7.0/include/deal.II/lac/solver_gmres.h> in
function
void dealii::SolverGMRES<VectorType>::solve(const MatrixType&,
VectorType&, const VectorType&, const PreconditionerType&) [with
MatrixType = dealii::TrilinosWrappers::SparseMatrix;
PreconditionerType = dealii::TrilinosWrappers::PreconditionILU;
VectorType = dealii::TrilinosWrappers::MPI::Vector]
The violated condition was:
iteration_state == SolverControl::success
Additional information:
Iterative method reported convergence failure in step 0. The residual
in the last step was -nan.
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.