When trying to solve a nonlinear heat equation system, for certain
parameters the calculation fails with
AztecOO::Iterate error code -4: GMRES Hessenberg ill-conditioned
while using the following code to solve:
SolverControl solver_control (dof_handler.n_dofs(),
(system_rhs.l2_norm() > 0) ? 1e-8 *
system_rhs.l2_norm() : 1e-8);
LinearAlgebraTrilinos::SolverGMRES solver (solver_control);
LinearAlgebraTrilinos::MPI::PreconditionAMG preconditioner;
LinearAlgebraTrilinos::MPI::PreconditionAMG::AdditionalData data;
preconditioner.initialize(system_matrix, data);
solver.solve (system_matrix, completely_distributed_update, system_rhs,
preconditioner);
What can I do to find and fix the problem for that error? Or should I try
to switch to a direct solver (like UMFPACK)?
Thanks!
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