[deal.II] Suggestions on PETSc SNES Nonlinear Solver?

[Lex Lee]

Hello all, 


In my FSI problem, there are 4 vector-valued variables + 3 scalar 
variables. Most of them are strongly coupled with each other. It's hard to 
decouple the system and design a good preconditoner. Previously, I solved 
the whole system with the direct solver (UMFPACK)  + Newton's iteration 
method. 

Several days ago, I added deal.ii's new nonlinear solver (SNES) into my 
code, and now its default method is jacobian-free newton-krylov. However, 
it behaves bad and never get converged in my case. Maybe I am using it in a 
wrong way, as I heard that SNES solver is powerful.

Do you have the experience in using this nonlinear solver? If yes, could 
you kindly give me some advice for multiple-variable problem? Do I need to 
create block containers for the matrix, solution and right-hand-side ?

Thanks a lot

Lex  

constraints_hp.distribute(dis_current_solution);
current_solution = dis_current_solution;

const double target_tolerance = 1.e-8;
PETScWrappers::NonlinearSolverData additional_data;
additional_data.absolute_tolerance = target_tolerance;
additional_data.snes_linesearch_type = "basic";
//additional_data.snes_type = "ngmres" ;

NonlinearSolver nonlinear_solver(additional_data,mpi_communicator);
nonlinear_solver.residual = [&](const VectorType &evaluation_point,
VectorType & residual){
compute_hp_residual(evaluation_point, residual);
};

bool user_control = false;
if (user_control)
{
nonlinear_solver.setup_jacobian =
[&](const VectorType &current_u) {
compute_jacobian_and_initialize_preconditioner(current_u);
};
nonlinear_solver.solve_with_jacobian = [&](const VectorType &rhs,
VectorType &dst) {
this->solve(rhs, dst);
};
//nonlinear_solver.set_matrix(jacobian_matrix);
}
else //jacobian-free newton-krylov
{
nonlinear_solver.set_matrix(jacobian_matrix);
nonlinear_solver.jacobian =
[&](const VectorType &current_u, MatrixType &, MatrixType &P) {
Assert(P == jacobian_matrix, ExcInternalError());
compute_hp_jacobian_matrix(current_u);
(void)P;
};
}
nonlinear_solver.monitor =
[&](const VectorType &, unsigned int step, double gnorm) {
pcout << step << " norm=" << gnorm << std::endl;
};

nonlinear_solver.solve(dis_current_solution);
constraints_hp.distribute(dis_current_solution);
current_solution = dis_current_solution;



-- 
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see 
https://groups.google.com/d/forum/dealii?hl=en
--- 
You received this message because you are subscribed to the Google Groups 
"deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to dealii+unsubscr...@googlegroups.com.
To view this discussion on the web visit 
https://groups.google.com/d/msgid/dealii/45f5da23-e270-4bc8-9323-c83a86f3abf6n%40googlegroups.com.