On Thu, 4 Sep 2014, Miguel Angel Salazar de Troya wrote:
> Thanks. Could you answer the last question please? Basically I want to know > if I still can use cg once I use mesh refinement? I did quick > calculations with equation (7) and I see the matrix is not symmetric so I > think I cannot use it. Sorry, I was kind of oblique: "Depending on the constraint options you select we fill in those zero blocks with the constraint equations themselves or with ones on the diagonal." C^T K C is obviously symmetric, but if we add constraint equations to the empty rows then we get something asymmetric; if you want to use CG you need to make sure you're setting asymmetric_constraint_rows=false (and then using enforce_constraints_exactly() or something to fix up your hanging dofs after each solve). > I would like to double check with you. Which preconditioner would > you recommend for adaptive mesh refinement in elasticity? I'm not the one to ask about preconditioners. My experience could probably be summed up as: AMG on each processor wins on problems where it works, ILU (usually with ~4 levels) wins otherwise, tweaking Block Jacobi vs Additive Schwarz to tie it together can speed things up slightly. > Also, I had a question about the load balancing in the adaptive mesh > refinement. Is this automatic? Yes > When is it done? Inside EquationSystems::reinit() > The vectors associated with a system are balanced as well? Yes. But they're either projected to the new grid or zeroed depending on the option you gave to add_vector() or afterwards. > What if we had created additional vectors that we initialize after each > refinement with the function init (const > NumericVector<T> other), i.e. > http://libmesh.sourceforge.net/doxygen/classlibMesh_1_1PetscVector.php#a1a9ed9f54cab101da906d976e0b7bea1 If you didn't use System::add_vector() to create it then the system doesn't know about it and it doesn't get touched upon refinement. --- Roy ------------------------------------------------------------------------------ Slashdot TV. Video for Nerds. Stuff that matters. http://tv.slashdot.org/ _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
