Re: [deal.II] Re: Assemble function, long time

Hermes, For large systems, Krylov solvers are faster and require less memory than direct solvers. Direct solvers scale poorly, in terms of memory and performance, with the number of unknowns. The only problem with Krylov solvers is that you need to use a good preconditioner. The choice of the

Re: [deal.II] Re: Assemble function, long time

Hi Bruno, Yes, for now, I have to use a direct solver due to the preconditioner. I am experiencing long computational times with the solver function. I am trying to use DoFRenumbering::Cuthill_McKee(dof_handler), DoFRenumbering::boost::Cuthill_McKee(dof_handler,false,false) but I get even

Re: [deal.II] University cluster installation issue: compilers

Stephanie, If you are still using the same compiler as before: icc version 19.0.4.243 (gcc version 4.8.5 compatibility) The problem is because of the standard library. The Intel compiler does not have its own standard library, instead it uses the library from gcc. In your case the compiler is

Re: [deal.II] Re: Assemble function, long time

Hermes, I think Cuthill-McKee only works on symmetric matrices, is your matrix symmetric? Also, the goal of Cuthill-McKee is to help with the fill in of the matrix.There is no guarantee that it helps with the performance. If you don't know which preconditioner to use, you can use ILU (Incomplete

Re: [deal.II] Re: Assemble function, long time

Thank you for your suggestions. Could you please suggest me what function can work well for using a Krylov solver? I can no see examples. My actual code is implemented using PETS (for sparsematrix, solver, etc). I can see that SLEPcWrappers::SolverKrylovSchur allows PETS matrices. Thank you

Re: [deal.II] Re: Assemble function, long time

If your matrix is symmetric definite positive, you use CG . Otherwise, you use GMRES . Here is the page for ILU

Re: [deal.II] Re: Assemble function, long time

Yes, you should use your system_matrix. AdditionalData can be used to modify the parameters used by ILU. The interface of PreconditionILU should work very similarly to BlockJacobi see https://dealii.org/current/doxygen/deal.II/step_17.html#ElasticProblemsolve There are several tutorials that use

Re: [deal.II] Re: Assemble function, long time

Dear Bruno, Thank you very much, I will try this. The last question if it is not too much to ask is about In the PreconditionILU matrix: PETScWrappers::PreconditionILU::PreconditionILU (const MatrixBase &

Re: [deal.II] Re: Assemble function, long time

On 3/10/22 07:00, Hermes Sampedro wrote: I am experiencing long computational times with the solver function.  I am trying to use DoFRenumbering::Cuthill_McKee(dof_handler), DoFRenumbering::boost::Cuthill_McKee(dof_handler,false,false) but I get even higher computational times. Am I doing