Thank you, we are also implementing block solvers/preconditioner as in these examples you suggested.
We also want to try GMRES on the entire block matrix with say ILU preconditioner, but does not seem to be possible, since all available ILU do not take block matrices. If we assemble into PETSc::BlockSparseMatrix, there is also no way to copy that into PETSc::SparseMatrix. So it looks like we have to switch to SparseMatrix during assembly itself for this purpose. I also asked on Petsc list, https://lists.mcs.anl.gov/pipermail/petsc-users/2026-March/052640.html and they may make it possible to use block matrices with ILU, but it does not work at present. best praveen On Mon, Mar 2, 2026 at 3:17 PM 'Wolfgang Bangerth' via deal.II User Group < [email protected]> wrote: > On 3/2/26 00:26, Praveen C wrote: > > > > Is it possible to use AMG preconditioner from Petsc or Trilinos with > > dealii::SolverGMRES ? > > The dealii::Solver* classes all just require the matrix and the > preconditioner > to be linear operators, i.e., classes with a vmult() function. In your > case, > these may be block operators that internally call AMG functions from PETSc > or > Trilinos. You may be interested in taking a look here, for example: > > > https://dealii.org/developer/doxygen/deal.II/step_22.html#step_22-BlockSchurcomplementpreconditioner > > Best > W. > > -- > 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 [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/dealii/af825aeb-780c-4c1b-88f0-90d5bd7be91a%40colostate.edu > . > -- 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 [email protected]. To view this discussion visit https://groups.google.com/d/msgid/dealii/CAEvUdM%2B9zgTTsue7HTkd4iFoPmMtgUbghAh8bnrBaf4mecvCew%40mail.gmail.com.
