What KSP are you using? DIVERGED_BREAKDOWN is very rare for KSPGMRES. If you are using one of its lesser cousins like bcgs you might consider switching to bcgsl or gmres.
I assume because of boundary conditions or the discretization you do not have symmetric positive definite and thus cannot use CG. Barry > On Oct 12, 2022, at 2:00 PM, Matthew Knepley <knep...@gmail.com> wrote: > > On Wed, Oct 12, 2022 at 1:38 PM Alfredo J Duarte Gomez <aduar...@utexas.edu > <mailto:aduar...@utexas.edu>> wrote: > Good morning PETSC users, > > I have a current solver that requires the solution of a Laplace equation to > be reused for all future time steps. > > The configuration is axisymmetric with Dirichlet BCs at the top and bottom > boundaries, and Zero Neumman conditions at the axis and far field. The grid > is curvilinear and structured. > > So far I have been using PCHYPRE boomeramg as the preconditioner, which often > works well, but I have also experienced DIVERGED_BREAKDOWN on many occasions. > When I use direct solver PCMUMPS it always produces a satisfactory answer, > which gives me confidence that the solution exists for the given grid in all > these configurations where boomeramg fails. > > I do not know why Hypre is breaking down. Did you try ML or GAMG? They are > easier to diagnose I think. > > Thanks, > > Matt > > I am looking for recommendations on other preconditioners to try in this > problem that can produce a solution faster than PCMUMPS, or recommendations > on which parameters to adjust on boomeramg. > > Thank you, > > > -- > Alfredo Duarte > Graduate Research Assistant > The University of Texas at Austin > > > -- > What most experimenters take for granted before they begin their experiments > is infinitely more interesting than any results to which their experiments > lead. > -- Norbert Wiener > > https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
