On Fri, Apr 5, 2019 at 5:27 PM Maahi Talukder <maahi.b...@gmail.com> wrote:
> Hi, > Thank you for your reply. > > Well, I have verified the solution on large problems, and I have converged > the solution to machine accuracy using different solvers. So I guess the > setup okay in that respect. > I am suspicious that it "worked" on large problems but failed on small. But you never know. > > The BC I am using is of Dirichlet type. > > > > On Fri, Apr 5, 2019 at 5:21 PM Mark Adams <mfad...@lbl.gov> wrote: > >> So you have a 2D Poisson solver and it is working on large problems but >> the linear solver is diverging on small problems. >> >> I would verify the the solution is good on the large problem. >> >> You might have a problem with boundary conditions. What BCs do you think >> you are using? >> >> On Fri, Apr 5, 2019 at 4:33 PM Maahi Talukder via petsc-users < >> petsc-users@mcs.anl.gov> wrote: >> >>> Dear All, >>> >>> I am solving a linear system arising from 9-point discretization of >>> Poisson equation to generate grid. KSP solvers are giving nice converged >>> result when I am dealing with a large matrix. But when I am trying to >>> implement KSP solvers when the matrix is smaller and the values are smaller >>> too, the solution is diverging. >>> Any suggestions how to get around this problem? >>> >>> >>> Regards, >>> Maahi Talukder >>> >>> >>> >>> >>>