[petsc-users] Structured (DMDA) vs Unstructured (DMPlex) meshes

[Barry Smith]

   The largest potential advantage of DMDA is likely the possibility of easily using geometric multigrid if it is appropriate for the problem (or subproblem of the problem) you are solving. The second advantage is, this depends on your PDE and discretization, the simplicity of your code, and what part of PETSc it depends on, if it doesn't depend on DMPLEX (and doesn't need to) then that is a good thing. Disadvantage of DMDA  is lack of flexibility in discretization, handling of non-standard boundary conditions, geometry.



> On Jul 17, 2023, at 12:42 PM, Miguel Angel Salazar de Troya <miguel.salazar at corintis.com> wrote:
> 
> Hello,
> 
> I am trying to understand if I should make the effort to make my code use structured meshes instead of unstructured ones. My domain is cartesian so that is the first check for structured meshes. However, the problem size I am looking at is ~20 million degrees of freedom. My understanding is that for this problem size, most of the time is spent on the solver. In this case, do structured meshes still have an advantage? Can they run Krylov methods faster than when using structured meshes? What about other solvers and preconditioners?
> 
> Thanks,
> Miguel