[petsc-users] SOLVE + PC combination for 7 point stencil (unstructured) poisson solution

[Vanella, Marcos (Fed) via petsc-users]

Hi, I was wondering if anyone has experience on what combinations are more 
efficient to solve a Poisson problem derived from a 7 point stencil on a single 
mesh (serial).
I've been doing some tests of multigrid and cholesky on a 50^3 mesh. -pc_type 
mg takes about 75% more time than -pc_type cholesky -pc_factor_mat_solver_type 
cholmod for the case I'm testing.
I'm new to PETSc so any suggestions are most welcome and appreciated,
Marcos