I am solving one of the PETSc 3D Laplacian examples with a 7 point stencil of width 1 and in a separate baseline with a 13 point stencil of width 2 (a more accurate mesh).
What worked fast in terms of solvers and pre-conditioner for the less accurate baseline was non-optimal (very slow) for the more accurate baseline. Are there a set of general rules for picking preconditioners and solvers when solving a 3D Laplace's equation? Thank you for your time John Alletto
