Adaptive meshing options

[rnpratoori]

Hello,

I am using pre split distributed mesh for my simulation and I want to use adaptive meshing. The initial mesh is at the finest I need and I need coarsening or refinement of maximum 3 levels.
The initial mesh is 400x200x200 which is also the finest I need. The coarsest can be 50x25x25. What options should I choose for the adaptivity?

I used the below options and the finest element I obtained is finer than the initial mesh I started with:

[Adaptivity]
        coarsen_fraction = 0.1
        refine_fraction = 0.7
        max_h_level = 3
    []

[GiudGiud]

Hello

The initial mesh is at the finest I need and I need coarsening or refinement of maximum 3 levels.

The initial mesh should start coarse and we can refine it, and coarsen back what has been refined.

Coarsening the initial mesh is not by and large not implemented as it is a very complex problem for a general mesh.

[rnpratoori]

So, I should start with 50x25x25 and use uniform refine before I use adaptivity? How would having a presplit mesh influence this?

[GiudGiud]

presplit is fine because we save the adaptivity pattern correctly when using split meshes.
So you can refine either before or after loading the split, as you prefer.

So, I should start with 50x25x25 and use uniform refine before I use adaptivity?

yes either that or set the adaptivity to do local refinement rather than coarsening, because it saves a step (the uniform refine)