NewMinLevel sets the minimum level that will be updated for the simulation. If you are running a simulation with MaxLevel==3, you will have four levels of AMR (0,1,2,3). If you want to restart the simulation in fixed grid you can set NewMinLevel=3. When the simulation restarts, it will take an entire root step while refining the entire domain out to level 3. From then on, it will only update level 3 - effectively allowing one to restart in fixed grid. The other levels will still be there - and they will be in the chombo dumps, but since the entire grid will have data on level 3, the out-dated data should not be used in visualizations or in analysis of fixed-grid stuff… I'm not sure how this will work with elliptic solvers - but if Info%level < MinLevel you probably shouldn't use the info data for any computation.

Since this keeps the tree structure, it still does the same time-stepping, so it would take 8 level 3 time steps each call to AMR.

It would be simple enough to coarsen the data back from level 3 if you wanted coarse data for levels 0, 1, or 2 and you could in principle drop minlevel back to 0, but that functionality is not there yet. Currently you can have modules increase minlevel during the simulation by setting newminlevel within b4rootstep on the master processor.

I've tested it with timestepmethod = 1 and 3, and in 3D-MHD and it doesn't complain about divergences so it seems pretty stable at this point, but let me know if you have any issues with it. ~JC