Multiple MR level

[MaxThevenet]

All MR simulation have been done with max_level = 1 so far. We should try and go to higher levels. That will probably require changes in the API and in the code (sub-cycling is not recursive so far).

[RemiLehe]

There is also an issue with charge/current deposition with max_level >= 2

Pasted discussion from Slack:

Let us consider particles that are in a patch of the 2nd refinement level. Then:

• The particles deposit in rhof[2]
• In SyncRho, rhof[2] (non-empty) is interpolated into rhoc[2], rhof[1] (empty so far) is interpolated into rhoc[1] (hence empty as well)
• Later in SyncRho, rhoc[2] is summed into rhof[1] and rhoc[1] (empty so far) is summed into rhof[0] (hence empty as well) So at the end of SyncRho, rhoc[1] and rhof[0] will be empty. In other other words, the information of the particles in the 2nd refinement level has not trickled down to the mother grid.