When creating the ghost tasks as well as the hydro-related subgrid tasks, only do so if the cell actually has any gas particle.

When linking the hierarchical gravity tasks, do not link to the parents if we are at the super-level.

Matthieu Schaller authored Nov 08, 2018 and Matthieu Schaller committed Nov 10, 2018

More uniform way of looping over pairs of top-level cells for the proxy construction, gravity pairs construction and hydro pairs construction.

Replace the absolute depth criterion for gravity tasks with a relative criterion based on the local depth of the tree.