Add cell links for gravity tasks

Add links for gravity tasks so that we can discover these from cells.

Also expunge external_gravity from cell.h.

mentioned in merge request !267 (merged)

I wonder if these should be 5 and 4, if other gravity tasks were enabled.

So, we should have 26 * 3 (density, force, grav) pairs and up to 4 (density, force, grav, ext_grav) self. So in total:

s->tot_cells * (26 * 3 + 4)

or for GIZMO:

s->tot_cells * (26 * 4 + 4)

Added 1 commit:

• 7f64ed3b - Change allocations of size_links as suggested by Matthieu

Thanks, that makes more sense. I've pushed the fix.

Added 1 commit:

• 6f12fe19 - Also update the counter of gravity self/pair tasks when linking them.

For consistency with the rest I have also added an update to the nr_grav counters. These counters are never used btw...

Now, shouldn't we do this (and the linking) in engine_count_and_link task as is done for the hydro-density tasks ?

If you think that makes more sense, but there are a number of engine_link calls scattered in other places, so I just went for the most obvious places. I'll leave the choice to you as the most familiar with this area.

Added 1 commit:

• babf1c74 - Add the gravity link in 'engine_count_and_link_tasks()'

Added 1 commit:

• 59d5eb87 - Added temporary variables in 'engine_count_and_link_tasks()'

Ok, I have done exactly that. Would you like to look at it before the merge ?

Reassigned to @pdraper

Yes, just merged this to mark_tasks_in_drift2 and external gravity is working, so it all looks good to go now. I'll accept.

Status changed to merged

mentioned in commit cd34c3b6

Spoke too soon, came across a missing (re)initialisation which is fixed in e90dd24b. Without that the Multitype test gets stuck in a loop when iterating the grav links.