Sorts bug fix

Fixes #488 (closed).

This possibly fixes an old bug that would seldomly lead to unsorted cells in the pair interactions. #488 (closed) was the first time I could catch it in an easily reproducible scenario.

Does the fix in the recursion of runner_do_sort() make sense to you as well? The idea is that we set the sort flag in the unskip based on the old value of dx_max_part so we should use that same value here and not the one obtained after the drift that just happened.

@jborrow could you run the hydro test suite on this to check that it does not break anything?

Wow, that was quite well hidden. Nice catch!

LGTM of course :)

assigned to @pdraper

I think I want a month of my life back....

You can have a month of mine.

Spoiler alert: it involves nappies and writing machine-learning papers.

mentioned in merge request !665 (merged)

resolved all discussions

mentioned in commit 46410b87

mentioned in commit 2a805a92

merged

mentioned in commit dfeb0527