Add a separate timer for subset sub-cell tasks. Write the timers to a file. Make sure we can compile without timers. Add a configure option to switch the timers on.

Don't lock the tree for the grav_init task. Don't call the unsorted pairs at all. Skip the entire zeroing loop when no xparts in runner_do_sort()

sort and drift on-demand in a consistent way. yes, even for the force loops as changes in the smoothing lengths may require a re-sort or interactions at a different level.

Call runner_doself1_density_vec in DOSUB_SELF1 if vectorisation is enabled. Changed all WITH_VECTORIZATION macros to WITH_OLD_VECTORIZATION.

one big messy commit for the status quo, forces sorts of the active cells in each step, does not use task_type_sub_*, and probably sorts some cells twice. but it works.

Check that the particles interacting in the SELF or PAIR tasks have been properly drifted to the current time

Added debugging checks to the pair and self tasks to make sure cells have been drifted to this point before they get updated.

Added debugging checks to the pair and self tasks to make sure cells have been drifted to this point before they get updated.

Check whether particles or cells are active via an inlined function rather than via a direct read of engine->ti_current

Replaced all calls to fminf and fmaxf by the macros that was added for the integer min/max functions.