Updated the way we converge towards the smoothing length. We now use a Newton-Raphson scheme. This applies to the Gadget-2 scheme.

Be more conservative when splitting self-task into subs. We don't want to trigger a rebuild straight after.

Modified the splitting rule for self tasks to be less conservative. Added proper documentation of the splitting conditions.

Also create functions to decide when to rebuild and when to split a task. Update the rebuild and split condition to correctly use kernel_gamma.

Add new function to decide on recursion with in a sub_pair task. Makes sure all recursion tests are identical.

Completes d8025de1

Use dx_max_sort_old and not dx_max_sort when checking whether cells have been sorted in DOPAIR1_BRANCH()

Updated the tests to use the new cell properties for sorting and not the old ones. All tests now run smoothly. Make sure the xparts array actually exist in a cell before reinitialising its particles.

Documentation update. The MPI and vectorization macros will be expanded when generating the doxygen files.

don't re-sort stale dimensions on cleanup as we don't know if we're going to need these at all. they will get resorted if and when needed.

change sort task flags to be zero by default and only switch on those that are needed, avoids pre-emptively computing all the sorts for a cell since they may never be needed between two sort cleanups.

Created a branching function for DOPAIR1, so that the scalar version is called if it is a corner interaction when the code is vectorised. Also fixed a bug with runner_dopair1_density_vec so that hi_max and hj_max are used to find how many particles to read into the cache.

replace 'wait' with 'implicit' in scheduler_addtask, as we weren't using the former and could use the latter.

Disabled GIZMO particle steering for vacuum particles. Disabled warning messages for unphysical values and pathological configurations.

Correctly initialise the signal velocity of the SPH particles in the Minimal and Pressure-Entropy cases.