Fix MPI tag collision Issue #68

Increased the maximum cell tag to 2^29 to prevent the MPI tag collision issue #68.

See merge request !82

Recover missing mpi_type definitions, remove unused variables, remove repeated drift flag, correct HAVE_MPI to WITH_MPI

MPI libraries offer affinity control so as a first guess we shouldn't attempt any control, this is really bad when running more than one rank on the same machine (threads pinned to same cores).

PASC paper



See merge request !80

Corrected the Wendland C2 kernel.

Still needs checking. @jwillis, can you check whether the number of neighbours is sensible with this version ?

The definition of kernels is still not completely optimal so minor changes may appear at a later stage in the project when nothing more urgent needs attention.

See merge request !77