Can be uninitialized when task is MPI

Use a dedicated MPI type for the pcells. Also use the m-pole MPI type for the communications instead of MPI_BYTE.

Traced the bug back to the splitting condition in scheduler_splittask not being symmetric because of rounding

Matthieu Schaller authored Aug 08, 2018 and Matthieu Schaller committed Aug 10, 2018

Allow the task splitting routine to split gravity tasks and replace them by M-M tasks when gravity is on.

Currently ParMETIS is used exclusively when it is available, it is not an error to configure with both METIS and ParMETIS

This reverts commit 004fd34d.

Use the correct PARMETIS defines, not the old style METIS

The position of these costs in the solution, so shouldn't be used in the weights

rolled back the changes to space_split_mapper as the old version was faster, but kept the part-gpart relinking changes.