Enabling Space Filling Curves parallel mesh partitioning in Alya

Larger supercomputers allow the resolution of more complex problems that require denser and thus also larger meshes. In this context, and extrapolating to the Exascale paradigm, meshing operations such as generation, deformation, adaptation/regeneration or partition/load balance, become a critical issue within the simulation workflow. In this paper we focus on the mesh partitioning, presenting the work carried out in the context of a PRACE Preparatory Access Project to enable a Space Filling Curve (SFC) based partitioner in the computational mechanics code Alya. In particular, we have run our tests on the MareNostrum III supercomputer of the Barcelona Supercomputing Center. SFC partitioning is a fast and scalable alternative to the standard graph based partitioning and in some cases provides better solutions. We show our approach at implementing a parallel SFC based partitioner. We have avoided any computing or memory bottleneck in the algorithm, while we have imposed that the solution achieved is independent (discounting rounding off errors) of the number of parallel processes used to compute it.