An Approach for Parallel Loading and Pre-Processing of Unstructured Meshes Stored in Spatially Scattered Fashion

This paper presents a workflow for parallel loading of database files containing sequentially stored unstructured meshes that are not considered to be efficiently read in parallel. In such a file consecutive elements are not spatially located and their respective nodes are at unknown positions in the file. This makes parallel loading challenging since adjacent elements are on different MPI processes, and their respective nodes are on unknown MPI processes. These two facts lead to a high communication overhead and very poor scalability if not addressed properly. In a standard approach, a sequentially stored mesh is sequentially converted to a particular parallel format accepted by a solver. This represents a significant bottleneck. Our proposed algorithm demonstrates that this bottleneck can be overcome, since it is able to (i) efficiently recreate an arbitrary stored sequential mesh in the distributed memory of a supercomputer without gathering the information into a single MPI rank, and (ii) prepare the mesh for massively parallel solvers.