Face coloring in unstructured CFD codes

We propose an algorithm for preventing race conditions in the evaluation of the surface integral contributions in edge-based CFD solvers by coloring the faces (or edges) of the computational mesh. We use a partitioning algorithm that separates the edges of triangular elements into three groups, the faces of quadrilateral and tetrahedral elements into four groups, and the faces of hexahedral elements into six groups. Our method is also applicable to hybrid meshes. We then extend this partitioning to adaptively refined, nonconforming meshes. We use the coloring to reduce code memory requirements by eliminating buffering. The coloring is also used to renumber and reorder elemental data to optimize reading and writing to memory, thus reducing access latencies and accelerating computations.