Effect of the storage format of sparse linear systems on parallel CFD computations

Implicit solutions of Computational Fluid Dynamics (CFD) problems require the iterative solution of very large systems of equations. This paper investigates the comparative costs of two storage formats for large sparse matrices, namely the Compressed Sparse Row (CSR) and BSR storage formats, for various solution strategies. The block structure of the BSR storage format is highly advantageous in applications which have several degrees of freedom per nodal point, such as CFD calculations. Depending on the solution strategy, overall reductions in both CPU time and memory can be as high as 30–50%. Such gains are especially appreciable in large 3D flow calculations.