The solution of sparse matrices in CATHENA

CATHENA presently uses the Harwell MA28 routines to solve the sparse matrices generated by the thermalhydraulics numerical method. The objective of this paper is to present an overview of commonly used sparse matrix solution techniques, and to examine the potential benefits of using other solvers in CATHENA. Previous out-board tests have shown that the SMPAK, Y12M, and IMSL direct solvers and the PCGPAK3 iterative solver may be competitive with the MA28 solver. In the present investigation the performance of these solvers was tested in-situ in CATHENA using a wide variety of different simulations. The results indicate the SMPAK and Y12M direct solvers show the best performance and can increase the overall simulation speed by up to a factor of 8 for the largest CATHENA simulations tested. (author)