Comparison between substructure method and domain decomposition method

Advantages and drawbacks of SSM [SubStructure Method (direct scheme)] in contrast with DDM [Domain Decomposition Method (iterative scheme)] is investigated. In higher-order nonlinear problem, several iterative methods show slow convergence or are hard to converge. In such case, the direct scheme will be inevitable. In this paper, direct scheme applied to substructure method which is suitable for parallel computer has been examined. In the previous year, a research-program was built to investigate parallel efficiency of both direct and iterative schemes by Cray-T3D. The program has been enhanced for this research by adding hierarchical substructure method as well as nonlinear capabilities and has been tuned up for VPP300 supercomputer. Using some test problems with over 1,000,000 DOF (degrees of freedom), are examined characteristics of substructure method and domain decomposition methods. Consequently, it has been shown that substructure method has superiority in some specific problems and requires much more memories comparing with the other in general. Domain decomposition method shows slow convergence in some problems, but it is superior in most cases to substructure method. It is shown that hierarchical substructure method has high efficiency in computational time, too.