Numerical Realization of Shallow Water Bodies’ Hydrodynamics Grid Equations using Tridiagonal Preconditioner in Areas of Complex Shape

Introduction. Mathematical modeling of hydrodynamic processes in shallow reservoirs of complex geometry in the presence of coastal engineering systems requires an integrated approach in the development of algorithms for constructing computational grids and methods for solving grid equations. The work is devoted to the description of algorithms that allow to reduce the time for solving SLAE by using an algorithm for processing overlapping geometry segments and organizing parallel pipeline calculations. The aim of the work is to compare the acceleration of parallel algorithms for the methods of Seidel, Jacobi, modified alternately triangular method and the method of solving grid equations with tridiagonal preconditioner depending on the number of computational nodes.

Materials and Methods. The numerical implementation of the modified alternating-triangular iterative method for solving grid equations (MATM) of high dimension is based on parallel algorithms based on a conveyor computing process. The decomposition of the computational domain for the organization of the pipeline calculation process has been performed. A graph model is introduced that allows to fix the connections between neighboring fragments of the computational grid. To describe the complex geometry of a reservoir, including coastal structures, an algorithm for overlapping geometry segments is proposed.

Results. It was found that the efficiency of implementing one step of the MATM on the GPU depends only on the number of threads along the Oz axis, and the step execution time is inversely proportional to the number of nodes of the computational grid along the Oz axis. Therefore, it is recommended to decompose the computational domain into parallelepipeds in such a way that the size along the Oz axis is maximum, and the size along the Ox axis is minimal. Thanks to the algorithm for combining geometry segments, it was possible to speed up the calculation by 14–27 %.

Discussion and Conclusions. An algorithm has been developed and numerically implemented for solving a system of large-dimensional grid equations arising during the discretization of the shallow water bodies’ hydrodynamics problem by MATM, adapted for heterogeneous computing systems. The graph model of a parallel-pipeline computing process is proposed. The connection of water body’s geometry segments allowed to reduce the number of computational operations and increase the speed of calculations. The efficiency of parallel algorithms for the methods of Seidel, Jacobi, modified alternately triangular method and the method of solving grid equations for problems of hydrodynamics in flat areas, depending on the number of computational nodes, is compared.

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