We investigate the parallel performance of an iterative solver for 3D heterogeneous Helmholtz problems related to applications in seismic wave propagation. For large 3D problems, the computation is no longer feasible on a single processor, and the memory requirements increase rapidly. Therefore, parallelization of the solver is needed. We employ a complex shifted-Laplace preconditioner combined with the Bi-CGSTAB iterative method and use a multigrid method to approximate the inverse of the resulting preconditioning operator. A 3D multigrid method with 2D semi-coarsening is employed. We show numerical results for large problems arising in geophysical applications.

The parallel performance of a numerical solution method for the scalar 2D Helmholtz equation written for inhomogeneous media is studied. The numerical solution is obtained by an iterative method applied to the preconditioned linear system which has been derived from a finite difference discretization. The preconditioner is approximately inverted using multigrid iterations. Parallel execution is implemented using the MPI library. Only a few iterations are required to solve numerically the so-called full Marmousi problem [Bourgeois, A., et al. in The Marmousi Experience, Proceedings of the 1990 EAEG Workshop on Practical Aspects of Seismic Data Inversion: Eur. Assoc. Expl. Geophys., pp. 5-16 (1991)] for the high frequency range.

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