CRAYFISHPAK

CRAYFISHPAK is a package of FORTRAN 77 subroutines for solving finite difference approximations to two-and three-dimensional Helmholtz equations in cartesian, cylindrical, and spherical coordinates with any combination of periodic or specifications of the solution or its normal derivative on the boundaries of a regular domain. Users may specify either standard (grid-centerd variables) or staggered (cell-centered variables) grids. Highly vectorized Fast Fourier Transform and cyclic reduction algorithms are used to solve the linear systems of equations. Following the style and spirit of the well-known and heavily-used FISHPAK package, the sixteen CRAYFISHPAK drivers convert a straight-forward description of the equation, domain, and boundary conditions into a linear system of equations and call an appropriate solver routine that computes the solution. All singular problems and coordinate singularities are treated automatically. Extensive error checking of input parameters is performed to detect improperly specified problems. Designed for time-dependent--e.g. fluid-dynamics--applications, all routines have separate initialization subroutines that significantly reduce repeated solution times. For time-dependent applications where the Helmlhotz equation may require one half of the total model execution time, this new package has proven to significantly reduce computer modelling costs.

Agnes O' Gallagher

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