OAHM: A fortran subroutine for solving a class of unsymmetric linear systems of equations
G. J. Makinson, A. A. Shah · Communications in Applied Numerical Methods · 1986
Abstract The discretization, by means of the usual 5‐point difference formulae, of an elliptic partial differential equation can give rise to an unsymmetric and sparse linear system of equations in which the matrix A of coefficients is an M‐matrix such that each element in the upper/lower triangular part is greater than or equal to the respective element in the lower/upper triangular part. In other applications, dense matrices with the same property can arise. A FORTRAN subroutine called OAHM is presented for the solution of such systems which can be easily modified to deal efficiently with the sparse case. The OAHM subroutine uses a regular splitting and the convergence is therefore guaranteed.