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We extend the frontal method for solving linear systems of equations by permitting more than one front to occur at the same time. This enables us to develop code for general symmetric systems. We discuss the orgamzation and implementatmn of a multifrontal code which uses the minimum-degree ordering and indicate how we can solve indefinite systems in a(More)
We describe the design of a new code for the solution of sparse indefinite symmetric linear systems of equations. The principal difference between this new code and earlier work lies in the exploitation of the additional sparsity available when the matrix has a significant number of zero diagonal entries. Other new features have been included to enhance the(More)
We describe the design of a new code that supersedes the Harwell Subroutine Library (HSL) code MA28 for the direct solution of sparse unsymmetric linear systems of equations. The principal differences lie in a new factorization entry that includes row permutations for stability without an overhead of greater complexity than that of the factorization itself,(More)
We describe the design of a new code for the solution of sparse indefinite symmetric linear systems of equations. It is intended to complement the Harwell code MA27. The principal difference between the two codes lies in the exploitation by MA47 of the additional sparsity available when the matrix has some zero diagonal entries. Other features have been(More)
We describe the design of a new code for the direct solution of sparse unsymmetric linear systems of equations. The new code utilizes a novel restructuring of the symbolic and numerical phases, which increases speed and saves storage without sacrifice of numerical stability. Other features include switching to full-matrix processing in all phases of the(More)
We describe the design of a new code for direct solution of sparse unsymmetric linear systems of equations from finite-element applications. The code accepts both the finite-element structure and the matrix coefficients in the form of finite elements. We show that the sparsity analysis using the knowledge about the finite-element structure is economic in(More)
An implementation of Tarj an's algorithm for symmetrically permuting a given matrix to block tmangular form is described. The discussion includes a flowchart of the algorithm, a complexity analysis, and a comparison with the earlier widely used algorithm of Sargent and Westerberg. T~ming results are presented from several experiments using the code(More)