Design of MA48: a code for the direct solution of sparse unsymmetric linear systems of equations

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 computation enabling the use of all three levels of BLAS, treatment of rectangular or rank-deficient matrices, partial factorization, and integrated facilities for iterative refinement and error estimation.