Design features of a frontal code for solving sparse unsymmetric linear systems out-of-core

We discuss design features of a code which solves sparse unsymmetric systems of linear equations using a frontal method. We consider in particular the user interface, the internal data structures, the pivoting strategy, and the isolation of machine dependencies. We illustrate the performance of our code on a variety of test problems on both the IBM 3033 and the CRAY-1.