HSL_MC68: Symmetric sparse matrix: compute elimination orderings

Given a symmetric sparse matrix \(\mathbf{A} = {\{a _{ij}\}} _{n \times n}\), HSL_MC68 computes elimination orderings that are suitable for use with a sparse direct solver. Currently the following choices are available

• Approximate minimum degree ordering (with provision for some dense, rows and columns) using MC47,

• Minimum degree ordering using the methodology of MA27,

• Nested bisection ordering using MeTiS,

• MA47 ordering for indefinite matrices which may generate a combination of both \(1 \times 1\) and \(2 \times 2\) pivots.