Towards a Tighter Coupling of Bottom-Up and Top-Down Sparse Matrix Ordering Methods

Most state-of-the-art ordering schemes for sparse matrices are a hybrid of a bottom-up method such as minimum degree and a top down scheme such as George’s nested dissection. In this paper we present an ordering algorithm that achieves a tighter coupling of bottom-up and topdown methods. In our methodology vertex separators are interpreted as the boundaries of the last elements in a bottom-up ordering. As a consequence, we are using bottom-up techniques like quotient graphs and special node selection strategies for the construction of vertex separators. Once all separators have been found, we are using them as a skeleton for the computation of several bottom-up orderings. Experimental results show that the orderings obtained by our scheme are in general better than those obtained by other popular ordering codes.