Minimal fill in O(n2.69)O(n2.69) time

We show that it is possible to find a minimal fill ordering of a graph in O(n2.69)O(n2.69) time. Previous algorithms for the problem required Ω(n3)Ω(n3) time on dense graphs. The algorithm uses fast matrix multiplication to produce the same ordering of vertices as Tarjan's well known LEX-M algorithm.