A note on preconditional diagonally dominant matrices

This note points out that the main results of [Appl. Math. Comput. 114 (2000) 255] is not true. We show that (1) Theorem 2.1 in [Appl. Math. Comput. 114 (2000) 255] is well known, (2) There are no nonsingular matrices satisfying the sufficient conditions for ensuring diagonally dominance given in Theorem 3.1, and (3) Theorem 4.1 for preconditioning p-cyclic matrices is not true. We also prove that p-cyclic matrices can be column diagonally preconditioned, with a special row permutation if required, to be row diagonally dominant under some assumptions.