 This solution was first proposed in 1986 by Ciccotti and Ryckaert under the title "the matrix method", yet differed in the solution of the linear system of equations.Ciccotti and Ryckaert suggest inverting the matrix formula_21 directly, yet doing so only once, in the first iteration.The first iteration then costs formula_49 operations, whereas the following iterations cost only formula_47 operations (for the matrix-vector multiplication).