Starting algorithms for a class of RK methods for index-2 DAEs

When semiexplicit differential-algebraic equations are solved with implicit Runge-Kutta methods (RK), the computational effort is dominated by the cost of solving the nonlinear systems, and therefore it is important to have good starting values to begin the iterations. For semiexplicit index-2 DAEs, starting algorithms without additional cost for RK methods with regular matrix coefficient were studied in a previous paper. However, the regularity condition on the matrix coefficient excludes some interesting methods like Lobatto IIIa and ESDIRK methods. In this paper, we study starting algorithms, without additional computational cost, for a class of Runge-Kutta methods in the case of index-2 DAEs.