DDE-SOLVER: A Maple Package For Discrete Differential Equations

Abstract: We introduce DDE-Solver, a Maple package designed for solving Discrete Differential Equations (DDEs). These equations are functional equations relating algebraically a formal power series F(t, u) with polynomial coefficients in a "catalytic" variable u, with specializations of it with respect to the catalytic variable. Such equations appear in enumerative combinatorics, for instance in the enumeration of maps. Bousquet-Melou and Jehanne showed in 2006 that when these equations are of a fixed point type in F, then F is an algebraic series. In the same paper, they proposed a systematic method for computing annihilating polynomials of these series. Bostan, Safey El Din and the author of this paper recently designed new efficient algorithms for computing these witnesses of algebraicity. This paper provides combinatorialists an automated tool in hand that solves DDEs using these algorithms. We also compare the timings of all these algorithms on DDEs from the literature.