Remarkably, many of the most basic aspects of collisional N-body simulations remain unknown. While much practical progress has been made over the last 45 years in terms of producing efficient codes, we know little of the general landscape of possibly quite different codes. What is needed for a more basic exploration is a flexible tool box that will allow far more fine grained investigations than are currently possible. I will report on a new effort, in collaboration with Jun Makino (see http://www.ArtCompSci.org) to build such a software environment. As an example, I will describe simulations were particle are allowed to use not only individual time steps, but also individual integration algorithms, from a choice that includes Hermite methods,
arbitrary-order multi-step methods as well as Runge-Kutta methods (which so far have not been available in individual time step form).
Back to Workshop II: N-Body Problems in Astrophysics
In addition, I will report on the first three years of the MODEST initiative, short for MOdeling DEnse STellar systems, (see http://www.manybody.org/modest.html). The goal here is to connect existing codes that can handle stellar dynamics, stellar evolution, and stellar dynamics. Issues related to interface specification, code validation, maintenance, and extensibility are the focus of ten different working groups
within the MODEST initiative. Each year, several MODEST workshops are held, some of which take the form of summer schools for graduate students and postdocs.