Geometric partitioning made easier, even in parallel

• Authors: Michael T. Goodrich
• Venue: SCG '93 Proceedings of the ninth annual symposium on Computational geometry
• Year: 1993

We present a simple approach for constructing geometric partitions in a way that is easy to apply to new problems. We avoid the use of VC-dimension arguments, and, instead, base our arguments on a notion we call the scaffold dimension, which subsumes the VC-dimension and is simpler to apply. We show how to easily construct (1/r)-nets and (1/r)-approximations for range spaces with bounded scaffold dimension, which immediately implies simple algorithms for constructing (1/r)-cuttings (by straight-forward recursive subdivision methods). More significant than simply being a conceptual simplification of previous approaches, however, is that our methods lead to asymptotically faster and more-efficient EREW PRAM parallel algorithms for a number of computational geometry problems, including the development of the first optimal-work NC algorithm for the well-known 3-dimensional convex hull problem, which solves an open problem of Amato and Preparata. Interestingly, our approach also yields a faster sequential algorithm for the distance selection problem, by the parametric searching paradigm, which solves an open problem posed by Agarwal, Aronov, Sharir, and Suri, and reiterated by Dickerson and Drysdale.