CudaPre2D: A Straightforward Preprocessing Approach for Accelerating 2D Convex Hull Computations on the GPU

An effective strategy for accelerating the calculation of convex hulls for planar point sets is to filter the input points by discarding interior points. In this paper, we present such a straightforward preprocessing approach by exploiting the modern Graphics Processing Unit. The basic idea behind our approach is to discard the points that locate inside a convex polygon formed by 16 extreme points. Due to the fact that the extreme points of a planar point set do not alter when all points are rotated with the same angle in the plane, four groups of extreme points with min or max x or y coordinates can be found in the original point set and three rotated point sets. These 16 extreme points are then used to form a planar convex polygon. We check all input points and discard the points that locate inside the convex polygon, and then use the remaining points to calculate the desired convex hull. Experimental results show that: when employing the proposed preprocessing algorithm, it achieves the speedups of about 4x ~ 5x on average and 5x ~ 6x in the best cases over the cases where the proposed approach is not used. In addition, more than 99% input points can be discarded in most experimental tests.