A general approach for cache-oblivious range reporting and approximate range counting

We present cache-oblivious solutions to two important variants of range searching: range reporting and approximate range counting. The main contribution of our paper is a general approach for constructing cache-oblivious data structures that provide relative (1+ε)-approximations for a general class of range counting queries. This class includes three-sided range counting, 3-d dominance counting, and 3-d halfspace range counting. Our technique allows us to obtain data structures that use linear space and answer queries in the optimal query bound of O(logB(N/K)) block transfers in the worst case, where K is the number of points in the query range. Using the same technique, we also obtain the first approximate 3-d halfspace range counting and 3-d dominance counting data structures with a worst-case query time of O(log(N/K)) in internal memory. An easy but important consequence of our main result is the existence of O(N log N)-space cache-oblivious data structures with an optimal query bound of O(logBN + K/B) block transfers for the reporting versions of the above problems. Using standard reductions, these data structures allow us to obtain the first cache-oblivious data structures that use near-linear space and achieve the optimal query bound for circular range reporting and K-nearest neighbour searching in the plane, as well as for orthogonal range reporting in three dimensions.