Improved Bounds and Schemes for the Declustering Problem

The declustering problem is to allocate given data on parallel working storage devices in such a manner that typical requests find their data evenly distributed on the devices. Using deep results from discrepancy theory, we improve previous work of several authors concerning range queries to higher-dimensional data. We give a declustering scheme with an additive error of Od(log d−1 M) independent of the data size, where d is the dimension, M the number of storage devices and d − 1 does not exceed the smallest prime power in the canonical decomposition of M into prime powers. In particular, our schemes work for arbitrary M in dimensions two and three. For general d, they work for all M ≥ d− 1 that are powers of two. Concerning lower bounds, we show that a recent proof of a Ωd(log d−1 2 M) bound contains an error. We close the gap in the proof and thus establish the bound. supported by the DFG-Graduiertenkolleg 357 “Effiziente Algorithmen und Mehrskalenmethoden”. Max–Planck–Institut für Informatik, Saarbrücken, Germany. Max–Planck–Institut für Informatik, Saarbrücken, Germany. Institut für Informatik und Praktische Mathematik, Christian-Albrechts-Universität zu Kiel, Germany