Practical parallel list ranking

Abstract

Parallel list ranking is a hard problem due to its extreme degree of irregularity. Also because of its linear sequential complexity, it requires considerable effort to just reach speed-up one (break even). In this paper, we address the question of how to solve the list-ranking problem for lists of length up to 2·108 in practice: we consider implementations on the Intel Paragon, whose PUs are laid-out as a grid.It turns out that pointer jumping, independent-set removal and sparse ruling sets, all have practical importance for current systems. For the sparse-ruling-set algorithm the speed-up strongly increases with the number k of nodes per PU, to finally reach 27 with 100 PUs, for k=2·106.KeywordsParallel AlgorithmInterconnection NetworkActive NodeDouble PointerSequential AlgorithmThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.