Abstract

In the collect problem [32], n processors in a shared-memory system must each learn the values of n registers. We give a randomized algorithm that solves the collect problem in O(n log 3 n) total read and write operations with high probability, even if timing is under the control of a content-oblivious adversary (a slight weakening of the usual adaptive adversary). This improves on both the trivial upper bound of O(n 2 ) steps and the best previously known bound of O(n 3=2 log n) steps, and is close to the lower bound of \Omega\Gamma n log n) steps. Furthermore, we show how this algorithm can be used to obtain a multi-use cooperative collect protocol that is O(log 3 n)-competitive in the latency model of Ajtai et al.[3] and O(n 1=2 log 3=2 n)-competitive in the throughput model of Aspnes and Waarts [10]; in both cases the competitive ratios are within a polylogarithmic factor of optimal.

Citations