List Ranking and List Scan on the

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Although parallel algorithms using linked lists, trees, and graphs have been studied extensively by the research community, implementations have met with limited success, even for the simplest algorithms. In this paper we present our results of a careful implementation study of parallel list ranking (and the related list-scan operation) and show that it can have substantial speed up over fast workstations. Obtaining good parallel performance for list ranking is a challenge for two reasons. First, although there are many asymptotic work-efficient algorithms, it is hard to keep the constants comparable to those of the sequential algorithm. In this paper we introduce a new parallel algorithm that both is work efficient and has small constant but sacrifices logarithmic time; it achieves only an O(log 2 n) time. We contend, however, that work efficiency and small constants are more important, given that multiprocessor machines are used for problems that are much larger than the...

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