Issue No. 10 - Oct. (1985 vol. 34)

ISSN: 0018-9340

pp: 965-968

Clyde P. Kruskal , Department of Computer Science, University of Illinois, Urbana, IL 61801

Larry Rudolph , Department of Computer Science, Carnegie-Mellon University, Pittsburgh, PA 15213

Marc Snir , Institute of Mathematics and Computer Science, The Hebrew University of Jerusalem, Jerusalem, Israel

ABSTRACT

The prefix computation problem is to compute all n initial products a1 ∘ … ∘ ai , i = 1, …, n, of a set of n elements, where ∘ is an associative operation. We present an 0(((log n)/log(2n/p)) · (n/p)) time deterministic parallel algorithm using p ≤ n processors to solve the prefix computation problem, when the order of the elements is specified by a linked list. For p ≤ 0(n

^{1-∊})(∊ > 0 any constant), this algorithm achieves linear speedup. Such optimal speedup was previously achieved only by probabilistic algorithms. Our algorithms assume the weakest PRAM model, where shared memory locations can only be exclusively read or written (the EREW model).INDEX TERMS

parallel prefix, Algorithms, parallel algorithms

CITATION

C. P. Kruskal, L. Rudolph and M. Snir, "The power of parallel prefix," in

*IEEE Transactions on Computers*, vol. 34, no. , pp. 965-968, 1985.

doi:10.1109/TC.1985.6312202

CITATIONS