Issue No. 10 - Oct. (1985 vol. 34)
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
The prefix computation problem is to compute all n initial products a
1 ∘ … ∘ a i, 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(n1-∊)(∊ > 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).
parallel prefix, Algorithms, parallel algorithms
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.