Abstract
In this paper we focus on the problem of designing very fast parallel algorithms for constructing the upper envelope of straight-line segments that achieve the O(n logH) work-bound for input size n and output size H. Our algorithms are designed for the arbitrary CRCW PRAM model. We first describe an O(log n · (logH + log log n)) time deterministic algorithm for the problem, that achieves O(n logH) work bound for H = Ω(log n). We present a fast randomized algorithm that runs in expected time O(logH · log n) with high probability and does O(n logH) work. For log H = Ω(log log n), we can achieve the running time of O(log H) while simultaneously keeping the work optimal. We also present a fast randomized algorithm that runs in Õ(log n/ log k) time with nk processors, k > logΩ(1) n. The algorithms do not assume any input distribution and the running times hold with high probability.
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Gupta, N., Chopra, S., Sen, S. (2001). Optimal, Output-Sensitive Algorithms for Constructing Upper Envelope of Line Segments in Parallel. In: Hariharan, R., Vinay, V., Mukund, M. (eds) FST TCS 2001: Foundations of Software Technology and Theoretical Computer Science. FSTTCS 2001. Lecture Notes in Computer Science, vol 2245. Springer, Berlin, Heidelberg. https://doi.org/10.1007/3-540-45294-X_16
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DOI: https://doi.org/10.1007/3-540-45294-X_16
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