NDLI: On Non-Approximability of Coarse-Grained Workflow Grid Scheduling

Content Provider	IEEE Xplore Digital Library
Author	Fujimoto, N.
Copyright Year	2008
Description	Author affiliation: Grad. Sch. of Inf. Sci. & Technol., Osaka Univ., Toyonaka (Fujimoto, N.)
Abstract	Scheduling a scientific workflow onto a computational grid is considered. A computational grid can be regarded as a heterogeneous parallel machine such that the speed of each processor varies over time. A scientific workflow can be modeled as a DAG of tasks. This paper focuses on a coarse-grained workflow. So, any communication delay between tasks is negligible because computation time of every task is much longer than the corresponding communication delay. Hence, in this paper, a coarse-grained workflow grid scheduling problem (WSP for short) is defined as an extension of the classical precedence constrained scheduling problem over a uniform parallel machine with processor speed fluctuation. The objective of our problem is to minimize the makespan of a schedule. It is known that no approximation algorithm exist if a grid has a very long period with zero spare computing power. However, such situation seems to be unrealistic. This paper gives a proof that, unless P = NP, WSP is not approximable within a factor of 1.5 even if accurate performance prediction is possible, all processors have the same peak speed, and speed of every processor at any time is restricted to either 50% or 100% of the peak speed. Since the quite restricted problem is not approximable, any more general problem such that accurate performance prediction is impossible and/or processor speed fluctuation pattern is not restricted is also not approximable. So, the proof implies that WSP is not approximable within a factor of 1.5 in realistic grid environment unless P = NP.
Starting Page	127
Ending Page	132
File Size	313876
Page Count	6
File Format	PDF
ISBN	9780769531250
ISSN	10874089
DOI	10.1109/I-SPAN.2008.35
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-05-07
Publisher Place	Australia
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Processor scheduling Optimal scheduling Grid computing Parallel machines Fluctuations Delay effects Concurrent computing Approximation algorithms Scheduling algorithm Parallel architectures non-approximability grid computing workflow scheduling
Content Type	Text
Resource Type	Article

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