AbstractIn this paper, we study the problem of emulating

T_Gsteps of anN_G-node guest network,G, on anN_G-node host network,H. We call an emulationwork-preservingif the time required by the host,T_H, isO(T_GN_G/N_H), because then both the guest and host networks perform the same total work (i.e., processor-time product), Theta(T_GN_G), to within a constant factor. We say that an emulation occurs inreal-timeifT_H=O(T_G), because then the host emulates the guest with constant slowdown. In addition to describing several work-preserving and real-time emulations, we also provide a general model in which lower bounds can be proved. Some of the more interesting and diverse consequences of this work include:

- a proof that a linear array can emulate a (much larger) butterfly in a work-preserving fashion, but that a butterfly cannot emulate an expander (of any size) in a work-preserving fashion,
- a proof that a butterfly can emulate a shuffle-exchange network in a real-time work-preserving fashion, and vice versa,
- a proof that a butterfly can emulate a mesh (or an array of higher, but fixed, dimension) in a real-time work-preserving fashion, even though any
O(1)-to-1 embedding of anN-node mesh in anN-node butterfly has dilation Omega(logN), and- simple
O(N^2/log^2N)-area andO(N^{3/2}/log^{3/2}N)-volume layouts for theN-node shuffle-exchange network.The abstract is also available as a LaTeX file, a DVI file, or a PostScript file.

Preliminary versionA preliminary version of these results was presented in: Richard Koch, Tom Leighton, Bruce Maggs, Satish Rao, and Arnold Rosenberg. Work-preserving emulations of fixed-connection networks (extended abstract). In Proceedings of the Twenty First Annual ACM Symposium on Theory of Computing, pages 227-240, Seattle, Washington, 15-17 May 1989.

Categories and Subject Descriptors: C.1.2 [Processor Architectures]: Multiple Data Stream Architectures (Multiprocessors) --parallel processors; C.2.1 [Computer-Communication Networks]: Network Architecture and Design --network topology; F.1.1 [Computation by Abstract Devices]: Models of Computation --networks of machines; F.2.2 [Analysis of Algorithms and Problem Complexity]: Nonnumerical Algorithms and Problems --computations on discrete structures; G.2.1 [Discrete Mathematics]: Combinatorics --combinatorial algorithms; G.2.2 [Discrete Mathematics]: Graph Theory --graph algorithms

General Terms: Algorithms, Design, Theory

Additional Key Words and Phrases: Graph embeddings, network emulations, parallel architectures, processors arrays

Selected papers that cite this one

- F. Thomson Leighton, Bruce M. Maggs, and Ramesh K. Sitaraman. On the fault tolerance of some popular bounded-degree networks. SIAM Journal on Computing, 27(5):1303-1333, October 1998.

- Bruce M. Maggs, Friedhelm Meyer auf der Heide, and and Berthold Vöcking. Exploiting locality for data management in systems of limited bandwidth. In 38th Annual Symposium on Foundations of Computer Science, pages 284-293, Miami Beach, Florida, 20-22 October 1997. IEEE.

- Bruce M. Maggs and Eric J. Schwabe. Real-time emulations of bounded-degree networks. Information Processing Letters, 66(5):269-276, 16 June 1998.

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