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1.4 Outline of the results

The basis of most of the results in this paper is a proof that a variant of Ranade's algorithm can be used to schedule any set of N packets whose paths have congestion c on a bounded-degree leveled network with depth L in tex2html_wrap_inline1961 steps using constant-size queues. The algorithm is randomized, but requires only tex2html_wrap_inline1963 bits of randomness to succeed with high probability. The proof of this result is included in Section 2. Curiously, the proof is simpler than the previous proof of the same result applied specifically to routing random paths in butterflies [29], and allows for improved constant factors.

In Sections 3 through 10 we examine the many applications of the tex2html_wrap_inline1965 -step scheduling algorithm for leveled networks. These applications include routing algorithms for meshes, butterflies, shuffle-exchange networks, multidimensional arrays and hypercubes, and fat-trees. Section 3 presents the simplest application: routing N packets in tex2html_wrap_inline1969 steps on a tex2html_wrap_inline1971 mesh. Another simple application, described in Section 4, is an algorithm for routing N packets in tex2html_wrap_inline1975 steps on an N-node butterfly. It is not obvious that the scheduling algorithm can be applied to the shuffle-exchange network because it is not leveled. Nevertheless, in Section 5 we show how to route N-packets in tex2html_wrap_inline1981 steps on an N-node shuffle-exchange network by identifying a leveled structure in a large portion of the network. In Section 6 we present an algorithm for routing kN packets on an N-node k-dimensional array with maximum side length M in tex2html_wrap_inline1993 steps. In Section 7, we show how to adapt the scheduling algorithm to route a set of messages with load factor tex2html_wrap_inline1995 in tex2html_wrap_inline1997 steps on a fat-tree [21] with root capacity M.

The fat-tree routing algorithm leads to the construction of an area-universal network: an N-node network with area tex2html_wrap_inline2003 that can simulate any other network of area tex2html_wrap_inline2005 with slowdown tex2html_wrap_inline2007 . An analogous result is shown for a class of volume-universal networks.

Our sorting results are included in Sections 8 through 10. In particular, we describe an tex2html_wrap_inline2009 -step algorithm for sorting on an N-node butterfly or hypercube in Section 8, an tex2html_wrap_inline2013 -step algorithm for sorting on a shuffle-exchange network in Section 9, and an tex2html_wrap_inline2015 -step algorithm for sorting tex2html_wrap_inline2017 items on a k-dimensional array with side length M in Section 10.



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Next: 1.5 Some comments on Up: 1 Introduction Previous: 1.3 The application of



Bruce Maggs
Mon Jul 22 22:57:44 EDT 1996