Emulating Direct Products by Index-Shuffle Graphs

  • Authors:
  • B. Obrenic

  • Affiliations:
  • -

  • Venue:
  • IPPS '98 Proceedings of the 12th. International Parallel Processing Symposium on International Parallel Processing Symposium
  • Year:
  • 1998

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Abstract

In the theoretical framework of graph embedding and network emulations, we show that the index-shuffle graph (a bounded-degree hypercube-like interconnection network, recently introduced by [ Baumslag and Obrenic (1997): Index-Shuffle Graphs, ...]) efficiently approximates the hypercube in general computations, by emulating the direct-product structure of the hypercube.In the direct product G = G1 脳 G2 脳 ... 脳 Gk let an factor Gi be an instance of any of the three following graphs: cycle, complete binary tree, X - tree. Given an N-node index-shuffle graph 驴n, where N = 2n, and any collection of 2l copies of G, such that: |Gi| 驴 2ni, for i = 1, ... k, where l+ 驴i=1k 驴 and 2驴log2k驴 驴 (max1驴i驴k ni) 驴 n, 驴n emulates any factor Gi, in all copies of G in this collection with slowdown O(log k + log ni) = O(log log N).As a consequence of these and previous results, the index-shuffle graph emerges as a uniqely "universal" bounded-degree hypercube substitute. The index-shuffle graph emulates (multiple copies of) multi-dimensional tori and meshes of trees (or X-trees) with slowdown doubly logarithmic in the size of the graph, which currently cannot be achieved by either butterfiles or shuffles. Furthermore, the butterfly is emulated by its (like-sized) index-shuffle graph with slowdown triply logarithmic in the size ofihe graph, which is currently impossible by shuffles. Finally the index-shuffle graph contains the (equal-sized) shuffle-exchange graph, thus demonstrating communication power not known to be present in the hypercube itself.