Deterministic on-line routing on area-universal networks

  • Authors:
  • Paul Bay;Gianfranco Bilardi

  • Affiliations:
  • Thinking Machines Corp., Cambridge, MA;Univ. di Padova, Padova, Italy

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1995

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Abstract

Two deterministic routing networks are presented: the pruned butterfly and the sorting fat-tree. Both networks are area-universal, that is, they can simulate any other routing network fitting in similar area with polylogarithmic slowdown. Previous area-universal networks were either for the off-line problem, where the message set to be routed is known in advance and substantial precomputation is permitted, or involved randomization, yielding results that hold only with high probability. The two networks introduced here are the first that are simultaneously deterministic and on-line, and they use two substantially different routing techniques. The performance of their routing algorithms depends on the difficulty of the problem instance, which is measured by a quantity &lgr; known as the load factor. The pruned butterfly runs in time O(&lgr;log2N), is the number of possible sources and destinations for messages and &lgr; is assumed to be polynomial in N. The sorting fat-tree algorithm runs in O(&lgr; log N + log2 N) time for a restricted class of message sets including partial permutations. Other results of this work include a “flexible” circuit that is area-time optimal across a range of different input sizes and an area-time lower bound for routers based on wire-length arguments.