Multiparty equality function computation in networks with point-to-point links

  • Authors:
  • Guanfeng Liang;Nitin Vaidya

  • Affiliations:
  • Department of Electrical and Computer Engineering, and Coordinated Science Laboratory, University of Illinois at Urbana-Champaign;Department of Electrical and Computer Engineering, and Coordinated Science Laboratory, University of Illinois at Urbana-Champaign

  • Venue:
  • SIROCCO'11 Proceedings of the 18th international conference on Structural information and communication complexity
  • Year:
  • 2011

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Abstract

In this paper, we study the problem of computing the multiparty equality (MEQ) function: n ≥ 2 nodes, each of which is given an input value from {1,...,K}, determine if their inputs are all identical, under the point-to-point communication model. The MEQ function equals to 1 if and only if all n inputs are identical, and 0 otherwise. The communication complexity of the MEQ problem is defined as the minimum number of bits communicated in the worst case. It is easy to show that (n-1) log2 K bits is an upper bound, by constructing a simple algorithm with that cost. In this paper, we demonstrate that communication cost strictly lower than this upper bound can be achieved. We show this by constructing a static protocol that solves the MEQ problem for n = 3, K = 6, of which the communication cost is strictly lower than the above upper bound (2 log2 6 bits). This result is then generalized for large values of n and K.