The power of negative thinking in multiplying Boolean matrices

  • Authors:
  • Vaughan R. Pratt

  • Affiliations:
  • -

  • Venue:
  • STOC '74 Proceedings of the sixth annual ACM symposium on Theory of computing
  • Year:
  • 1974

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Abstract

We are interested in combinational circuits synthesized from and-gates and or-gates. We first show that n3 distinct and-gate inputs are needed to form the product of two Boolean matrices, and hence O(n3) two-input and-gates are needed to compute the transitive closure of a Boolean matrix. While this result has the flavor of Kerr's (achievable)lower bound [Kerr 1970] of n3+-gates for computing the min/+ product of integer-valued matrices using only min-gates and +-gates, the problem turns out on closer inspection to be considerably more subtle, and in fact we have been able to come only to within a factor of two of the best known upper bound of n3and-gates. Secondly we use this result to study the effect on combinational circuts of not using not-gates inverters).