On the Complexity of Negation-Limited Boolean Networks

  • Authors:
  • Robert Beals;Tetsuro Nishino;Keisuke Tanaka

  • Affiliations:
  • -;-;-

  • Venue:
  • SIAM Journal on Computing
  • Year:
  • 1998

Quantified Score

Hi-index 0.00

Visualization

Abstract

A theorem of Markov precisely determines the number r of NEGATION gates necessary and sufficient to compute a system of boolean functions F. For a system of boolean functions on n variables, $r\leq b(n)=\lceil\log_2(n+1)\rceil$. We call a circuit using b(n) NEGATION gates negation-limited. We continue recent investigations into negation-limited circuit complexity, giving both upper and lower bounds.A circuit with inputs x1,..., xn and outputs $\neg x_1, \ldots, \neg x_n$ is called an inverter, for which $r=\lceil\log_2(n+1)\rceil$. Fischer has constructed negation-limited inverters of size O(n2 log n) and depth O(log n). Recently, Tanaka and Nishino have reduced the circuit size to O(n log2 n) at the expense of increasing the depth to log2 n. We construct negation-limited inverters of size O(n log n), with depth only O(log n), and we conjecture that this is optimal. We also improve a technique of Valiant for constructing monotone circuits for slice functions (introduced by Berkowitz).Next, we introduce some lower bound techniques for negation-limited circuits. We provide a 5n+3 log(n+1)-c lower bound for the size of a negation-limited inverter. In addition, we show that for two different restricted classes of circuit, negation-limited inverters require superlinear size.